How To Repair a Large Hole in a Wall

How do you repair a large hole in a plaster wall?

A hole is a different problem from a dent, and it needs a different technique. There is nothing behind a hole for filler to grip, so filler alone will either fall through or sit as a fragile plug that cracks the first time the wall is bumped. The answer is to give the filler something to hold on to: a self-adhesive fibreglass mesh patch over the hole, then Selleys Spakfilla Rapid worked through and over the mesh in two or three thin coats.

Done this way it is a quick, low-mess repair. The thing that makes it work is the mesh: it turns an unsupported void into a surface, and Spakfilla keys into it from both sides. The thing that makes it fail is impatience — each coat has to dry before the next, and for anything over 2 mm deep the technical data sheet gives 24 hours, not 30 minutes.

Technical specification

Product	Spakfilla Rapid — ready-mixed, lightweight filler
Technology	Water based
Sand / paint time — less than 2 mm	30 minutes
Sand / paint time — more than 2 mm	24 hours
Shrinkage	Virtually non-shrinking, non-cracking
Also suits	Wallboard, wood, masonry, plaster, primed nail heads, plasterboard

Indicative data only, not intended for the preparation of specifications.

A note on the all-in-one option

Selleys also publishes a Spakfilla Wall Repair Kit for exactly this job. Its data sheet describes it as an all-in-one kit for patching and repairing holes and cracks in interior walls up to 8 cm wide, containing a self-adhesive wall patch, a sanding block, a spatula and a 100 g tub of Spakfilla Rapid. If your hole is inside that size and you do not already have mesh and a blade in the shed, it saves assembling the parts yourself. The method below is the same either way.

What you need

• Selleys Spakfilla Rapid
• An adhesive fibreglass mesh patch
• A spatula, and a putty knife or flexible filling blade
• 240 grit and fine sandpaper
• A Stanley knife
• A cloth

How to repair the hole

1. Clean around the hole. Clear away any loose debris. Anything hanging off the edge of the hole will end up under your patch.
2. Apply the mesh patch. Peel away the backing and place a square of adhesive fibreglass mesh firmly over the hole, allowing at least 2–3 cm around the outside edge. That margin is what carries the load into sound plasterboard rather than into the fragile edge of the hole.
3. Work filler through the mesh. Apply a layer of Spakfilla Rapid, using a spatula to gently force some of it through the holes in the mesh. Make sure it completely covers the mesh square around the sides of the hole. For the best seal, use a putty knife or flexible filling blade to take the Spakfilla across the area in multiple directions — crossing your strokes is what pushes filler into the weave instead of skating over it.
4. Strike off the excess. Once the hole is covered, use a single downward stroke to remove any excess product.
5. Sand, then apply a second layer. Using fine sandpaper, lightly sand the area and spread a second layer of Spakfilla over it.
6. Repeat if the mesh shows. Depending on the size of the hole, or if the mesh has been exposed by sanding, you may want to repeat the process once more — after allowing a day for drying. Your wall is then ready to paint.

Why you build it up in layers

It is tempting to fill the whole thing in one thick pass. The drying figures are the reason not to. Under 2 mm, Spakfilla Rapid is sandable and paintable in 30 minutes. Over 2 mm, it needs 24 hours. A single thick fill over a mesh patch is well over 2 mm, so you would be waiting a day anyway — and a thick fill is more likely to sink slightly across a wide span and leave a shallow dish that catches light across the wall.

Two or three thin coats, each feathered wider than the last, give you a flat repair and let you work in half-hour cycles for the top coats. The final coat should extend well past the mesh so the edge disappears into the wall rather than stopping at a visible line.

Limitations — what this repair will not do

• Do not nail into it. Spakfilla Rapid's data sheet says do not nail the product. A patched hole is not a fixing point, and a mesh-and-filler patch has no timber behind it.
• Do not use it where load or compression occurs, as the product may be crushed — for instance behind a door where the handle strikes the wall.
• Not on plastic, metal, or exterior timber likely to swell or shrink as it absorbs water.
• Not below 5°C or in wet conditions.
• Where movement occurs, use Selleys No More Gaps.

