How To Repair Crack In Cement House Foundation
Taj Lash
We're in the process of remodeling our kitchen and we just pulled up the tiles. We found a few spots where there are large gouges or holes if you will, in the foundation. I'm guessing they were there from a previous remodel?
Anyway, we need to repair them and I was wondering if there was a certain type of cement that is required. The last guys just filled the holes in with the stuff you use for tiles and it chipped up and didn't stick at all.
There's a product called sand mix that you should be able to find at most hardware stores & home centers. It is a mix of cement and sand rather than cement and large aggregate, so it's good for filling shallower imperfections.
Note that for uses in thicknesses under 1" you'll probably need an additive (read the data sheet for details). There are adhesion promoters you can look into as well - again, they'll be mentioned in the data sheet for the product.
Your foundation literally supports your entire house, so you have to make sure it is sound. Not only do cracks in your foundation look bad, but they can also lead to the eventual loss of structural integrity, which can mean high-cost repairs. Take a look at your foundation now to check for any cracks that need to be repaired. The faster you fix cracks before they can grow, the easier and cheaper the repairs will be.
In most cases, you can determine what is causing foundation cracks by the cracks themselves. Settling soil usually causes horizontal cracks and can be thin or wide, depending on the extent of the soil movement. This is usually the most common reason for foundation cracking.
The second most common cause is excessive moisture around the foundation. Too much moisture can lead to water infiltrating the concrete and seeping through to the other side inside your basement, which can spell problems as well. As the water works its way into the concrete, the pressure inside the foundation wall can lead to cracking. In addition, soil swells when it is wet, which creates excess pressure and stress on concrete. Cracks from water usually are vertical or diagonal.
For cracks wider than a hairline, clear out any loose material, such as broken or cracked bits of concrete, dust and debris, using an old flat head screwdriver and a stiff wire brush. To facilitate patch adhesion, use a hammer and chisel to slightly widen the crack and undercut the crack edges. This will give the patch more area to adhere to and keep it from slipping out of the crack. Simply hold the chisel at an angle and chip away. Clear out bits of debris and dust with the wire brush and then rinse the crack with water from a garden hose. Pat the area dry with an old towel.
Thin hairline cracks can usually be repaired with a vinyl concrete patching compound. If recommended by the manufacturer, apply a concrete bonding adhesive or primer/additive to create the best bond possible between the old surface and the patching material. Use an old or inexpensive paintbrush to work the liquid into the crack and around the crack edges. Wash the brush immediately after use with soap and water or discard it.
If you can, paint the inside of the crack with the thinner cement mixture. This will act like a primer. Then pack the paste mixture firmly into the crack with a putty knife or trowel. Level the mixture with a straight-edged concrete-finishing trowel. Let the patch sit undisturbed for about an hour, then go over the entire surface with a float or trowel in a circular motion, blending it well with the surrounding surface.
You can also use hydraulic cement to fill in cracks, using a putty knife. Following package instructions, mix hydraulic cement with water in a bucket. Use a trowel to mix it and combine the two until the mix is homogenous. Dampen the crack by misting it with water from a spray bottle then push the hydraulic cement mixture into the crack with a putty knife. Let this dry for an hour or two then add another layer of cement mixture over the crack. Use a trowel to make the cement patch level and smooth with the wall surface.
Avoid having shrubs or small trees close to your foundation. Watering them may allow too much water to collect in that area and undo the work done by gutters. Also, make sure that driveways and walkways slope away from your foundation to prevent water from collecting in the soil there.
We have had this hole in our exterior foundation for a few years. The way we discovered it was that water was leaking into our basement finished room, and when I looked outside, I discovered this hole in a corner where the porch foundation and the house foundation meet. It is now the size of a peach. We have dealt with it temporarily by covering the whole area with tarp and duct tape, and have never had any water in the basement since then.
You need to clean up that area and fill it up with gravel. Compact it the best you can shoving the gravel down and to the back. When you're a few inches from the hole pour in cement. Pour in enough so it's a few inches above the hole and then slope it down away from the hole to deflect water from there. Fixing the gutter problem, maybe adding another downspout, should be done too. Good luck
Here is the front of my house. As you can see it is a 2-story dwelling on the left with a garage on the right that is connected to the main house by a "sunroom" (porch/breezeway/whatever). The main house has a basement, but there is nothing underneath the sunroom or garage.
