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Title: USDA Miscellaneous Publication No. 579: Building with Logs
Author: Fickes, Clyde P.
Language: English
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Transcriber Note
Text emphasis denoted by _Italics_ and =Bold.= Whole and fractional parts
of numbers as 12-3/4.
BUILDING
with LOGS
Miscellaneous Publication No. 579
U. S. Department of Agriculture
Forest Service
The art of log construction is relatively simple, once a few basic
principles are understood. The pioneers who opened the lands beyond the
eastern seaboard did not have boards with which to build such shelter as
they needed. Logs were so plentiful in the forested area of our country
that, with their resourceful ingenuity, the settlers built their homes in
conformity with those principles of log construction which prevailed in
the countries from which they migrated. Those principles have remained
the same down through the years.
The pioneer had but an ax for a tool and consequently made only those
articles which could be hewed out of wood. Today there are many tools
available, and to do a first class job of log construction one must know
how to handle the double-bitted or single-bitted ax, the broadax, saw,
adz, chisel, slick, ship auger, and drawknife. In this bulletin it is
assumed that the reader is familiar with the ordinary frame building
methods used where wood is the principal construction material.
Washington, D. C. Issued September 1945
BUILDING WITH LOGS
By Clyde P. Fickes, _Engineer_, and W. Ellis Groben, _Chief Architect,
Forest Service_
Contents
Page
Building the foundation 1
Preparing the logs 1
Dimensions of the building 2
Framing the corners 3
Round-notch corner 4
Other log corners 7
Door and window jambs 12
Floor joists 12
Laying the wall logs 12
Window and door openings 14
Window and door frames 16
Roof framing 22
Shake roofs 23
Partitions 23
Flooring 24
Interior wood finishing 25
Calking 25
Chinking 27
Chinkless log cabin construction 28
Milled-log construction 31
Hewing timbers 31
Fireplace framing 31
Oiling and painting 35
The finished structure 35
Furniture 39
Chairs and stools 39
Bed and bunk 39
Chest and buffet 47
Settee 47
Dining table 49
Table, bench, book rack, and wood hod 50
Building plans 53
Additional information 56
BUILDING THE FOUNDATION
A building should have a good foundation, and a log structure is no
exception to the rule. For the sake of economy in labor and material it
is sufficient, in some instances, to place small buildings on piers of
concrete or rough native stone, but usually it will be more satisfactory
to use continuous walls of stone masonry or concrete to provide
uninterrupted support for the logs and thus avoid their tendency to sag.
These walls, however, should be provided with small openings for the
circulation of air to prevent the wood from dry rotting. Furthermore, the
continuous foundation wall has the additional advantage of preventing
rodents from getting under the building. In no case should the logs be
placed directly upon the ground since wood tends to decay when in contact
with the earth.
The two end walls of the exterior foundation should be higher than the
side walls in order to offset the difference in level of the logs on
adjacent walls, the end-wall logs being half their thickness higher than
those on the side walls.
In building a log wall the chief problem is in closing the opening
between each pair of logs. There are various ways of doing this, but
only those regarded as most satisfactory will be described in this
publication. The width of such openings is affected by several factors:
(1) The manner of placing the logs upon each other; (2) the type of
corner used where two walls meet; (3) the openings for doors and windows;
and (4) the natural shrinkage of wood in the process of drying.
PREPARING THE LOGS
The selection of straight, smooth, even-sized logs is the prime
consideration (fig. 1). Top diameters should be as uniform as possible,
but as a rule not less than 10 nor more than 12 inches. (Slightly
smaller or larger dimensions may be used if no others are available.) The
taper should be as slight as possible. For logs longer than 40 feet, the
top diameter may be less than 10 inches in order to avoid an excessive
diameter at the large or butt end.
[Illustration: Figure 1.--Starting to build the log cabin--laying the
foundation.]
Cedar, pine, fir, and larch, in the order named, are most desirable
for log construction. All knots, limbs, or bumps should be trimmed off
carefully when the log is peeled. It is best to cut the logs in late fall
or winter, for two important reasons: (1) Logs cut in spring or summer
peel easier, but crack or check to an undesirable degree while seasoning.
(2) Insect activity is dormant during the winter months; hence, if the
logs are cut and seasoned then, they are less liable to damage by insects
or rot-producing fungi.
Logs should be cut, peeled, and laid on skids well above the ground
for at least 6 months before being placed in the building. This may
not always be possible, but it is a good rule to follow. Logs should
be stored in a single deck with 2 or 3 inches between them to permit
complete exposure to the air. Logs having a sweep or curve should
be piled with the curve uppermost so that their weight will tend
to straighten them while they are drying. Where the skidding space
is limited, logs may be double-decked, using poles between tiers.
Unrestricted air circulation materially aids seasoning.
Sort the logs carefully before starting construction, using the better
ones in the front or other conspicuous walls of the building. If the logs
are not uniform in size, the larger ones should be placed at the bottom
of the walls.
DIMENSIONS OF THE BUILDING
For practical reasons the dimensions of a log building are the inside
measurements taken from one log to the corresponding log in the opposite
wall. Outside dimensions vary somewhat with the size of the logs, thus
accounting for the use of inside measurements. Where projecting corners
are desired, logs should be at least 6 feet longer than the inside
dimensions of the building. In erecting the walls, the logs should be
kept even or plumb on the inside faces if it is desired to finish the
interior with wallboard or plaster.
FRAMING THE CORNERS
The corner is one of the most important aspects of log construction. On
it the appearance and stability of the structure depend. Different types
of corner construction are in use in the United States, each varying in
accordance with local building customs or individual taste.
[Illustration: Figure 2.--The round-notch or saddle corner. This is
an unusually fine example of scribing and fitting logs together. The
square-cut logs have yet to be dressed and shaped with the ax to give
them a pleasing appearance.]
[Illustration: Figure 3.--Ranger station, Gallatin National Forest,
Mont., illustrating effective use of round-notch corners. _A_, and _B_,
Dwelling under construction; _C_, barn.]
