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How to Fit a Flat Pack Kitchen: A Step-by-Step Installation Guide

Fitting your own kitchen is one of the most rewarding home improvement projects you can take on — and with the right preparation, it's well within reach for a competent DIYer. This guide walks you through the full process, from clearing the old kitchen to fitting the final door.

Before You Start: What You'll Need

Tools:

  • Tape measure
  • Spirit level (a long one — at least 1,200mm — is ideal)
  • Drill and drill bits
  • Screwdrivers (flathead and Pozidrive)
  • Pencil
  • Jigsaw (for worktop cutouts)
  • Mitre saw or handsaw
  • Clamps
  • Stud finder
  • Safety glasses

Materials to have ready before fitting day:

  • All units checked and accounted for (check against your order before your fitter arrives)
  • Wall plugs and screws appropriate for your wall type
  • Cabinet leg adjusters (included with base units)
  • Plinth clips (if not included)
  • Silicone sealant
  • Filler and decorator's caulk for finishing

Important: Do not book your fitter for the day of delivery. Check and count every item when your order arrives and contact us immediately on 02920 007 948 if anything is missing or damaged — before fitting begins.

Step 1: Strip Out the Old Kitchen

Before any new units go in, the old kitchen needs to come out cleanly.

  • Turn off the water supply at the mains or isolation valves before disconnecting the sink
  • Turn off the electricity at the consumer unit before disconnecting any hardwired appliances. If you're not confident doing this, use a qualified electrician
  • Gas appliances must be disconnected by a Gas Safe registered engineer — never attempt this yourself
  • Remove all old units, taking care not to damage walls or floors you plan to keep
  • Once clear, check walls for damage, damp, or uneven surfaces that need addressing before installation begins

Step 2: Check Your Walls and Floor

Rarely are walls and floors perfectly flat or level — especially in older UK homes. Identify problems now rather than when a unit is half-hung.

  • Use your spirit level to check whether the floor is level across the full width and length of the kitchen run
  • Check walls for bumps, old fixings, or plaster damage
  • If your floor is significantly uneven, the adjustable legs on your base units will compensate — but note the degree of variation so you can set your leg heights accordingly
  • Locate and mark all wall studs using a stud finder — you'll need to know where they are for fixing wall units securely

Step 3: Find Your Datum Line

A datum line is a level horizontal reference line marked on your wall that everything else is measured from. Getting this right is the most important single step in a kitchen installation.

  • Measure up from the highest point of your floor (floors are rarely level) and mark a point on the wall — typically 900mm from the floor, which is standard worktop height
  • Using your spirit level, extend this mark as a level horizontal line along every wall where units will be fitted
  • All your base unit heights and wall unit positions will be referenced from this line

Step 4: Assemble the Base Units

Assemble each carcass before installing it. Our cabinets use pre-fitted cam and dowel joints — follow these steps for each unit:

  1. Lay out all panels and identify each piece
  2. Insert the dowels into the pre-drilled holes
  3. Connect the panels and tighten the cam locks with a flathead screwdriver — do not overtighten
  4. Fit the back panel
  5. Fit the drawer runners if applicable (these clip or screw into the pre-drilled positions)
  6. Attach the adjustable legs to the base of the unit

Assemble all your base units before you start positioning any of them — it's much easier to work this way than to assemble and install one at a time.

Step 5: Position and Level the Base Units

  • Start from the most visible or most fixed point in your layout — typically a corner, or the unit that houses the sink or hob
  • Place your first unit in position and adjust the legs until the top of the unit sits exactly at your datum line
  • Check level in both directions (front to back and side to side)
  • Once level, move to the next unit and repeat — use a long spirit level across multiple units to keep them consistent
  • When two adjacent units are level, clamp them together and drill through the side panels to join them with screws (use the pre-drilled fixing holes where provided)
  • Work along the full run before fixing any units permanently to the wall

Once the full run is level and aligned, fix the units to the wall through the hanging rail at the back of each cabinet, using appropriate fixings for your wall type (masonry anchors for brick or block, timber screws into studs for stud walls).

Step 6: Fit Corner Units

Corner units require a little extra care. Leave a clearance gap between the corner unit and the adjacent run to allow doors and drawers to open without catching. The size of this gap depends on the unit and door style — check the dimensions on your product pages.

If you're using a carousel or pull-out corner unit, fit the mechanism before the unit goes in — it's much easier with access to all sides.

