Beneath the pool coping, and behind the tile is what is referred to by pool builders as the bond beam, or just the beam. The pool bond beam is subject to many forces acting on it, and for this reason it is usually poured to be thicker and stronger than the lower section of the pool wall. It was and is (unfortunately) common practice for gunite pools to be built so that the bond beam is not reinforced in any way and just sits there not mechanically attached to your pool structure. Many companies however are including rebar in the bond beam or using other measures to shore up its strength.
Bond beam damage is typically caused through the natural process of frost and thaw. There are also cases where a pool wasn’t level when it was built and the mason laying the coping had to add layer of mortar to level the coping. After a few years the mortar can leak and form cracks which require extensive repair work.
Water is the natural enemy of your bond beam. Water typically gets access to the bond beam through poorly done or poorly repaired expansion joints. Once in the space between your deck, coping, and bonding beam; water can freeze and expand in all directions, pushing until some part of your pool structure gives – and it’s usually going to be the bond beam. The inward pressure on the bond beam will cause your tile to pop off or crack and this means your beam is cracked.
You may not see the telltale long, horizontal cracks in the pool tile that are the end result of years of expansion and contraction of the concrete in a pool until the bond beam has already cracked. If the expansion joint between the pool beam and the pool deck is not true -- does not extend through to the ground, then the pool and deck push against each other. If the deck pushes up against the beam, or if it was built right on top of the beam (a poor building practice) you may see the top 6" - 12" of the pool wall cracking and separating. This is an advanced stage of bond beam failure, and unfortunately where it often finally noticed.
Repairing a broken bond beam is very involved. Remove all the coping, all the tile and chip down to solid beam. Remove all debris. Form and pour hydraulic cement, using steel rebar plugs wired together to create the new beam. Strip the forms, and set new tile and coping and caulking between a true expansion joint. This is a very labor-intensive repair. Typical costs for beam repair run an average $70 per linear foot. A vertical pricing structure is sometimes used, depending on the depth of the crack. If the crack forms just below the coping the job is less expensive. If the crack below the tile band, prices are higher.
Additional costs can be accrued if your tile or coping are no longer produced – which is a common problem. If your coping or tiles are unusable there are two often costly options. Either replace all of your tile band or find the original materials at a pool company that keeps used materials in stock. You can expect to pay a premium for out of production tile and coping.
How do you prevent all this? Inspect your expansion joints! Look for caulk that is cracked, delaminated or missing. If you have any of these conditions you will need to re-caulk, this is ideally done in the spring right after you have removed the pool cover. Make sure you get a good quality of backer rod with a slightly larger diameter than your gap and caulk to a ¼” depth. Self-leveling joint sealer makes the process easier – as long as your deck is level!
When it comes to your bond beam, an ounce of prevention is worth much more than a pound of cure. Be sure to visit our Service Repair Supplies page for coping repair supplies.