Sealant or mastic?

Jul 21, 2011 2 Replies

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Bert Coules 15 years ago

The various online guides to installing uPVC windows all recommend sealing the interior edges with silicone sealant and the exterior with frame mastic. But is there any reason why I can't use a weatherproof silicone for the outside? I don't in the least mind getting mastic if it's essential, but is it? I have to confess that I don't know the essential differences between mastic and sealant.

I've installed a uPVC window into a wooden frame set into the side of my sectional concrete garage. The exterior seal will be between the uPVC and the timber, with a second bead between the timber and the concrete.

Many thanks.

Bert

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Information here may be outdated?

Dave Plowman (News) 15 years ago

I *think* the main difference is a sealant sets, a mastic not.

I've used exterior silicone round my windows successfully. I'm not sure a non setting stuff would be ideal if you could rub up against it. ;-)

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Bert Coules 15 years ago

I was looking at a tube of Evo-Stik Frame Mastic in Wickes today: there's nothing on the label about a setting or curing time, but it does say "forms a tough, flexible, weatherproof seal". So maybe it hardens, maybe not...

That's handy to know. Thanks.

Bert

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