Round-Notch Corner
The round-notch, or saddle, corner (fig. 2) is generally considered the
most satisfactory from every standpoint. This type of corner gives the
most distinctive appearance because the logs project sufficiently beyond
the corner not to appear dubbed off (fig. 3). It is a good, self-locking,
mechanical joint, relatively easy to construct, and holds the logs
rigidly in place.
[Illustration: Figure 4.--Method of marking saddle corners.]
In cutting the saddle, the material is taken out of the under side of the
upper log without disturbing the top surface of the bottom log. All the
moisture thus drains out at the corner and, consequently, the wood is
much less subject to decay than if other types of corners were used. The
shrinkage in the outer area of the log's circumference tends to open up
the space between the logs. Finally, in the round-notch corner, one-half
of the shrinkage between the logs is allowed to remain in the corner. The
separation, therefore, is not as great as if each log had been cut down
to the heartwood, a disadvantage common to most other types of corners.
The tools required to make a round-notch or saddle corner are: A pair
of log dogs to hold the log in place, 10- or 12-inch wing dividers with
pencil holder and level-bubble attachment, sharp ax, 2-inch gouge chisel
with outside bevel, crosscut saw, spirit level, and plumb board. The
framing of this corner, described in figure 4, should be relatively easy.
[Illustration: Figure 5.--Chopping the notch in a saddle corner.]
First, the bottom logs should be set in place on opposite sides of the
foundation. Hew a flat face of 2 to 3 inches in width on the under side
of the log where it rests on the foundation, so that it will lay in
place. Then place the bottom log on each end-wall and accurately center
it so that the inside face of all four logs is to the exact interior
dimensions of the building. Dog the logs into place so they will not
move while being marked for the corner notch. The wing divider is now
set for one-half the diameter of the side log. With the lower leg of the
divider resting on the side of the under log and the other leg, with the
level-bubble uppermost, resting against the bottom of the upper log and
directly above the lower log, start moving the divider upward, with a
side motion, so that the lower leg follows the curvature of the under
log. The pencil point of the upper leg makes a mark on the surface of the
upper log which will be the intersection of the surfaces of the two logs
when the notch has been cut from the upper one. Repeat this operation
four times to mark all four sides of the corner. A little practice will
make you adept at keeping the points of the divider perpendicular to each
other.
After the notch has been marked at both ends of the log, turn it over
on its back. It is a good idea to intensify the divider mark with an
indelible pencil so that it will be easily followed. Chop the notch
out roughly, as illustrated in figure 5, then chip down as closely as
possible to the mark, supplying the finishing touches with a gouge
chisel. The finished notch should be cupped out just enough to allow the
weight of the log to come on the outside edges, thus insuring a tight
joint.
When the next side log is rolled into place, the dividers should be set
apart for the width of the space between the top of the first and the
bottom of the following log, and the marking repeated as before. If you
wish to have the upper log "ride" the lower one a little, so that an
especially tight joint is obtained, the dividers should be set a little
wider apart than the space actually requires.
Other Log Corners
The dovetail, or box, corner (figs. 6 and 7) is a strong corner, and
considerable experience is required in order to make a neat-looking
job. This type has several undesirable features: (1) The logs are apt
to develop a wide crack because the corner is framed from the part of
the log in which the least shrinkage occurs, and (2) since the logs are
hewed down to form the corner, the wood has a tendency to collect and
retain moisture which soon results in decay. Also, this corner detracts
noticeably from the "loggy" appearance so characteristic and desirable in
log structures. The drawings in figure 6 show the most practical methods
of marking and framing the dovetail, or box, corner.
The flat, or plain, tenon corner (fig. 8), is also common. It may be
made in two ways. In one, only the bearing surfaces are framed, while in
the other, all four sides of the tenon are framed flat. The plain tenon
corner does not have the highly desirable feature of being self-locking.
However, it is simple to make and economical, and therefore especially
suitable for temporary structures. The logs must be pinned together, as
shown in figure 11. All the framing can be done on the ground, before the
logs are put in place. Carefully fitted, this makes a neat-looking job.
_Directions for constructing the flat, or plain, tenon corner._--Square
one end of log, as in figure 8, at point _A_, then measure required
length and saw the opposite end square, at _B_. If the log has any
curvature, turn it on the skids until its back is up. Determine the
thickness of the tenons, based upon the average top and butt diameters
of the log. Then take an 18-inch length of board the same width as the
thickness of the tenons, driving a nail through its center and into the
center of the log. Place the spirit level on top of the board and mark
lines on the log at the top and bottom edges. The width of a tenon
varies with the diameter of the logs; 8- to 10-inch diameters will
produce 6- to 7-inch wide tenons.
[Illustration: Figure 6.--Marking and framing the dovetail, or box,
corner.]
[Illustration: Figure 7.--Ranger Station, Lolo National Forest, Mont.
Note the meticulous construction of box corners.]
[Illustration: Figure 8.--Framing the flat, or plain, tenon corner.]
Nail a 1 inch by 1 inch cleat on the pattern board to points _C_ and _D_
and then make saw cuts on each end, cut chip off and smooth the surface.
Turn log over and repeat on the other side. After framing out the sides
of the tenon, the log is ready to be placed on the wall. Some fitting
between corners is usually necessary but, if the logs are fairly straight
and smooth, the work will be minimized.
The upright, or groove-and-tenon, corner (fig. 9) is used to a
considerable extent in the West. It has desirable features from a
mechanical standpoint: (1) The weight of the building is carried on
the full length of the logs and does not rest solely on the corners,
as in other types, and (2) it makes a tight wall because no openings
will develop between the logs. Although not difficult to construct, the
upright corner requires considerable mechanical skill and accuracy.
A good carpenter can frame the entire building on the ground before
any logs are placed on the foundation, after which it can be erected
in a very short time. Next to the round-notch corner the upright, or
groove-and-tenon corner, probably has the best appearance.
[Illustration: Figure 9.--Framing the upright, or groove-and-tenon,
corner.]
