Fitting sealed units into wooden frames. Methods?

[frosenman77]

Hi, I'm looking to replace all my failed DG units. The frames are still in good condition, but the existing sealed units are quite thin at 12mm (3x6x3). The windows have a 15mm external beading, and approximately 2mm of putty on either sides. Basically I have a 31mm rebate to play with.

If I got 24mm sealed units (4x16x4), I would only have 7mm for the beading. Would this be sufficient? Has anyone ever fitted wider sealed units that finish flush and then secured beading over the glass and frame?

Another question I have is regarding fitting. On other posts I have seen double sided security tape used on both sides. Other things I have read suggest butyl putty or tape is better? I have also read that it is critical to add suitable ventilation in the form of drilling holes etc.

Can anyone suggest the strengths and weaknesses of each fitting method? Thanks

 

[squowse]

drained and ventilated dry glazing (not butyl or silicone) is the way to go.
allow 2mm for compressed 3mm tape each side. i would use security tape on inside rebate only for downstairs externally beaded windows.

your idea for fitting beading to the face of the frame is an interesting one and i can't think why not off the top of my head. need to get some compression of the tapes when fixing the beading.

you could also look at stepped units.

you will certainly struggle with such a small rebate otherwise. beading should be roughly square and 14mm is about as low as you can go.. you will never get a decent fixing on a 7mm thick bead.

 

[frosenman77]

Thanks for your input Squowse.

You say only using security tape on the downstairs. What would you use elsewhere? Are there different types of tape?

Also, what would be the best way of getting proper ventilation to the sealed units?

 

[squowse]

i get my tape from reddiseals -

EPDM tape with lip is very good for the outside as it gives you a couple of extra mm coverage of the spacer.
EPDM tape or Security glazing tape on the inside. Give the security tape a good wetting on the glass side. It will help you position the unit. It can still be a pain, grabbing the unit too early sometimes.

Have a read of this - http://www.thewindowman.co.uk/wood_drainage_files/wooden_windows_drainage_new.pdf

 

[frosenman77]

Very useful links. I know a lot more now, than I did when I started!

Thanks for your help.

Do you think that in a reasonably thin unit (4x12x4) it would be worth the extra for argon fill?

 

[squowse]

argon fill costs pennies (well ok a few quid) if your manufacturer has the facility to do it.
my local guy doesn't so has to bring them in from elsewhere = £££

 

[frosenman77]

Thanks for the pdf about adapting timber frames. It's pretty much what I want to do.
My only concern is about fixing using the glazing tape on the inside. My rebait is only 12.5mm high, so with the recommended 5mm spacer block, i'll be sticking mostly to the sealed unit's edging tape (about 8mm I believe) and not to the glass. I read on another post that you should really stick to the glass?
What do you think?

 

[squowse]

haven't seen sealed units with edging tape. modern ones have a butyl rubber seal on the edge between the glass panes.
you may want to plant a small bead on the inside so the edge seal (usually specified as 12mm max) is not visible. it is very important to cover it on the outside so UV doesn't degrade it.

 

[frosenman77]

OK, thanks. I had thought of putting some beading on the inside anyway, purely as a cosmetic thing.

On the outside i'm probably going to use some 34mm D-shaped timber, covering both the glass and the frame. This way, I can have a 28mm sealed unit that nearly fills the existing rebait. This is then retained by glazing tape and the D-shaped timber on the outside, pinned to the frame.

I'm looking into sealed unit prices at the moment. They seem to vary wildly! Most of the better prices seem to be in the North (so hefty delivery cost). Do you know anyone good in the South-East?

 

[squowse]

OK, thanks. I had thought of putting some beading on the inside anyway, purely as a cosmetic thing.

On the outside i'm probably going to use some 34mm D-shaped timber, covering both the glass and the frame. This way, I can have a 28mm sealed unit that nearly fills the existing rebait. This is then retained by glazing tape and the D-shaped timber on the outside, pinned to the frame.

I'm looking into sealed unit prices at the moment. They seem to vary wildly! Most of the better prices seem to be in the North (so hefty delivery cost). Do you know anyone good in the South-East?

not in the south east i'm afraid.
paying about £40 per sq.m incl VAT from system3 in manchester, don't think they would that they have a distributor down south.
That's for top spec - soft coat low-E, warmedge spacer and argon fill.
safety glass is extra.

 

[frosenman77]

The nearest place to me is KalGlass, but seem pricey: 4mm Softcoat Planitherm / 4mm Clear Diamont Glass 20mm Cavity Warm edge
spacer bar @ £92.59pm2 + Vat. £10 per unit extra for argon fill.

At the other extreme is Oakland Glass in W.Yorkshire: 4mm Clear / 4mm Low E (G Fast) - £28m2 +Vat, + £1.5 per sqM for argon fill, +£2.00 per sqM for warm edge spacer + £2.4 energy surcharge? = £40. Exactly what you said!!

It nearly seems worth hiring a van and driving up to collect!?

 

[squowse]

might be worth asking system3 for the name of a distributor that would deliver to you or a similar manufacturer down south