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A Quick Guide to Repairing Old Walls

How to repair old plastered walls

When it comes to renovating, sometimes there's this idea that everything needs to be ripped out and replaced with new; whether that's the plaster on the walls, the skirting boards or even the boiler. But renovating doesn't have mean replacing everything for new and you can in fact restore many areas of the home too. And if you're on a budget like us, you may find this a much more favourable route.

I'm a firm believer of keeping an old house as original as possible, if possible. That means celebrating it's original plastered walls, the lath and plaster ceilings, the chunky (if i a little damaged!) skirting boards. It's all truly original; hundreds of years old and something I believe should be repaired and restored where possible - not replaced for new. Of course, lots of old houses have plaster falling off the walls, ceiling literally ready to collapse and skirting boards so badly rotten that they disintegrate at the touch. That kind of stuff has to go, I totally agree. But walls that aren't perfectly straight, or ceilings that have a bit of a wobble in them - these imperfections can be beautiful and they can add character to the room too. 

So in the name of keeping our house as legit original as possible, I wanted to fix up our original plastered walls and not re-plaster over them. After all, 100+ year old walls in fairly good nick isn't something I wanted to go tearing down. That being said, they still needed a bit of work. From cracks, to badly repaired plaster spots, to lumps and bumps and a bazillion little holes. All things though, that can be repaired easily and once painted - you'd never know they had ever been there!

I had lots of questions on Instagram about this, so I thought a blog post was in order.

What To Use
When it comes to repairing old walls, the first thing you need is the right tools for the job. I've tried a few different methods of patch-repairing walls in the past, but the absolute best (in my opinion!) is using a pre-mixed plaster skim. Now don't let the words 'plaster' put you off - it's nothing quite like actual plaster, trust me. This stuff is more like a glorified polyfilla. It's white like polyfilla, it's completely sandable like polyfilla the only real difference to it not being polyfilla, is that its consistency is much better for working over large areas and it's stronger too. There's all kinds of different brands on the market and they're all very much the same and you can find these near to the bags of plaster in any DIY store.

The second thing you need is the right tool to apply the plaster skim with. Using a short little filling knife is absolutely NOT the way to go here. You'll end up making a right mess and causing more work than needs-be. A wide blade is absolutely vital here if you want a decent finish and I recommend using either a plastering trowel or a very large jointing/taping knife. We're most likely patching up large areas remember, not just filling small holes.

skim plaster finish for repairing walls
how to use skim plaster

So you may find your walls are imperfect in several different ways. You may have places where plaster has fallen off the walls, you may find your plaster has a lumpy/bumpy texture to it, or you may find the plaster has already been patched - but badly so and sticks out like a sore thumb from the rest of the wall. All three of these situations can be fixed by using this product. The really important thing to remember is that old walls have natural curves in them. They'll feel smooth to touch, but if you put a straight edge against the wall (a large spirit level or something), you'll see how the plaster isn't perfectly straight. If you feel over the wall with your hands, you'll probably be able to feel these curves. When you repair old walls you need to bare in mind that the finished result may not be a perfect straight bit of wall. You'll be adding to the curves and it wont be spirit level straight consistently across the wall - but if done right, it will feel smooth and you shouldn't noticeably be able to tell visually.

For existing bulges in the wall or raised cracks, you'll want to apply the plaster skim over the area in question and then the surrounding area to that too. Whatever area you're trying to fix - you need to go over more than you think. This is how it will be cleverly hidden into the wall. A slight curve in the wall over a large area wont be noticed - a slight curve over a small area, will be noticed. Like a gradual hill a guess. The less steep, the less noticeable. That kind of logic!

repairing dodgy plaster DIY

This section here for example, was a bulging mottled section of plaster. You can see the fine line in the middle which is the highest point of the bulge. I've then added a fair amount of plaster skim either side to cleverly even it out to be subtly hidden. Once painted, unless you feel the wall or plonk a straight edge against it - you wont visibly be able to tell.