DOOR AND WINDOW JAMBS
Door and window jambs should be framed just like the corners except that
only the back should be grooved. The door side, or face, may be rabbeted
or left smooth so that a separate wood door stop may be nailed in place.
If the logs are reasonably dry, from 3 to 4 inches should be left at each
corner for settlement due to shrinkage; otherwise, more or less space
should be allowed, as conditions require. In about 6 months the cap log
will come down and close this gap. Similar provisions should be made for
settlement over door and window openings.
FLOOR JOISTS
As soon as the first round or tier of logs is laid, the floor joists
should be set in place, notching them into the bottom side logs. If the
building has a continuous masonry foundation, the joists may be set on
top of it, as in a frame building.
In order that the ends of the joists may have sufficient bearing on the
wall, it is necessary either to notch the ends into the side logs or
hew the latter off on the inside. A simple method is to cut the notches
in the side logs before they are rolled into place. Pole joists should
be from 4 to 8 inches in diameter and hewed level on the upper side to
provide a solid bearing for nailing the flooring. Several different ways
of framing the floor joists are shown in figure 10.
LAYING THE WALL LOGS
In laying the successive rounds of logs in the walls, several details
must be observed to keep them lined up so that the top logs form a
level seat for the roof framing. The corners should be kept as level as
possible as each round is laid. This can be done by measuring vertically
from the top of the floor joists, from time to time, as a check. A
variation of 1 inch in height will not cause a serious difficulty.
The height of the corner's is regulated in two ways: (1) By increasing or
decreasing the depth of the notch, and (2) by reversing the top and butt
ends of the logs when laying them in the wall.
The logs should be fitted together as tightly as possible. In the case
of somewhat irregularly surfaced logs, it may be necessary to smooth off
certain portions of the under side of the upper log to secure a tight
fit. Only in exceptional instances, however, should this be done to the
top of the lower log.
The face of the logs on the inside of the building must be kept plumb,
that is, in the same vertical plane. An ordinary carpenter's, or spirit,
level may be used, but a 6- to 8-foot plumb board is considered most
satisfactory because of its greater length.
The logs should be pinned together with a wooden pin or large spike (fig.
11). Spiking is done by boring a 3/4-inch hole halfway through the upper
log and continuing with a 7/16-inch hole through the bottom half. Then
drive a 10- or 12-inch spike into place, or until it penetrates half the
next log below. The spikes should be staggered in alternate rounds or
tiers of logs. If wooden pins are used, fir or oak logs are preferable.
Neither wooden pins nor spikes, however, offer interference to the
settling of the walls.
[Illustration: Figure 10.--Framing floor joists.]
The spike method is easier and quicker, and just as satisfactory as
the wooden pin. The logs should be pinned approximately 2 feet from
each corner and at each side of the window and door openings. For small
structures, where the alignment of the walls is not so important, pinning
may be eliminated, but it is essential to align larger buildings
accurately in order to prevent individual logs from springing out of
place.
[Illustration: Figure 11.--Pinning logs together.]
Where the use of logs having a decided curve, or sweep, is unavoidable
they should be set in the wall with the bow or back up. Such logs may
be straightened by making enough saw cuts in the upper side of the
curved surface to allow them to straighten out. The cuts should be
from one-third to one-half the depth of the log, or slightly more, if
necessary (fig. 12).
[Illustration: Figure 12.--Straightening a curved log.]
WINDOW AND DOOR OPENINGS
Early American log structures were characterized by relatively dark
interiors because window openings, designed for protective purposes,
were small and far apart. Since protection is no longer a consideration,
window frames may be of standard size and located where they are most
suitable for adequate day lighting.
As soon as the first round of logs and the floor joists are laid in
place, mark the location of door and window openings on the inside face.
Next saw out the door openings and chop out the notch in the doorsill log
to within an inch of the true or finished line, as shown in figure 13.
Leave final cutting of the openings to the exact dimensions until the
window and door frames are to be placed in position, thus insuring a good
finished wood surface. Also, determine the height of the openings above
the floor line and mark them in figures on the bottom log for reference
from time to time. The necessary cuts should be made in the log directly
over each opening before placing it in position. When the log which
carries the window frame is reached, a notch must be made for it as for
the doors.
[Illustration: Figure 13.--Cutting window and door openings.]
To provide the necessary doors and windows, openings must be cut in the
walls after the logs have been placed in position. As soon as a log in
the wall is cut in two, the problem arises of how to hold the loose ends
in place. Also, the doors and windows require the proper kind of frames
to insure airtight closure between the latter and the ends of the wall
logs. The most practicable and satisfactory method is to frame a vertical
notch in the ends of the wall logs, into which can be fitted a spline
attached to the back of the jamb or side-pieces of the door and window
frames. This method of framing holds the wall logs in place, allows them
to shrink and settle without hindrance, and makes a weathertight joint
between them and the door and window frames. The vertical notch in the
end of the wall logs may be framed by boring a 2-inch auger hole in each
log as it is laid in place. The hole should be located so that, when the
wall logs are sawed out for the opening, the saw cut passes down through
the edge of the hole nearest the opening. It is then a simple matter to
frame the notch to take the spline. The inside face of the notch can be
left rounded and the spline chamfered to fit. To keep the holes in line
from log to log, use the plumb board illustrated in figure 14.
[Illustration: Figure 14.--Method of marking openings.]
WINDOW AND DOOR FRAMES
There are two ways of making window and door frames--in three pieces
(two side jambs and one head jamb), or in four pieces (two side jambs,
one head jamb, and a sill piece). When a three-piece frame is used, the
bottom log of the opening is cut or shaped to make the window or doorsill
and the jamb pieces are then fitted to the sill. If the jambs are framed
from pieces of log slabbed on two opposite sides, a presentable frame in
keeping with the log character of the structure is obtained. The window
or door face of the jamb pieces may be rabbeted for the windows and
doors, respectively, or they may have separate wooden pieces, known as
stops, nailed on. The spline on the back of the jamb may be rabbeted out,
or a 2 inch by 2 inch piece of straight-grained wood nailed on. The head
jamb can be framed in the same way; it does not require a spline on the
back. Each side jamb has a dowel framed on each end. The bottom dowel
fits into a mortise in the sill and the top dowel into a similar mortise
in the head jamb.
