Glazing bead.

[Dave Plowman (News)]

I have a large custom made 2nd floor window which forms virtually the entire end wall of what was an attic room. All architect designed, and it does what I wanted perfectly. Lots of lovely light.

The load bearing frame is made from 4x2" timbers, dividing the window into

15 off 22inch square double glazed units (3 rows of 5)

The glazing units are fixed on both sides by what I think it called Staff Bead, mitred to fit and pinned in place.

Most of those beads on the outside have rotted. Despite having been painted regularly. Which isn't an easy job as there is a conservatory underneath which means scaffolding.

The structural frame appears to still be in very good condition. So I'm assuming water finds its way behind the bead and causes it to rot.

Any suggestions for a better material/shape for those glazing beads? PVC? Hardwood? Material cost isn't much of an issue given the overall costs of getting at them and painting etc. A bit of Googling shows companies who sell a wood/PVC mixture supplied primed. But I've no experience of this, hence the questions.

It faces almost due south and is as exposed as it could be. So recommendations for the best paint to use (white) would be good too.

[Capitol]

I'd go for some foamed plastic beading as used for trimming internally. You can get white, about 10mm x 10mm triangularish section. Probably a bit of acrylic filler would seal it in place, with a few stainless pins for good measure.

[Dave Plowman (News)]

Can it be painted over? Or does it come in white? The idea of a non setting compound oozing out doesn't delight. ;-)

[Dave Plowman (News)]

Is there a best buy brand? Do Toolstation etc sell it? What to ask for?

[Stuart Noble]

Accoya sounds like the business. IME no wooden beading stands a chance in a south facing aspect, whatever the species and however it's treated. Memories of various Magnet windows come flooding back

[Andrew]

The normal method for fitting DG units to a timber frame is to mount them dry-vented.

First seal the frame using something dulux weathershield high performance primer or their equivalent base coat sealer for hardwood doors or windows, or use the stuff the pros use, like Teknos

more details here :-

Then mount the DG units on plastic or fibre spacers leaving a 3mm gap all around. It is usual to actually stick the DG unit to the back of the rebate with double-sided butyl tape. Stick the glazing bars to the front of the glass using the same stuff and pin then to the frame with stainless stell pins. Run a bead of clear low-modulus silicon around the junction between beading and glass. Done.

Take a look at the pictures of Ron Curries bespoke timber windows for more details.

[Dave Plowman (News)]

So what you're saying is Phil's method of using a butyl glazing compound isn't correct?

[Dave Plowman (News)]

I'm easily confused. Tape may be fine for holding the glass in - which isn't the problem here - but isn't going to seal the bead all the way round. And it's short bead life which is my problem.

[Robin]

I'm confused as to why uPVC bead is deprecated.

[Dave Plowman (News)]

Me too. That's what I thought of initially as being a cure. But perhaps different expansion rates between PVC and wood make it a bad idea?

I've ordered up 100 quids worth of staff bead of the artificial wood kind from Mighton. Let's hope the product is better than their website. Took three attempts to get it ordered and paid for via Paypal.

[Andrew]

I assume this beading is on the outside ?. If so, then its just poor quality timber combined with the fact that it faces the prevailing wind, rain and sun.

Ron Curries clearance page lists some hardwood beading, if thats any help, but the main problem is Dulux Weathershield high performance primer is now water based (since VOC 2010) so using it on oily, not- so-porous hardwoods is tricky.

Pre-soaking new beading in clear cuprinol and allowing a full week to dry before sealing *all* sides including the cut end before pinning into place might extend their lives.

If they are rotting to quickly then water is seeping into a gap between two bits of wood or between wood and glass and it is just sitting there. Hence the reason why modern DG units in timber windows are dry installed so the any water that gets behind the bead can drop down and drip out under the bottom J moulding.

[Dave Plowman (News)]

Odd then the timber frame to the window has lasted very well. Originally when it was constructed, all the timber used came from the same merchant.

[Stuart Noble]

Small sections never last long, but when the bead is machined on the edge of a larger section (as it is in proper joinery) it has a much longer life

[Dave Plowman (News)]

The same staff bead is used on all the original sash windows in this Victorian house. Some has obviously been replaced over the years - but non has rotted in short order like this stuff.

[Dave Plowman (News)]

Not quite sure what you mean. The window was constructed on site by the chippy employed by the building firm doing the alterations.

[Stuart Noble]

The classic Vic sliding sash normally has putty on the outside. The staff bead is on the inside. Parting beads are invariably rotten at the bottom, mainly because they are a separate and very thin section

[Dave Plowman (News)]

Eh? You need an outside runner for the top sash too. I've seen staff bead used for that.

[Dave Plowman (News)]

What would you use for the top sash runner?