It is always great to arrive at a house and find one specific area that is causing all the problems with a foundation. It is like showing up and discovering a large, blinking, neon arrow that points to where you need to fix something. Of course this has never happened, but occasionally the fix is pretty straight forward. Spreading epoxy and injecting a small crack on an unfinished basement wall can sometimes be completed in less than two hours. And then there are the others... I inspected a home a few weeks ago that had basement walls that were a little crumbly in places as if they had been wet for a long time. The homeowner wanted the cracks injected but it was pretty obvious that there were bigger issues outside. The yard next door was for some reason about three feet higher than his, and it was only about 8 feet away. The gutters emptied out right on his yard about 3 feet from his foundation. There was a low spot against his house and really no where for the water to go. On the other side of his house the downspout for the gutter emptied out in to another low spot against the house. Yikes! It seemed that the previous owners were trying to find out how much water they could direct to the foundation walls. And finally we found that the shingles and deck from the most recent roof replacement went "over" the gutter. Yes, the water was passing right over the gutters and a small pond was being created along the upper side of the home. The gutters have now been connected to pipes that will carry the water away from the house. A french drain has been installed to collect the water from the neighbor's yard, and dirt has filled the low spots along the foundation. In a few days a gutter crew will work their magic so the roof water goes in the gutters rather than over them. We are looking forward to the next rain to see how well we have protected the concrete foundation. With any luck the walls dry out and we can finish the project by injecting the cracks. It might have been simpler to do this first. But in the end I stand by my work, and in this case it meant putting all the pieces together.
If you have a crack (or two) in your foundation, you probably want to know how it got there. I will give a you dozen reasons, and be aware that there are many more options!
1. - Stress. When cement dries it shrinks a bit and pulls together tightly. If it pulls too much, it cracks. These cracks often occur at corners off of windows and beam pockets. These happen on most foundations and are not cause for concern about the safety of your house. You probably want to have them filled however to prevent ground gases, water or bugs from entering your basement.
2. - The Mix. When cement is mixed there are many additives that can be used for extra strength, to deal with either hot or cold outside temperatures, or simply because it was specified by the engineer who approved the plans. These mixes can impact drying times and can be effected by outside conditions such as humidity.
3. - Humans. Working with cement can give you a little anxiety because it is very heavy, it is on a timer and will harden whether you are ready for it or not, and if it arrives before you are ready, it has to sit. A team of people with a variety of jobs all have to be perfectly coordinated in order to arrive at the desired outcome. And as we know, if something can go wrong, it will. The guy at the plant ran out of raw materials. The driver got stuck in traffic. The site was muddy and the truck couldn't back all the way to the basement area. The new guy was running his first pour and waited too long between trucks...
4. - Bad Drainage. When the yard tilts toward the house and wet dirt presses against the foundation for long periods of time, something has got to give. When you have matching diagonal cracks on either end of a wall you may want to check what's going on with the ground outside. Lateral pressure can eventually crack the wall and even push it in or bow it. Relieving the pressure is optimum but sometimes you also have to straighten the wall if it gets too bad.
5. - Soil. When it rains after a long dry period you get wet dirt. But if that dirt has a high clay content, it also expands and pushes everything near it. When you have a big hole in the ground surrounded by clay soil, you get an entire yard pushing in at your basement. Being aware of the soil types in your area can sometimes help you prepare for and prevent pressure build up.
6. - Rust. Metal rebar is put inside concrete walls to add strength. It is ironic then that sometimes that metal is the cause of cracking. If the metal gets wet because it is too close to the surface or micro cracking, it starts to rust and expand. it happens slowly but the power of rust can cause horizontal cracks that can eventually cause serious damage if not treated early.
7. - Utility openings. Ok, the water pipe doesn't "cause" the crack, but it gives the stressed concrete a head start and an opening. Water can enter through a utility entrance that hasn't been correctly sealed or it can find the crack that commonly forms off a portion of the penetration. These used to be filled with thin rope and tar or sometimes with hydraulic cement. Injecting an expanding urethane will fill all the gaps and provide a permanent fix.
8. - Settling. When the ground under your house moves your foundation can lose some of it's support. This could be a tiny pocket that opened right after your house was built due to a small glitch when the ground was being prepared. Or this could be an ongoing problem due to earth being washed out under your footing that needs immediate attention. In either case your footing and foundation are impacted by the ground that surrounds it. Determining if your issue is dormant and non-essential or if your situation requires piering or other measures to stop further damage can be a complex task. It is worth getting up to speed on diagnosis and options if you suspect settling.
9. - Hydrostatic pressure. Ground water can build up under and around a foundation under the right (or wrong) conditions with enough push to force its way through seams and micro fissures to create problems. Often water can be diverted away from a house with gutter extensions, french drains, and catch basins. But when the ground water level rises above your footing, there is often the need to create, or rehabilitate your perimeter drainage system. The standard system collects water below the top of your footing and pumps it outside where it can drain away from the foundation.
10. - Seismic activity. This could be a local quarry that blasts at 4:20 every day or it might be that 5.2 earthquake from a few years ago. When the ground moves suddenly there is always the possibility that big solid objects like a foundation can crack.
11. - Freezing. If you live in the northern half of the country the ground around your home goes through freeze thaw cycles. In the Winter when you get a warm day and the snow melts, it freezes again at night. The problem occurs if you had small cracks that the water entered as it will freeze and expand when it gets cold again. Rather than causing cracks, this environmental condition primarily turns your small cracks in to bigger cracks.
12. - Creep. This is when the garage slab, driveway, and/or the street combine to treat your foundation with no respect. Locally we have an area where the soil allows the street to move which pushes the driveway against the garage floor, which pushes laterally against the foundation wall. This is not a stress that foundations are designed to deal with and the the wall gets pushed away. A crack will open up at the outside corner under the garage and several things need to happen in order to repair the foundation. A section needs to be cut out of the driveway to stop it from pressing against the house and the corner of the foundation needs to be reinforced. Sometimes this can be done with carbon fiber strapping.