[Illustration: Figure 15.--Window frames.]
In a four-piece frame, the sill log is cut with a slope, in the customary
way, and the jambs are fitted as for a three-piece frame. Figure 15
illustrates the installation of three- and four-piece window frames.
When the head jamb or top log over the opening is reached, the frames are
ready for installation. The opening is now cut out, the sill fashioned,
the vertical spline slot framed, and the head jamb log cut out to fit
over the opening. At this point, the amount of settlement resulting from
the shrinkage of the wall logs, as they dry out, must be determined and a
corresponding allowance provided in the opening. This allowance is made
between the upper side of the headpiece of the frame and the bottom of
the log directly over the opening, and should be from 2-1/2 to 4 inches
for a door 6 feet 8 inches to 7 feet in height, or 1-1/2 to 3 inches
for an ordinary double hung window. The log over the opening should be
notched out on the under side so that it can be dropped in place after
the frame has been set in position.
When the type of window or door frame here described is used, neither
outside nor inside casings, sometimes called wood trim, are required. The
logs selected for the jamb material should be from 2 to 3 inches larger
in diameter than the wall logs, in order to fit properly. Also, they will
be much easier to work if well-seasoned (fig. 16).
[Illustration: Figure 16.--Log jamb window frame.]
[Illustration: Figure 17.--Typical log-wall section, taken through
window.]
If standard mill work frames are used, false side jambs of sawed
material, usually 2-inch planks, should be fitted in the openings to hold
the logs in place. For a wall made of 10-inch logs, a plank 2 inches by
10 inches should be used for the jambs and the standard frame fitted in
place between them after providing the necessary allowance for the wall
logs to shrink or settle. The head casing ordinarily will cover the space
allowed for shrinkage.
Some kind of insulating material which will take compression, such as
crumpled newspapers, asbestos wool fiber, or rock wool, may be used to
fill the space over the head allowed for settlement. Insulating material
must be installed loosely, so as not to take any weight as the headlog
gradually settles.
[Illustration: Figure 18.--Various ways of framing eaves. Despite the
fact that sawed rafters, as shown above, are often used for convenience
in framing the roof, sawed or milled material is incongruous in
appearance in the exterior of log buildings Hence, pole rafters,
hand-made shakes, and similar hand-riven features are preferred.]
For the log-type frame, copper or galvanized steel flashing should be
fastened to the bottom of the cut in the top log, leaving the lower edge
of the flashing free to slide on the face of the log head jamb. As the
wall settles, the bottom of the flashing can be trimmed off if too much
of the face of the head jamb is covered. This makes a weathertight joint
and protects the insulating material with which the shrinkage space has
been filled. See figure 17, Head section.
[Illustration: Figure 19.--Framing log purlins for shakes.]
ROOF FRAMING
Roofs may be framed in several ways, depending upon the kind of material
available and the appearance desired. The framing for a shingle roof,
whether of sawed material or round poles, is done in the same way as that
of a frame building. The top log on the wall may be cut with a flat seat
for the rafters to rest upon, as at _Y_, in figure 18, _A_ or notched out
to receive them as at _Z_ in figure 18, _B_. The gable ends may be run
up with the logs, which is preferable for architectural appearance, or
framed like the gables of a frame structure, and then covered with wood
siding, shingles, or shakes (fig. 19).
The shingles may be laid over sheathing boards in the usual manner or on
shingle strips placed across the roof rafters, parallel with the ridge
and exactly spaced to receive them, commonly known as "barn-fashion."
The particular method to be followed in framing the eaves depends largely
upon their projection. Where the effect of a considerable overhang is
desired, an eave purlin log may be used to support the projecting shakes
as shown in figure 19, _A_. To support 30- to 36-inch long shakes having
a 6-inch lap, the log purlins should be spaced at approximately 24-inch
intervals, as in figure 19. In regions of heavy snows, the eave log may
be placed slightly forward to help support the overhang, or an additional
eave log may be placed in position, as shown in figure 19, _B_. The gable
logs should be run up at the same time as the roof logs, and both rigidly
framed together.
[Illustration: Figure 20.--Splitting shakes with the froe.]
Shake Roofs
It is often desirable to use hand-split shakes for the roof covering.
These are usually made from cedar, but may be of any straight-grained
wood, free from knots, which splits easily. First, the logs are cut in
lengths of 30 to 36 inches and then the shakes are split off with a tool
called a froe (fig. 20).
After the log cuts are set on end, the froe is held on the upper end of
the block and then struck a blow with a wooden maul which causes a piece
of the block or shake to split off. Being hand-split, the thickness
varies somewhat; the minimum is 1/2 inch. A roof of thin shingles,
lacking sufficient scale, is never as effective as a rough textured one,
using 3/4- to 1-1/4-inch thick shakes, to harmonize with the sturdy
appearance of the log walls. The width, normally 6 to 8 inches, is
governed by the size of the blocks of wood and varies accordingly, while
the length is governed by the spacing of the roof logs or purlins. Shakes
are always laid on the purlins in single courses, lapping the sides 1-1/2
to 2 inches and over-lapping the ends at least 6 inches, as illustrated
in figure 19. Nailing is usually done with six- or eight-penny galvanized
box nails. Copper nails may be used for greater permanence. A good shake
roof will not leak although from the inside of the building it may appear
to have many holes.
The ordinary, uninteresting, straight-line effect at the butts may
be broken up by staggering them from 1 to 2 inches, as is often done
with shingles. This method produces an effect more in keeping with the
log walls. Although involving greater care and additional labor it is
preferable, from an architectural point of view, to the more common
custom of laying them to uniformly straight lines.
At the ridge of the roof, where the shingles or shakes intersect,
provisions must be made for weatherproofing. The shingled Boston ridge,
comb intersection, or pole ridge, shown in figure 21 are practical and
much more satisfactory from the standpoint of architectural effect than
stock metal ridges, ridge boards, and other methods.
