Settlement and drainage issue with cement pool deck

Apr 29, 2018
9
Macomb/MI
Hello, I greatly appreciate your advice and recommendations in advance. Ok, so let me start by providing some highlights of what's happening. The settlement issue was identified while trying to replace our original ladder anchors that were badly damaged from the Michigan weather conditions over the years. The anchors were removed using a 3" core drill bit. The holes exposed an 8-10 inch backfill void below the 4" concrete decking. The extent of the void is unknown as I can only feel or see about 8-10 inch diameter inside the holes. There are no obvious concrete cracks or major damage visually above group besides some minor heaving with the slabs at the joints where the pool deck joins our previously poured patio. FYI, a few years ago I installed a drainage tile along the exterior of the pool deck away from the house after the original slabs caved in from runoff from my landscape grade.

Potential options:
1a) Drill 1" holes around the entire pool deck every 4-6 feet to identify all settlement issues
1b) Pour/inject backfill material (not sure what process or material is recommended) up to current cement level
1c) Install new ladder anchors and ladders
1d) Use cement saw to cutout and install drainage/channel tile to properly drain water to attach to existing basin in backyard
or
2a) Remove/replace all existing cement slabs on house-side of pool (about 45-50' x 4') to expose all damage area
2b) Backfill and
Install drainage system
2c)
Drill 1" holes around the remaining pool deck and fill needed areas with recommended material
2d)
Replace cement decking
2e) Install new ladder anchors and ladders

Highlights:
1) Fiberglass pool 42' x 16'
2) 10-11 years old
3) SWG
4) Pool deck - all concrete from pool to house (about 20' from house to closest pool edge)
5) We live in Michigan with heavy concentration of clay soil and are miles away from any major water source

Pictures:
1) Picture of drainage tile installed on far side of pool
2) Deep-end ladder holes exposing the 8" void
3) Joint damage/expansion between patio and pool cement decks at shallow end (patio is raised about 6" higher and is 20 feet long)
4) Partial pool picture

Drainage Tile.jpgLadder view.jpgPool Deck Joint.jpgSideview.jpg
 
Wow.. That's a tough one. I would have a real hard time demolishing or even drilling holes in a perfectly good slab. You would think if there was going to be a issue it would have happened by now. I would imagine it is the large pour on that side that preventing the slab from tipping toward the pool. Basically the concrete is holding itself up because of how large it is. I do not have any experience with materials injected under concrete to support it but I would be a little concerned about putting any type of expansive material next to the fiberglass walls fo fear of putting to much pressure on them.

If you core and inject you will have unsightly plugs to look at.

If you wait and see you may have a additional crack and then unsightly plugs to look at or you might not have any issues at all.
Difficult to say without actually seeing all the issues and potential issues however I think I might fill the area under the ladder and wait to see if any other issues arise.

What is the material under the slab?
 
Google slab hacking and mud jacking. They drill and use non shrink grout under the concrete. The foam works but I'm not a fan of it. I demo'd a garage slab last year that was foam jacked in 2009 and the foam was broken down in spots already but I have heard new stuff is better. I would fix all voids and then spend the money for new concrete deck on a paver overlay or a kooldeck type coating to hide the plugs. And do whatever drainage needs to be done first then patch and cover it all up
 
I agree with Jimmy, option one with an overlay if you don't like looking at the plugs. Poly foam is better for some applications, but for something like this I'd go with standard mud. Find a local company that specializes in mudjacking / slab jacking and let them determine the size and spacing of the holes.
 
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