Replacing Window Board

[EdTurtle]

Hi, I would like to replace the window board on a timber frame wall. I can see a bit of lead flashing coming from outside, and wrapping up to the window frame - sealed with silicone on top, and plastered plasterboard underneath. I have included a picture below, and a closeup (can take more if required). How would i go about fitting a wooden window board here, can i just put a small amount of expanding foam along the reveal, then press the board on with something heavy? Will this cause problems with water penetration or similar? We did have some water coming in the corners of the window, but since i put foam in the gap between the wall and frame, then sealed the lead to the window with silicone, the window is dry (the dark plaster to the right of the window is dry, just a different colour).

Thanks

IMG_20170924_161205

• EdTurtle
• 25 Sep 2017

IMG_20170924_161211

• EdTurtle
• 25 Sep 2017

 

[EdTurtle]

Any ideas?

Thanks

 

[Doggit]

That looks like cement in the second picture, so how is it a timber framed wall. Can you post a picture from outside, as the flashing coming through suggest the outside cill isn't fitted properly. You may need to cut some of the silicone away so we can see what the gap is like at the bottom.

 

[EdTurtle]

On reflection, the wall to the left is timber frame (dormer) and the wall underneath is thermalite - so yes, not timber framed - sorry my mistake :S I will get a picture of the outside tomorrow

Thanks

 

[Blagard]

Since there appears to be no reveal you don't have a structure for a window board. all you need is an architrave suitably rebated to accomodate the leadwork. Or perhaps you are thinking of fitting a shelf in which case use shelf brackets and again rebate the back of the shelf butting up to the window to go around the lead.

 

[EdTurtle]

Ok, pictures as requested:
This show the window from outside, so the wall underneath the window is thermalite as noticed earlier, and the wall to the left is timber, the wall surrounding the window is timber frame (hence my confusion)

IMG_20171001_073220

• EdTurtle
• 1 Oct 2017

This is the outside.

IMG_20171001_073416

• EdTurtle
• 1 Oct 2017

Those pictures helpful?

Since there appears to be no reveal you don't have a structure for a window board. all you need is an architrave suitably rebated to accomodate the leadwork. Or perhaps you are thinking of fitting a shelf in which case use shelf brackets and again rebate the back of the shelf butting up to the window to go around the lead.

I think i understand - cut a piece of architrave to fit - (so cut the back right corner off?) then attach to the plaster. Do i need to remove a bit of the wood from the back (at the bottom of the architrave so it sits over the led - i think this is what you mean by rebate the back?). If so, how would I attch this architrave?

Thanks

 

[Blagard]

I think i understand - cut a piece of architrave to fit - (so cut the back right corner off?) then attach to the plaster. Do i need to remove a bit of the wood from the back (at the bottom of the architrave so it sits over the led - i think this is what you mean by rebate the back?). If so, how would I attch this architrave?
Thanks

Yes you need to remove a bit from the back. It can be done neatly with a router although you could also do it with a chisel since it is nothing more than a long shallow mortice (in a similar way you let in a the faceplate of a lock).

Because your window is upvc you would fix to the structure below the lead, it would normally be timber (behind the plaster) in which case fixing is easy, alternatively you could use a grab adhesive. Once fitted and painted I would further consider a fillet of white silicone sealant to the top edge of the architrave if the joint is not tight as it will tidy up the gap. (no silicone before painting as paint on silicone does not work!)

 

[Doggit]

It's a dormer window, hence the wooden frame, and they've taken the lead flashing up under the window, so you need to make sure that this stays as high as possible when you fit the window board.

I'm not sure what your skills are like, nor your tools, but if we assume that you want a small lip of a window board, then I'd see if your local woodyard can trim a windowboard for you that's maybe 4 or 5 inches deep, and a couple of inches wider than the window frame. Then clean off the the silicone, push the lead up as high as the window, and then fit the window board underneath that, and gripfil it in place. You want to be able to push it in under the window and make sure the lead is above it, and then you'll need to glue a small peice of plastic trim against the window to hide the lead.

 

[EdTurtle]

Ok, thanks both. Was i wrong to put the silicone in between the lead and window then?! Should i have just pushed it tight against the window and left it at that? No other sealant at all?

You want to be able to push it in under the window and make sure the lead is above it, and then you'll need to glue a small peice of plastic trim against the window to hide the lead.

Can i seal this with a bit of silicone or not?

Thanks again

 

[Doggit]

The sealant really needs to be done from the outside, so you need to push the lead up from inside, and then hang outside and put the sealant between the lead flashing and the underside of the window cill. But is the window glazed from the inside, or the outside. By sealing from the outside, you stop water getting in to the sides of the reveal under the window cill.

 

[Blagard]

Ok, thanks both. Was i wrong to put the silicone in between the lead and window then?

That's fine. My own dormer is the same except my frame is hardwood. The outside part of the lead slopes away from the window cill across the tiles. There is no need for any external sealant. With the middle turned up behind the window it really does not matter that you used silicone there. With the middle OK, the most important parts are what happens to the lead at the ends. The lead under the window should extend beyond the window itself and soakers from the sides should be dressed down over that lead. It is nearly always the lack of detailing at the ends that causes water ingress.

 

[Doggit]

I agree with you Blagard, but it sounds as though the detailing wasn't done properly, otherwise the water wouldn't have come through.so unless he gets a roofer up there to check it out, it's going to require a bit of sealant outside to keep things watertight, as he won't now there's a leak from yourside untill the dormer start to rot.

 

[EdTurtle]

Ok, all makes sense, i'll get it sorted. The roofs on these houses werent done properly at all, the flat roof slopes back towards the house for one, and as you say the detailing at the edges is more than likely rubbish on all the windows. I shall get outside and put some extra sealant in the gaps!

Thanks for all your help

 

[chappers]

Back to your original question looks like you have enough reveal to get a little stub sill on there say 50mm or so deep. Cut out all that gash silicone fit the sill rebated around the reveal. Glue it down or better still fix with a couple of screws and plugs if you have enough reveal.
Not sure what all this hooha is with the lead and rebating architrave. Just trim off the lead flush with the window tidy up the reveal and paint the lot.
No point weathering the thing on the inner side of the frame do it on the outside

 

[bobsuerita]

as above