Some simple glazing questions

[DigitalM]

I've made some wooden window frames for my workshop. I want to fit double glazed units int hem. There's quite a bit of advice on the web about this, but a lot of it is for places outside UK and there's also lots of conflicting advice.

A few quick questions:

1. How much smaller than the window should I order the glass? The windows are rebated behind a routed ovolo profile by about 15mm. I was thinking taking away 6mm from each dimension to allow 3mm gap on each side. I guess the pertinent question is, what margin of error do most glaziers work to?
2. Some tutorials recommend 'glaziers points', but others don't. Are they necessary?
3. Plastic packing wedges - same as above! Loads of tutorials that use putty don't seem to bother with these things at all. I take it they're mainly for larger windows?
4. In another (v. old) thread on this forum someone recommended butyl rubber glazing compound. I bought some f the everbuild stuff and tried spreading some onto the frames as a test fit. The stuff is really sticky and just as likely to stick to the knife as the frame. Maybe it's too warm, it being summer. I can't stick it in the fridge as it says to keep it above 5c. Is it always like that?!

Well, left to my own devices I'm just going to use the butyl compound like putty, angled at 45 to make a bed, wadge the window in, maybe space it with some small hardwood spacers, then secure it with a wooden trim and panel pins or stainless nail gun.

 

[ColeyS1]

4-5mm smaller overall.

Run a bead of silicone around the rebate (the bit that will touch the inside surface of the glass.

Stand the pane of glass on a few plastic packers. Are glazier gives us a handful everytime they come out. It's just plastic about 2.5 mm thick 15mm wide and about an inch long.

Fill up the gap around the edges of of the unit completely with silicone.

Nail in the top and bottom bead first, lastly the sides.

Finally 'cap off' the outside beads by running a bead of silicone between the bead and glass edge.

Slightly off topic but are glazier always use to state a 15mm rebate. I've found a 14mm rebate is better as less of the glass spacer gets seen. That might influence how much gap you allow around the edges. If you've got a sample of there double glazing you could measure how big the spacer is around the edge of the unit. If you're not too bothered about seeing a tiny bit of spacer, crack on !!
Coley

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[Doug71]

Few different ways of doing it. I go for 3mm gap all round so 6mm in total. Use butyl glazing tape which is on a rolll instead of in a tub like putty. Tape round back of window rebate, stand glass on 3mm plastic packers, packers at top and sides also if a sash to stop it sagging. Silicone round the edge of unit, make sure it is suitable for use next to edge sealant of units as some are not. Butyl tape again on back of glazing beads, good practise to use stainless steel pins on beads.

This is for totally sealing an externally fitted unit, if you are doing drained frames or internal glazing it's a bit different. Reddiseals is a good source of tape, silicone, advice etc.

Doug