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Unfortunately, I have recently found a crack on the foundation of my townhouse and this kind of scares me. I have recently bought this place, but neither I nor the inspector have caught this crack. I think it's because it's behind the lower deck of my walk out basement, on the corner, close to the other unit. As far as I could figure out, this is a concrete block foundation and I could possibly use epoxy concrete repair kits to fix it. But I would appreciate any opinions and suggestions about dealing with this problem.
Thanks a lot!
Depending upon the soil in the area it could be common and may or may not be the beginning of a continuing issue. Your best bet is to get a local evaluation.
I have had homes with slab on clay soil that had to be fixed (used perimeter drill pipe support) and one on a more stable soil that was just a settling crack that could be patched.
The problem and fix will vary widely across the country.
There are only two things that would really concern me about a crack in a foundation wall. One is if the two sides of the crack move out of alignment, this would mean one side is sinking below the other and can cause some structural issues and warping in the house above. The other would be, with a block foundation below grade, if the crack is along the mortar lines, it may indicate hydrostatic pressure and the possibility for the wall caving in (seen this happen in houses near me). This crack doesn't seem that bad to me. I would just keep an eye on it and mark it so you can monitor if it gets bigger.
From a common building standpoint, it's well known that concrete materials have minimal tensile strength compared to their compressive strength. Since concrete is inherently weak in tension (your pictures substantiate that fact), it has been used as compressive member material in the more common building structures. Even though static tensile loads on concrete members are avoided, it is difficult to isolate concrete members from other stresses, or tensile stresses. With that being said, horizontal or stair-stepping cracks are more immediately threatening of serious collapse than vertical cracks in any concrete wall especially block walls.
However, cracks occurring near foundation corners are often from water and frost; and you may have the culprit staring you in the face- you have no flashing were the deck meets the foundation wall. Any penetrations (bolts that hold the ledger board) through the foundation wall are allowing water to penetrate into the wall cavity.
Arlington, Virginia may not be the coldest place around- but it can certainly get below freezing and stay below freezing for several days.
Why on earth the deck would be mounted so low is beyond me- generally the ledger is mounted to the framing band/rim joist of the floor system; and usually just a inch or two below the finish floor of the interior.
Unfortunately, I have recently found a crack on the foundation of my townhouse and this kind of scares me. I have recently bought this place, but neither I nor the inspector have caught this crack. I think it's because it's behind the lower deck of my walk out basement, on the corner, close to the other unit. As far as I could figure out, this is a concrete block foundation and I could possibly use epoxy concrete repair kits to fix it. But I would appreciate any opinions and suggestions about dealing with this problem.
Thanks a lot!
First off you can find a prescriptive guide for deck building here http://www.awc.org/Publications/DCA/DCA6/DCA6-09.pdf. I was not able to find the earlier year ones but this is fine as this issue has not changed that much over the years.
The photos are not all clear but yes it does appear your deck ledger is attached to Concrete Masonry Units (CMU blocks) for the foundation. You can attach a ledger board to CMU foundation walls but there are potential issues you are looking at here. To begin with this is a two level deck (your first picture) which is an entirely different creature from a simple single level deck. This type of deck should have been engineered for attachment to this structure. There are all types of loading issues that must be considered with this style and size of deck along with how it is attached to the home. It is hard to tell but it also appears that the crack is over ungrouted CMU's (CMU's that have not been filled in with concrete/mortar). It is possible that the size of this deck might be excessive for the method of connection here and the deck possibly should have been engineered and installed as a freestanding deck. This just means that instead of obtaining its support from the ledger board it would have actual columns under it and against the home for its support. The ledger board then just becomes an attachment method to the home and provides little in the way of support.
What you really need now is a licensed Engineer to look at this installation as well as compare it to local building requirements. As K'ledgeBldr stated it could be water penetration inside the CMU that is causing a freeze/thaw issue. That is always possible and it could also be, either by itself or in concert with the freeze/thaw, an excessive weight/improper support and attachment issue causing the damage. It could also be from other causes as well.
This is not something that I would recommend you attempt to repair yourself without first having an Engineer review this. To begin with if that is ungrouted CMU then a simple epoxy injection is not going to repair it and will cost you a lot of money as you pump a lot of expensive epoxy into the hollow CMU cells. Also you have not mentioned if you belong to an HOA and how much of the unit's exterior you even control or are responsible for upkeep and repair. The last thing you want to do is try a repair that costs more money to undue, or that can hide signs or symptoms the Engineer needs to see.
So you should, in this order:
Call a licensed Engineer to review the cracks and the deck construction as well.
Speak with your HOA if any of that is not under your control. It is always possible this issue is occurring at other Townhomes as well and might already be in the process of corrections or reviews.
fill it, make some horizontal marks across it with a sharpie and have a beer and move on with life. every six months or so check to see if your sharpie line is still intact.
I have the crack checked by a home inspector and he thought it was not a structural issue, there is no up-down and inside-out movement in the wal. He told me to just fill it out and paint it with drylok paint.
About the ledger attachment to CMU foundation, I checked the county codes (http://www.fairfaxcounty.gov/dpwes/p...ks/details.pdf), and I believe the previous owner had the necesary permits for the deck. I have talked to one of my neighbors and he has a small crack in the blocks eventhough he doesn't have a deck installed. So I am thinking that the attachment of deck to CMU might not be an issue. I wanted to bring in a structural engineer but I think their rates are too expensive (I have graduate degree and their hourly rates seem to be 5 to 6 times higher than mine), I don't think I can afford one right now.
So for now, I think I'll fill the crack and leave some marks on it so that i can check it every 3-6 moths.
The deck band was bolted through the CMU, the wood was not properly dried when installed, band dried and contracted, and the blocks broke. Thats my 10 second guess!
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