How to make indoor rendered walls smooth?

[dstanley]

Hi there 👋🏻

We are renovating our apartment and I'm looking to give the walls a bit of a refresh as they are currently quite bumpy and uneven.

I'm not sure of the material or finish of the walls but they are solid (not drywall) and I would guess painted cement render or lime render? The existing paint appears to have been applied directly to the cement/render and is not plastered.

Any suggestions for how to smooth the walls before painting? Hoping it won't be a full plaster job!

I've attached some photos of the wall showing unevenness and scraped away some of the existing paint to expose the render. (We are removing the wall I have scraped the paint off so no need to patch up).

Thanks in advance.

Daniel

 

 

[MitchellMc]

Welcome to the Bunnings Workshop community Daniel (@dstanley). It's terrific to have you join us, and many thanks for your question about smoothing a rendered wall.

That's a fairly typical level of finish for concrete walls in an apartment. I suspect plastering over the existing paint wouldn't be an option as it will fail to adhere adequately. The only option that comes to mind is having the walls ground or sanded back to a smooth finish. As you can imagine, that is a fairly intensive and dusty job that you'd want to enlist the services of a professional to do. Due to the safety implications of grinding concrete, I highly advise against conducting this work yourself.

Please let me know if you have any questions.

Mitchell
 

[dstanley]

Hi Mitchell,

Thanks for the quick response. Is there any paint product which could provide a smoother finish than existing if we primed and repainted?

If we went down the sanding route, would we need to remove the existing paint before sanding or could we sand existing paint and concrete back at the same time with an orbital sander?

Thanks

Daniel

[MitchellMc]

No specifically designed paint for that purpose, @dstanley. However, if the stippled effect is from the texture of the concrete/render, then additional coats of paint will smooth it out to a certain extent. It might be worth doing a test section in an inconspicuous area. Apply three coats of standard wall paint, waiting for them to dry in between and see how well it disguises the texture.

No need to remove the paint before sanding. To reiterate, though, I'd only go down that route with professionals conducting the work; even then, it's a messy process, and the room would need to be cleared of all possessions. Please read this document on the hazards of crystalline silica and silicosis. These are very real dangers, and if the correct procedures are not adhered to, including suitable PPE and isolation of the areas, there's a significant risk to your health and those around you. I would put this job firmly in the basket of your dislike of the stippled effect simply doesn't warrant the risk to your health in removing it. It's best to call in the professionals.

Mitchell

[dstanley]

Okay great - thanks for that advice Mitchell. I think we'll avoid sanding back the cement render for the reasons you describe.

I will test applying additional coats to see if that produces a smoother finish. Would you recommend giving the walls a light sanding (existing paint only) before applying the first coat of primer?

[EricL]

Hello @dstanley 

A light sand to the surface of the existing painted wall should be sufficient to prepare it for painting. Remember to wipe the surface clean with a sugar soap wipe to remove all the sanding dust before painting. I propose an area of at least 500mm x 500mm to give you a fair idea of what it will look like once painted.  

Please remember to wear personal protection such as gloves, goggles and a mask when working on your project.

If you need further assistance, please let us know.

Eric

[Ready2go]

I've been wondering the same thing as my internal walls are really rough- rendered and painted.

I had a thought of either plaster or smooth render over the texture. chipping it off is a real pain. some of it is loose while other sections are stronger than the bessa-blocks themselves

[MitchellMc]

Certainly a tempting option, @Ready2go. However, as with @dstanley's problem, the paint layer makes applying coatings over it prohibitive. The paint is not porous, so plaster or render cannot stick to it.

You might like to post an image on your wall, which could give some of our helpful members some ideas.

Mitchell

[Ready2go]

you make a valid point @MitchellMc my walls are quite similar to @dstanley and it is something I have not liked since I bought the house.

one of the walls was just painted bessa-block which I cladded with gyproc but I grinded enough spots through the paint to use gyproc glue. it worked but also had flow on affects such as the door frame, cornice and skirting all posed challenges. my solutions were not standard and took me a long time to come up with but it looks okay to the untrained eye now.

I think when i repaint the other rooms, I will need to chip off whatever is loose then reapply more textured render. not a fan of that but removing it properly will be a huge job.

thanks for the input- has possibly saved me a real nightmare