There is also a size beyond which a mesh patch is the wrong answer. The Spakfilla Wall Repair Kit is rated for interior wall holes up to 8 cm wide. A hole substantially larger than that, or one where the plasterboard is broken across a stud, wants a cut-in plasterboard patch rather than mesh.

Finishing and clean up

Before painting, clean dust and loose filler particles off using Selleys Sugar Soap or Selleys Super Kleen, then apply an undercoat before your topcoat. Allow 24 hours before painting with oil-based paints. Uncured filler washes off with water; cured filler has to be scraped or sanded.

Safety: repeated contact is the risk on a multi-coat repair

Spakfilla Rapid is classified Warning, with H317, may cause an allergic skin reaction and H319, causes serious eye irritation. The cleaners named at the finishing stage carry their own: Sugar Soap concentrate is Danger — H318, causes serious eye damage, and Super Kleen is Warning — H315 skin irritation and H319 serious eye irritation.

This repair is three coats, not one, and that is what makes H317 worth naming here. Skin sensitisation is not irritation that washes off at the end of the day. It is the immune system learning the material, it is generally permanent once acquired, and it is built from repeated low-level contact rather than one heavy exposure. Working filler through a mesh patch is a job people do with their fingers, because a fingertip reads the mesh better than a blade does — and then they do it twice more over the following day. Wear a disposable nitrile glove for the coats where you want the feel; it costs nothing and keeps the whole repair off your skin.

H319 and the sanding are the same problem. Sanding back three coats over a patch produces a lot of fine airborne material, and a hole big enough to need mesh is often high on a wall, in a stairwell or close to a ceiling — which means sanding overhead, looking up into it. Safety glasses for the sanding, not just for the filling.

The cleaner is the step people leave unprotected. Sugar Soap's H318 belongs to the concentrate, and the exposure moments are measuring and pouring it, and using it neat on a sponge. For clearing filler dust before undercoating you need neither: a weak dilution does the job, and Super Kleen — classified as eye irritation rather than eye damage — is the lower-classified of the two products this page names for that step.

An H318 splash needs fifteen minutes of irrigation with the eyelids held open and urgent medical attention, not a rinse at the tap. Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.

Common questions about repairing a large hole in a wall

Do I really need the mesh patch?

For a hole, yes. Filler needs something to bond to and something to span the void. The mesh provides both, and Selleys' method depends on forcing filler through the weave so it locks in from both faces.

How much overlap should the mesh have?

At least 2–3 cm around the outside edge of the hole.

How long between coats?

30 minutes for a thin coat under 2 mm. If a coat is thicker than that, allow 24 hours. Selleys' own instruction for the third pass is to allow a day for drying.

The mesh keeps showing through when I sand.

That is normal on the first pass and is exactly why the method calls for another layer. Spread a further coat of Spakfilla over it and feather the edges wider.

How big a hole can I fix this way?

The Spakfilla Wall Repair Kit is rated for interior wall holes up to 8 cm wide, which is a reasonable guide for the mesh-and-filler method generally. Larger damage needs a plasterboard patch.

Can I hang a picture over the repair?

Not on the repair itself. Do not nail the product, and there is nothing solid behind a mesh patch.

Do I have to sand between every coat?

Selleys' method sands lightly before the second layer. Sanding knocks off ridges so the next coat starts flat, which is what keeps the total build thin.

What paint can I use?

Water-based paint after the stated drying time, with an undercoat first for best results. Allow 24 hours before painting with oil-based paints.

Why does my patch show as a shiny or dull area after painting?

Usually because the filler and the old paint absorb differently. Clean the dust off with Sugar Soap or Super Kleen and apply an undercoat over the whole repair before the topcoat.

Is Spakfilla Rapid the right choice, or should I use a heavy-duty filler?

Spakfilla Rapid is the product named in this method, and it suits plasterboard and plaster. For substantial filling in mortar, brick, masonry, stone, concrete or primed metal, Spakfilla Heavy Duty is the product intended for that work.

What if the wall keeps cracking around the patch?

Cracking that follows a line rather than radiating from the patch suggests movement. Selleys directs you to No More Gaps where movement occurs.