We've lived in the house for 4 years and this is the first time this has happened. I believe water caused this hole (we live in upstate NY and the cold winters and ice have chipped away at it year after year). The concrete patio was never poured correctly so it slopes (slightly) towards the house, and in the Spring when the snow melts the water funnels towards the house.
This part of the foundation is most likely spreading out a roof load from a sizable portion of the sunroom roof. If the soil supporting the foundation has eroded away, this will need to be rectified some time next year.
For now, get a bag of ready mix mortar, the kind you just add water to, it has sand and cement already mixed in in the correct proportion. Mix up a small amount, keep the water to a minimum so it will stay where you put it and not slump down. Patch the hole. That's all this is right now, a temporary patch.
If the hole opens up beyond such that you feel like it's sort of a bottomless pit, cut a short length of something like a paint stick. Thin enough to push through the hole but long enough to wedge inside when turned 90 degrees. Tie a length of wire to the center so you can keep it pulled tight when you push mortar up against it.
As you suspect, water and freeze/thaw cycles chip away at the foundation over time. There was probably once a innocuous hairline crack there at one point. Water got in there and froze, opening the crack. Repeat dozens of times a winter and over the years you get what you see now.
The solution is keep water away from the foundation. I see you have a gutter system over this area. That is good. The patio sloping towards the house is really bad. Not only does it get into foundation cracks and erode the material, water gets under the house structure and can cause uneven settlement, stressing members in ways that was never intended. Some people think crooked floors in old houses are "charming". In reality it is a sign of an unstable structure. Even if the house stays stable, water can be the source of toxic mold. Water has no place in your house other than inside plumbing.
You need to correct the drainage issue. Ideally, it should slope by gravity away from the house at least with a 2% slope. Another solution, not nearly as good, is to place a sump at the lowest point and pump collected water away. I can't emphasize enough how a natural gravity solution is far superior to a mechanical solution. Sometimes you do what you have to do though.
Combine this with the possibility of needing to correct erosion under the foundation. You my be digging up the patio anyway. OTOH, if the foundation is still properly supported and you correct the drainage issue, your little mortar patch could possibly be considered a permanent fix.
For question number 1, no, its not supposed to be solid concrete, it could, but in this case you have hollow core block, the solid concrete is above this block that makes the floor. The vertical lines I see in the picture are the head joints of the block and they should be about 16 inches apart.
The freeze/thaw cycles affected this particular block where the surface is eroded away to expose the open cell of that part of the block. Some block are affected differently than others, this one happened to be the weakest in this run of block work, and the patio sloped the wrong way expedited the erosion.
Question number 2, the worst case scenario is foundation settling and mold as mentioned by bcworkz. Both issues though depends on existing factors, soil type, for the foundation concerns, and how well the soil was compacted when the house was built, for the settling of the interior slab. And what type of organics are present in the soil to feed the presence of mold. It usually has to have something to feed on to grow, and it may only need the dirt to do this, although I have only seen it grow on drywall, wood or wood chips and other construction materials.
Instead of a temporary fix, it should be the first step of the permanent fix. Repair the hole by chipping away at the hole to expose the whole core of that block, at least in it's width. That will serve two purposes, it will let you see how strong the block is as you chip away at the opening (if it is weak, it will turn to sand as you chip away at it) I am presuming this is concrete block not slag block or cinder block, the textures in the picture don't suggest that it is, yet I don't see any aggregate for it being concrete block either. Either way the chipping away will ensure a sound surface for the new masonry cement to bond to. The second purpose is the larger hole will allow masonry rubble or even gravel of one sort or another to go into the web of the block to give a base to support the repair cement to fill the hole. Only issue you may have is there is a long crack that may allow multiple cores to be exposed, no problem, more of the same remedy, read on. As you fill the hole, have other masonry rubble (positively no organic material!) to shove in the hole as you place the cement in the hole. that way the cement will not "slump out". If it insists on slumping out, it may be too wet, let it set for a while to a semi hard set and scrape off the slumped out part flat enough to be even with the rest of the block, the fill the rest after it has set a day. Cement should be peanut butter consistency, for example. Toothpaste consistency is too wet. With care and proper prep, it can be done in one shot, the trick is having enough brick or block rubble to shove in the hole in layers as you fill the hole with cement, like laying really small bricks.
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