A cavity slider buys back the floor area a swinging door wastes, which is why they end up in bathrooms, ensuites, laundries and any room where a door swing fights the furniture. They are also the item most often installed badly, because the part that matters is buried in a wall.

The unit goes in at frame stage and cannot be corrected once the wall is sheeted. If the frame is out of plumb the door runs away from the jamb. If the track is not level it rolls open on its own.

So the cavity unit is set, plumbed and braced before the plasterer touches it, and the opening is checked in both directions rather than eyeballed. Ten minutes at frame stage is the alternative to opening a finished wall later.

We supply and install single and twin units, heavy duty tracks for solid core and full height leaves, and soft close hardware in both directions so a door cannot be slammed into the pocket or into the jamb.

Leaf weight drives the track. A full height solid core slider on a light domestic track feels loose within a year, and that is not something a client can detect at handover.

Jamb and head detail is where a slider looks bought or looks made. Square set into the wall, a shadowline reveal, or a traditional architrave, and in every case the gap around the leaf is kept even so the pocket does not read as a slot.

Where a wall carries services we set out with the electrician and the plumber before the unit goes in. A power point or a pipe in a cavity wall is a problem found late and solved expensively.

If the frames are up, now is the time to call. If the walls are already sheeted we will tell you honestly what it costs to do it properly, rather than fitting something that will annoy the client for a decade.