Over 15 years and 9 rental properties, I have re-caulked more bathtubs, kitchen sinks, and exterior window frames than I can count, and the single question I get asked most by tenants and other landlords is simple: silicone or acrylic? Pick the wrong one and you are back on your knees with a caulking gun in 8 months instead of 8 years. Pick the right one and you save yourself a callback, a bag of moldy caulk strips, and around 3,000 yen in wasted material.
I used to buy whichever tube was cheapest at the hardware store. That habit cost me two bathroom call-backs in my first three years as a landlord, so now I choose based on where the bead is going, not what is on sale.
What Acrylic Caulk Does Best (and Where It Fails)
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Acrylic caulk, sometimes labeled as latex caulk, runs about 400 to 600 yen per tube and is the caulk I reach for on anything that will eventually get painted. It bonds well to wood trim, drywall seams, and plaster cracks, and it cleans up with water while it is still wet, which matters when you are working solo and do not have a helper to hand you a rag. The problem is flexibility. Acrylic can only stretch about 5 to 8 percent before it cracks, so in a spot with any moisture or movement, it fails fast. I have seen acrylic beads split open in as little as 1 to 2 years in a humid bathroom.
Where Silicone Sealant Earns Its Higher Price
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Silicone runs 800 to 1,200 yen per tube, roughly double the cost of acrylic, but it stretches up to 25 percent without cracking and sheds water instead of absorbing it. That is why I use it around every tub, shower pan, kitchen sink, and exterior window frame across all 9 of my units. A properly applied silicone bead in a wet area has lasted 8 to 10 years for me before it even needed a touch-up, versus 1 to 2 years for acrylic in the same spot.
The Bathroom and Kitchen Test I Run on Every Unit
My rule of thumb is simple: if the surface is porcelain, tile, stainless steel, or glass, it gets silicone. If the surface will be painted, it gets acrylic. In a building I bought that was already 22 years old, the previous owner had used acrylic caulk around the tub surround. It failed within 14 months, and when I pulled the old bead off I found mold growing underneath in 3 separate spots. That single repair, plus the mold treatment, cost me more than 30 tubes of silicone would have.
Paintability, Cost, and the Checklist I Use Before I Buy
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Acrylic takes paint within about an hour of application, which is why it is the right choice for baseboards and window trim you plan to finish. Silicone will not take paint at all; roll a brush over it and the paint just beads up and peels. Across my 9 properties I go through roughly 40 tubes of caulk a year, and even though silicone costs more per tube, the labor I save by not redoing a bathroom job every 18 months more than makes up for it. Before I buy, I run down this short list:
- Bathtub or shower surround: silicone
- Kitchen sink backsplash: silicone
- Around the toilet base: silicone
- Exterior window trim facing rain: silicone
- Interior drywall cracks before painting: acrylic
- Baseboard gaps in a dry hallway: acrylic
My Simple Rule After 15 Years
Cure time matters too. Acrylic is dry to the touch in about 30 minutes and fully cured in roughly 7 days. Silicone skins over in about 30 minutes as well, but full cure usually takes 24 to 48 hours in normal humidity, and I have seen it stretch to 10 days during a dry winter week when I was working on an unheated unit. My rule after all these years is short: wet or moving, use silicone; dry and painted, use acrylic. It is not complicated, but skipping it is what causes most of the caulk failures I get called about.
That is the approach I use across all 9 of my properties, and it has cut my caulk-related callbacks by more than half over the last 5 years.
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15 years of landlord experience u00b7 3 apartment buildings u00b7 DIY renovations that saved millions of yen. Browse all articles at diytosan.com
