Window boards and trim fitted before or after plastering?

[larrylamb11]

Be gentle with me here, as I have a lot to learn! We are currently extending and have had professional builders build a waterproof shell. I am doing first fix electrics and plumbing (with assistance from a couple of buddies in those trades) in preparation for bringing in a pro plasterer to plaster the whole lot.
Planning ahead, do I need to have the window boards and trims fitted (i.e the internal 'frames' that box in the walls) before plastering? or are they fitted after? At present I have the bare blocks of the inner leaf and the exposed wall cavity, then the outer leaf where the window frames are secured and am wondering how the plasterers will finish to the windows without a 'hard edge' to work to....

Also, electrical boxes and cables - I assume I can surface mount cables then cap with PVC capping for plastering over and had planned to cut in electrical boxes so they protruded no more than 13mm from the bare blocks. Does that sound right?

 

[Alastairreid]

we generally would fit window boards 1st depending on the detailing.
the rest you seem to have pretty well sussed.

 

[larrylamb11]

Should window boards be wood or plaster board? Obviously the 'shelf' I plan to do in mdf, but what about the sides and top of the window recess? Would you normally plaster into the window recess? Essentially what I have at the moment is the bare blocks of the inner leaf, then the cavity (there are 'cavity closers' in the vertical cavity) and a little bit of the outer leaf before the window - is it a question of bridging over this with a piece of cut plaster board in preperation for a finish skim? What would I bed the board on or how to attach to the blocks, plasterbaord screws? Do I need to treat or waterproof or treat the back face which will be open to the cavity?
Sorry for the questions, I have never attempted this task before and am not sure where to start! Thanks

 

[trowelmonkey1]

normally i would fit cavity closers in all the open cavities, cut them back so that you have enough to fix them to the brick and blockwork but exposing enough brickwork to stick dabs of plasterboard adhesive onto and then plasterboard.

so yes in answer to your question, fit board around all 4 sides of the reveal ready for skimming, you may want to get your spread to do this though, sounds like you are having your wall float & set? meaning your spread would use the edges of the boards to rule off, so the boards not only need to be fitted nice and square to the window frame and to each other they need to protrude out from the reveal enough to allow a backing coat to be applied to the wall flush to the edges of the board and deep enough to cover your capped cables and back boxes.

Ideally around 15mm depth, the fitting of these boards is important as the edges of these boards will dictate the shape (not the best word here but can't think of a better one right now) of the final wall, the edges of the board would then be beaded with thincoat bead before being skimmed.

this may be a little confusing to you i'm afraid if you have little knowledge of floating and ruling off and the importance of well set boards in the reveal may escape you and if wrong will need ripping off and re-doing before any plastering can commence.

this is just the way i do it, there are more ways to skin each cat as they say.

 

[1john]

bury all your cables in conduit into the blockwork, you can pull cables through the conduit if you ever need to at a later date say they were to get damaged, they will also be behind the render and be less likely to crack, i hate it when you see a hairline crack up a wall and know that the render is flush with the capping and the capping only has skim over it, you can even hear it when you tap it.

same for any pipework you want concealing, put it in pvc conduit so it can expand and contract within it.

Just my opinion mind.

 

[trowelmonkey1]

absolutely john! you want a good few mills of float over the top of anything on the wall! all the more reason to get the window reveals boarded spot on otherwise you'll be floating the wall out and when you get to one end of it with the pipes say you'll can end up too shallow.

 

[larrylamb11]

Thanks for the replies. Do you think I would be better to leave the window reveals for the plasterer to board out then so that they can get them plumb and the right distance off the blockwork? Equally the window shelf - leave that til after plastering?
I see your point about running cables in conduit - thats quite a bit more work though isn't it?

 

[Alastairreid]

i would leave the reveals to the plasterer if you dont feel confident.
i would fit the cill before plastering as well.

 

[larrylamb11]

Thanks for that, yeah I think I will leave the reveals for the plasterer - it isn't like I don't have plenty of other jobs to do!
Talking of window shelves/cills (what is the right term?), these are my windows -

Untitled

• larrylamb11
• 28 Jun 2010
• 1

Untitled

• larrylamb11
• 28 Jun 2010
• 1

Untitled

• larrylamb11
• 28 Jun 2010
• 1

In fact the frame covers the outer leaf of the wall, so I can only bed the shelf on the inner leaf (was planning to use expanding foam as seen elsewhere on here) - do you think I need to positively attach the window shelf/cill to the window frame? and if so how? Use the expanding foam there too? I am wondering if I need to be glueing a strip of wood on the underside of the window frame at the bottom to act as a 'shelf' for the edge of the window shelf/cill to sit on and secure to. How would you do it?