making up window sill

[trowelmonkey1]

hi chaps,

nice to be back, been working abroad for a while and had no flamin' internet

anyhoo, back to plastering this week, taking 4 rooms back to brick before floating and setting, now to the question: 2 window reveals/sills etc in one room have disintegrated at the mere threat of a chisel.

So i'm left with the cavity gap between inner wall and window now and about 70mm from brick to bottom of window, was simply going to dab on say 4 boards to build up the height, sound ok to you chaps?

assume some careful skimming will be fine to cover the board edges?

thx in advance!

 

[Richard C]

Welcome back; but didn't realise you had gone Don’t bridge the cavity or you may end up with a nice damp patch on the inner leaf under the sill, keep the inner & outer brick skins isolated. I generally use a lump of proprietary plastic cavity closer but you probably won’t want to buy a full length of that stuff unless your doing the whole reveal. You can use a lump of suitable width DPC or even a piece of plastic damp membrane under the first board but bridge the cavity to prevent any chance of damp in the cavity penetrating into the underside of the board. Bring it up inside between the boards & the frame & cut off flush before you fit the sill; assuming you are fitting a sill! I generally fix 2 x 12.5mm boards over the cavity (grab or drywall will do it) & then fix a 25mm proprietary composite sill over that using grab adhesive, that adds up to around 55mm or so all in & is generally enough; 70m is quiet a lot but I don't see any real problem in adding more boards under the sill. Composite sill boards are more expensive than timber but it looks so much better & has an integrated damp proof layer on the underside for good measure.

 

[trowelmonkey1]

wasn't away that long really mate, just felt like i've been away for ages not being on the forum for a while, when you log back in and see stacks of unfamiliar posts it makes it feel like ages!!

anyway, thx for the reply mate, comprehensive as ever

i think i'll get some cavity closer, not that expensive and straight forward to fit, can then just dab my boards over the top, having finished taking all the rooms back to brick today i've got 4 windows the same now, only sills but a length should just about do it.

will a single flange type be ok? as i may have trouble getting the second of the double flanges under the window frame.

 

[roughcaster]

Welcome back; didn't realise you had gone

Ohhhh no,,,, Rich,,,, how could you,,,,,,,,,, it's oor TM your talking about. Never mind,, i missed ya TM, good to see ya back.

Roughcaster.

 

[trowelmonkey1]

Thx RC! was beginning to feel left out and unloved

 

[roughcaster]

hi chaps,

nice to be back, been working abroad for a while

Not the Isle of Wight again!!!!

Roughcaster.

 

[trowelmonkey1]

part of france that is isn't it!?

Lisbon last week, paris next week (i know, name dropper) hope i can get some internet over there to stay in touch.

 

[Richard C]

will a single flange type be ok? as i may have trouble getting the second of the double flanges under the window frame.

You need to cover the top of the outer leaf to provide a damp barrier, you don't want the underside of the board or adhesive in direct contact or any damp could wick up into the board; if you cant get the outer flange of the cavity closer under the frame, trim it so it'll sit flush with the inside.

Thx RC! was beginning to feel left out and unloved

Sorry I neglected you so badly.

 

[trowelmonkey1]

hey that's ok RC2!

so a single flange closer will be ok then mate? would prefer to get the double and get some of the outer flange under the window but it isn't going to happen looking at them again today.

so think i'll go with the single if you think it's ok, and cover the bottom plasterboard ( the part over the cavity with DPC a fold it over and around the edges before sticking the second board on.

 

[Richard C]

Sorry TM, either I'm getting confused or I seem to have confused you ; I would use a double flange closer & if you cant get the outer flange under the bottom of the frame, trim it back (cutting disc is easiest) until it sits flush with the inside of the frame so the outer brick leaf, the cavity & part of the inner brick leaf is covered by the closer; you won’t a DPC under the boards as well.

 

[trowelmonkey1]

that makes sense mate, was being over cautious with the DPC, if you think i'm ok without then great.

found a company in town that sells cavalok closers which can be trimmed to fit cavities from 50-100mm so that makes life easier, as the cavities range from 50- 72mm, all different too.

be much easier if i could just fit without trimming the flange though.

one steep learning curve mate, glad i've got you boys here to help