Begin With A Good Foundation
The first home in a permanent community, outside a tree or a cave, was constructed long before we were born – about 11,000 years ago. That was before we were born. Although these homes were made of reeds and mud, they had a stone base. About 1000 years later (c.8000 BC), in the town of Jericho, homes were built by using bricks made from baked mud. Wall and roof construction certainly had improved, but foundations were still made from stone. Later the Egyptians and the Romans used cementing materials to mortar joints and help stabilize things. However, the use of Portland cement – the kind that is used to make modern concrete – wasn’t developed until 1824. Our nephew still thinks that Fred Flintstone invented concrete. We told him it was Wilma.
With the advent of concrete, the process of building a foundation has become a relatively simple task. No more stacking and cementing heavy stones that were hard to lift and even tougher to transport. Once mixed, the pasty, gray substance is simply poured directly into an earthen trench or wooden (or paper) forms. Imbedded steel bars are used to improve its strength, and a myriad of steel gadgets are strategically placed into the wet concrete to help with the attachment of wood and other building materials.
It’s true, not every structure needs a foundation. A light weight storage shed can be placed on a four-inch thick concrete slab – without a foundation. However, when it comes to room additions or a wood deck building, a sturdy foundation is a must to ensure that the structure is strong and sturdy.
But before you pour the concrete it must be mixed. You can purchase it from a ready mix plant or mix it yourself. Keep in mind that mixing is hard work and should be reserved for smaller projects like walks and small patios. It really is as simple as 1-2-3! By volume, use 1 part Portland cement, 2 1/4 parts sand (don’t use sea sand — salt destroys concrete), and 3 parts rock (3/4” to 1 1/2” rock is OK). Everything you will need can be purchased at your local home center.
As we mentioned earlier, forms are used to create the desired shape of the concrete. The forms hold the wet concrete in place until it dries. In the same sort of way that a cake pan holds and shapes batter. The concrete is poured into the forms which remain in place until after the concrete dries. At that point the forms are removed. With an addition, money can be saved by using framing materials for the forms. After the forms have been stripped away from the foundation they can be cleaned and recycled . Being used as form material has no negative impact on framing lumber. Form oil can be sprayed onto the forms before they are used to make them easier to remove from the dried concrete.
Steel reinforcing bars greatly improve the strength of concrete. The bars are usually placed horizontally within the foundation wall and run continuously throughout the entire structure. A foundation that costs $2,000 may only have about $100 dollars worth of steel in it – a great deal of added strength for a little money. Most residential foundations only contain two or three bars of reinforcing steel. By adding an extra bar or two, you can substantially increase your foundation’s strength without adding a great deal of cost.
Anchor bolts are imbedded into the top surface of the foundation wall so that you can securely bolt the wood framing to the foundation. When it comes to anchor bolts, the more the merrier.
A house foundation has two basic design components: the footing and the wall. The footing makes up the foundation’s base and is located underground – beneath the earth’s surface. The footing size and depth is engineered to carry and evenly distribute the weight of the house onto the earth. Sometimes the footing is a continuous concrete beam that is wider than it is tall, sometimes it is a square or rectangular pad, and in other instances the footing is cylindrical. Here, a hole is dug straight down into the ground (diameter and depth vary). A deep round footing is known as a “pier footing” or “pier”. In all cases, the footing is always built to rest below the frost line. The frost line is the deepest point at which the earth freezes during the winter. Naturally, the depth of the frost line varies depending on the climate in a given part of the country.
Note: It is extremely important that the foundation wall be at least eight-inches above the ground.
At this distance it can be used to safely separate the wooden parts of the structure from the earth. The wall protects the wooden parts from water damage (fungus and rot) and reduces the chance of a termite attack. Whenever earth and wood are in contact with each other, termites can travel into a wood structure unnoticed. With a concrete wall separating earth and wood, termites must tunnel up the concrete wall to get to the wood. These tunnels make them easy to discover.
Most folks believe that you have to “strengthen the walls” to carry the extra load when adding a second story to a home. Actually, you don’t have to strengthen the walls – a wall built with 2×4 studs spaced sixteen-inches apart will easily carry a second floor without modification. Instead, it is the foundation that usually won’t carry the extra weight.
Finally, when adding on, the new foundation should exactly match the size and shape of your existing one. Both the new foundation and the old one need to react to ground movement in the same way. Can you imagine your addition remaining solidly at one level while the old portion of the home rises or falls an inch or more? Using the same size and shape foundation doesn’t mean that you have to sacrifice strength. Use the same shape and size, but include stronger concrete, more steel, more anchor bolts, and modern hold-downs. And, good luck!
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