How is a kitchen unit actually built?

British kitchens are far more standardised than they look. Behind the doors, a £400 kitchen and a £14,000 kitchen are usually the same box in the same material with the same hole spacing, and the money has gone into the doors, the worktop and the drawer mechanisms. That standardisation is good news when something breaks, because the failed part is almost always a stock item.

Step by step

1. Look at the carcass material.18mm melamine-faced chipboard on the great majority of kitchens, MFC or MDF on better ones, plywood on a few. It holds a screw once. It does not hold a screw that has been in and out, and it destroys itself if it gets wet.
2. Find the 32mm system holes.A vertical line of 5mm holes down the inside of each side panel, 32mm apart. Shelf supports, hinge mounting plates and drawer runners all locate on that grid, which is why parts from different manufacturers usually interchange.
3. Look at what is holding the corners together.Cam locks — a round steel cam in the panel face turned by a screwdriver, pulling on a bolt in the adjoining panel — plus wooden dowels for location. They are strong in tension and weak in racking, which is the back panel's job.
4. Understand the back panel.A 3 to 6mm hardboard or MDF sheet, either in a groove or pinned to the back edges. It is the only thing making the box rigid. A unit whose back panel is loose, missing or fitted only at the corners will rack, and every door on it will drift out of alignment.
5. Look underneath at the legs.Four adjustable plastic legs screw into sockets in the base panel. They are the only contact with the floor, and they are how a kitchen is levelled on a floor that is never flat. The plinth clips onto the front pair and carries nothing.
6. Look at the top of the unit.Base units usually have rails front and back rather than a full top, so a sink or hob can drop through. The worktop is screwed up into those rails from underneath through slotted or oversized holes.
7. Note that the units are joined to each other.Adjacent units are screwed together through the side panels with short connecting screws, so a run behaves as one structure. That is what stops individual units drifting apart, and it is why a run that has opened up at a joint usually just needs those screws found and tightened.
8. Map the fault back to the part.A door drooping is a hinge plate screw in chipboard. A unit rocking is a leg. A run gaping is connecting screws or an unfixed back. A bulge in the worktop is water in the core. The construction tells you where to look before you take anything apart.

Tips

• The 32mm grid is genuinely a standard, not a coincidence. It means a shelf support, a hinge plate or a drawer runner bought from anywhere will usually line up with the holes already drilled in your unit.
• Melamine-faced chipboard is sealed on its faces and raw on any cut edge. Every cut edge in a kitchen — the sink aperture, the end of a run, a shortened panel — is an unsealed edge until somebody seals it.
• If you ever have a unit out, look at the back edges. Manufacturers often pin the back panel at eight points and fitters often knock half of them out getting a pipe through.

Common mistakes

• Treating the back panel as packaging — It is the structural diaphragm. Cutting a large hole in it for pipework without adding a rail across the opening is how a unit ends up out of square with doors that will not line up.
• Driving a screw straight into chipboard without a pilot hole — Chipboard splits along the panel rather than gripping, and a split panel edge cannot be repaired invisibly. A pilot hole is not optional in this material.

Questions people ask