Crawl Space Foundation – No Footing?
Hi All —
I’ve got a 1930s story and a half (Zone 5 — Eastern Iowa) where the previous owner built a 10×20 addition onto the back of the house somewhere around 1960 according to city records. They decided on a flat roof. Unfortunately for me, that meant water infiltration all over the place (should have seen that coming); it needed to be blown up. I decided to do as much as possible to make this place as airtight as possible — since it’s safe to assume that energy and insulation will not be getting cheaper anytime soon. Albeit late in the year, I decided to get the crawlspace foundation tackled first. I was getting the foundation all dug out to put in a footing drain when after digging and digging — we hit no footer.
Nearest we can tell, the original contractor dug a trench, filled it with concrete up to ground-level. And then it appears they came back and did an additional pour that had the stamping for the faux brick facade. So, now I have a 4′ tall 8” thick footing? My soil has a lot of clay in it, so I don’t know if that has anything to do with it? We didn’t appear to hit any gravel along the way.
I’m just curious to know if anyone has ever seen this before and has ended well (I’m afraid my endeavor may not). There is copious amounts of cracking in the “upper”(?) foundation, where the form attachments were. I assumed this was water. My plan, then, was to get all the cracks sealed up and put peel ‘n stick and dimple mat to combat the water. But now I think I might have a different problem altogether. Is what I’m describing even code compliant?
I’ll get some pictures posted here shortly.
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Replies
What is your code required width for your Load-Bearing Value of Soil (psf)? 8" can be fine.
I would argue that if the footing has been there for 50 years and hasn't shifted or split it's probably adequate.
Analytically, here are three things to look at:
1. Is it deep enough to prevent being moved by frost. This is usually mandated by local authorities and the required depth should be easy to find.
2. Is it strong enough to keep from breaking? Usually this means reinforced with steel.
3. Does it have enough bearing surface to keep from sinking into the soil? This is a matter of calculating the loads on the building and figuring out how many pounds each square foot of footing is holding. Then you have to find the bearing capacity of your soil and compare it. So if the addition is 10' wide, each linear foot of footing is holding up five square feet of the building (five on each side). For a one-story building let's be generous and say the floor is holding 50 pounds per square foot and the roof is holding 50 pounds per square foot with snow loads. (Your local code will have numbers for them but bear with me). So each linear foot of footing is holding 500 pounds of building. If the footing is 8" wide that linear foot is 2/3 of a square foot, so the footing is holding 750 pounds per square foot.
You need to find out what your local soil is like. But that doesn't sound like much. Around here we are allowed to assume 1500 pounds per square foot with no testing, and if we have the soil tested whatever it tests out to.
I watched a TOH episode a few years ago in which the project home had a similar foundation (poured below the frost line but no footer). In that case, the foundation was mostly exposed in the dirt-floor basement, and the contractor decided to dig around the perimeter and pour a new footer/bulkhead. I seem to recall they only went this route because the renovation was adding a lot of new structure on top of the existing foundation. Otherwise, and since the foundation had not moved in 50+ years, they probably would have left it alone.
Seems like this is a can of worms and the smart move is to do a little as possible.
If they cut corners on the foundation to save $20 on concrete you can bet they cut every other corner.
I say it has stood for 60 years the less you know the less you must put on the disclosure form when you sell the place.
Walta