[Illustration: Figure 21.--Ridge treatments.]
PARTITIONS
If the log building is to be divided into several rooms, at least two
different methods may be used to construct the partition walls. If the
log construction plan is to be carried throughout the structure by using
interior log-wall partitions, these should be laid out and framed in,
and the door openings cut in the same manner as previously described for
exterior walls. If a log partition comes at a place in a cross wall where
it is not considered desirable to have the log ends project into the room
beyond the opposite face of the wall, they may be sawed off flush with
the face of the cross wall, as shown at _X_, figure 22, Plan _A_. This
will not weaken the joint since the logs are both pinned and locked in
place.
[Illustration: Figure 22.--Interior partitions.]
Where frame partitions are used, they should be constructed as in a frame
building. A gain or a 3- to 4-inch deep groove should be cut in the log
wall into which the end studding of the frame partition is to be set
(fig. 22, Plan _B_). The cut should be made in each log before it is
placed in the wall. In no case should the studding at the ends of the
partitions be nailed to the log walls which they intersect in order not
to interfere with or be affected by their shrinkage and settlement.
FLOORING
A subfloor should be laid first using shiplap or sheathing. Over this a
finished floor of such hardwoods as maple or oak, or the harder softwood
species such as Douglas-fir, western larch, or southern pine, may be
laid. Vertical grain and flat grain may be had in both softwood and
hardwood, but the vertical grain shrinks and swells less than the flat,
is more uniform in texture, wears more evenly, and the joints open much
less. Finished flooring consists or tongue-and-groove material of various
thicknesses and widths.
Despite a slight tendency to splinter and wear irregularly over a period
of years, plain wide planking of random-width boards makes an appropriate
floor for a log building. An attractive effect may be had by using screws
instead of nails, countersunk to a depth of 1/2 inch and concealed by
inserting false wooden dowels glued in place as shown in figure 23, _B_.
Keying the boards together with wood keys, at random along the edges,
adds to the attractiveness of the flooring.
INTERIOR WOOD FINISHING
Hanging doors and windows, and many other customary details of building
construction should be done in the usual manner in building with logs.
Whenever cupboards or other built-in units are constructed, they must
be framed to be independent or entirely free of the log walls, like the
furniture. However, such fixtures as lavatories may be attached to two
adjacent logs without any subsequent structural complications.
[Illustration: Figure 23.--Flooring. _A_, Plain tongue and groove; _B_,
random-width planking.]
CALKING
When round logs are laid up in a wall there is always an opening between
them unless they are grooved on the under side to saddle the one below,
as described later under chinkless log cabin construction. In exterior
walls, this opening, or crack, must be closed in order to make the
structure weathertight. There are several methods of doing this. If
the logs are reasonably straight and uniform in size and the corners
carefully made, the opening between them will be small, often barely
perceptible. When this is the case, the openings should be filled with
some sort of calking compound applied with either a pressure gun or a
trowel (fig. 24).
[Illustration: Figure 24.--Examples of tight joints well calked. _A_,
Interior calking; _B_, exterior calking.]
In recent years several kinds of calking material have been put on the
market. They are applied best with a gun having a pressure-release
trigger whereby the calking compound is forced through a nozzle made in
various shapes and sizes to meet different requirements. These calking
compounds are not adversely affected by heat or cold, retain their
natural flexibility, and have an adhesive property which causes them to
adhere to the surface to which they are applied.
A good plastic compound will adhere to the logs under all conditions
and can be patched easily by simply applying more material. A black
fiber seal is not objectionable and, at the same time, gives a practical
finish. The seal should be applied to both sides of the exterior and
interior log walls, producing an almost hermetically sealed building.
When applied with a pressure gun having a 3/8-inch nozzle, 1 gallon will
fill about 300 linear feet of opening. If applied in cold weather, the
material should be heated to a temperature of 60°F.
CHINKING
When using logs that are somewhat rough and irregular in shape, the
resulting space between them may be so large that the calking material
cannot be used satisfactorily to fill the opening. In such cases, it
will be necessary to insert "chinking," which usually is applied to the
interior and exterior walls in one of two ways:
1. _Split chinking._--Segments of a log are split out in sizes which fit
the opening and, after being carefully shaped with the ax to make a tight
fit, are securely nailed in position. This kind of chinking requires
considerable work and patience to secure a good appearance.
2. _Pole chinking._--Small round poles may be used to fill the openings
(fig. 25). Usually they are cut in sizes and lengths to fill the opening
from wall to wall. This sort of chinking may be applied rapidly to either
inside or outside walls and makes a neater job than the preceding method.
Unless the logs are thoroughly seasoned these small poles sometimes
have a tendency to pull away from the nails. When the chinking has been
completed, the openings will have been reduced sufficiently in width to
allow the calking material to be applied successfully.
[Illustration: Figure 25.--Pole chinking.]
It is always a serious problem in log construction to devise a practical
method for permanently fastening the plaster daubing in place on both
inside and outside walls. In some instances, shingle nails may be driven
into the logs 2 to 3 inches apart for the full length of the opening or
2-inch wide strips of metal lath may be used and the plaster applied to
fill it. Cattle hair may be added to the plaster to increase its adhesive
consistency and thereby hold it more rigidly in place. Sometimes, wood
strips are nailed on the lower log to hold the plaster in position, as
shown in figure 26, but they are unsightly.
[Illustration: Figure 26.--Wood daubing strips.]
CHINKLESS LOG CABIN CONSTRUCTION
Chinkless construction, associated with the building of log structures in
Scandinavian countries, eliminates the chinking and mudding so prevalent
in many log buildings. It consists of grooving the under side of every
log in each tier so that it saddles the log beneath, making a close
joint for its entire length. The groove is marked by a tool which, for
convenience, may be called a cabin scribe or a drag (fig. 27).
_Directions for chinkless log cabin construction._---Mark and cut out
the notch just as is done for a round-notch corner. Next, dog the log in
place and scribe, making the additional mark shown by dash line (_X_,
fig. 27). Then, cut to line and, finally, drop log in position.
