Any FENSA folk in here?

[Tim Lamb]

The window installer fitted the frames in my extension and then went on holiday. A week or so later I realised the builder and a mate were fitting the glazing units themselves.

From various discussions in here, I have realised that window fitting is not quite as simple as just whacking the nails through the beading and walking away. When I queried the lack of silicone sealant, I was given a load of guff about drainage and how the beading was self sealing. Afterwards I noticed that some frame seal had been applied to the bottom bead only.

What is the proper sequence of fitting? These are softwood frames, sealed double glazed units with diamond lead finish on the outside leaf. The softwood beads were pre-cut and supplied with the frames.

I am sure they got the glass the right way round and put spacers underneath .......

regards

[the_constructor]

Although I would be extremely frustrated at the actions of the builder, I would leave a message on the DG fitters answering machine for him to contact you as quickly as possible upon his return from holiday. James

[Dave Plowman (News)]

The important thing with double glazing panels is to avoid stress on them

- both when cold and heated by the sun. This usually means making sure the frame is fitted square and not distorted by the fixings - which there's no need to anyway as the foam sealer will hold it securely. If the glazing is fitted afterwards the same applies - it should be bedded in a flexible 'putty' all round and between glazing bar and bead - so it isn't stressed with any frame movement due to heat or moisture.

[RubberBiker]

You mean the sealed units have silicon rubber beading strips round all

4 sides between timber and glass?

Or you mean you have external timber beading, and they just nailed the timber against the glass?

If the latter, they've got to be kidding! Moisture will *soon* be inside.

Is the timber fully finished on all sides of the beading and within the glazing recess?

Again, if not there's not the rot's soon going to be in there.

My french tilt-and-turn units are built with silicon rubber beading strips, and have no other sealants on the glazing. The openers are screwed together wooden components with u-channels for the sealed units (so no separate timber beading for retaining the sealed unit), and can be dismantled to replace the sealed unit. They also have drainage channels through the timber from the space around the sealed unit, and all the timber components are finished on all sides - prior to assembly.

The windows I made myself, I used butyl rubber glazing tape (a non- setting 3*10mm malleable strip), and again attention to drainage from around the sealed unit, and fully finished all the timber components prior to assembly.

I'd also be concerned about how diligent/experienced your builder was about getting a perfect seal between timber and glass all the way round with whatever technique they used.

[Stuart Noble]

For "flexible putty" read mastic, or something acrylic, rather than linseed putty.

[Tim Lamb]

In message , RubberBiker writes

That may have been what the builder meant but there aren't!

Exactly. Worse than that, the diamond lead holds the beading away from the glass by about 2mm!

Yes.

Where do these drainage channels drain? The lower bead is lipped to form a drip and fits tightly against the window frame.

Yes.

The original windows here, fitted prior to 2002 (fensa rules) had a low modulus silicone seal applied: sealing the glass to the beads, after the glass and beads were fitted.

There are no drainage arrangements for either vintage of window.

regards

[Cicero]

==========================================

The method you describe would have been normal practice in the days of single glass / wooden beading, although most windows would have been finished with 'nibs' and putty. The theory was that the small amount of rain water that entered the top or sides of the window would drain down and be shed by the putty seal along the bottom beading.

I doubt if the same method is really acceptable for double glazed units which aren't intended to be exposed to excessive moisture.

You could ask the double glazing manufacturer for their recommended sealing method in wood frames. In any case you could check that there are drain holes in the bottom rebates.

Cic.

[RubberBiker]

The french-made tilt-and-turn drain from the sealed-unit rebate, through a long slot centre-bottom of the rebate, into the opener rebate, and from there through a pair of drain-holes to the exterior of the frame (being tilt-and-turn, they are inwards opening, so the opener rebate is more vulnerable to rain penetration).

My own (all fixed lights) drain down through the rebates to the unit below (they're stacks of 4 units in tall/narrow chapel windows), and then onto the sloping stone sills. (I figure there's going to be very little moisture penetration until the frames are in a sorry state, so that so long as there's *some* route to prevent the sealed units sitting in a pool, then all will probably be ok).

[PeterK]

In the past 3 years I've fitted pre-glazed softwood windows by Jeldwen and another major UK manufacturer plus unglazed frames from one of them. The guidance received for fitting the units was double sided glazing tape (neoprene?) on the inside rebate. Plastic glazing blocks on the bottom. Offer up the unit and ensure equal side clearances. Fit glazing bars (brass pins) with a small bead of low modulus silicone sealant on the glass edges. There was also an opinion offered that the glazing bars could be fitted dry and a minute bead of sealant along the glass/timber borders. I treated the glazing bars and rebates with Sikkens wood stain before fitting. So far they have survived 2 winters on south & west facing windows in a very exposed situation (horizon 100% visible and between 5 and 15++ miles away) with no signs of any "wear". Also the bottom glazing bar is a "L" shape with plastic spacers to hold it above the frame rebate and ensure drainage (I hope!)

In the past I've had solid bedded units fail in 3 years and the manufacturer of the units AT THAT TIME (System3 Ltd. Denton Hall Farm Road, Denton, Manchester M34 2SY. Tel: [phone] Fax: [phone] E-mail: [e-mail] Web:

said words to the effect "Timber frames over 12mnths old not warranted".

I'd give them a ring and ask for "technical" and pose your question. I think they supply most independant glass merchants in the NW England. So a "my grandmother in Wigan is worried that they didn't use putty...." opening should avoid any who supplied/fiitted questions.

The timber reasearch and development association (trada.co.uk?) may have some info.

Peter K

[Tim Lamb]

In message , PeterK writes

This sounds exactly what should have been done. I think they need to start again. Pulling the beads is likely to wreck them. Maybe the frame suppliers can supply beads only.

Thanks. I'll phone around on Monday and see what can be done.

regards

[Stuart Noble]

It's a relatively simple matter to bed the units in an acrylic seal and re-fix the beads. If you really want to add some protection, melt candle wax on the inside of the bottom rebate. Softwood windows have a short lifespan unless they're set into the brickwork like the typical sliding sash design. Anything flush with the surrounding brickwork and/or facing south/west should really be hardwood or plastic.

[Dave Plowman (News)]

Indeed. Wish I'd known that when I had a larger window fitted to the kitchen years ago. The builder fitted it flush with the outside wall - despite it replacing a sash type. Needed constant attention for rot before I finally replaced it with a UPC one.

[Tim Lamb]

In message , Tim Lamb writes

Hmm...

Local double glazed unit supplier says...

Butyl strip round inside of rebate.

Spacer blocks to support the glass

Fill voids with low modulus silicone

Second layer of butyl

Brass pin beads

trim off butyl below bead

seal with low modulus silicone.

regards