uPVC Window fixings - large window - how many?

[Tim Watts]

Hi,

New uPVC window arrived today for daughter's bedroom (that's teh last of the iron single glazed windows going).

It is 1480 wide x 880mm high.

Side fixings are no problem - I reckoned on 3-4 each side of my personal favourite Fischer FS 8x100mm frame fixings with caps. All into solid brick.

However - how many should I be looking to do along the top and bottom?

I've seen some forums saying "none".

The top could be fixed into a "beam" of 1.5 x 3" high timber (not a lintle). TBH the window frame is probably stonger than this wood anyway, but a few SS screws are easy enough. Anything more robust would need some steel straps back to the inner brick leaf - that's a bit more fiddling than I'd like...

The bottom is harder - big (30mm ish) gap then clay tiles then brick. Reckon I could put some long frame fixings through this lot with some difficulty of not cracking the tiles *and* drilling against a 20 degree slope. I'm wondering if it will contribute that much compared to the foam... The windows do have immensely strong steel inside.

I will of course be foaming round afterwards (where space permits - these windows should (hopefully!) be a "nice fit" into the unrendered brick leaf and the massive gap at the bottom will be covered with trim strip.) The final sealing will be some acrylic frame sealant. That set of techniques all went very well on some tiny windows I fitted last year, but they were tiny so not many fixing needed.

Cheers

Tim

[<me9]

I was researching that point last week for a window 1790x1050. The document I found (can't locate -- on other computer[1]) reckoned 2-3 for that height, and similar spacing for top and bottom if possible. It pointed ot that the frames were strong, and would be ok to 1200(IIRC) unreinforced top and bottom, or 1800 if reinforced with alu/steel, I can't remember which.

Reinforcement -- see above.

It also said fixing with foam is adequate in the absence of something to drill into.

Of teh professionally fitted windows I have, up to 2400x1350, none have top/cill fixing, although I've had to fill the gaps round them with foam, maily to stop ghostly whistles in windy weather.

that's why (if I replace the wooden DG ones) i'll do it myself. Seals are starting to fail in the 20-25 year old wooden DG windows, cheaper and easier to replace with PVC and no need to paint!

[1] will post link when I find it on other computer.

[Dave Liquorice]

3 or 4 over 880mm seems a bit excessive. Our windows are the best part of 2m high (I'm 6' and can stand upright in the reveal without worrying about hitting my head) and only have 4 fixings. For 880mm I'd go for two each side around 200mm down/up from the top/bottom. 1/3rd spacing for a couple more along the long side top and bottom. With good strong packing in the 30mm gap(*) to stop the fixings distorting the frame when tightened.

(*) I guess there must be a good reason but seems a bit excessive to me.

[Tim Watts]

Thanks for that. I just also found a document that advised against bottom fixings as you penetrate the drainage channel - and if you

*must*, to seal the screw with silicone.

Perhaps I'll try without any bottom ones. My metric is "fairly solid without foam" - if that passes, the foam is optional and just adds to the overall rigidity (and lack of howling gales!).

Given the tiles and their slope, probably be easier to drill the bottom if needed with the frame solidly fixed anyway.

[Tim Watts]

Probably. I'll do 3 up each side - I always like a bit extra (ooh err).

See my comment to BThumbs re bottom. But yes, I'll certainly start with the top - your 2 sounds like a good bet - that's one dead centre of each opening. I have a massive selection of graded plastic frame packers - I always have the fixing bear down on something solid :) Just need to make sure I have the correct selection of glazing packers - They were generous on bridge packers ('cos I nagged them) but they've sent me only

2 thicknesses of shims. Luckily I think I have loads left over from the last window in every thickness. Those are a PITA to buy 'cos most sheds don't do glazing shims and they're sold in boxes of 1000 online!

I'll see how it goes. The windows from Croft Glass are bloody strong[1] (as I found out last time when I tried to drill the holes in the frame - new HSS drill on shopping list this time!). The windows our old landlord had put in, the bloke just pounded an SDS masonry bit straight through (probably tinplate reinsforcing). Don't think you'd do that with mine - at least 3mm steel box in there.

