How do I fix cracks in a concrete pool deck?

Sort the crack before you buy anything

A narrow, flat crack in a concrete pool deck is a small, inexpensive repair: clean it out and fill it with a flexible sealer so water does not get into it. A wide or stepped crack is a different problem, and filling it only hides what is going on underneath.

Start by looking at width and level. Quikrete's Concrete Crack Seal is formulated to fill cracks on any horizontal concrete surface, including sidewalks, walkways, steps, patios and decks,^[1] which covers a pool deck. But the data sheet is plain about the limit: do not apply in cracks wider than 1/2 inch (12 mm).^[1] Run a finger across the crack. If one side stands higher than the other, skip to the section on when to call a pro.

Choose the day and clean the crack

The product has weather limits. Temperature should be between 45 and 100 degrees Fahrenheit, and the product should not be applied if rain is expected within 24 hours.^[1] In Virginia that usually points to a dry spell in late spring or early fall.

Preparation decides how long the repair lasts. Clean all loose dirt, dust and gravel from the crack, and the surface should be free of oil and grease.^[1] Sunscreen and suntan oil build up on a pool deck, so scrub the edges of the crack with a stiff brush and a degreasing cleaner, rinse, and let it dry. Quikrete's polymer sealant sheet states the same rule for joints: the substrate must be clean, frost free, sound and free of any oils, greases, or incompatible sealers, paints or coatings.^[2]

Fill it

If the crack is deeper than 1/4 inch, use backer rod or sand to fill it to within 1/4 inch of the surface.^[1] Backer rod is a foam rope sold at hardware stores; it keeps you from burying a lot of sealer in a deep gap.

Cut the tip of the spout to make a 1/4 to 3/8 inch hole, then squeeze the product into the crack, over-filling slightly to allow for shrinkage.^[1] Work slowly and keep the bead centred on the crack. A second coat can be applied after 24 hours as needed to provide a uniform finished surface.^[1] Keep wet feet and toys off it until it has cured.

Joints are not cracks

The straight lines cut or tooled into a pool deck are control joints, and the gap where the deck meets the coping or the house is usually an expansion joint. They are there so the concrete can move. Do not fill them with a rigid patch. Old expansion joints must be maintained, and existing control joints should be maintained,^[3] which means resealing them with something that stays flexible. Quikrete's Advanced Polymer Concrete Crack Sealant is a one-component sealant that cures on contact with moisture in the air to form a durable flexible seal, for horizontal or vertical control joints or expansion joints,^[2] and its typical dynamic joint movement is plus or minus 25 percent.^[2]

If you plan to resurface later

Tell yourself now, because the crack filler you choose can limit what goes on top. Do not use Concrete Crack Seal on a surface that will later be coated with anything other than acrylic water-based paint,^[1] and the Re-Cap data sheet says not to apply its resurfacer over acrylic or polyurethane crack fillers, including Concrete Crack Seal.^[3] Even a perfect repair may not stop a crack from showing through: reflective cracking into a new surface cannot be completely prevented, especially if the slab does not contain adequate control joints or if slab settlement occurs.^[3] The comparison is covered in whether to resurface or replace a pool deck.

Stop and call a pro if

• The crack is wider than 1/2 inch. That is beyond what the sealant is made for.^[1]
• One edge sits higher than the other, or a slab is heaving, tilting or sinking. Los Angeles County's guide for inspectors of public pools says to mark a pool deck as out of compliance if it is damaged by major cracks, uplifting, or broken or missing deck tiles or deck drain covers, and to note that repairs are needed.^[4] A home deck is not inspected that way, but a raised edge is a trip hazard for bare feet in any case.
• Cracks keep reopening. A repair that fails within a season points to movement in the slab or the ground under it, which a sealer cannot fix. Settlement beside the pool can also be a reason to rule out a leak, so read how to find a leak in a pool.
• The slab is crumbling, or water pools against the pool. Surface and drainage problems are the usual sign that the deck needs resurfacing or replacing, not crack filler.
• The job is bigger than a few cracks. Concrete contracting covers finishing, coloring, curing, repairing, testing, sawing, grinding, grouting, sealing and waterproofing of concrete.^[6]

Getting help in Virginia

If the work you are considering is valued at $1,000 or more, a valid Virginia Contractor's License is required for the license category in which the contractor is to work.^[5] Look up the licence on DPOR before you sign, and expect a contract in writing: Virginia law requires all licensed contractors to provide a written contract for residential work.^[5]

For the budget side, see how much it costs to redo a concrete pool deck in Virginia. More pool questions are collected under Pool and spa answers, and you can browse Virginia pool and spa pros.

When you are ready, describe the deck once and licensed local contractors quote it.