Summary

Kitchen unit installation is one of the most common and most technically varied jobs a general builder or carpenter undertakes. The difference between a professional result and a poor one is almost entirely in the preparation: surveying the floor level accurately before ordering, understanding the wall construction before selecting fixings, and taking time to achieve a truly level run of base units before any worktops are cut.

A poorly levelled kitchen will cause worktop joins to be uneven, appliance doors to not close properly, and integrated appliance gaps to be incorrect. These are expensive callbacks. Getting the setting-out right at the start — including accounting for out-of-square rooms, stud wall positions, and floor undulation — is the professional approach.

The British Standard for kitchen furniture installation is BS 6222 (domestic kitchen equipment), which covers worktop height, clearances, and structural requirements for wall cabinet fixing. Kitchen manufacturers also publish installation guides that must be followed to maintain warranty. Where the two conflict, the more stringent requirement applies.

Key Facts

  • Standard worktop height: 870–900mm from finished floor level (FFL); BS 6222 recommends 870mm as nominal
  • Wall cabinet height: bottom of wall unit typically 450–520mm above worktop; allows for splash tiles
  • Standard wall cabinet fixing height: bottom rail at 1,370mm from FFL (870mm worktop + 500mm)
  • Adjustable leg range: typically 100–150mm; handles floor undulation up to 50mm
  • Base unit kick height: standard 150mm (to accommodate legs plus kick clip); some ranges 120mm
  • Cabinet connector screws: 5×30mm machine screws or 6×40mm cross-dowels for clamping adjacent cabinets
  • Masonry fixings (solid wall): 7.5×75mm or 8×80mm frame screws into plugged masonry (minimum 30mm plug engagement in brick/block)
  • Timber stud fixings: 4.5×50mm woodscrews into studs; identify stud centres (usually 400mm or 600mm) before cutting holes
  • Plasterboard fixings alone: not acceptable for wall cabinets — must hit stud or use horizontal timber batten
  • Minimum fixings per cabinet: 2 per unit into structural wall/stud; never rely on single fixing per cabinet
  • Weight limit: most wall cabinet hanging rails rated to 60kg per 600mm section
  • Cornice/pelmet joint: 45° mitre at corners; glue and pin gun (18-gauge brad nails) or panel adhesive

Quick Reference Table

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Component Standard Dimension Adjustment Range Fix To
Base unit leg height 100mm nominal ±25mm per leg Self-contained
Worktop height 870–900mm FFL Shimmed via legs —
Plinth/kick board height 150mm Adjusts with legs Kick clips on legs
Wall unit bottom 1,370mm FFL Client preference ±50mm Wall
Wall unit top 2,050–2,150mm FFL Cabinet height Wall
Cornice 40–80mm profile Cut to fit Top of unit
Pelmet 50–80mm profile Cut to fit Underside of wall unit
Cabinet connector 5×30mm or 6×40mm N/A Adjacent cabinets

Detailed Guidance

Setting Out — Floor Survey and Reference Line

Before installing a single unit, survey the floor with a spirit level (minimum 1.2m) or laser level across the full width of the kitchen.

  1. Find the highest point in the floor. This is your datum for the front leg height.
  2. Measure the difference in level across the run — any undulation more than 20mm will require leg adjustment and may require shimming or cutting at the end panels.
  3. Strike a level horizontal line at worktop height (typically 870mm) on the walls. Use a laser or water level — a 3m tape and spirit level is not accurate enough.
  4. Check the room is square. Measure diagonals and strike a 90° line from the most prominent wall. Note any out-of-square for unit setting-out.

For an L-shaped or U-shaped kitchen, the corner unit is the datum: set it level and plumb first, then work away in both directions.

Installing Base Units

Step 1: Set and clip legs

  • Expand all legs to the calculated height for the datum unit
  • Adjust individual legs to compensate for floor undulation — the unit carcase must be level both front-to-back and side-to-side
  • Confirm worktop height with a 870mm gauge block at multiple points along the run

Step 2: Connect cabinets

  • Clamp adjacent cabinets with 5×30mm cabinet connector screws (2 pairs per joint — top and bottom)
  • Check face frames are flush before tightening — a rubber mallet corrects small misalignments
  • Use a straight edge across the front of the run to verify alignment

Step 3: Secure to wall

  • Some base units have a back rail for wall fixing; others require a screw through the back panel
  • On masonry walls: Rawlplug or Liebig anchor, 7.5×75mm screw — check wall type (solid brick, block, or cavity) before drilling
  • On stud walls: locate studs with stud finder or magnetic stud finder; 4.5×50mm wood screw into stud
  • Securing to wall is secondary to levelling — it prevents tipping but does not bear the vertical load (that's the legs)

Wall Cabinet Installation

Wall cabinets carry significant weight — a fully loaded wall cabinet can weigh 25–40kg. The fixing must be into structural material.

