Demolition of the old riser toilet partition wall

In older flats, especially in prefabricated concrete blocks, the partition is often part of the original bathroom unit. In other cases someone built it later. Its job is mostly cosmetic: it hides the pipes and gives you a surface for tiles. The trouble starts when someone needs to reach the pipes. Behind the partition there are often the main water stopcocks, water meters and sometimes electrical cables as well as the risers.

The usual reasons for taking it out:

• The building is replacing the risers and the contractor needs clear access to the pipes
• You are refitting the bathroom or toilet and moving the fittings around
• The partition is soaked, mouldy or has become a home for insects
• The old structure has worked loose and part of it could collapse on its own

This job often goes together with removing an old laminate bathroom pod, stripping tiles or taking out a bath. If you plan everything at once, the rubble goes down the stairs only once and the new pipework can be prepared without breaking anything open again.

1. Agreement with the building management. The risers are shared parts of the building, so the date is agreed with the building management or owners' association. If the water has to be shut off for the whole riser, the management usually does it, and the neighbours need to know in advance.
2. Preparing the room. The toilet pan, and the basin if needed, come off, along with any tiles on the partition. The floor and door are covered, and openings to other rooms are sealed with plastic sheeting to keep the dust in.
3. Finding out what is inside. The partition is carefully opened at one small spot to see what it is made of and exactly what runs behind it. Only then are the tools chosen.
4. The demolition itself. The partition comes down gradually from the top, in small pieces. For brick, a chisel and a light electric breaker on a low setting are used. Plasterboard and timber only need a knife, a saw and a pry bar. Near the pipes the work is done by hand, never with a heavy breaker at full power.
5. Removing the rubble. The waste goes into strong bags and is taken to a site that legally accepts construction waste. It does not belong in the household bins outside the building.
6. Cleaning and checking. The room is vacuumed, and the pipes, stopcocks and surrounding walls are checked so the next trades can start.

The material decides how much dust and rubble you get and how carefully the work has to go.

• Brick or thin partition blocks are common in masonry buildings. Removal is dusty, there is more rubble, and near the pipes it has to go bit by bit.
• Aerated concrete blocks cut and break fairly easily, but they bond well to mortar, so the edges need cleaning up afterwards.
• Chipboard, laminate panels or timber can usually be taken apart in pieces without much dust.
• Plasterboard on a metal frame is the simplest: the boards are cut and the studs unscrewed.

Older blocks of flats are a special case, because the waste riser may be made of asbestos cement. Pipes like this must not be cut, broken or sanded. If you suspect asbestos, stop work and have the material tested. Only a contractor licensed for asbestos work may remove it.

How much work the job takes, and so what it costs, depends mainly on:

• The material, since a masonry partition takes more effort than light boxing
• Whether the partition is bonded into the surrounding walls or stands on its own
• How many pipes run behind it and their condition, as old corroded pipes need a lot of care
• The size of the room, because a small toilet leaves little space for tools and rubble
• The floor and whether there is a lift, as all the rubble has to go down somehow
• Whether you clear the room and remove the fittings yourself or the contractor does it

Sometimes the pipes turn out to run deeper inside the wall, and part of the surrounding masonry has to be cut back too. It is worth mentioning this possibility when you agree the job with the contractor.

A riser partition is usually not load-bearing, but check this before anyone starts, especially if it is unclear how the bathroom core was built. If there is any doubt, a structural engineer should have the final word.

Whether your particular alteration needs a permit, a notification or nothing at all depends on local building regulations and on the building itself. Check with your local building authority rather than relying on a quick phone call. Separately, you need approval from the building management or owners' association, because the work touches shared pipes.

There may be electrical cables behind the partition. Disconnecting or altering them is a job for a qualified electrician only. If a gas pipe runs through the shaft, it must not be damaged or touched, and any work on it belongs to a qualified, registered gas engineer. If you smell gas, stop work at once, open the windows, do not use light switches and call the gas emergency line or 112.

Think about what comes next as well. The new boxing must give access to the stopcocks and meters, usually through an access panel. In some buildings the service shaft also acts as a fire barrier, so it is wise to discuss the new design with the building management.

• Breaking in blind without knowing what is behind the partition, which risks drilling or cracking a pipe
• Using a powerful breaker right next to old risers that cannot take the vibration
• Starting without agreement from the building management, so nobody can shut off the water if something goes wrong
• Underestimating the rubble, as even a small masonry partition fills a lot of bags
• Knocking it out with no plan for the new boxing and where the access panels will go

• The partition has been removed to the agreed extent and the wall edges are clean of old mortar
• Risers, branches and fittings show no cracks, scrapes or loose joints
• Once the water is back on, nothing drips and the waste pipes do not leak
• Stopcocks and water meters are intact and can be operated
• Electrical cables in the shaft are undamaged or have been made safe by an electrician
• The rubble has been taken away and the shared areas of the building are left clean
• The room is vacuumed and ready for the next work