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Sand around foundation

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MgTech

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So we purchased a house about 6 months ago. When I went down into the crawl space, it’s clear moisture has caused some issues with bowing with the joists. I will sister those. I’d say it’s a 30’ or so span, with one support in the middle. They look like 2X10. Anyway, this center support holding them up in the center has a “line” in the floor above, feeling raised maybe 1-2”. Enough to trip over. The entire crawl space is lined with sand, and when digging around the foundation in the front, about 4” of top soil then the rest is a gray/black sand, at least the 12-14” that I dug. This foundation is near a river( about 6-7 blocks away from the river bank) and the first house built in this “ plot” of land in 1988. The backside of the house facing the river is normal dirt all around, so it’s extremely confusing. The previous owner said he tried everything and couldn’t keep the water out of the crawl space. I’m going to fix the gutters and install interior French drains. But why on earth would sand be around the foundation? The rest of the yard is dirt. Seems like to me this would allow water to quickly reach the foundation, but I don’t know.
 

joecaption

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The best way to water proof is from the outside, not the inside.
It's anyone's guess why it was done that way.
Often times I've seen where they dumped there leftover brick sand in there to get rid of it.
 

MgTech

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that seems crazy to do, should I dig all that out? That would be the area under the house when it rains water just pours in from that general area. Personally I have never seen anything like it before.
The reason I wanted to do it from the inside is because it would definitely be easier than the outside. The guy who “ redid” the house put a sump pump in the lower corner already, but he didnt install anything else, water just kinda naturally accumulates in that area and goes that way.
The main issue I’m having is the joists/floor boards warping due to moisture. I’m concerned because the water table is so high ( every new house around here has to be built up, imagine a walk in basement that’s usually underground, but above ground). I almost think water has come up from the dirt if that’s possible. I’d like to repair the joists, and get the huge hump out of the floor but seems pointless without fixing the reason it happened.

I have to also redo the gutter, they put on a metal roof and the water just overflows the current ones when it rains( originally it was shingle).
 

MgTech

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When it rains hard anyway. It has a package unit, a deck and porch in the way preventing me from doing it outside for at least half the house.

I have no knowledge on it, so I’m open to ideas.
 

nealtw

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Normally there is a drain pipe on the outside of the footing and sand would be great to let the water get to the pipe and away.
 

MgTech

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Thanks, I’ll have to take a look and see, I’m glad to hear it’s normal to find sand around the foundation though.
 

tomtheelder2020

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If you install interior drain, be VERY cautious! Soil above the bottom of the foundation helps provide some of the foundation support so removing it could potentially result in a "bearing failure" that causes it to settle. If the sand extends below the foundation bottom, removing the soil along more than just a couple of feet has a very high chance of bearing failure because sand has no cohesion. Cohesive soil has less risk of bearing failure - but still be cautious. You can do a rough cohesion test by molding a ball from moist soil and drying it completely. The easier the ball breaks when dry, the less cohesive the soil. If you do dig, the hole distance from the foundation line (base of footing, not stem wall) should be at least 1.5x the hole depth.

If the water is infiltrating from above, anything you can do to direct it away from the foundation will help. Like planters a few feet wide with plastic lining the sides and across the bottom (i.e. a bathtub) with outlets away from the house. Plastic sheeting under decks will also help.

If water is coming up from below, the only thing I can think of is a series of sumps fed by drain lines. Designing that would take a professional using details of the soil stratigraphy and hydrologic properties - or trial and error. An adequate system will likely need multiple sumps and drain lines spaced far closer that you think.

This is going to be a very tough nut to crack. Good luck.
 

MgTech

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I did not know that either, Thank you. It is indeed, Complicated from my research. When In the crawlspace, The entire floor is sand. I don't know how far down it goes exactly. I feel like this was added later, potentially the same time the sand may have been placed outside. They didn't put sand around the blocks holding the joists in the center, so they are sitting on dirt and have about 6" of space around the blocks that is about 5-6" deep without sand, matching the rest of the " floor". So I'd say the sand in the crawlspace was to try to alleviate water/moisture issues. From my research, a few companies "pump" sand for this reason. The outside portion did have dirt about 3" -4" thick, with a plastic layer then the sand. The backside of the house doesn't have this. It does have a deck, Which I need to figure out a way to divert that water away.

So your saying I should dig a small spot down to the foundation bottom, and see how much of that is actually sand, following your statement " the hole distance from the foundation line (base of footing, not stem wall) should be at least 1.5x the hole depth ".

The house isn't very large, 1400 Sq ft or so. I haven't spent a ton of time down there, But I did watch water come in at a few different spots while raining, so it seems I do need to fix a few things outside first. I think I will also dig a hole away from the foundation a bit, to see if water is coming up into the dirt, and when that happens. The origina/last owner ( it was a forclosure flip house) said it was impossible to keep water out and he had " tried everything".

The main location of water entry is in the deepest corner of the crawlspace, However, I DO NOT see any water coming in, So I fear it's coming up. The grading is the steepest in this location too, so it should technically have the best chance of no water coming in. We shall see.... Thanks guys!

I'll do my best, The inspector recommended having interior french drains, then encapsulation.
 

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