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Can you use plasterboard for window jambs, reveals, sills?

hey guys - i've been here asking a few related questions and some of the helpful answers are now leading me to this question.

I had new PVC windows fitted but i refused to have any timber surrounds.

After browsing the internet, most suggestions are to use plasterboard - But now it has been pointed out that any moisture resting on the plasterboard is not healthy so i would like to ask for advice on what i should use/do?

There are also suggestions to use insulated cavity closers, but i cant see how i would fit them as the windows are attached to the outside wall (double-brick). I don't want to use wood anywhere - Can i use PVC or something moisture resistant instead of the plasterboard?

As always, your help is massively appreciated and my hurting head will be forever thankful 🙏🙏😁

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Comments

JacobZ

Hi @elbow,

This is a bit of a challenge you've given us. The only alternative I can think of, outside of timber, is render.

Could you please clarify your hesitation towards using timber? In this context, timber seems like the optimal choice for finishing off the windows. It provides a robust surface that, when properly painted, offers superior weather resistance compared to plasterboard.

I'm eager to hear the reasoning behind your reluctance to use timber. In the meantime, I'll also reach out to some of our knowledgeable members for their input: @Dave-1, @Jewelleryrescue, @Nailbag.

Jacob

elbow

https://www.workshop.bunnings.com.au/discussion/comment/36459#Comment_36459

Hey Jacob Re the wood - we live in the blue mountains and want to avoid the possibility of termites as much as possible and also maintenance - The previous architraves were a sight to behold and a lot of timber, some of which had shown signs previously of termites and rotting. 🙂

EricL

https://www.workshop.bunnings.com.au/discussion/comment/80466#Comment_80466

Hello @elbow

Thank you very much for the explanation on your reluctance to use timber. Would it not be possible to safeguard against termites say a chemical barrier placed in front and around the window? Aside from the suggestion of rendering, have you considered putting something like DECO Western Red Cedar Deco Clad End Cover Channel.

It might be possible to assemble it into a square to act like a window frame, however, my only worry is that it might not be deep enough to cover the gap you currently have.

Let me call on our experienced members @TedBear, @diy_hausdesigns and @JoeAzza for their recommendations.

If you have any other questions we can help with, please let us know.

Eric

elbow

https://www.workshop.bunnings.com.au/discussion/comment/104766#Comment_104766

Hey Eric, thanks for the shout.

I'm not a fan of the chemical barrier stuff as I've read that it can be hit n miss. I'd rather just avoid the little blighters altogether 😁

the cladding would break the bank - ive got a lotta window to fix up! 😪

Hopefully the other chaps can advise when they get a moment, massive thanks Eric 🙏

Dave-1

Morning @elbow

Following on with some more ideas 🙂

How about Ekodeck 137 x 23mm 5.4m Riverbank Red Designer Edge Board Composite Decking as the window sill and plaster the vertical and the top?

I wouldnt normally suggest it as its a composite with plastic in it but termites wont go near it is my main thinking.

Will keep mulling it over 🙂

Dave

Noyade

https://www.workshop.bunnings.com.au/discussion/comment/36476#Comment_36476

That looks good Dave.

Do we have the dimensions?

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/80475#Comment_80475

Morning @Noyade

hahahha I just realised you were asking for dimensions for the window sill and edge 🙂 You know when you have too many things going on in your mind 🙂

Just to have the info at our fingertips the ekoboard is

137mm * 23mm plus 5.4m long

Dave

elbow

https://www.workshop.bunnings.com.au/discussion/comment/36476#Comment_36476

Hey Dave

Nice idea - i'm still concerned about whether there is a possibility of damp coming thru the plaster. I have seen this in the past but only occurred to me now i have to do it myself 🤔 The other thing is i really just want a plaster - look around the whole window, so no wooden sill, at all. It seems a lot of youtubers go with plaster-board all round but my concern is still the damp - i have no experience on what happens if i do use plasterboard everywhere and should i be concerned about the damp? still confused about that 😕

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/80480#Comment_80480

Afternoon @elbow

I am not particulary worried about vertical surfaces with moisture, just window sills/door ways ect that have the potential of water sitting on a flat surface.

Garage lining for stud walls stage 1 step 3 shows how I have put plaster up to edges on brickwork but always have timber on the bottom. I have attached plaster directly to brick to save space and its still there 3ish years later 🙂

As to the look around the window you could still do with timber/timber pieces, you could source thnner timber (12mm) and paint it the same so it looks like plaster but has a better stand up to water. Just remember youtubes showcase perfect stuff, generally they dont show what happens down the path. I get my ideas from them 🙂 but ballance that out with what I think cna happen.

Dave

elbow

https://www.workshop.bunnings.com.au/discussion/comment/104770#Comment_104770

Hey Dave, love your project and thanks for sharing, even the mistakes. 😁

From what i can see, your main concern is about water sitting on top of the sill - are you assuming that would be from say, a spillage or even condensation running off the window onto the sill?

Noyade

https://www.workshop.bunnings.com.au/discussion/comment/104768#Comment_104768

Hi @Dave-1

"hahahha I just realised you were asking for dimensions for the window sill and edge"

Yes - the dimensions on the window as indicated - was what I was after. 😁

Do you have them @elbow ?

My vote would be...no - to plasterboard/gyprock.