The scribe is 12 inches long, made preferably of 3/8-inch square steel
or iron bent in much the same manner as the spring in a steel trap; the
two ends are turned down about 1-1/2 inches like two fingers, diverging
to about 3/4 of an inch at the points, and then sharpened with a flat
surface on the inside of the point toward the loop. The loop should be
hammered out thin to provide sufficient flexibility to allow the points
to spread or close easily. A ring is welded around the two halves of the
tool which, when slipped up or down, makes it possible to adjust the
points and thereby prevent any further spreading while the tool is in
use. A link from a small chain, placed over the legs before the points
are turned, will serve the same purpose and, to prevent the points from
springing together, a small piece of wood may be forced between them.
[Illustration: Figure 27.--Chinkless log cabin construction.]
To fit a log, first frame it at the ends and then fit it down to within
about 2 inches of the lower log where the opening is the widest It is
difficult to do a good job of scribing when the logs are too close
together. The scribe must then be adjusted at the point where the
opening is the widest so that, when holding the tool parallel to the
opening, the lower point of the scribe will ride on the surface of the
bottom log. By exerting sufficient pressure, the upper point will score
the top log. Repeat this operation to score the upper log on the other
side. The corner tenons must be marked likewise. Next, turn the log over,
work the tenons down and then cut a =V=-shaped groove to the marked lines
in the remaining portion of the log, using a double-bitted ax. This
groove should be cut deep enough along its center to permit the outer
edge of the groove to rest continuously on the lower log. By removing the
least amount of wood to make the smallest possible groove, the closest
fit is obtained with the least effort.
[Illustration: Figure 28.--Fine example of milled-log
construction--ranger's dwelling, Whitman National Forest, Oreg.]
The principle of the scribe is based on parallel lines, and it can
readily be seen that if there is a hump on the lower log there will
have to be a gouge in the upper one. When the work is done carefully,
the space remaining is negligible. Where an airtight wall is desired,
a strip of plumber's oakum should be laid on the bottom log before the
upper log is dropped into place. If this material is not available, dry
moss is a fairly practical substitute.
Milled-Log Construction
Sometimes it is feasible to take advantage of a portable mill to face the
logs on three sides rather than to hew them by hand. The level beds seat
the logs so well that calking is minimized, the smooth interior surfaces
permit of easy finishing, particularly where wood wainscoting or plaster
is used, while the round-log exterior effect is undisturbed, except where
the logs project at the corners. Figure 28 illustrates a structure built
in this way.
HEWING TIMBERS
The facing or hewing of round timbers to obtain one or two sides surfaced
flat for framing purposes, as shown in figure 29, requires considerable
skill in the use of the ax and broadax. There are, however, a number of
mechanical aids (fig. 30) which should be used by anyone undertaking
log construction in order to simplify the work as much as possible. The
carpenter's spirit level, the steel square, and chalk line and chalk are
necessary for laying off the lines to be followed in hewing timbers. In
framing logs they should be laid up on skids, or sawhorses, dogged fast
in place with iron dogs, and the dimensions laid off on each end of the
log with the level and square to insure that the lines are parallel to
each other. Then, with the chalk line, carefully snap lines on the side
of the log connecting corresponding points at each end. For squaring the
ends of a log and cutting pole rafters, use the miter box to guide the
saw. To measure lengths accurately the steel tape, or a board pattern cut
to the exact length, may be used.
FIREPLACE FRAMING
The living-room fireplace, invariably the most prominent interior
feature, harmonizes best with a log interior if built of stone and
provided with a crude log shelf. The fireplace itself may be either the
traditional masonry type or the more modern metal-lined one equipped with
a heatilator.
The masonry of the fireplace and its chimney should always start on
solid earth, below the frost line, like the foundations of the building
itself. Masonry does not settle, unlike the surrounding log construction.
Consequently, it is recommended that a self-supporting log framing be
built around and entirely free of the masonry of the fireplace and
chimney, as illustrated in figure 31. The opening should be framed in
the same way as window and door openings. The fireplace and chimney
masonry should not be erected until the opening has been framed for it.
Upon completion, the intersection between the stone and wood should be
thoroughly calked to make an airtight, weatherproof job. This method
allows the wall logs to settle, because of the unavoidable shrinkage,
without structural failure.
[Illustration: Figure 29.--Framing hewed timbers.]
[Illustration: Figure 30.--Mechanical aids in cutting timbers. Method:
Cut both miter boxes at angle _X_ for 1/3 pitch. Fasten them securely to
the floor or to a log, used as a sawhorse, and space exactly the required
distance apart to insure that all rafters are cut alike. Then place each
rafter in the boxes, back down if any curvature exists, dog rigidly in
place and saw to the pattern.
Line A represents the exterior wall face and, if sawed off on line _B_,
parallel with the wall face, overhang of eave will be 1 foot, 6 inches.
Any desired overhang may be had and sawing eliminated by fixing the
distance _C_. The irregularly hewed rafter end is preferable to the
uniform elliptical saw-cut ends. Finally, hew the upper surface of the
rafters to a smooth even bearing to receive the roof sheathing boards.]
[Illustration: Figure 31.--Framing around the fireplace. Framing logs
around fireplace and chimney varies with the effect desired: (1) By using
an exposed vertical slabbed log and spline, as at _A_, with space _X_, to
allow for the shrinkage settling of the logs above the mantel, or (2) by
using a concealed vertical slabbed log and spline, as at _B_, where the
masonry is exposed above the mantel.]
[Illustration: Figure 32.--A useful type of modern log dwelling--ranger
station, Gallatin National Forest, Mont.]
In building an ordinary fireplace, the firebox and inner hearth should
be made of firebrick to withstand intense heat and the various parts
proportioned in accordance with standard practice to insure efficient
operation.[1]
[1] For this purpose the following publication will be found useful:
Farmers' Bulletin 1889, Fireplaces and Chimneys.