Step 7: Hang the Wall Units

Wall units are hung from a metal hanging rail fixed to the wall. The rail must be level and securely fixed — these units will carry significant weight once filled.

  • Fix the hanging rail to the wall at the correct height. Standard practice is to leave 450mm–550mm between the top of the worktop and the bottom of the wall units. Mark this position from your datum line
  • Ensure the rail is fixed into solid material — studs, masonry, or a batten — not just into plasterboard
  • Hang each wall unit onto the rail and adjust the hooks for height and depth until the units are level and flush
  • Join adjacent wall units together through the side panels, as with the base units

Step 8: Fit Tall Units

Tall units — larder units, oven housings, fridge housings — should be fitted after base units are in position but before worktops go on. They are fixed to the wall through the back panel and, where possible, joined to adjacent base or wall units for additional stability.

Step 9: Fit the Worktop

Worktops are not supplied by Flat Pack Kitchens and will need to be ordered separately. General guidance:

  • Measure and cut worktops carefully — measure twice, cut once
  • For sink cutouts and hob cutouts, use a jigsaw and follow the template provided by the appliance manufacturer
  • Seal all cut edges with worktop sealant, especially around the sink cutout, to prevent moisture ingress
  • Fix the worktop to the base units from below using worktop connector bolts at joins and metal clips at the front and back rails
  • Seal the join between the worktop and the wall with decorator's caulk or silicone — never leave this gap open

Step 10: Fit the Doors and Drawer Fronts

  • Hang doors on the pre-fitted hinges. Most hinges have three adjustment points — height, depth, and horizontal — use these to get every door perfectly aligned
  • Step back and check each door from a distance as well as up close — misalignment is easier to spot from across the room
  • Fit drawer fronts using the adjustable fixings on the drawer box. Again, step back and check alignment across the full run
  • Fit handles once all doors and drawers are aligned — drilling through the door into a handle is much easier before the kitchen is fully loaded

Step 11: Fit the Plinth

Plinth clips onto the front of the adjustable legs to conceal them and finish the base of the kitchen.

  • Cut plinth to length using a mitre or handsaw
  • Clip into the plinth clips and check it sits flush to the floor
  • At corners, use a plinth corner piece or mitre the join at 45 degrees for a neat finish
  • Use flexible silicone or caulk where the plinth meets an uneven floor

Step 12: Connect Appliances and Plumbing

  • Plumbing — reconnect the sink waste and water supply. If you've moved either, a plumber should do this work
  • Gas — reconnect the hob or range through a Gas Safe registered engineer only. This is a legal requirement, not optional
  • Electrics — connect hardwired appliances through a qualified electrician. Plug-in appliances you can connect yourself once the kitchen is otherwise complete
  • Run a final check on all water connections before leaving them — check under the sink with the water on and look for any drips

Step 13: Final Checks and Finishing

  • Open and close every door and drawer — adjust hinges as needed
  • Check all units are still level after the worktop has been fitted (fitting can shift things slightly)
  • Apply decorator's caulk along the join between wall units and the wall, and between the worktop and the wall — a neat bead of caulk is the mark of a professional finish
  • Fit handles if not already done
  • Clean all surfaces thoroughly before loading the kitchen

When to Call a Professional

DIY installation is well within reach for most competent home improvers, but there are jobs that require qualified tradespeople regardless of your skill level:

  • Gas connections — Gas Safe registered engineer, no exceptions
  • New electrical circuits or consumer unit work — Part P qualified electrician
  • Moving soil pipes or waste stacks — plumber recommended
  • Structural work — removing walls, changing openings — requires building regulations sign-off

Useful Tips From Experience

Don't rush the levelling. Getting your base units perfectly level before fixing anything is the most important step. Every problem that comes later — doors that won't close, drawers that stick, worktops with gaps — traces back to units that weren't level at the start.

Check your order before your fitter arrives. Go through every item against your order confirmation the day delivery arrives. Replacements can be arranged quickly, but not if you only discover something missing on fitting day.

Work from fixed points outward. Always start from your most constrained position — a corner, a chimney breast, a window — and work outward. Never work toward a fixed point or you'll find yourself with a gap you can't account for.

Take photos as you go. Photograph the wall before units go up, showing where pipes and cables run. You'll be glad you did the first time you need to drill into that wall for something else.

Need Help?

If you have questions about your installation — or want to check your plan before ordering — call us on 02920 007 948or email info@flatpackkitchens.co.uk. We're happy to help.