Hi All,
As a finish carpenter I don’t have much experience with footers and foundations. The wife and I are house hunting and wanted to educate ourselves as to what causes cracks and moisture in a foundation. We’ve looked at several that have ranged from hairline horizonal cracks to 3/8″ step cracks that run up several courses of the block.
What are the causes and solutions to these problems? Are there some instances that are easily fixed or do we run for the hills!
Thanks in advance.
Edit:
Sorry to be so cryptic. Here’s more info.
We live in western Pa where the frost line is about 36″. I’m mainly concerned about mold growth and settlement.
Edited 3/21/2008 9:08 pm ET by ubc
Replies
Are those "3/8" step cracks that run up several courses of the block" on the side walls of a walkout basement? Common here, not a good sign.
PAHS Designer/Builder- Bury it!
No they were just on an outside wall.
Indicates movement. (duh) The question is whether the foundation is still moving.
Here, those cracks often show several repairs. Walkout basements commonly have inadequate buried wall footings. Stress shows in the side walls when the buried wall and the exposed wall lean together (toward the exposed side).
Cracks on one wall, without parallel cracks on the opposing wall, are something else.
Is this the case? PAHS Designer/Builder- Bury it!
where are you? what is the soil? earthquakes/hurricanes, or are you concerned about heaving and settling?
k
Coal mine subsidence? Just kidding, used to live in that area.
I only know a little about it. It is common for block walls to suffer small cracks. Most occur within a few years. If the houses are decades old and the cracks are not large then it is likely that they won't get any worse. For a better judgement a home inspector can give you a first hand look.
Common causes -
Lack of horizontal reinforcement (truss or ladder-type)
Walls not thick enough (8" where 10" or 12" required)
Lack of vertical reinforcement where required.
Poor mortaring technique and/or mixing
Poor backfill technique (like putting poorly-draining native soil back against wall)
Poor water management/drainage (saturation and freeze/thaw action)
Failure to damp-proof or waterproof where required.
Jeff
ubc
I bought a home with a wide crack in the foundation.. decades later the crack hadn't grown any or changed anything.. It was probably caused when the foundation was backfilled and the dozer operator pushed a tiny bit too much.
There isn't much strength on cement block walls.. IF you doubt me grab a big sledge hammer and wail away on them. Very quickly it starts popping apart. But it's strong enough for the way it's loaded ..
Now if it's growing that is another whole matter. That will indicate that you may havea tree root or some other problem.
It could be a forecast of the world ending but that's pretty unlikely as long as it's not growing <grin>
"Now if it's growing that is another whole matter. That will indicate that you may havea tree root or some other problem."
We looked at a place yesterday that would make ya cringe. A 2 story colonial with brick veneer on exterior and a block foundation. The first thing I notice are several courses of brick to the side of the front door leaning a good 1/2" out from the face of the wall.
The foundation had step cracks everywhere. And above one of them on the outside, the patio was sloped/caving in towards the center of the foundation wall.
I don't have the experience to know what caused it. Settlement of the soil maybe? Poor drainage? Sink hole? Black hole? lol. There is a large (3' diameter) maple tree about 10' off the patio side of the house. So maybe you're right about the tree roots. The house was 50-60yrs old. Seems to me you would have to rule out settlement.
Edited 3/22/2008 1:43 pm ET by ubc
ubc
you got it,, see if you can site alng the basement wall on the inside and if it's bowing then there is no question remaining.. if you do buy make sure the price reflects major foundation repairs. (plus the down market destress prices)..
In general, hairline cracks are normal and don't indicate any sort of a problem. Cracks that simply open up (up to maybe 1/8") are less normal but still not an indication of a problem. Wider cracks, or cracks where the two sides slide relative to each other (either in/out or parallel to the crack) are indication of a potential problem. Also be alert for signs of a wall bowing inward from the pressure of the soil.
Some consideration should be given to the age of the structure as a whole and the apparent age of the cracks. Fresh cracks or cracks showing recent movement are obviously more worrisome.