Fenestration frustrations.

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loughran

Original Poster:

2,731 posts

135 months

Saturday 19th April 2014
quotequote all
I'm a cabinet maker and there are times when the gap between cabinet maker and joiner is larger than I'd like. smile

Last year I made new windows for our house, sash and casements and glazed them with double glazed units with... butyl compound. I'm a bit of a traditionalist and would have used linseed putty but the argument for butyl compound seemed pretty convincing. At the time.

6 months and one mild winter later the butyl has failed on most of the windows and water has got into the rebates. Fortunately I made the windows in oak so a bit of damp isn't really a long term problem and as the weather gets better I'll strip the double glazed units out and start again.

But what should I use to bed the units in this time?

I've been doing some work in a house where all the windows have been replaced and the manufacturers have used a dry glazing system. Instead of putty/butyl they've used a black neoprene gasket, 2 or 3mm thick and the casements have drain holes to allow any moisture that gets past the gaskets out.

Now this sounds like quite a good idea (although having drain holes seems a bit like admitting defeat before you've started) and they do look good, so I spent 45 quid on a roll of neoprene gasket ready for the off.

Then this week I've been working on a new build with all new sash windows and the joiners are telling me these glazed units are bedded on U9 glazing silicon. Very neat it looks too.

Does anyone have experience of dry glazing systems or of the glazing silicon ? I'm favouring the silicon method at the moment but it can't be that straight forward can it ? What's special about this U9 silicon and if it's that good, why doesn't everybody just silicon their glass in place ?

Or is the dry glazing (and holes) the way to go ?

Evoluzione

10,345 posts

242 months

Saturday 19th April 2014
quotequote all
It's silicone.

Butyl is rubbish, did you paint the rebates before using it?

Have you pointed them off like you would with putty or used a bead?

The best ones are glazed from the inside. On the outside the moulding pattern is put on to look like traditional putty pointing, the beads on the inside just look like a traditional moulding (ovolo etc) when fitted.
Bed on with glazing silicone, it is said that non glazing types (acetoxy curing IIRC) attack the material holding the units together.

wolfracesonic

6,940 posts

126 months

Saturday 19th April 2014
quotequote all
Here's a little night time reading, http://www.acornglazing.co.uk/wp-content/themes/ac... I used the flexi strip on my two softwood bays and I've had 3 units fail out of 20 in 9 years. I don't think the U9 silicone is anything special, just that it is a neutral cure(doesn't give off acetic acid,that vinegar type smell)and is low modulus which means easily stretched/compressed. Most silicone manufacturers offer something similar. I see plenty of units fail in U.P.V.C windows which are much better equipped in sealing against and getting rid of water. What ever system you use, don't plan on the units lasting your lifetime(unless you're really, really old!)

ETA It says to use sherardized pins in the PDF, but your best using brass ones and pre-drill(or stainless if you can get them) if you're using oak, but I'm guessing you know about that. Sorry if I've stated the obvious to yousmile

Edited by wolfracesonic on Saturday 19th April 21:38

226bhp

10,203 posts

127 months

Saturday 19th April 2014
quotequote all
Using butyl is futile. wink

Wings

5,808 posts

214 months

Saturday 19th April 2014
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You can get both clear or brown glazing silicone sealant. When replacing my double glazed units i use a plastic spacer for the unit to sit on, thereby giving the units a chance of not being sat in rain, moisture.