How often should I re-caulk around my bathtub, and what type of caulk lasts the longest in a humid bathroom?

Plan to inspect your bathtub caulk every six months and re-caulk every one to two years as preventive maintenance — or immediately if you see any cracking, peeling, discolouration, or gaps. Failed caulk around a bathtub is one of the most common causes of hidden water damage in GTA homes, and the repair is simple and inexpensive compared to the thousands of dollars in subfloor and joist repair that water infiltration can cause.

The caulk joint around your bathtub serves a critical function — it seals the gap between the tub edge and the wall tile or surround where water constantly flows during showers and baths. This joint is under constant stress because the bathtub moves slightly when it is filled with water and a person's weight (a full bathtub with a bather can weigh over 500 pounds), then returns to its original position when emptied. This repeated expansion and contraction cycle, combined with Toronto's significant humidity swings between winter heating season (very dry indoor air) and summer humidity, causes caulk to fatigue and fail faster than in more temperate climates.

The Right Caulk Makes All the Difference

100% silicone caulk is the only type you should use around bathtubs and showers. Not silicone-modified acrylic, not latex with silicone additive, not painter's caulk — pure 100% silicone. Here is why the distinction matters:

100% silicone remains permanently flexible after curing, bonds well to non-porous surfaces like porcelain tubs, ceramic tile, and glass, and is inherently waterproof and mould-resistant. It handles the expansion and contraction of a bathtub without cracking or pulling away. Quality brands like GE Silicone II, DAP 100% Silicone, and Mono 100% Silicone are readily available at GTA building supply stores for $8 to $15 per tube. Look for formulations labelled "kitchen and bath" or "tub and tile" — these contain antimicrobial additives that resist mould growth on the caulk surface.

Acrylic latex caulk (even varieties labelled "siliconized") hardens over time, loses flexibility, and cracks within 6-12 months in a wet bathroom environment. It is paintable, which makes it popular for trim work, but it has no place around a bathtub or in a shower.

Polyurethane sealants offer excellent adhesion and durability but are more difficult to apply cleanly and nearly impossible to remove when re-caulking is eventually needed. Silicone remains the best all-around choice for bathtub joints.

How to Re-Caulk Properly

The most common mistake is applying new caulk over old caulk. This never works — the new caulk cannot bond properly to the deteriorated old caulk, and the joint will fail again within weeks. Complete removal of the old caulk is essential.

Remove all old caulk using a razor scraper, utility knife, or oscillating multi-tool with a scraper blade. For stubborn silicone residue, apply a silicone caulk remover (such as DAP Caulk-Be-Gone) and let it soften for several hours before scraping. Clean the surfaces thoroughly with isopropyl alcohol to remove any soap scum, body oils, or residue — silicone will not bond to dirty or oily surfaces.

Fill the tub with water before caulking. This is a professional tip that most homeowners miss. The weight of the water pulls the tub down to its maximum deflection point, opening the joint to its widest gap. When you caulk in this position and then drain the tub, the joint compresses slightly, keeping the caulk under gentle compression rather than tension. This dramatically extends the life of the caulk joint.

Apply the silicone in a continuous bead, then smooth with a wet finger or caulk finishing tool dipped in soapy water. Allow 24 to 48 hours of cure time before using the shower or bath — silicone cures by reacting with moisture in the air, and premature water exposure before full cure compromises the bond.

This is a manageable DIY project that can save you $150 to $300 in service call fees. However, if you notice water damage, soft spots in the wall, or mould growth behind the caulk line when you remove the old caulk, stop and call a professional — you may have water infiltration that needs assessment before re-caulking will solve the problem.