[1] They're expensive too. I might go with windowsanddoors.co.uk for the upstairs - security and robustness is slightly less of a concern - not that I *know* that the latter are weaker in any way, but if they are, I won't care. About 30% cheaper though...

Cheers

[<me9]

Found the documents Not exactly what I said, but you'll find them on the links at the right hand side of this site. I found them quite useful.

Their prices would be quite reasonabe if I were nearer, or ordering more than one window, I'll have to chase up locally.

[sm_jamieson]

Be careful with that one. I drilled my PVCu french doors for mounting, with a HSS drill, and it must have dislodged the metal reinforcing strip in the door, which proceeded to jingle every time the door was closed. After fiddling for ages with a coat hanger and extra holes to find the problem and pack it with something, the only way I could stop the jingle was to bend the frame slightly by tightening the middle screw up without packing ** I ended up with a bend of about 5mm half way up the vertical. Has caused no problems, but a rattle / jingle on every door close would have driven me insane !

** come to think of it, I could have filled the profile with foam. But we all know the story of the canoe (see uk.d-i-y wiki) !!

Re: top fixings, I drilled my cavity wall lintel to take a long self- tapping screw in the centre at the top. I've seen may doors that wobble in the middle when shut. Of course, the foaming stabilizes the whole thing too.

Re: bottom fixings, I always fix and level the sill to the brickwork (silicone in the holes) and then screw the window to the sill. I dont like a long frame fixing right through the frame, sill and into the wall.

Hope that helps, Simon.

[Tim Watts]

On an aside, I found this video which seems most helpful:

always had trouble with that - those little bridge packers are buggers for wandering off while you put the glass in. I see the trade solution is glue them in with silicone first. Makes sense.

Back to the frame... It's in, and boarded up tonight. Getting too dark to do glazing properly.

Little bit of buggering about chiselling bits off the wall here and there (non rendered wall - need a good outside fit - don't like to use trim unless necessary).

Went for 3 frame fixings up each side, 4 SS screws in the top into the random bit of wood. Sides are rock solid, so's the top. Bottom was a bit wibbly and I ended up with a 2" plus gap. Due to framing over a 20 degree sloping clay tile cill, I always get a fair gap at the bottom. This usually gets foamed and here I do use trim. On the current window, the inside tiled cill is higher than normal, so as the frame sits on that, I got an even bigger gap.

To solve this, I cut out a pair of tight fitting oak blocks (from scrap bin) with one edge sloped to match the cill. Drilled through the frame at about 1/3 and 2/3 along the bottom, through the blocks and into the cill. Slavered the top of the blocks with silicone and popped the frame fixings right through and tightened down. Seems to have done the trick.

Hence ran out of time to glaze. Never mind - weather's nice tomorrow...

I'm in two minds whether to mortar up the bottom as the gap is massive or foam it. Probably the latter. Looks like I'll have to nip into the shop and get a length of even wider trim for this one.

Overall though, the window was a good fit round the top and sides - 5mm gap to foam and seal.

Not too pleased about one thing though, having praised the suppliers before. I specified egress hinges and it seems I appear to have easy-clean hinges. Not only that, the hinge screws aren't holding too well (seem to be into plastic only - not sure how... I'll have a word and see if they can supply the correct hinges for me to swap (assuming it's not a technical problem due to the fairly wide casement).

Easy enough to remove them - I took the casement out anyway for better drilling access. That's when I noticed they weren;t holding well. No I didn't use a power driver!

As for the screws, I guess I can switch them to the next size up - only self tappers.

Photos tomorrow of most stages...

[David WE Roberts]

I've been watching with interest as I am about to finally fit my pair of B&Q windows. One thing - if you were contemplating filling a large gap below the frames with mortar, would it have been an option to lay and level a bed of mortar before hand, let it cure and then stand the frame directly on that? Or at least, have a 5mm gap for the final sticky foam but the rest mortar?

I have some minor adjustments to make vertically and am trying to decide if a plastic frame extender (10mm deep) screwed to the top would be a better option than a small bed of mortar at the bottom or some extra foam.

Cheers

Dave R

[Dave Plowman (News)]

I have two rather wider than that - from Screwfix - and the original fitting instructions only mentioned side fixings. And given I have pre-stressed concrete lintels above I'm pleased about this. The important thing is the window should sit on a good solid level base, and any fixings not distort it. The foam used for gap filling will hold it solidly.

