Short answer
Caulk usually means a paintable acrylic for filling gaps before decorating. Sealant means a flexible material that keeps water and air out of a joint that moves. Adhesive holds parts together. Choose by the job, not the word on the tube.
People ask us for caulk, sealant and adhesive as if they were the same thing, and plenty of labels use the words loosely. The useful question is what the bead has to do: fill a gap for paint, keep water out of a moving joint, or hold something in place.
Caulk: fill it, then paint it
In the trade, caulk usually means a water-based acrylic that fills gaps around skirting, architraves, frames and cracked plaster so they can be painted over. It tools easily with soapy water and becomes part of the finish.
Pereseal 702 is our acrylic. It takes paint very well, skins in about 20 minutes and handles up to ±15% joint movement. That suits frames, partitions, ducting and wall cracks. It doesn’t suit a joint that moves a lot or one that stays wet: keep it dry for the first 24 hours and never use it where it will be submerged.
Sealant: keep water out while the joint moves
A sealant stays flexible so it can stretch and squash as the building moves with heat and load, without letting go of either side. Silicone is the usual choice for windows, façades, glazing and wet areas.
Our silicones take more movement than acrylic: ±25% for 802 and MP, ±30% for N and AF. The trade-off is paint. Silicone won’t hold it.
Any sealant only works if the joint is built right: the right width and depth, bonded to two sides and not three. See joint design basics.
Adhesive: hold it in place
An adhesive carries load between two parts: a panel on a wall, a skirting board, a mirror. What matters is the bond area, how long the part needs propping while it cures, and what happens if it lets go.
We don’t make a construction adhesive. A sealant bead isn’t designed to carry weight. For anything heavy, overhead or likely to hurt someone if it falls, use an adhesive made for the load, plus mechanical fixings.
Adhesive-sealants do both, within limits
Hybrid (MS polymer) and polyurethane products are often sold as adhesive-sealants. They can bond and seal, but a hidden bonding bead behind a panel and a neat weather joint between panels are laid differently. Decide which job matters more and lay the bead for that one. Our silicone vs polyurethane vs hybrid guide compares them.
Which one do you need?
Painted gap round a frame, skirting or cornice
Acrylic caulk: Pereseal 702. Paintable, up to ±15% movement.
Window or door perimeter, outside
Neutral-cure weather silicone: Pereseal N.
Bath, shower, sink or worktop
Anti-fungal silicone: Pereseal AF.
Glass to metal, glazing top seals
Acetoxy glazing silicone: Pereseal 802. Keep it off natural stone and sensitive metals.
Fire-rated gap in a wall or floor
Pereseal FR, installed to the tested joint detail.
Holding up a panel or fixture
A construction adhesive, propped while it cures. We don’t make one.
Not sure which you need?
Send us a photo of the gap and tell us what’s on either side. We’ll tell you what to use.
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