How to repair bulges in plaster

You also want to make sure you smooth out the plaster skim as much as possible whilst it's wet. You don't want to overload the wall with the skim - just put on what you need, nothing more. You'll be able to sand it, yes - but you don't want to have to sand it all off, just a light sand to smoothen it up should be all it needs.

repairing old plaster

For lumpy bumps areas, instead of applying "more than the area in question" I actually remove *almost all* of the plaster skim, leaving behind just enough to fill in the recessed areas between the lumps and bumps. So essentially, I apply the plaster skim to the wall and then I take it back off and what's left behind is enough to fix up the wall, bringing the recessed areas to the same level as the lumps and bumps. If you have any flaky plaster, do make sure to scrape this down to remove it first though!

old mottled plaster
repairing bumpy plaster
after plaster repair

You can use this product to repair smaller areas where the plaster may have blown off the wall. And you can also use it to repair chips, scuffs and other smaller imperfections. I've also used it to repair cracks in plaster too, although I wouldn't use it if very large areas of plaster have blown. That's definitely a re-plastering job!

repairing plaster above skirting
repairing cracks in plaster

Before And After of a dodgy patch of plaster in the alcove...

old plaster needs repair
before and after plaster repair
before and after plaster repair
repairing lime plaster
repairing plaster and paint

You can also use this product on ceilings too - although repairs on ceilings are always more noticeable than walls due to the way they catch the light and generally just being more difficult to work on (upside down woes!) - so do expect to be able to see the curves a little more, especially if it's a bright room. But you can certainly save yourself a wad, if you're happy with the end result this way around. You could also try lining paper on the top (something I'm planning to do in other rooms!) to disguise any imperfections even more if your not happy with the finish. Also worth noting, old plaster may have lots of spiderweb hairline cracks - these become completely invisible after painting, so if you can't feel it - don't worry about it!

paint to cover hairline cracks

Once I've repaired the bulk of a wall, I then give it a flat coat of paint as this will help show up anything you've missed, or anything that will be visibly noticeable underneath the paint. I'm quite fussy about holes and little dips, so usually I end up filling any little detail. It takes a fine eye - but trust me, it's worth it in the end and gives a much much better finish.

painting old walls

I definitely wouldn't say this is an *easier* method than re-plastering walls - there is after all, lots of sanding involved and lots of dust, ugh! BUT it will save you a lot of money doing it yourself this way rather than employing a plasterer. It took me a couple of hours to fill/patch the living room, cost me very little to do and our walls now look 98% perfect! Because naturally, there's anyways bits you miss/more visible. But I'm OK with that ;)

If you have any other tips to add, please do leave them in the comments below!


  1. This is really interesting to me, as I've been researching plaster skim for my craft room/guest room! Which brand did you use? I think I'm actually going to go for lining paper then paint on the walls (my tried and tested method) and I'm going to try a lot of patching and some flexible paint on the ceiling - that's an experiment!

    1. I've used a different brand for every room I've done to be honest! This one was by Knauf but I've also used Wickes own-brand as well, although they all seem very much the same to me! I haven't ever lined and painted on the top, but planning on trying that out on a ceiling in the next room we do. Although I'm not sure how easy wallpapering a ceiling is going to be!! You'll have to let me know how your experiments go - I'll try anything to save on having to re-plaster ;)

  2. This is a Great guide thank you! Do you think you can use this to fill in after having a rewire over the chasing? Or if not do you have a guide for this? (I couldn't find one on your blog but may have missed it!) Thank you for the amazing content it's really so useful, I've bookmarked so many of your blog posts for later haha! x

    1. Yes! I usually fill in the gap with bonding plaster first (or browning) but don't bring it up to the same level as the rest of the plaster. Once that's dry, then use the plaster skim over the top! It's not really meant to deep gaps like chasing - hence why I would use bonding/browning for that. But you can definitely get a smooth finish over the top with this stuff.

      So glad my blog has helped you!! That's really nice to hear my posts are useful :) We've certainly learnt a lot through our DIY renovation - and sharing is caring, as they say :P

  3. Very nice, easy to follow guide. Repairing and touching up walls is never a quick or easy job. Do you find that any imperfections such as curves or dips that are left once the repairs have been done are less noticeable in light or dark colours when you paint them over?