The heatilator is a built-in recirculating steel unit consisting of metal
sides and back to form a heating chamber, adjacent to the fire pit, which
draws cold air through a register at each side near the floor and after
the air is heated ejects it through similar registers above. It should be
installed in conformity with the manufacturer's directions, taking care
to select a stock-size unit suitable for the dimensions of the fireplace
opening and to erect the surrounding masonry accordingly.
OILING AND PAINTING
After all the openings have been properly calked and the logs brushed
clean, it is often desirable, although not absolutely necessary, to treat
the log surfaces with some sort of preservative material. Logwood oil is
excellent for the exterior. The colorless variety is preferable in most
cases but, if some color is desired, add just enough burnt umber, or raw
sienna paste, to give the proper shade. For interior finish, apply a coat
of clear shellac and then one or two coats of dull varnish. The trim can
be treated in a similar manner to preserve the pleasing effect produced
by the natural surface and color of the wood.
THE FINISHED STRUCTURE
Examples of modern log construction are shown in figures 32, 33, and 34.
Early types of log structures are illustrated in figure 35.
[Illustration: Figure 33.--Modern structures showing effective use of log
construction in recreation buildings on national forests in Montana. _A_,
Dude ranch; _B_ and _C_, recreational and mess hall, Seely Lake.]
[Illustration: Figure 34.--Organization camp at Seely Lake showing log
work In greater detail. _A_, Entrance wing; _B_, cabin group. Note the
wedges under porch post to provide for settling of walls. Wedges are
gradually driven out as necessary.]
[Illustration: Figure 35.--Early types of log structures built by the U.
S. Forest Service in the West. _A_, Ranger station, Gallatin National
Forest, Mont.; _B_, ranger's dwelling, Nezperce National Forest, Idaho;
_C_, log cabin in Arizona.]
FURNITURE
The matter of interior furnishings is always of great concern to those
who build log cabins. Odds and ends or too many "what-nots" may prove
to be misfits. Pieces of Early American design are perhaps the most
appropriate ready-made furniture, but sturdy, rustic pieces yield the
greatest satisfaction.
Many cabin owners have found a great deal of pleasure in making essential
furniture, such as bunks, beds, tables, chairs, settees, and similar
items. In the East, birch is preferred as a material, and in the West,
lodgepole pine is most satisfactory. Other native species, however,
will do just as well. In making furniture it is advisable to remove
the bark from the logs because bark collects insects, causes the wood
to deteriorate and eventually falls off, leaving imperfect, unsightly
surfaces. Figures 36 and 37 show types of furniture suitable for log
residences.
For rustic effects, the use of a stain of the following proportions gives
a satisfactory appearance: 2 quarts turpentine, 2 quarts raw linseed oil,
and 1 pint liquid drier, to which add 1/2 pint of raw sienna, 1/2 pint
of burnt umber, and a touch of burnt sienna. The top surfaces of tables,
buffets, chests, and rawhide seats should have two coats of spar varnish.
Where countersunk screws are used in connection with a stain finish,
insert false wood, dowel-like plugs in preference to plastic wood to
conceal the screwheads.
Simplicity, both in construction and appearance, is the keynote for
producing the most harmonious effects in furniture, in keeping with log
interiors.
Chairs and Stools
Armchairs can be built with well-seasoned lodgepole or eastern pine, or
birch (fig. 38). The cornerpieces should be mortised and tenoned to the
frame and rail and anchored in place with 3/8- by 15-inch lag screws. The
arms should be fastened to the cornerpieces with 3/8- by 5-inch carriage
bolts and to the slab support with 3/8- by 4-inch lag screws. The
vertical slab support should be rigidly secured to the frame with 3/8-
by 3-inch carriage bolts. Cushions may be of the filler type, without
springs, and covered with homespun fabric. Use 2-inch wide heavy canvas
strips, securely fastened with furniture tacks, to support the cushions.
Upright chairs and stools (fig. 39) can be made from the same material as
the armchair. Cross the poles to impale the legs rigidly. The crosspieces
of the chair back should be curved to fit the human back. The joints must
be tightly glued, mortised, and tenoned.
[Illustration: Figure 36.--Furniture suitable for log cabins--convenient,
sturdy, and easy to make. _A_, Bed; _B_, bed and armchair.]
[Illustration: Figure 37.--_A_, Dining table appropriate for log cabin;
_B_, book rack and hod.]
[Illustration: Figure 38.--Plan for making an armchair suitable for log
residence.]
[Illustration: Figure 39.--Plan for making an upright chair and stool.]
[Illustration: Figure 40.--Plan for making a double bed for log
residence.]
Bed and Bunk
Birch or well-seasoned lodgepole or eastern pine is suitable for making
a bed or bunk. In making a bed (fig. 40) the crosspieces should impale
the corner posts tightly; the joints should be glued and toe-nailed from
below. Do not cut the side or end pieces until the bedspring has been
measured and then allow for a slight play in both directions in setting
the angle irons, in order to facilitate the insertion and removal of the
mattress. Use 14- by 3-inch carriage bolts to fasten the angle irons
to the wood frame. Figure 40 is a plan for making a double bed 5 for a
single bed, reduce the width accordingly.
A double-deck bunk is made in much the same way as a bed (fig. 41).
[Illustration: Figure 41.--Plan for building a double-deck bunk.]
[Illustration: Figure 42.--Plan for making a combination chest and
buffet.]
Chest and Buffet
No log residence is complete without furniture for storing clothes. A
combination chest and buffet suitable for log cabins can be made from
well-seasoned lodgepole or eastern pine, tamarack, or birch (fig. 42).
The ends, doors, shelves, and drawer fronts should be cut from No. 2
tongue-and-groove commercial pine lumber.
Settee
A settee can be made from well-seasoned pine or birch (fig. 43). Join the
corner poles to the slab frame and rail with mortise-and-tenon joints;
then anchor the joints by means of 3/8- by 6 -inch lag screws. Fasten the
arms to the corner poles with 3/8- by 5-inch carriage bolts and to the
slab support with 3/8- by 4-inch lag screws. Use 3/8- by 3-inch carriage
bolts to fasten the slab support to the frame. The 1- by 2-inch hardwood
crosspieces should be securely fastened at the top ends and notched into
the legs at the bottom ends, held by 2-inch wood screws, driven into
place at an angle. Back slats should be mortised and tenoned to the rail
and frame. The cushions should be the filler type, without springs if so
desired, and covered with homespun fabric.
