Summary

Kitchen cabinet installation order is one of the most-debated topics on UK building sites. The "correct" sequence is the one that protects finished work, holds tolerances, and lets the next trade in without rework. The KBSA (Kitchen Bathroom Bedroom Specialists Association) and most manufacturer fitting guides agree on a core sequence — tall units first to set the datum, wall units before base units to avoid working over finished worktops, and plinths last to absorb floor irregularities.

Where fitters disagree is the wall-vs-base argument. Older tradespeople were trained "base first" because base units were heavy timber and gave a stable platform to set wall units off. Modern kitchens — flat-pack carcasses on adjustable legs and rigid factory-built units — are lighter, levelled by leg-screws, and easier to install with wall units already up. Working above finished base units risks scratching worktops, dropping screws into drawers, and damaging soft-close hinges with ladder feet. Wall-unit-first is now the standard taught on most City & Guilds and CITB courses.

This article gives a defensible, sequenced fit-out for a domestic UK kitchen — applicable to handle-less, in-frame, slab and shaker styles — and notes where the order changes for islands, peninsulas and integrated appliance runs.

Key Facts

Quick Reference Table

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Stage Sequence Reason Common error
1 Survey & set datum line All units reference one horizontal datum, not the floor Using floor as datum on out-of-level slab
2 Mark wall unit fixing line Worktop height + 450mm clear Marking from floor not datum
3 Install tall units Set vertical alignment for run Forgetting cooker hood vent route
4 Hang wall units No worktop yet — clear working area Damaging finished worktop with ladders
5 Position base units Adjust legs to datum Setting legs from floor, not level
6 Template & install worktop Scribe to wall, mitre joints with biscuits/bolts Cutting hob hole without manufacturer template
7 Fit plinth Cut to suit final floor finish Fitting before LVT/tile and being too short
8 Install integrated appliances Carcass and door alignment Fridge door fouling worktop overhang
9 Fit cornice / pelmet Mitred and scribed Mitre gaps from poor measurement
10 Handles & silicone Last to avoid damage Silicone before handles fitted (joint disturbed)

Detailed Guidance

Setting the datum

The single most important step. Find the highest point of the kitchen floor with a long spirit level or a laser level. From that point, measure up the base unit height (typically 870mm to top of carcass — 720mm carcass + 150mm legs) and strike a horizontal datum line around the room using a laser or chalk line. Every unit references this line, not the floor.

The datum line is also the top-of-worktop minus worktop thickness. If you mark a second line at top-of-worktop plus 450mm, that's the bottom of your wall units. Strike both lines.

On uneven floors, the leg-adjustment range (commonly 100–170mm) should comfortably absorb the variation. If the floor has more than 20mm fall across the run, flag it to the customer — the plinth will need scribing.

Tall units first

Tall units (larder, oven housing, fridge/freezer housing) anchor the run vertically. They are usually fixed to a structural wall and set the height of the cornice line. Fit them, plumb them in both planes, and check the front face is flush across all tall units in the run.

If two tall units sit either end of a run with wall units between, both ends must be plumb before the wall units go up — otherwise the cornice line dog-legs visibly.

Wall units before base units

The argument for wall-unit-first:

The argument for base-first (older trade preference):

On modern installs, wall-unit-first wins on damage prevention. Use a wall-unit lift or two-person handling. Standard wall unit weight: 12–18kg empty.

Fix to the structural wall with cabinet hangers (Camar, Hettich Wing) onto two M6 wall plugs per unit minimum. For plasterboard with no stud behind, use Geefix or equivalent heavy-duty plasterboard fixings rated 50kg+ per fixing. Two fixings per cabinet hanger.

Base unit installation

Base units sit on adjustable legs. Set the front legs of the first carcass to the datum, then the back legs, then plumb the unit front-to-back and side-to-side. Move to the next carcass. Clamp adjacent carcasses together at the front and back rails with quick-grip clamps, then fix through with M6 connecting bolts (one top, one bottom — minimum two per joint).

For an L-shaped run, start at the internal corner and work outwards. The corner unit (typically a 900x900 magic corner or carousel) sets the position of both legs of the L.

For islands, set out from the centreline of the room or a feature wall. Islands are usually fixed to the floor via timber battens screwed to subfloor; the carcasses sit over the battens and are screwed down inside the cabinet.

