Any advice for fitting replacement double glazed units?

[DJG]

Hi,

I've got double glazed sealed units in swivel wooden (softwood, I think) timber frames. Glazing beads are fitted on the outside of the frames. Some of the sealed units misted up and I got replacement units from a local glass merchant.

I was going to order linseed oil putty from Screwfix, when I came across a web page that said linseed oil putty should never be used on double glazed units, as it dries out the rubber compound that seals the units, causing premature misting. It omitted to suggest an alternative.

If this is correct, what sealant should I use instead? If I need sprigs to hold the units in place until the beads are replaced, where can I buy them? (I've not found anyone selling them.)

I've spent a wasted day searching the web for this information, and found nothing useful. I'd really appreciate any advice. Thanks.

 

[DJG]

I forgot to ask whether I need to use spacers or glazing blocks?

Also, I read somewhere about dry glazing systems. Are they worth while considering?

Any other hints or tips appreciated. This is my first 'go' at glazing (though I'm a fairly experienced DIY'er).

 

[masona]

If this is correct, what sealant should I use instead? If I need sprigs to hold the units in place until the beads are replaced, where can I buy them? (I've not found anyone selling them.)

Not many people know this, you need Double Sided Security Glazing Foam Tape and are available in difference thickness.

The tape is so strong and sticky so you have to be careful to get the unit in the correct position before pressing onto these tape otherwise there are a bugger to get it off again

Found one here. I didn't buy it from them though.

Give me a bit more time to find the company supplier I've used.

ps: always use glazing blocks for the unit to rest on

 

[masona]

Found it here, click onto the link from my post, they're in Colchester and will deliver anywhere.

 

[biffvernon]

Masona's diagram is spot on for double glazing in a wooden frame. It's exactly what I do. You should be able to get a roll of tape from your local double glazing firm.

 

[masona]

Looking at the diagram, the glazing tape should be flush or slightly higher on the external beading side preventing rainwater trap.

 

[biffvernon]

Ah, we're getting into detail now. Adding a bead of silicone onto the top of the glazing tape gives a belt and braces approach to water penetration defence. As you say, Masona, you don't want a puddle of water sitting there.

Actually, I've not heard a really convincing reason why linseed putty behind wooden beading should not work. I did that to a window on my own house, about 20 years ago, before I knew better. It's still fine!

 

[DJG]

masona and biffvernon, thanks for your comments.

If this is correct, what sealant should I use instead? If I need sprigs to hold the units in place until the beads are replaced, where can I buy them? (I've not found anyone selling them.)

Not many people know this, you need Double Sided Security Glazing Foam Tape and are available in difference thickness.

I presume, then, I don't need sprigs?

Any idea what thickness of tape I should use? Assuming it's guaged by the size / weight of the glass panel, I'm installing double glazed sealed units approx 1m x 1m.

The tape is so strong and sticky so you have to be careful to get the unit in the correct position before pressing onto these tape otherwise there are a b*****r to get it off again

Any tips -- other than by being bloody careful! -- to avoid premature adhesion?

ps: always use glazing blocks for the unit to rest on

Do I need just two blocks for each unit, one under each corner? I presume 20mm wide for a 4-12-4 unit? Does the thickness matter? Or just what fits in the gap?

Incidentally, what's the purpose of the blocks?

Ah, we're getting into detail now. Adding a bead of silicone onto the top of the glazing tape gives a belt and braces approach to water penetration defence. As you say, Masona, you don't want a puddle of water sitting there.

That sounds like a great idea, though does it cause any problems down the line when you subsequently have to replace the glass?

P.S. Apologies for not replying sooner, I was in hospital for tests.

 

[masona]

Any idea what thickness of tape I should use? Assuming it's guaged by the size / weight of the glass panel, I'm installing double glazed sealed units approx 1m x 1m.

All depends how deep the rebate is, measure the thickness of the unit plus external beading minus the rebate then divided by 2 for the thickness of the tape.

The tape is so strong and sticky so you have to be careful to get the unit in the correct position before pressing onto these tape otherwise there are a b*****r to get it off again

Any tips -- other than by being b****y careful! -- to avoid premature adhesion?

Put the unit in without the tape in the rebate and see if it all line up correctly, if not pack with glazing packs until you're happy, then put in the tape then glazing packs in the correct position, rest the unit on the glazing packs then carefully push it back.

Do I need just two blocks for each unit, one under each corner? I presume 20mm wide for a 4-12-4 unit? Does the thickness matter? Or just what fits in the gap?

Normally only 2 blocks for a average size window unless it's a large unit then 3 or 4.

Ah, we're getting into detail now. Adding a bead of silicone onto the top of the glazing tape gives a belt and braces approach to water penetration defence. As you say, Masona, you don't want a puddle of water sitting there.

That sounds like a great idea, though does it cause any problems down the line when you subsequently have to replace the glass?

Not really you can trim it off with a stanley knife blade, very rarely a unit need replacing these days.

 

[biffvernon]

I get my tape from this firm:
http://www.ukindustrialtapes.co.uk/
12mm wide 3mm thick (which squashes down to about 2mm) is a suitable standard pvc foam tape.

 

[DJG]

Thanks masona,

Any idea what thickness of tape I should use? Assuming it's guaged by the size / weight of the glass panel, I'm installing double glazed sealed units approx 1m x 1m.

All depends how deep the rebate is, measure the thickness of the unit plus external beading minus the rebate then divided by 2 for the thickness of the tape.

Okay, I understand.

The tape is so strong and sticky so you have to be careful to get the unit in the correct position before pressing onto these tape otherwise there are a b*****r to get it off again

Any tips -- other than by being b****y careful! -- to avoid premature adhesion?

Put the unit in without the tape in the rebate and see if it all line up correctly, if not pack with glazing packs until you're happy, then put in the tape then glazing packs in the correct position, rest the unit on the glazing packs then carefully push it back.

Are the glazing blocks all the same thickness?

Normally only 2 blocks for a average size window unless it's a large unit then 3 or 4.

Who sells these blocks? Can I order them online?

Thanks again for your help.

 

[DJG]

I get my tape from this firm:
http://www.ukindustrialtapes.co.uk/
12mm wide 3mm thick (which squashes down to about 2mm) is a suitable standard pvc foam tape.

I notice as well as the PVC foam tape, they also do a FoamLink PE tape.

Similarly, Adhere (recommended by masona) have both a Standard and Premium quality.

On another thread, someone mentioned Reddiseals (www.reddiseals.co.uk) and they do both a Security Glazing Tape and Butyl Tape Sealant.

What are the differences between them all? Are any better than the others? Is it worth paying extra for a 'premium' product?

 

[masona]

Who sells these blocks? Can I order them online?

Thanks again for your help.

Useful guide for DG packs, I think I bought the last packings from Screwfix

http://www.seac.uk.com/download/pdf/SEAC_Glazing_Guide.pdf

Just found another one here