Patio & Spa Pad Over Fill Questions

deckman22

I have a 8'x8' spa pad & a 12'x15' patio to pour on my next project. The back yard has a retaining wall all the way around it, 3-4' of gravel next to the retaining wall then whatever the home builder could find to fill it in. The fill is mainly dirt/limestone from what I can tell. The area where the spa pad is going to be has about 8-10' of fill & the patio/pergola has about 6-8' of fill. I plan on getting a driller to drill 16" holes thru the fill to virgin soil. 4 holes, 1 on each corner, 5/8" rebar cages w/ 18"x12" beams around the perimeter for the spa pad. Same deal for the patio except the holes will be 12' outside to outside w/ beam running 3' past the hole plus a beam going thru the center. For beams I'll have 4 - 5/8" rebar, 2 at the top, stirrups & 2 at the bottom, then 1/2" rebar 24" oc to fill in the rest of the area. My question is does that seem to be enough to support a 7'x7' spa, 350 gallons water, & 5 people max. load? Same question for the patio that will support a 12'x12' RSC pergola. Also can I pour the piers first let them set up then pour the pads over them or is it best to pour the whole deal at once? The HO is worried the typical 4" patio & spa pad would settle because of the fill. The pool builder working next door told him his yard would settle about 18" in a years time, seems a little much to me. I would post a drawing, but I'm not the most computer savy person around. Thanks for any comments.

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Deckman
www.alscustomdecks.com

dirt diggler

ok - so the area that you are placing the pad on ... let's talk about it


it has about 6 or 8 feet of fill (from when they did grade on the home's construction??) and who is telling you this??

correct?

how long ago was the fill placed?



you can beef up the pad all you want ... won't make a difference in the world if you're installing it on top of an old trash pile


2Bcontinued ...

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Thanks in advance!!!

deckman22

Dirt,

The home was completed a couple of months ago. I can tell how much fill is there by the height of the retaining walls. Also the pool builder next door has pics of the lot before backfilling.

I know that putting in more concrete & beams isn't going to solve the problem of settling. However with the piers to virgin soil up to the beams it should hold in my mind. I could hire an engineer, just trying to keep from the added expense & time factor. I do not want to waste all the time/money drilling/installing piers only to have it fail inspection. Engineer would be safest thing just the only other job I had for Jan. ain't happening. Got a sales appointment in a few minutes so that could change.

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Deckman
www.alscustomdecks.com

derek1175

This plan you have will work the piers to natural soil i like go just a little deeper a foot or so the steel plan is good i like to pour peirs first pouring with the floor is ok but inmy mind all at once seems to put too much weight on the ends and may cause a crack hope i was of help

concretemasonry

All the fill you see will at a lower level in a few months and there be little supporting any floating slabs and the slabs will need to be structural.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.