How to choose foundation for your log cabin
Full foundation sounds easier to build than a slab. The only catch is that you'll probably have to do a lot more digging. This is especially true if you live in northern part of our country. A little north of New York City we usually extend our foundations down 4 feet. You'll want to find out how far down wall and footings should go; local building inspector or mason can tell you.
With this information in mind, lay out outlines of building as described above and start digging. The walls that form your foundation will probably be built of 8-inch concrete block. This wall should rest on a footing. The illustration at side shows one way such a footing can be made.
Like beam described above, dirt may be cut square and be used as form. The footing should be at least 6 inches thick and project 2 or not more than 3 inches beyond thickness of wall. This concrete footing is made of I part portland cement, 3 parts sand, 5 parts coarse aggregate, or a transit mix that will have a minimum compressive strength of 1,500 pounds per square inch in 28 days.
If you are making walls of block, mortar you should use is composed of I part portland cement, 3 parts sand by volume, and lime not exceeding 25 per cent of cement by volume. Stagger blocks so that joints of second row of blocks fall over mid-sections of blocks below. Use closed-end blocks for corners.
Moistening blocks before laying them will help hold mortar. Pour concrete into top row of blocks and insert 6-inch bolts, 8 feet on center, for sill.