by Rob Cox August 22 2014
Let me get right to the point. "G" in the picture is the subject of today's blog post. The expansion joint on an inground pool is the most crucial piece of equipment on your pool.
I say 'equipment' - because it allows movement and motion, and performs a very critical function - that of separating your pool deck and your pool wall.
As outside temperatures go up during the day, your pool expands, just a few millimeters. Your pool deck is also stretching out in the sun an equal amount.
During the day, your pool and pool deck are pushing towards each other. At night, or during cooler temperatures, your pool and deck contract and separate.
Your expansion joint, the air gap between your pool and your pool deck - is what keeps them from hitting each other as they expand.
The problem is - when pool builders pour the pool deck right on top of the pool, and don't place proper space between the pool and the deck.
The expansion joint should run clear to the earth. When it doesn't, and the pool and the deck are actually touching each other, guess who wins?
Over time, the pool deck will push on the beam, mud bed, tile and coping, and then you have a problem like we see below.
Here, on the back of the pool wall (beam) we see the mud bed and the beam touching the pool deck.
Over time, this crumbled the mud bed, resulting in loose stones, and cracked the top row of tile off (shown already cleaned up).
The slow but strong pressure also eventually loosened these other two coping stones, on a radius corner.
Fortunately, the beam was not damaged, only the mud bed. Forms were set using sheet metal and lags. Cardboard and newspaper were used as a gap, although a roll of 1/2" wide foam is made specifically for this job, to maintain the gap as the pool deck (or mud bed) is poured. Medium bed mortar is used to set the stones, using a level and a rubber mallet to get them lined up just right.
With the new stones in place, the tile bed is cleaned up by applying a smooth layer of plaster mix.
Ready for new tile, with it set onto the vertical surface using Thin Set mortar, and grouted with waterproof grout.
Here's the finished product, with the exception of the grout used (sanded waterproof grout) in between the coping stones. Choose a color that will best match your coping stones, or the grout between the other coping stones.
MORAL OF THE STORY: Caulk your expansion joints, and if you start to see cracking tiles or loose stones, you may need to make the same repair as was done above.
Act fast if you suspect that the pool deck is pushing into the pool, and your repair can be as easy as this one was. (they can be much worse, with cracks and crumbling extending far down into the beam. In this case, only the mud bed was affected.