[Illustration: Figure 43.--Plan for making a living-room settee.]
[Illustration: Figure 44.--Dining table plan.]
[Illustration: Figure 45.--Plan for making benches.]
Dining Table
Peeled pine or birch is ideal material for building a dining table (fig.
44). Make a tight saddle joint between _B_ and the legs. Cross poles to
impale the legs tightly. Notch _E_ for the cross poles. Upper surface
of _C_ should be slab-faced and fitted between _D_ and cross poles, all
rigidly braced together. Top pieces of tables should be doweled at places
indicated in the drawing with 1/2- by 4-inch wood dowels, glued and
clamped to insure tight joints. Notch top pieces A 1-inch deep to receive
_B_ and _D_. Top outside edges of _A_, _C,_ and _E_ should be hewed.
[Illustration: Figure 46.--Plan for a book rack.]
Table, Bench, Book Rack, and Wood Hod
Well-seasoned lodgepole or eastern pine, tamarack, cedar, or birch are
suitable for benches (fig. 45). The joints should be glued. Countersink
any screws, then conceal the heads with false wooden dowel-like plugs.
If the furniture is to be painted, use plastic wood. A book rack may be
made of the same material used for the bench, except cedar, which is
unsuitable (fig. 46). The sides and bottom shelf should be rabbeted and
thoroughly glued. The two intermediate shelves can be made adjustable by
boring 3 holes in each side-piece 2 inches apart, above and below the
position shown for the shelves in figure 46, into which loose wooden pins
may be inserted for their support. Screw the top in place, countersink
screwheads and insert wood cover plugs or false dowels for concealment
where stained finish is used. If painted, plastic wood may be used.
[Illustration: Figure 47.--Plan for a fireplace wood hod.]
A fireplace wood hod (fig. 47) may be made of wood and metal. Use
well-seasoned lodgepole or eastern pine, tamarack, or birch. Make a tight
cradle joint between horizontal and vertical side-pieces, using 14- by
2-inch carriage bolts except that by 3-inch lag screws should be used
for fastening the lower side-pieces and bottom. Secure the wrought-iron
handle to each side toppiece with 3- by 1-1/2-inch carriage bolts. The
wood sides should have hewed edges of 3/4 inch minimum thickness.
[Illustration: Figure 48.--Floor plan for a four-room log residence.]
BUILDING PLANS
Selection of the site and preparation of building plans varies with
individual taste. In choosing a location one must consider availability
of transportation, shopping centers, water supply, sewage disposal,
electric facilities, and kindred factors.
[Illustration: Figure 49.--Floor plan for a four-room log residence with
somewhat different orientation than that shown in figure 48.]
Before undertaking construction it may be desirable to consult an
architect or competent builder to make sure that (1) your desires are
satisfied with respect to the necessary accommodations; (2) rules and
regulations enforced by local authorities will be observed; and (3)
provisions are made for installing telephone, electricity, water, and
plumbing facilities. Failure to take these precautions may necessitate
costly changes after construction has begun.
Plans for suitable four-room log residences are given in figures 48 and
49, and for a five-room structure in figure 50. Figure 51 shows the
layout of a United States Forest Service two-room guard cabin adaptable
for summer residence use.
[Illustration: Figure 50.--Floor plan for a five-room log residence,
including three bedrooms, living-room, kitchen, and two porches.]
[Illustration: Figure 51.--U. S. Forest Service two-room fireguard cabin
adaptable for summer residence use.]
ADDITIONAL INFORMATION
Additional useful information on building log cabins may be obtained from
the following publications:
UNITED STATES DEPARTMENT OF AGRICULTURE
FIREPLACES AND CHIMNEYS. Farmers' Bul. 1889, 52 pp., illus. 1940.
PROTECTION OF LOG CABINS, RUSTIC WORK, AND UNSEASONED WOOD FROM INJURIOUS
INSECTS. Farmers' Bul. 1582, 20 pp., illus. 1929.
USE OF LOGS AND POLES IN FARM CONSTRUCTION. Farmers' Bul. 1660, 26 pp.,
illus. 1931.
OTHER SOURCES
LOG BUILDINGS. Wis. Agr. Col. Ext. Stencil Cir. 158, 39 pp., illus. 1940.
LOG CABIN CONSTRUCTION. A. B. Bowman. Mich. State Col. Ext. Bul. 222, 54
pp., illus. 1941.
LOG CABINS AND COTTAGES; HOW TO BUILD AND FURNISH THEM. W. A. Bruette,
ed. 96 pp., illus. New York.
THE REAL LOG CABIN. C. D. Aldrich. 278 pp., illus. 1934. New York.
SHELTERS, SHACKS, AND SHANTIES. D. C. Beard. 243 pp., illus 1932. New
York.
U. S. GOVERNMENT PRINTING OFFICE: 1954
For sale by the Superintendent of Documents,
U. S. Government Printing Office
Washington 25, D. C. -- Price 25 cents
* * * * *
TO KEEP THE TREES GROWING
Here in the United States we are cutting trees faster than new ones are
growing for the future. And because science is showing us how to use wood
better and in new ways we are likely to want more trees in the future
than we use today. In fact we must double the annual growth of usable
wood. This can't be done easily or quickly. It will require decades of
good forestry. So we must take steps now--
To protect all our forests well from fire, insects, and disease;
To stop wasteful and destructive cutting;
To keep plenty of trees of all sizes growing to replace those we cut;
To restore commercial tree growth on millions of acres of forests
that have been badly treated or burned;
To give farmers and other small owners more help in growing,
harvesting, and marketing their tree crops;
To put wild land into public forests when private owners cannot take
care of it or the public interest calls for special treatment.
* * * * *
Transcriber Notes
All illustrations were moved so as to not split paragraphs.
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