Comparison

Silicone sealant vs Grab adhesive: which should you use?

One seals and does not hold. The other holds and does not seal well. People reach for the wrong one constantly.

The short answer

Silicone when the job is keeping water out. Grab adhesive when the job is holding something up. If it is both, neither: use MS polymer.

Side by side

	Silicone sealant	Grab adhesive, no-nails
Strength	Medium	High
Flexibility	Very flexible	Not established
Gap filling	High	High
Water resistance	Waterproof	Not established
UV resistance	Good	Not established
How it cures	Moisture cure	Mixed
Clarity	Varies	Varies
Typical working time	5 to 20 minutes	5 to 30 minutes
Typical full cure	Several days, depth dependent	24 hours to several days
Maximum temperature	200C	70C
Needs clamping	No	No
Two part	No	No
Removable later	Yes	No

Highlighted rows are where the two genuinely differ. These describe the families in general, not any particular product, so check the datasheet of whatever you buy.

Choose Silicone sealant when

Baths, showers, sinks, glazing. Permanent flexibility. Constant water. Nothing is being supported.

Choose Grab adhesive, no-nails when

Fixing panels, trim, coving and battens indoors, on porous surfaces, where instant grab saves you propping things up.

What actually separates them

Silicone has the movement capability and the water resistance; grab adhesive has the strength and the instant tack. Neither does the other job. The common mistake is siliconing something that needed holding, then wondering why it fell off.