new sashes

[Jezmaster]

Hi people,

got to make 3 pairs of sliding sashes, they are 35mm thinck, with 14mm double glazed units going in them.

with a bevel outside and beads inside.

what depth should i make the rebate, to give a nice bevel depth on outside. I will make up ovolo beads to suit.


cheers jez

 

[RogerS]

How are you meeting Building Regs with only a 14mm double glazed unit?

 

[Bradshaw Joinery]

Regs will be fine if repairing an existing frame.

Id leave 7mm outside, 2mm glazing gap then bead. Seal unit in with silacryl or similar.

 

[RogerS]

Regs will be fine if repairing an existing frame.

.....

True. If they are replacements.

Also if they are replacing single glazed sashes then if it's a traditional box sash, is there enough room to take the extra weights that are needed for the double-glazed units?

Another suggestion is to change the sash profile and fit the dgu's from the inside. Make a false putty bead as part of the sash..

Lots of sash stuff over on woodworkuk.co.uk

 

[Ollie78]

Hi jezmaster.

I have some experience with this (sash window restoration).

First the point about the glazing. I would suggest you stay away from bevel or bead on the outside on the outside, it is not a good solution and usually fails quickly with inevitable water ingress.
When converting existing sashes to double glazed units or replacing with new sashes. I would use flexibond glazing tape (like a strip of mastic) or a silicone (specifically design for the purpose, not normal silicone) to bed the units on. then a few glaziers points.
To face the units in I use a product called Dryseal which is a specially designed putty replacement that will set to a solid rubber but looks like putty and is paintable, there are a few similar products.

Also investigate thinner units 14mm is quite a fat unit considering you only have 35mm overall. The thinner you can go the better 12mm units don`t cost much more at all and 2mm extra is worth it.

Another thing to consider is the sight line of the units. Check the thickness of the sight line on the units you wish to use against the rebate in the sash. Some units have very thick framing which makes it look rubbish if you have not allowed for it. My local glass guys would guarantee a unit with a sight line of 8mm but no smaller and only in foam edge. Sash lite units have only 5mm sight line .
I have seen some appalling looking replacement sashes, because people forget a few things. The scale overall is very important, and it doesn`t take much to make them look weird.

And of course as mentioned check the pockets for weight size and make sure you have room to almost double the weight.

ps.
I use the CMT sash set for 35mm sashes, it works well but you need to make a bigger rebate after for double glazing.


Ollie

 

[RogerS]

.....
First the point about the glazing. I would suggest you stay away from bevel or bead on the outside on the outside, it is not a good solution and usually fails quickly with inevitable water ingress.
.....

Ollie

if by that you mean a separate glazing bead or bevel that is pinned on after the glass has gone in then I'd agree with you. But if you are saying that a bevel or bead that is inherently part of the rail/stile/glazing bar is not a good solution then I beg to differ. Seen too many windows where maintenance after the event is none existent and any putty dries out and cracks letting in water.

 

[Ollie78]

RogerS.
I did generally mean a seperate bead, however even if the outside bevel/ bead is integral as suggested, I have seen many rot out from water just sitting in there unnoticed for a period of time. You are more likely to notice cracks in a face putty rather than small pin holes in a hidden back putty.

It is true that maintenance is key hence why I like the dryseal (even though its pricey) . It wont crack and really sticks well to the glass and sash, bit of a knack to applying it though.

Ollie

 

[Bradshaw Joinery]

Ive tried the dryseal working for another joinery shop. Honestly didnt like it. How are you using it? Same way as single glazing putty? Or in conjunction with bead?

I use beads on the outside, and have got no issues with it, could see there being issues with the likes of butyl putty and beads but i use beads bedded in onto silacryl.

Replaced some units after 4/5 years due to a break and they were still stuck in perfectly.

If maintenance isnt any good then The window will fail.

 

[RogerS]

RogerS.
I did generally mean a seperate bead, however even if the outside bevel/ bead is integral as suggested, I have seen many rot out from water just sitting in there unnoticed for a period of time. You are more likely to notice cracks in a face putty rather than small pin holes in a hidden back putty.


Ollie

I don't use putty! Use proper glazing silicon...no pin holes...no leaks!

......
I use beads on the outside, and have got no issues with it, could see there being issues with the likes of butyl putty and beads but i use beads bedded in onto silacryl.

...

Trouble with beads and silacryl etc is that it inevitably gets onto the surface of the bead where you want to paint it... AT least with an integral bead on the outside, you can paint it all up before fitting the glass then put in a decent bed of silacryl and fit the dgu in from the inside.

 

[Bradshaw Joinery]

i use silacyl (sovereign) its an acrylic sealant, that i bed the unit in with, then leave to set. it knives off really well to leave a crisp rubbery edge, it almost sticks the units in so seals really well, better than silicone, and is overpaintable.

has to be dry, and frost free for quite a while to use though, so is limitedin that respect.