Hot tub slab issue

wanavet2 · Aug 24, 2009

I'm getting ready to pour a slab for the hot tub which is coming in a few weeks. I think I've run into an issue on the location. I'm planning on starting the slab 3' away from the house which was constructed last year. I'm afraid the backfill is not compacted enough and the slab may sink next to the house. If I take a 2x2 and pound it into the ground 3-6 feet from the house I can push the 2x2 down to a depth of about 4-5 feet by just pushing on it after the first foot. Am I going to have to pour footings down 5' on the house side of the slab? The soil is very sandy.
Thanks for your thoughts
Greg

CurlyDave · Aug 24, 2009

I would worry about the house even more than the hot tub.

Get your contractor to come out and see the 2x4 trick.

Document everything -- write him a letter.

buggyman1 · Aug 25, 2009

Thats scary!!! Forget about the hot-tub, you have major issues with your backfill that needs attention ASAP. I would get a professional to look at it now!! if I were you.

wanavet2 · Aug 26, 2009

Spoke with my concrete contractor who is a second generation concrete guy who has been doing foundations in this area for over 30 years. He said do to the sandy soil on my property the backfill may never pack down. We've had 10+ inches more than our normal rainfall this year and the backfill has been through a freeze thaw cycle. Basically he said to pour a footing for the slab on the side closest to the house and I should be fine. We live in a small community and people like him depend on word of mouth for advertising so I don't think he would point me in the wrong direction.

foggy1111 · Aug 26, 2009

If you can push a 2x2 into the ground by hand......then I dont care what your contractor has for a reference......but, your gonna have problems placing a hot tub or slab on that soil. Sounds to me like your backfill has some bridgeing that has not allowed compaction....yet. Soorner or later that fill will have to compact. Good advice above.

I have a hot tub that sits on a bed of crushed rock. I built a perimeter from 2x 4's (cedar) and put about 4" of crushed rock and leveled it. Then I put down a small patio using paver stones where you come and go from the tub. Worked well for me.....and it was low cost and easily repairable if the ground shifts (freeze / thaw here). May be a good option for your situation???

CurlyDave · Aug 26, 2009

Despite the contractor needing word-of-mouth recommendations, I would invest in a soils engineer coming out and taking a look at the backfill.

If your house starts to settle unevenly, it is going to mean big trouble.

Charlton John · Aug 26, 2009

I agree w/ most others. If you can push by a hand a 2x4 4-5 ft. in than theres a problem w/ the compaction of the backfill around the house. I have had my last 2 houses built and yes they did bring in sand for the backfill around the house for better drainaige around the foundation but I still cant push a 2x4 even 1/2 foot in the ground w/o breaking out a shovel. Have it checked out by someone else.

Good Luck!

wanavet2 · Aug 26, 2009

CurlyDave,
I don't believe the backfill will have any issue with the house settling. The footings under the foundation of the house were undisturbed ground when they poured the foundation. This is just the backfill that was pushed in after the foundation was finished. I can't see where this would be an issue with the foundation of the house. The area around the house has been backfilled for over a year now and shows no signs of settling. I did have one area that settled last fall after they ran the pipes for the GEO in but other than that I've seen no settling whatsoever. As I've stated this is very sandy soil, basically like beach sand on most of my property. I really don't think we have any issues with the house foundation. Even if the backfill wasn't packed that wouldn't have any impact on the house foundation.

foggy1111 · Aug 27, 2009

wanavet2 said:
CurlyDave,
I don't believe the backfill will have any issue with the house settling. The footings under the foundation of the house were undisturbed ground when they poured the foundation. This is just the backfill that was pushed in after the foundation was finished. I can't see where this would be an issue with the foundation of the house. The area around the house has been backfilled for over a year now and shows no signs of settling. I did have one area that settled last fall after they ran the pipes for the GEO in but other than that I've seen no settling whatsoever. As I've stated this is very sandy soil, basically like beach sand on most of my property. I really don't think we have any issues with the house foundation. Even if the backfill wasn't packed that wouldn't have any impact on the house foundation.

If the soil was not disturbed under the house when built.....I doubt that you have foundation problems too. I built a house a few years ago.....and after putting granular fill over the tile surrounding the house....they backfilled with the original soils. To eliminate the bridging......I ran a water hose aournd the perimeter of the house to get the soils to "slump" into the overdug area. Worked like a charm....but you need to use a little care or you could cause undue pressure from the water against the walls (espesially if unsupported ...as during cornstruction). It can take a few years for soils around the overdig to slump into the foundation.