Masonry (solid brick/block):

  • Mark cabinet position on wall from the setting-out line
  • Drill 7mm holes for 7.5mm frame screws at top rail of cabinet position
  • Plug with appropriate Rawlplug (brown for 7mm hole in brick)
  • Screw cabinet through back rail with minimum 2 fixings per cabinet
  • Check level and plumb before fitting next cabinet

Plasterboard on stud wall:

  • NEVER fix only into plasterboard — plasterboard toggles are not rated for kitchen cabinet loads
  • Locate studs with stud finder; mark stud centres on wall above cabinet line
  • Where studs don't coincide with cabinet back rail positions, fix a horizontal timber batten (47×75mm minimum) spanning at least 2 studs, then hang cabinets from the batten
  • Alternative: steel hanging rail system (e.g., Häfele AXILO 36 or equivalent) fixed to 3+ studs, cabinets hang on rail

Hollow concrete block or thermalite aerated block:

  • Avoid standard frame screws — use specialist expanding fixings (e.g., Rawlplug Throughbolt or Fischer GB anchor) rated for the block type
  • Test 1–2 fixings with pull test before hanging all cabinets

Fitting Cornice, Pelmet and Kick Board

Cornice:

  • Cornice runs along the top of wall units and covers the gap between unit tops and ceiling
  • Cut internal corners at 45° mitre using a mitre box or compound mitre saw
  • Test-fit both pieces before gluing — dry fit is essential for tight joints
  • Fix with 18-gauge brad nails (15mm) or panel adhesive (small blobs, press and hold)
  • Fill nail holes with matching filler or coloured wax crayon

Pelmet:

  • Pelmet attaches to the underside of the front of wall units
  • Most kitchen ranges have a pelmet track clipped to the front of the unit base, or the pelmet is screwed directly through the front of the base cabinet from inside
  • Run a continuous bead of hot-melt or clear grab adhesive along the inside face
  • Mitre internal and external corners as for cornice

Kick board / plinth:

  • Kick boards attach to kick clips snapped onto the adjustable legs
  • Cut kick boards to length with a fine-tooth saw; cope at external corners (45° mitre) or butt at internal corners with filler strip
  • Floor to kick gap must be <5mm to prevent debris accumulation; adjust legs as needed
  • Where appliances are integrated (dishwasher, fridge), a plinth strip spans the gap — measure appliance kick height carefully; typically 10–15mm taller than standard kick

Frequently Asked Questions

The walls are badly out of plumb — should I pack the wall cabinets away from the wall?

Yes. If the wall leans more than 10mm over the cabinet height, pack with spacers at the top so the cabinets hang plumb and the doors open freely. Use flat plastic packers or cabinet-depth scribing strips. The gap at the wall can be concealed with a scribing strip or silicone if less than 15mm. For gaps over 15mm, fit a scribing panel — a full-height panel trimmed to follow the wall profile.

How do I handle a corner base unit — Lazy Susan or L-shaped?

For Lazy Susan (carousel) corners: the corner unit is always installed first; it must be level in all directions. Align the adjacent base units to the corner unit front face. The door overlay of the corner unit typically determines the setback of the adjacent unit face — follow the manufacturer's template.

For L-shaped false corner units: install the corner unit with 40mm clearance from the adjacent unit's door path. The gap is concealed by a false door/filler strip.

Can I fix wall cabinets into a chimney breast?

Only with extreme caution. Old chimney breast masonry may be:

  • Lime-mortared soft brick from 1900–1940 (holds fixings poorly)
  • Hollow flue liners (drill hits an air void)
  • Corbelled brickwork with large voids

Probe drill holes before fixing. If there is insufficient solid material, fix a 47×100mm timber batten horizontally, spanning solid masonry on each side of the chimney breast, and hang the cabinet from the batten.

What height for wall cabinets above a hob?

Approved Document J (combustion) and the hob manufacturer's installation guide specify minimum clearances above a hob. Typically:

  • Electric hob: minimum 420mm from hob surface to bottom of cabinet
  • Gas hob: minimum 650mm to bottom of cabinet (or as per hob manufacturer — whichever is greater) Always check the hob installation guide — some manufacturers specify 750mm for gas.

Regulations & Standards