If there are two parts of your home that are most important that would be your roof which keeps rain out which will ruin everything in your home and your foundation which supports your home.
Foundations can be built in a variety of ways
Many homes have a full basement with solid poured concrete walls which support the first floor that are set on heavy concrete perimeter footings.
Some foundations start with the same perimeter footing but use concrete block to build up the foundation wall. The top of the wall is capped and concrete and rebar is used within the voids to provide strength.
The final foundation design is built on piers. The footing is poured in a hole large enough to support the weight supported by the individual pier and wood column beams are placed on top of the footing attaching to the first floor structure. There may be a mixture of concrete block that is used instead of the wood columns especially on corners and horizontal beams will normally be positioned between the piers to allow for load carrying and attachment.
These three basic types of foundation can be modified to meet the conditions in your location. For instance if you are building at the beach then sand will not support your home. Instead of pouring a footing that is 2 feet deep you will need to install caissons that can reach as deep as 40 feet until they land on material that is stable enough to carry the load of your home.
Knowing when Foundation Settling is Normal or Damage
All foundations will settle over time and this can cause structural problems for the rest of your home.
When concrete foundations are first poured it is not uncommon to have some slight cracking. This can occur in walls and also in the slab of your basement. If the cracks are under 1/4 inch wide and they do not result in out of level or out of plumb surfaces … meaning one side of the crack lifts out higher then the other.. or inward on a wall… then you can consider these cracks to be normal.
The same may be true for cracks on block walls. However with block walls if the problem is not structural the cracking will normally occur vertically and not on steep angles. And it is more of a problem if the crack occurs through the block rather then at the joints.
It is not to say that cracks in your foundation are a good thing but cracks will occur for many reasons. Most often it is the time that the concrete or mortar was allowed to cure before a load was placed on it. This often happens in hot summers when moisture is sucked out of the concrete before it has had a good 7 days to set.
Signs of Structural Failure in Foundations
Often the first sign of structural problems will be doors that do not align or drywall that cracks.
You may also have windows that do not work properly, gaps around your baseboard, cracks in tile floors or uneven floors.
This is common when the home is first built due to settling of your wood framing but if the home is over 10 years old and you notice problems you should also look at your foundation.
In worse conditions you will find floors that are out of level. If you are purchasing a home then you can measure this with a marble or small ball. The ball should not roll on its own. More accurate testing is done with laser levels.
Exterior problems can be found in cracked masonry, bricks or stonework that has mortar joints cracking.
Your chimney could be cracked or leaning.
Concrete pads near the home could be pulling away or cracked.
Inspecting the foundation
All foundations should be plumb meaning they are straight up and down and they should be straight from one corner to the other.
If your basement is unfinished you can use a mason’s string to measure if your foundation is in align by adding a weight to the end and hanging it from the top of the wall about an inch out and measuring the distance between the string and the wall .
You can also use a mason’s nail hammered into the corner or have a helper hold the string at one corner then measure the distance between the string and the wall horizontally.
If you have a combination of cracks and measurable movement then you want to call in a foundation contractor to tell you if the damage is old and stable or if you need emergency repairs.
If you actually see failure in the wall or if it is more then 3 inches out of plumb then expect to have repairs made immediately.
Pier Foundations are slightly different however the same rule applies. Your foundation was installed plumb and level so it should remain plumb.
If you see deteriorated wood, cracking block or footings that have moved or columns that are slanted then you will need to make repairs.
The good thing about repairing pier foundations is that normally the problem is restricted to a small area .. the bad thing is that making the repairs means getting into cramped working spaces.
When purchasing a home you should get an inspection then if there are any cracks in the masonry you want your inspector to make note and tell you where and how large.
If you see movement over time then you should take closer notice of the condition.
You need to inspect your home after any heavy rains for many days, droughts or earth quakes. Yes thats right a drought can cause problems when the clay soil around the home dries and crushes the walls of the foundation.