Sunset's Cabin Plan Book

by Unknown

CABIN FOUNDATIONS

Foundations are the backbone of your cabin. From the structural standpoint they are probably the most important part of the building. So, just because they are going to be hidden, don’t skimp or hurry through with them because you want to get started quickly on the cabin itself. If the basic framework is out of line, the whole house will sag and tilt at odd angles. As one cabin expert says, “Wear out your spirit level and try-square—don’t save them for another job.”

One of the simplest foundations for the amateur builder is made by resting the sills on supports made of two large somewhat flat boulders. If your cabin site is on solid rock, then all that is necessary is to bed the bottom boulder securely on the rock. But if the terrain is ordinary earth, you should dig down past the “forest floor” of black humus until you reach rock, sand, gravel or other solid ground below the frost line. Then you pour concrete piers to the grade level and seat your boulders thereon, as shown in [Fig. 3]. Do not use any mortar between the two boulders. Dampness will creep up past the first boulder, but if it is not bonded to the top boulder with mortar, the dampness will stop there and not reach the post supports or sill timbers of your cabin. Of course the concrete piers themselves, if built above grade, are perfectly good supports for the sills. But the boulders have more of a cabin “look.”

Fig. 3

FLAT TOP BOULDERS CONCRETE PIER FOOTING

Fig. 4

WOODEN FORM FOR PIERS

The number of foundation supports or piers will be determined by the size of the house. “Not less than seven feet on centers” is a good rule of thumb.

Concrete piers are not hard to make. Their size will depend on how deep you must dig to reach solid earth or rock. First, build several tapered box forms of rough lumber. ([Fig. 4].) These should be about 24 inches square at the bottom and taper to about 12 inches at the top. The taper makes it easier to get the forms off the finished concrete. Pour a footing of concrete at least 10 inches thick and six inches larger than the bottom of the pier on all sides. Then set the form for the pier on top of this footing.

A satisfactory mixture for foundation piers is one part Portland cement, two parts clean sand, and three parts gravel—two-inch aggregate is about right. It is a good idea to add to the mixture hydrated lime—about 10 per cent of the bulk of the cement—to prevent the mass from setting too rapidly and to make it work more smoothly.

This type of foundation allows perfect ventilation under the cabin, but it will not keep out wandering rabbits and other night prowlers.

A boulder foundation is quite enough for the average semi-permanent summer cabin unless you plan to spend time there during the winter, in which case an all-around foundation is advisable to keep out the cold.

Full concrete or rock foundations are more expensive and more work to build but hard to beat for permanence. To construct them, dig a trench to the dimensions of your cabin but at least twice as wide as your finished foundation wall is to be and to solid ground below the frost line. Pour in a “footing” of concrete to a depth of 10 inches. This base will distribute the weight of the cabin. ([Fig. 5].) On this footing build wooden form walls to the proper height—about one foot above ground level at the highest point of your grade is usual—and fill them up with the proper mixture of concrete. To prevent dry rot of the wood construction, air vents should be constructed at intervals in the concrete wall above grade. These should be covered with screening to keep small animals out. Thickness of foundation walls varies according to the weight of the building. A good rule is to make the top of the foundation two inches wider than the logs or timbers it is to support.

Fig. 5

BOLT FOR SILL LOG METAL TERMITE GUARD CROSS SECTION OF FOUNDATION WALL

The sill logs or timbers are laid on top of the foundation. If your cabin is to be of logs, select a number of the strongest and straightest and lay them so as to form the outside “frame” of the cabin. They should be bolted tightly to the concrete by means of long iron bolts previously buried in the foundation walls. If the sills are to rest on piers or boulders, spike them together. The weight of the cabin will hold the sills in place. The 2×6 floor joists are cut in or notched over the sills. They should be set with the 2-inch side uppermost and securely spiked.

The footing for the fireplace is made just like the concrete foundations—6 or 8 inches beyond the dimensions of the fireplace plus the hearth. Pour a slab of concrete about 10 inches deep, in which are buried ½ inch steel rods laid in both directions—checkerboard fashion—and wired at the intersections. This may seem like a lot of extra work but the steel rods prevent settling and cracking. On this slab build a wooden form to the height of the bottom of the floor joists and fill with a mixture of concrete, sand and plenty of small boulders. At this point block off the section to be used for the hearth and fill in the fireplace proper up to the floor level. This will leave a space to be filled in later with hearthstones, brick or whatever you decide to use for the hearth.

Reinforcing rods in fireplace base.