Answer: The most obvious symptom of a worn out foundation is exposed aggregate. Concrete is comprised of Portland cement, sand and aggregate. Aggregate can be either pea gravel, or commonly in older homes stones from 3/4″ across to large softball sized rocks. When the flat surface wears away, exposing the stones, that’s a good sign that the concrete has reached the end if it’s life.
Answer: Foundation bolts are bolts that connect the wood sill plate to the concrete perimeter foundation. In California, foundation bolts were required by code in 1949 and later. While some houses built prior to 1949 have foundation bolts, most Craftsman and Spanish style houses built in the 20’s and 30’s do not have bolts. An inspection of the crawlspace should reveal bolts at 4-6 foot intervals. The function of bolts is to hold the house to the foundation in case of an earthquake.
Answer: If the condition of an older home’s foundation is good, then a house can be retrofitted. Earthquake retrofitting a house consists of connecting the sill plate to the concrete foundation to prevent the house from moving off the foundation during an earthquake. Straps are bolted to the foundation at 4- foot intervals, and 12″ from each corner. Bolts are epoxy doweled into the concrete to hold the straps to the foundation. If the concrete is not sound, the only way to retrofit the house is to remove and replace the foundation.
Answer: A crack of this size is relatively small. First, you should try to determine the cause of the crack. Is there a leak under the slab? Poor drainage? No gutters? Once these issues are addressed, a crack of this size most likely could be repaired by Epoxy Injection. The concrete is bonded back to original condition, and should not crack again provided the cause is properly addessed.
Answer: Current code (California) is to have 18” of clearance below the floor joists. Get married and gain twenty pounds (happened to me) and it doesn’t seem enough. Unfortunately, there are only two ways to fix it. Excavate with small digging hammers and drag the dirt out with trays. Very hard work. Or lift the house. If you are replacing the foundation anyway, lift the house. If you have impediments (chimney, good foundation) start digging.
Answer: Sloping towards the downhill over ½” in 20 feet. Recent paint and patching of drywall and stucco. Doorways that slope or stick. Try to pull carpeting to examine the slab. I recommend hiring a soils engineer if you have any questions. Better to know ahead of time!
Answer: Expansive soil and poor drainage are the culprits. Many older slab homes have slabs poured directly on clay soil, with little or no reinforcement. Water soaks under the slab, expanding the soil, and lifting the middle of the house, where there is relatively little weight. Small lifting and cracks can be addressed by epoxy injection and drainage improvements. Extensive lifting needs to be repaired by removal and replacement of slab and subgrade. Removing soil under the slab and replacing with sand, and pouring a thicker, reinforced slab (as well as drainage improvements) usually does the trick.
Answer: While you might need to be concerned, what you are describing is pretty normal. Most houses with plaster walls have cracks, or have cracked over their lifetime, and the patch jobs can be less than adequate. It is a result of movement, but over 80 or 100 years you are going to get some movement, no matter what. What you want to know is it an immediate concern, or just due to the old age. Taken in context, it’s not really that big a deal. But, of course, it wouldn’t hurt to check out the foundation to make sure it isn’t a symptom of a larger problem.
Answer: While you may have a drainage problem, more likely you have a leaking pipe or excessive irrigation. The sub area of a house does take months to dry out, but if there is moisture in summer or fall it is probably caused by man and not God. Check your water meter to see if there is any indication of a leak. You may want to consult with a leak detection service.
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