Two fixings per side were as supplied.

[Tim Watts]

I agree if the gap is fairly small (say < an inch or so) - foam will pack that and get a good grip - especially if you are fitting a window with cill into an all brick opening. I was reusing the original tiled cills and short of building them up (don't have any spare clay tiles) there wasn't much I could do about the arrangement.

That >2" gap under mind I felt, after fitting the sides, did demand a little extra than foam alone. Window was actually supporting itself fairly well on side fixings alone, but the middle was a bit wibbly. I think bolting through 2 wooden blocks was a good idea - but it's not a very typical opening that one.

[Dave Plowman (News)]

I'd pack the window using temporary wedges so the gaps top and bottom are reasonably equal and it's level, then pack mortar between it and the cill. Let that go off, remove the bottom wedges and fill those gaps with mortar.

Fixings as required to the sides.

Fill all gaps with foam and let it go off. Cut it back about 3/4 in below the brick and run a mortar fillet over it.

[Man at B&Q]

But why such a large gap, did you measure correctly? It should be no more than a few mm all round and the window should be *well* supported on suitable spacers that take the weight of the window. A couple of side fixings if you want but foam will hold it.

MBQ

[Tim Watts]

That wasn't possible: Have a look here:

see the internal cill behind - I needed the window frame to sit on that. For some infathomable reason, some mushroom had made the external cills much lower. If I'd had some clay tiles, I might have built that up

2 more courses.

Anyway, it worked out OK with those oak packers there. Now the foam (built up in layers) has set, it is incredible firm and rainproof.

That is another option.

Cheers

Tim

[Tim Watts]

Of course - several times to make sure(!)

See my reply to Dave - there's a photo link in there, or from the URL down below. This isn't your typical Barrats house with simple rectangular openings. This is the 1950's when builders were creative with whatever that found lying around ;-#> I have to be grateful the hole was even square (mostly)!

The fit is as perfect as the opening will allow - in fact I have 5mm sides and top which need nothing more than a bead of acrylic to finish off (and foam of course, injected mostly from inside).

If you look at the photo, my house generally has cill like this end section:

= internal tiles

• Bricks

= Outside tiles, 20 degree slope.

====== ***** ***** === ***** **=== ***** *****=== ***** *****

Anyway, in case no one saw my post last night, the job is done bar trimming (when it stops raining!) and here's the process:

bought strong windows that have decent steelwork in them - in fact they proved capable of hanging on side fixings alone. The only niggle was slight front-back wobbliness in the midspan. Foam would probably have been enough (they do partly sit on the internal tiled cill - but only just - I would have put them another cm back if I could but then the fixings would have been right on the edge of the brick which wouldn't have worked).

2 fixings through the bottom supported on solid wedges which are now buried in foam did the job :)

Thanks again for the general advice on number of fixings - I went for a few more (I always do) but it worked really well, despite the non standard opening.

Someone may ask - why not have got windows with a psuedo-cill (I forget the name, but it's a cill that doesn't protrude forward of the frame - smaller than a stub cill) and mount the frame in front of the internal cill in the same way the iron one was. Bearing in mind the uPVC frames are 3 times thicker than the iron frame...

Possibly - if I had had the luxury of taking the old iron out first to see how far the internal cill went forward (it could easily have gone another inch). I hadn't so I couldn't - so had to make some inspired guesses about the structure in the frame area. The other thing is it would have brought the frame too far forward WRT the wood at the top. Adding trim there would mess up trying to remove that soffit down the line when I get round to replacing it.

Cheers

Tim

[<me9]

Don't you believe Barratt's have simple rectangular openings, anything but in this Barratt house. Inner cill was found to be resting on thin air and a couple of broken bits of floorboard as (vertical) packers. Outer bodge covered with weatherboard. At least it made vertical adjusment easy. All the

6 foot windows in the house were a standard width (6 feet imperial), except the one I didn't measure because it was difficult to access. That was the one I got the replacement for, which was 1800mm.

Fortunately with wooden frames I was able to plane enough off each end to get it to fit.