Crumbling plaster behind wallpaper – is it dangerous? How to fix it, now!

Is plaster crumbling behind wallpaper as you’re trying to remove it? Don’t panic, it’s common and it can be fixed!

There was a knot in the pit of my stomach as we started to remove wallpaper in our new (but old) bedroom and the plaster started to come away with it. Honestly, seeing exposed brick around our window frames was scarier to me than seeing Jack Torrance peeping through the wooden door in the shining *shivers*.

I immediately called my Dad (never too old to call my Dad for help) and asked him what to do.

“You’ll need to replaster,” he said.

“Jeez,” I thought with my stomach sinking even lower, “wasn’t that going to cost thousands?”

Luckily not, our bedroom is roughly 11×11 and it was a couple of hundred pounds to get all four walls replastered. We went off a recommendation from a friend, it took two half days to get the room done and about two weeks for it to dry.

The walls looked incredible once they were finished and we soon forgot about the crumbling plaster behind the original wallpaper.

My only regret – not replastering the ceiling too!

crumbling plaster behind wallpaper. Plaster falling off around window frames.
photo: Wesley Tingey

What causes plaster to crumble?

Moisture is the biggest cause of crumbling plaster, it’s common in older properties and you’re more likely to see the plaster falling off around the window frames. It can also appear elsewhere, if the property has an issue with damp.

Read more: do pink and red go together in a room?

powdery wall plaster. Crumbling plaster in old house.
photo: Lucas Van Oort

Can you wallpaper over crumbling plaster?

To wallpaper, you want the surface to be as smooth as possible, otherwise you won’t get the finish you’re after so no, wallpapering over crumbling plaster isn’t recommended.

spotty wallpaper john lewis

Spot wallpaper – John Lewis £15

Should I remove old plaster?

It’s not always necessary to remove old plaster, however, if the plaster has started to crack or crumble then it’s best to get rid and replaster. You can remove or knock off any parts that have already started to come away from the wall.

wallpaper stripper

Harris seriously good 4 inch super stripper – Homebase £10

Does plaster crack with age?

Since plaster is a solid substance which doesn’t have much flexibility, it’s liable to crack with age as the building around it warps through the seasons. As plaster ages, it can separate from the lath, which causes cracking.

When should I worry about cracks in plaster?

As your building expands and contracts in different weather conditions, a small crack may appear in your plaster which, other than looking unattractive, shouldn’t cause any real issues. If the crack is wider than 5mm then it might need some more investigating.

Does wallpaper ruin plaster?

Wallpaper won’t ruin plaster and many layers of wallpaper can bind plaster together, however, removing wallpaper may damage the plaster that’s behind it.

Does wallpaper need to be removed before plastering?

It’s best to remove old wallpaper before plastering. Even if that means removing the old plaster with it, you’ll get a much better result in the long run.

Do I need to re-plaster after removing wallpaper?

You won’t always need to re-plaster after removing wallpaper; it depends on the condition of the walls and how old the plaster is. If you’re planning to re-wallpaper, the surface needs to be as smooth as possible, otherwise any lumps and bumps will show through the wallpaper – it won’t look pretty!

How do professionals remove wallpaper?

Professionals will use a chemical solution or they will use an electric steam stripper.

wagner wallpaper stripper

Wagner wallpaper stripper – Homebase £45

paint stripper

Paint predator – Homebase £25

wallpaper stripper

Solvite wallpaper remover – Homebase £11

How do I know if my plaster needs replacing?

It’s quite normal for plaster to shrink and move overtime so if you’re renovating an old property its very likely you’ll need to replace the plaster. If the plaster has large cracks, sounds hollow when you knock on it or starts to crumble then you know its time to call your plasterer.

Does water damaged plaster need replacing?

This depends how bad the water damage is and how long the plaster has been wet for. Small leaks may just require the plaster to be dried out, but significantly wet plaster will need replacing.

How to fix crumbling plaster behind wallpaper

To fix crumbling plaster, you will need to replaster. Plastering is a very specialised skill so it might be best to hire a professional. Before plastering, remove all the old wallpaper and any parts of the plaster crumbling or coming away from the brick and the laths. If you knock on the old plaster and it moves and sounds hollow then it’s going to need to be replaced.

Read more: my husband won’t let me decorate our home

Is powdery plaster dangerous?

Old plaster may contain asbestos. If it does contain asbestos and it begins to crumble or go powdery then it can cause harm. If your house was built before the late 80s then it’s best to call an asbestos specialist to check it out before you get to work.

wallpaper floral animal zebra

Galerie zebra wallpaper – Homebase £39

leaf wallpaper

Galerie leaf trail wallpaper – Homebase £60

greige wall paint

Farrow and Ball Drop Cloth paint – Homebase £43.20

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