Cutting Metal Door Frames in Reinforced Concrete Panels up to 15 cm

A frame in a concrete panel is not simply screwed in place. Its fixing lugs, and sometimes the whole profile, are set in concrete, so you cannot lever it out with a crowbar. The tradesperson cuts it into sections and frees it piece by piece. A typical sequence looks like this:

1. Cover the floor, furniture and nearby doors with sheeting, and seal off the entrance to the flat with a dust screen.
2. Switch off the electrical circuit for that part of the flat and use a detector to find cables and pipes near the opening.
3. Mark the cutting lines on the frame profile and on the concrete.
4. Cut through the steel profile, usually at the corners and near the fixing lugs, so the frame can come out in sections.
5. Cut the concrete along the frame with a diamond blade. On a thicker panel, cut from both sides of the wall.
6. Carefully break out the remaining concrete and remove the frame sections.
7. Cut protruding lugs and reinforcement flush with the concrete.
8. Clean dust and debris out of the opening and prepare the edges for the next stage.

Once the frame is out, a rough opening remains in the wall. Making good the edges with mortar, plastering the reveals and fitting the new frame are usually separate jobs.

The main difference is the thickness of concrete that has to be cut. It decides the tools, the time and how much care the work needs.

• Panels up to 10 cm are usually internal partitions between rooms or next to the bathroom. A large angle grinder with a diamond blade can normally cut through from both sides. The work goes faster, makes less dust and wears the blade less.
• Panels up to 15 cm are often load-bearing walls in panel buildings. A standard grinder only reaches roughly halfway, so the wall is cut very accurately from both sides or with a more powerful diamond saw. The concrete tends to have denser reinforcement, cutting takes longer, and the structural side has to be sorted out before work starts.

You cannot tell whether a wall is load-bearing from its thickness alone. Check the building drawings or ask the building management or owners' association.

The tool depends on the panel thickness and on whether the opening will be enlarged.

• An angle grinder with a diamond blade suitable for both concrete and steel is enough for the frame profile and thinner panels. It handles tight spaces well, but without extraction it creates a lot of dust.
• A handheld diamond concrete saw cuts deeper and straighter. It suits 15 cm panels and openings that need clean edges, for example for a wrap-around door lining.
• A track-mounted wall saw is used when the opening is being widened or raised at the same time. The cut is accurate and the wall gets very little vibration.
• Core drilling makes holes at the corners of a future cut-out so the saw cuts do not overrun, or holes for anchoring reinforcement when the opening is strengthened.

Wet cutting, where water cools the blade and binds the dust, is very practical in an occupied flat. If water cannot be used, the tool is connected directly to an industrial vacuum extractor.

How demanding the job is, and therefore what it costs, depends on a few things you can usually find out before work begins.

• Panel thickness and reinforcement: thicker, more heavily reinforced concrete means longer cutting and more blade wear.
• How the frame was fixed: a frame cast in concrete along its whole length is harder to remove than one held only by lugs.
• Access: a narrow hallway or an opening right next to a corner or a built-in cupboard slows the work down.
• Services in the wall: cables or pipes near the opening call for a more careful approach or rerouting.
• Edge quality: if a new lined frame goes in straight away, the edges must be straight, which is more work than just removing the old frame.
• Waste: scrap metal and concrete rubble should be separated and taken away.

In a partition wall, removing the frame is routine finishing work. A load-bearing wall is different. Cutting out the frame alone usually leaves the size of the opening unchanged, but careless cutting can easily sever the reinforcement around it. Widening or raising the opening is an alteration to the load-bearing structure. That needs a structural engineer's assessment, and a steel frame or lintel may have to be installed.

Local building regulations decide whether altering an opening in a load-bearing wall needs a notification, an approval or nothing at all. Check with your local building authority and do not assume no permission is needed. In a block of flats, tell the building management or owners' association beforehand, because load-bearing walls are part of the shared structure. It is also courteous to warn your neighbours about the noisy days.

If there is a gas pipe near the opening, do not cut. If you smell gas or a pipe is damaged, leave the flat and call 112 or your local emergency number. Any gas work belongs to a qualified, registered gas engineer, and electrical cables that need rerouting should be handled by a qualified electrician.

The same problems come up again and again in practice:

• Cutting blind: without a detector it is easy to cut through a cable running alongside the frame.
• Overcutting at the corners: the cut runs past the corner of the opening and leaves a notch that can later turn into a crack.
• Forcing it out: levering the frame before it is cut through properly breaks off the panel edges.
• The wrong blade: a blade made only for steel or only for concrete wears out quickly and leaves an uneven cut.
• Underestimating dust: dry cutting without extraction covers the whole flat and the stairwell in dust.
• Altering a load-bearing wall without an engineer: when widening the opening, this is the most serious mistake.

Inspect the opening before plastering starts or the new frame goes in:

• The whole frame has been removed, including the fixing lugs
• Protruding reinforcement is cut flush with the concrete
• The panel edges are not badly broken and there are no overcuts past the corners
• There are no new cracks in the wall around the opening
• The opening matches the size agreed for the new door
• Electrics nearby work and no cables are damaged
• Rubble and scrap metal have been removed and the area is clean