What top coat on cement rendered wall?

[christopherbmas]

I removed the vermiculite ceiling in my bedroom in this 1980’s apartment. Wow what a job… probably 500kgs of plasterboard, wire and cement removed. In hindsight a dropped ceiling would have been the way to go but you live and you learn during DIY renovations.

During original construction, builders have rendered the ceiling into the walls with a “chicken wire” prior to applying the vermiculite; as a result the walls were damaged/tops lowered while removing the ceiling and therefore needed to be filled up to prevent adding a cornice and allowing a square set ceiling. I did that using “Australian Builders - Mortar mix with sand cement and line”.

FYI my intention is to do a “square set ceiling with gyprock sheets butting up to the cement rendered wall, hence why I opted to remove the ceiling originally.

I now need to add a blending/leveling top coat to level the mortar and square/flush the wall with my fill. I attempted to do this with a thinner coat of the same mortar mix but as it was so thin it just crumbled away and with what remained it’s not sturdy and can be wiped away easily.

I'm thinking of using Gyprock CSR 20kg Hardwall Plaster and Australian Builders 20kg Hydrated Lime. What’s your thoughts on this?

And if yes, how long do I need to let the mortar mix already applied cure? Also if you think this is a good option, how would you prime prior to adding the hardwall plaster?

What do you recommend for getting the texture as close as possible to the original wall prior to paint? Any help is appreciated… What I thought would be a relatively simple job has become a bit painful.

 

 

[JacobZ]

Hi @christopherbmas,

Thank you for your question and welcome to the Bunnings Workshop community.

Apologies for the late reply, as it is not a very common scenario, allow me to do some investigation with our suppliers as to the best method of going about your project.

In the meantime, allow me to tag some of our knowledgeable members to see if they have any advice for this scenario @Dave-1, @Nailbag, @Jewelleryrescue. 

Jacob

[Dave-1]

Good Afternoon @christopherbmas 

Mmmmm This is something that is new tome Interesting for sure. All I can offer is multiple thin layers to slowly fill the area in and blend it. Days drying inbetween maybe. I am not sure what product I would recomend as Ive only done a few small patches of leveling plaster dips and joins out. 

Will wait and see what @JacobZ comes back with from the suppliers as it would be good to know as well

Dave

[MitchellMc]

Hi @christopherbmas,

There doesn't appear to be any specific information available through our suppliers that deals with a corner transition from a rendered wall to a plaster ceiling.

I'd recommend you repair the top half of the wall with render and use a sponge to mimic the wall's texture. Once you've completed the repair and the render has dried, you can install your plaster sheets. You might wish to use a stopping bead on their edges where they meet the wall. After the sheets are installed, you'll either plaster over the edge of the beading and/or run a bead of Sikaflex 11FC between the beading/sheets and the wall. The purpose of the filler is to allow the transition between the rough wall and the smooth beading/sheets.

Please let me know if you have any questions.

Mitchell

[Nailbag]

Hi @christopherbmas I am leaning towards @Dave-1 suggestion to blend in another product with layers until you reach the desired finish. A couple of thoughts on product would be Dulux's textured paint, which I have used a few times and would allow multiple layers to match the original finish. The other would be one of the pre-mix render products, though this may be too course straight out of the tub?

Regards, Nailbag

[christopherbmas]

Much appreciated @Nailbag @MitchellMc @Dave-1 @JacobZ, great suggestions. I will give it a run. Plan is to do another thin coat of render followed by the textured paint x a few.

Regarding the square set ceilings, I’m indeed going to use a stopping bead and plaster @MitchellMc.

thanks all, photos to follow

[MitchellMc]

Keep us updated @christopherbmas, and please reach out again if you have further questions.

Mitchell