Worktop installation

Template the worktop AFTER base units are installed and squared. For laminate postform tops, scribe to the wall using a compass scribe, cut with a router and template, and join with worktop bolts and biscuits (mason's mitre at internal corners). Use brown or clear silicone (matching laminate edge) on joins, not white — it discolours.

For solid surface (quartz, granite, sintered stone), the template is taken by the worktop supplier after base units are fixed. Lead time is typically 5–10 working days. Plan the install around it — don't fit appliances until the stone is in.

Worktop sequence within the day:

  1. Dry-fit and check
  2. Apply silicone bead to top of base unit rail
  3. Lower worktop into position
  4. Pull joints tight with worktop bolts
  5. Apply continuous silicone bead along wall-to-worktop joint
  6. Apply mitre adhesive (CT1 or similar) at joint, clamp, wipe excess

Plinth fitting

The plinth is the kicking strip below the base units, typically 150mm high. Fit it AFTER:

The plinth clips to the cabinet legs via plinth clips (one per leg). Scribe the bottom edge to the floor finish if uneven. Leave a 5mm gap at the floor — capillary draw will suck water in if the plinth touches a wet floor.

Integrated appliance order

  1. Built-under dishwasher and washing machine — slide in, level, plumb, electrical, screw to adjacent carcass
  2. Built-under fridge — same
  3. Integrated tall fridge/freezer — slide in, fix carcass to wall, fit appliance to carcass per manufacturer, then fit cabinet door to appliance bracket (sliding hinge or fixed)
  4. Built-in oven — slide into housing, screw through oven flange into housing
  5. Built-in microwave / coffee machine — same
  6. Hob — drop into worktop cut-out, seal with supplied gasket or silicone, connect electrical/gas (gas requires Gas Safe registered installer)
  7. Cooker hood — fix to wall or chimney unit; align with hob centreline; ducting before the hood is fixed

Gas hob installation is Gas Safe notifiable work. Electrical hob and oven on a dedicated 32A circuit is Part P notifiable.

Cornice, pelmet and handles

Cornice (top trim) and pelmet (bottom trim of wall unit) are fitted after wall units are aligned and tall units are in. Mitre at external corners (45° unless ornate cornice requires compound mitre). Scribed to wall at terminations.

Handles last — drill from inside the door using a handle jig. Common heights:

Common edge cases

Out-of-square room: Set out from the longest run. Use a packer-and-scribe strategy at the corner that doesn't square up. Don't try to force the run square — the wall is the wrong reference.

Tile splashback fitted by another trade: Coordinate with the tiler. Worktop must be in before tiling. Wall units must be either in before tiling (so tiler scribes to unit) OR after (so tiles are continuous behind unit — rare).

Existing kitchen strip-out: Allow a day for strip-out and making-good. Cap services before disconnecting. Photograph the existing wiring before cutting.

Frequently Asked Questions

Wall units or base units first — what's the right answer?

Wall units first is now the dominant UK practice for modern carcass kitchens. The reasoning is damage protection (no working over finished worktop) and clean working area. The "base units first" tradition came from heavy timber base cabinets that gave a stable platform; modern flat-pack and rigid factory units don't need it. Both methods are technically valid; wall-first is safer.

Why are plinths fitted last?

Two reasons. First, the plinth absorbs the floor finish thickness — if you fit it before LVT or tile, you'll either have a gap at the floor or have to recut. Second, fitting plinths after worktop and appliances means damage during install lands on the cabinet, not the plinth.

How high should wall units be above the worktop?

UK convention is 450mm clear between worktop and underside of wall unit. KBSA recommends 500–600mm above a hob. Cooker hood manufacturers usually specify 600mm above induction and 650mm above gas — always check the hood's installation instructions and treat that as the minimum.

Can I fit a kitchen on uneven floors without skimming first?

Yes, within reason. Adjustable legs absorb up to 70mm of variation. If the floor falls more than 20mm across the run, scribe the plinth and warn the customer the plinth line won't be straight. If fall is more than 40mm across the room, recommend a self-levelling compound before fitting.

Is kitchen fitting notifiable under Building Regs?

The carpentry isn't. But the work around it usually is:

Regulations & Standards