Missing brick. Hole in stair wall

Cut back the plaster to expose the void
• Fix a timber noggin or pattress securely between solid structural members (joists or studs)
• Re-plaster over it
• Fix the bracket into the timber

This gives a solid fixing and meets safety expectations for a handrail.

Dont just fill it with plaster. Pack the void first with brick or block pieces set in sand and cement, or use bonding mortar, then finish with plaster.

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It sounds like the handrail bracket was fixed into plasterboard with no solid backing — quite common near stairwells where there’s a void or boxed-in area. Simply filling the hole won’t be strong enough to refix the bracket, as it needs a solid anchor.

The best solution is to create a solid fixing point:

Cut back a small section of plasterboard where the void is.

Fit a noggin or timber batten (e.g. 2x1 or 2x2) securely between the nearest studs or joists behind the plasterboard.

Re-board, fill, and then refix the handrail bracket into the new timber backing.

Alternatively, if cutting back isn’t possible, you can use a heavy-duty cavity fixing system (such as GripIt or toggle bolts), but a timber backing is the strongest and most reliable option — especially for handrails.

use a backer material like expanding foam or sand and cement to bulk out the void, allowing it to be solid enough to hold the new fixings

To fill the void behind the plaster where a stair banister bracket came off, you'll need to first create a solid base, then use a filler. Since there's no wall behind, you can build a support using wood or backer rod, then fill the remaining space with expanding foam or lightweight filler, and finally, finish with a standard filler and sand it down

Fill the void with expanding foam, trim it, then cover with setting plaster before refitting the bracket.

If there’s a big void behind the plaster with no solid wall to fix into, you’ll need to create a secure fixing point. One option is to use cavity wall fixings, but for something weight-bearing like a banister, it’s better to add support behind the plaster.

You can do this by cutting a neat hole around the bracket area and inserting a timber noggin or batten between the studs (or fixing it securely to existing joists or structure). Once it’s in place, refit the plasterboard or use filler, then screw the bracket into the timber for a solid hold.

Alternatively, if you don’t want to open the wall, consider using a toggle bolt or spring toggle fixing, which can spread the load behind the plaster—just be sure it’s strong enough for a handrail.

For the safest result, especially for stair safety, securing into a solid backing is best.

For a big void behind plaster with no brick backing, you’ll want to fill it with something strong and stable to securely fix the banister bracket. Here are some good options:

Expanding foam filler – Use a high-density expanding foam to fill the void. Once cured, you can trim it flush and screw the bracket into it with heavy-duty wall plugs or anchors.
Rigid backing panel – Insert a piece of plywood or MDF cut to size inside the void, securing it from the inside if possible, then plaster or fill around it. This gives a solid base for the bracket.
Metal or wooden fixing plate – Attach a mounting plate that spreads the load across a larger area, screwed into surrounding solid areas or joists.
Use chemical anchors or resin fixings – These can bond into hollow spaces and provide a strong hold if the void is deep.
Make sure when you refit the bracket you use heavy-duty wall plugs or toggle bolts designed for hollow or unstable walls.

If the void exposes the underside of the bathroom floor, check for any moisture or structural concerns first before filling.

Brick it up or use some bonding and filler depends on how bad

Put a peace off brick in with sand and cement then the finish can be applied either board and skim or bonding and skim make sure to have before any plaster works

It sounds like you’ve encountered a void between the plaster and the wall, possibly due to missing or insufficient support behind the plaster. Here’s how you can fill it effectively:

1. Clean the Void

First, remove any loose debris, dust, or broken plaster from the void to ensure that whatever you fill it with adheres properly.

2. Support the Bracket

Before filling the void, make sure the bracket is secure. If it needs to be fixed again, you can:
• Use a wall plug (rawl plug) and screws for extra support.
• If there’s no wall or stud to secure it to, you could consider using chemical anchor resin or expanding foam to help hold the bracket in place, but this depends on the type of load the banister will bear.

3. Fill the Void

Since there’s no brick or solid structure behind the plaster, you’ll need something that can support the weight and also fill the void. Some options are:
• Expanding Foam: If it’s a large void, you can use expanding foam to fill the space. Be careful not to overfill, as the foam will expand quite a bit. Once dried, you can trim it down and plaster over it to smooth the surface.
• Plaster or Fillers: If the void is small and you just need to fill the gap, plaster or a wall filler might do the job. You can use filler for smaller voids and smooth it with a trowel. If it’s a deeper hole, use plaster bonding compound to fill and provide a smooth surface for painting or fixing the bracket back on.
• Wall Repair Compound: If you’re concerned about long-term stability, you could use a wall repair compound (like a plaster mix that also works for hollow walls). Once it’s filled and set, you can reinstall the bracket.

4. Reinstall the Bracket

After the void is filled and set (and the material has had time to cure or harden), reinstall the bracket. Depending on what you’ve used to fill it, ensure the bracket is firmly anchored. If you’re unsure of the material, screw into the filler/foam once it’s fully set to test its strength.

5. Plaster Over the Filled Area

Once the bracket is securely in place, plaster over the void to create a smooth, even finish. Sand it down after it dries if necessary, and then repaint the area.

Final Check:

If you’re unsure how much weight the wall or bracket will bear, you might want to consider adding additional support, like backing plates or reinforcing the area with a larger bracket to distribute the load more evenly.