Concrete decking around pools

I'm wanting to install a concrete deck/patio around a soon to be installed inground fiberglass pool. I live in a Michigan climate where a lot of side walks and driveways (floating slabs) heaved badely this year. Is the heaving typical or is it due to whats under (or not)the slab. Should I be concerned about this, should the concrete be bonded to the pool rim, should there be an expansion joint between the pool and the concrete? Should there be a foundation wall for the patio deck around the pool. Whatshould it cost me to have 13 cubic yds poured around the pool. Can anyone speak to these issues and/or provide any specifications for the do-it-your-selfer.

 

[Ron]

The heaving was probably frost heave. To reduce this, make sure you place the concrete on a free draining layer of soil, preferably a coarse sand or fine gravel.

You should have an isolation joint between your pool and the deck. This should be cast with you place the concrete by using a styrofoam block placed against the pool, place the concrete, then remove the block (a little paint thinner will melt it right out!). Then put a continuous strip of backer rod (closed cell foam rod) that is 150 percent larger in diameter than the joint width (if 1/2-inch joint, use 3/4-inch rod). Push it down below the surface of the joint to create a sealant reservoir that is about 1/4 to 3/8-inch deep at the center over the rod. This creates somewhat of a "dog bone" shape in cross section to the sealant. After you do this, seal the joint with a urethane sealant. Don't use silicone or latex.

The deck should have joints to prevent random cracking. The joints may be decorative (using redwood strips is a good way), or just functional. For a thin slab on grade, I would suggest your joint spacing be no more than 8 feet in any direction, except if your deck is only about 4 feet wide, the joints should be at about 4 to 5 feet. Sawcut the joints to a depth of 1/4 the thickness of the slab and saw them within 8 hours after you place the concrete (same day!!!)

No need for a foundation wall, provided you don't have an erosion problem.

It should cost you somewhere between $75 and $100 per cubic yard for the concrete. More if it has to be pumped.

Good luck.

 

[JAE]

Heaving is sometimes a nasty issue to deal with. The heaving is due to the presence of high moisture in the subgrade directly below the slab which freezes. Sand backfill should be avoided - better to use a uniformly graded (all the same size) aggregate where there would be plenty of air space bewteen the particles and a drain tile around the base of the pool to get the water away.

I would not tie the slab to the fiberglass pool as this is just asking for trouble. An expansion joint is preferred as there will be some differential movement no matter what you do. But you want to make sure that the sealant is very good around the pool as pool water will want to penetrate the joint.

A foundation wall around the pool tank would be great, but expensive. Concrete ordered, reinforced and placed by a contractor could be in the $300 to $400 (US) range per cubic yard. If you just order it, and do the work itself, you would probably be charged $50 to $70 per cy. depending on where you live.

The perimeter slab could be tied into the foundation wall, but you would then have the same concern of heaving the slab and separating from the wall.