How to smooth walls without plastering

by Daniel Berry | Last Updated: 16/02/2021

Smooth walls are one of the keys to a modern, clean-looking house. Wallpaper is seen as old fashioned and painted plaster is the go-to aesthetic. But what do you do if your walls aren’t smooth? Well, you can hire a plasterer, but not everyone has the budget to spare or wants all that mess. So we have built this guide to show you exactly how to smooth walls without plastering.

Old plaster wall

Old plaster wall

Sanding the plaster

You can sand existing plaster walls to help smooth out any bumps and hollows. Depending on the size of the bump you will want to use a medium or high grit sandpaper. Something around 100 for larger bumps and higher for smaller and finishing.

You need to be gentle when sanding plaster as it is soft and will sand very easily if you get carried away you could easily end up creating a bigger problem than the one you started with.

Work slowly and gradually even out the plaster until you achieve a finish you are happy with.

There are a few large downsides to this option. It is very time consuming and labour intensive. On a bad wall, you could spend days sanding to achieve the perfect finish.

Then there is the issue with the type of plaster used. Some plasters will have a very thin surface layer quickly followed by a much rougher undercoat. This is particularly relevant in older homes which also tend to be the ones with the bumpier walls! As soon as you sand through the top layer of finishing plaster you will have a very rough and bumpy surface, the exact opposite of what you are after.

Rough plaster when sanded down

Rough plaster when sanded down

And to round up the list of potential issues we have the big one, the mess. Sanding plaster will cause dust to go everywhere, and we mean everywhere. If you are planning on doing this a respirator is essential to protect your lungs.

Filling bumps and cracks

Filling bumps and cracks with polyfiller (or any off-brand alternative) is a good way to smoothen those walls. This is a great option if you just have a few rough areas you want to smoothen out but won’t work on large bumpy walls.

Skim the polyfiller to the wall and then smooth with a trowel. If filling large gaps expect shrinking. This shrinking occurs when the filler dries and “shrinks” back into the crack. This is expected and is nothing to be concerned about, just wait until it is fully dry and then apply some more filler. Multiple coats is no issue at all.

Filling bumps on old plaster

Filling bumps on old plaster

If you make a mistake and apply too much filler or apply it in the wrong place then you can always sand it down to a nice smooth finish.

Plasterboard the existing wall

For really bad walls you can always fit plasterboard to the existing wall using studs to achieve a perfectly smooth wall. This is great for older cottages with incredibly uneven walls. In fact, this is what we did in a 200-year-old cottage we are renovating at the moment. The wall had huge bumps and hollows in it, the plaster was rough under the finishing layer so we had two options, replaster or use plasterboard.

Due to being an awful plasterer, we went with the second option. I will walk you through the process below so you can decide if this is the correct course of action for you.

Step 1 – Attach studs to the wall

Use wood batons to make a stud framework on the existing wall, this is what you will then attach your plasterboard to. Creating a stud frame like this rather than attaching the boards directly to the wall allows for a much smoother finish on really rough walls.

I used a really thin wood so that we took away as little area from the room as possible. When laying our you batons you need to arrange them so that the middle of the wooden beam is exactly where your plasterboard sheets will meet.

Starting the studwork framing

Starting the studwork framing

This is essential for screwing the plasterboard to the framework. If the edges of the plasterboard are not directly above a wood stud then they will be flexible and move all over the place, you need a beam behind every single joint.

Step 2 – Fix plasterboard sheets to your stud framework

Now it is time to attach your plasterboard to the framework you have just built. Depending on the size of sheet you have got you may need to attach lots of sheets like us or only a couple if you have full-size boards. We would have preferred full-size sheets but this house is in an off the beaten track location where truck deliveries arent really feasible so we had to make do with whatever we could fit in the boot of a ford fiesta!

Use plasterboard screws (thin, black screws) to attach the plasterboard. Secure it in place around the edge and for larger boards in the centre too. You want there to be as little movement in the plasterboard as possible as it is this movement that will cause cracks to form in your joints down the line.

Boarded out with plasterboard

Boarded out with plasterboard

The screw heads need to be sunk into the plasterboard a little so you can fill over the top.

Step 3 – Fill the gaps

Now its time to fill the gaps between your boards and cover the screw heads. There are specialist jointing compounds that can be used for this but any form of plaster or filler will work. Jointing compounds are intended for this purpose and may offer more flexibility but it is something I am yet to properly test out.

FIlling in the gaps

FIlling in the gaps

The professional way to joint boards involves using a jointing tape with compound over the top of it. I have tried this before but have never really been able to get it to work properly and usually end up with a worse standard of finish that just filling the joints directly as I did here.

This may be setting myself up for more cracks but I haven’t seen any issues as of yet.

Step 4 – Sand the filler

Now we are nearly done, sand down the filler with high grit sandpaper to achieve a really smooth finish. Avoid sanding the plasterboard as much as possible as you don’t want to rough up the paper finish.

how to smooth walls without plastering

how to smooth walls without plastering

Step 5 – Paint

painted with mist coat

painted with mist coat

Now comes the time to paint the plasterboard in whatever colour you like. You will want to do a mist coat first (a watered-down emulsion) we talk more about this in our can you paint straight onto plasterboard article, so if you have reached this step them make sure you give that article a read here.

First coat of paint

First coat of paint

Hey, I'm Dan, I studied computer science with artificial intelligence at Loughborough University. I try to bring my tech knowledge to the posts where it is needed while also offering a DIY view to go with Sam's professional view on tools. I am a very keen DIY'er and have experience of doing everything the completely wrong way.