If we're voting. 😁

elbow

https://www.workshop.bunnings.com.au/discussion/comment/119469#Comment_119469

yeah the window to the inside edge is 100mm and there is another 40mm to the edge of the outside edge of the wall - total 140mm from out wall edge to window

so, no plaster anywhere? ☹️

TedBear

https://www.workshop.bunnings.com.au/discussion/comment/128363#Comment_128363

Hi @elbow , I can see that you certainly have a problem to solve here. Those windows are normally mounted in a window opening has already been lined (usually with timber, but could be another type of cladding).

If the possibility of dampness on the bottom sill is what is making you hesitant to use plaster, then maybe you can create that edge at a slight angle, so that it slopes downward, inward a little.

Water should be kept out of that area by the sealing of the windows, so there shouldn't be much, apart from a possible few drops of rain if the window was left open.

Perhaps you could render that inside opening with cement to form flat surfaces to which plasterboard strips could be attached. (Glue some mesh over the cavities between the walls so the render has something to stick to. Liquid Nails.)

You could seal the brickwork before rendering to prevent moisture from the walls if that's a concern, but given that your existing walls aren't affected (I assume) then you probably don't need to. If you are concerned about moisture traveling in the opposite direction, then seal the cement render before plastering over it.

Then, when all joints are filled, paint the lower sill at least, with a waterproof paint.

(Ideas created without seeing the actual job, of course.)

elbow

https://www.workshop.bunnings.com.au/discussion/comment/134092#Comment_134092

thanks for coming back.

I originally thought to just use plasterboard for all sides but i saw mentioned about about moisture created via heating on inside and cold outside temps or cold air coming through the gaps in the wall cavity which is why i posed the question. I don't want to be doing a job to then have to rip it back down in a yr or 2 because the plasterboard gets ruined by moisture over time. From what i'm understanding, you are suggesting plasterboard would be ok in normal circumstances?

Nailbag

Hi @elbow what about filling the cavity with expanding foam and trim. Line the inside reveal with this aluminium flashing for increased moisture retardant. Then use Aquacheck Gyprock which is designed for wet areas like bathrooms and square-set finish the reveal. This is essential the process I used on a small window that copped every bit of the weather on the open side of a hill. The outside wall was flashed and rendered.

Regards, Nailbag

Screenshot 2024-04-09 at 9.36.39 PM.png

elbow

https://www.workshop.bunnings.com.au/discussion/comment/36509#Comment_36509

Hey Nailbag

thanks for your response. i like this.

Re the foam - when you say 'trim', do you mean cut off the excess?

Do you have a link to the aluminium flashing? i'm not sure what i would need.

And when you say, "square-set finish the reveal", what do you mean exactly?

Apologies, i'm way down on building language so i just want to be clear what you mean 🙏

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/80487#Comment_80487

Apologies @elbow

Yes spot on with the expanding foam and if you haven't used it before check out a few YouTube videos so you can see what little you need and how much it will expand. I would tape up the inside of the window frame and use some cloth tape over the cavity openings as this will assist containing the foam as it will continue to expand until dried.

You have two options with the flashing, plastic or what I use which is the aluminium as I can use it on other projects and bend it to suit the applications.

And lastly to "square set" basically means to have the edges of the plasterboard exposed which gives it a clean modern look over tradition architraves around a window in your case or cornice. So the picture I supplied was the window finished off by a plasterer ready for painting.

Hope that all make sense 😁

Regards, Nailbag

elbow

https://www.workshop.bunnings.com.au/discussion/comment/104782#Comment_104782

Hey @Nailbag

thank you so much for your explanation and links - super helpful!

one question tho - re the square-set - from what i understand that is to push the plaster upto the window frame which i had intended but i wasnt quite sure if your were talking about that edge or the edge facing into the room - i was going to use some beading for that?

EricL

https://www.workshop.bunnings.com.au/discussion/comment/119475#Comment_119475

Hi @elbow

I'm thinking putting beading would make the edge stronger rather than just having it as plain plasterboard, but if it gets chipped it would still require the same type of repair procedure. Let me tag @Nailbag to get their opinion.

Eric

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/119475#Comment_119475

Both the corner edge to the several and up to the window frame @elbow . Clean finish that your plasterer can sort as its a pretty standard finish this days.

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/128367#Comment_128367

Shouldn't be an issue at all @EricL @elbow to have the edge finished without any timbers. The corners/edges like any other corner plasterboard edge are reinforced with external metal angles. Of course if they get a good knock they will be damaged just like any other edge. This is a standard edge for any plasterboard finish square-set or not.

JoeAzza

Hi @elbow, all great suggestions in resolving your window surrounds, after reading all the comments, you certainly do not want to use timber , especially going to to expense of using pvc windows, I found some websites that use and supply pvc reveals, please see attached, I have also attached a pvc edging if you want to go the way of rendering and hard plaster.

https://www.upvc.com.au/products/reveals

https://www.networkbuilding.com.au/shop/pvc-reveal-trim-60mm-3-5mm-build-3000mm/

https://youtu.be/jWa0R8PeiAg?si=lIe5od1rzQhsiOtQ

Hope these will help you to decide.

elbow

https://www.workshop.bunnings.com.au/discussion/comment/36530#Comment_36530

super awesome, thanks for the links and advice 🙏

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