Laying a floor looks like one of those “one weekend, job done” projects — until you hit a dip in the subfloor, the boards start clicking, or the whole room develops that maddening squeak you can’t un-hear.
Most DIY flooring problems aren’t caused by the planks you buy. They come from what’s underneath: a subfloor that isn’t flat, moisture that hasn’t been checked, the wrong underlay, or edges fitted too tight with nowhere to move.
This guide focuses on the part most blogs skip: diagnosing issues before you lay anything, levelling properly, choosing the right underlay, and getting clean cuts around awkward bits like frames, pipes and door trims.
Step 1: Diagnose squeaks, dips and movement before you buy flooring
Before you touch underlay or click a board together, find out what’s going on under your feet.
Quick checks that tell you everything
1) The slow walk test
Walk slowly around the room in socks. Pay attention to:
- squeaks (high-pitched, rhythmic)
- soft spots (slight bounce)
- dips (heel drops into a low area)
- clicking (subfloor movement or loose boards)
2) Straight-edge check (no fancy kit needed)
Use something rigid and long:
- a long spirit level
- a straight plank
- even a long piece of laminate packaging (in a pinch)
Slide it across the floor. Any gap under it tells you where the dips are.
3) Knock test for hollow spots (especially on old floors)
Tap with your knuckles or a rubber mallet. Hollow sounds can indicate:
- delaminated ply
- loose chipboard
- sections not fully supported
What squeaks usually mean
- Timber subfloor squeak: loose boards rubbing on nails/joists
- Chipboard squeak: joints moving, or boards flexing due to poor fixing
- Concrete squeak (rare): usually the underlay/LVT moving rather than the slab
Fixing squeaks after you install flooring is possible, but it’s always worse than doing it right at the start.
Step 2: Identify your subfloor (because it changes everything)
Most DIY floors fail because the prep didn’t match the subfloor.
Timber floorboards
- often uneven
- movement between boards is common
- gaps and bounce need addressing
Usually best approach: re-fix boards + overlay with ply (if needed) + correct underlay.
Chipboard / OSB (typical upstairs subfloor)
- often flat but can squeak on joints
- edges can swell if moisture’s been around
Usually best approach: screw down properly + fill joints/low spots + appropriate underlay.
Concrete / screed
- great base if flat and dry
- moisture is the big risk
- dips and ridges show up badly under LVT
Usually best approach: moisture check + leveller where needed + correct underlay/adhesive system.
Step 3: Fix movement and squeaks properly (so they don’t come back)
Timber / chipboard squeaks: the proper fix
1) Find the joists
- look for nail lines
- lift a board if needed
- use a stud finder if you have one
2) Screw the subfloor down
- use proper flooring screws
- hit the joists where possible
- add extra screws around squeaky areas and joints
- remove any loose nails (they’ll keep rubbing)
3) Check for bounce
If the floor flexes a lot, you may need:
- extra noggins between joists (more work)
- or a ply overlay to stiffen the surface
Step 4: Levelling compounds — when you need them (and when you don’t)
Levelling is the difference between a floor that feels “solid” and one that clicks and creaks.
When levelling compound is needed
You almost certainly need leveller if:
- you’re laying LVT (click or glue-down)
- the floor has dips/ridges you can feel underfoot
- there’s a noticeable slope or uneven joins
- you can slide a coin under your straight edge in multiple places
Laminate is more forgiving than LVT, but it still needs a stable, reasonably flat surface. A few mm of dip can become a click-point or wear spot over time.
When levelling compound isn’t the answer
Leveller won’t fix:
- loose subfloor boards
- bounce from weak joists
- damp problems in concrete
- rotten or swollen chipboard
If the base moves, leveller will crack. You must stabilise first.
Step 5: How to apply levelling compound (without creating more problems)
This is where DIY jobs can go sideways: poor priming, wrong mix, or trying to patch dips like filler.
1) Clean and prep properly
- vacuum thoroughly (dust ruins adhesion)
- remove paint blobs, high spots, grit
- seal big cracks or gaps so leveller doesn’t disappear underneath
2) Prime the surface
Primer isn’t optional. It controls suction and helps bonding.
You’ll save hours if you get Trade Building Supplies like leveller and screed primer on day one.
Without primer:
- leveller can dry too fast
- it can debond
- it can go patchy and weak
3) Mix carefully (don’t freestyle it)
- follow the bag water ratio
- mix thoroughly (lumps = weak spots)
- don’t over-water to “make it flow”
Watery leveller sets weaker and can crack or crumble under traffic.
4) Pour and spread (work with the clock)
Leveller starts setting faster than you expect.
- pour in a controlled way
- use a smoothing trowel
- feather the edges out
- don’t keep going back over semi-set areas
5) Let it cure fully
Dry-to-touch isn’t the same as ready-for-flooring. If you trap moisture under laminate or LVT, you’ll regret it.
Step 6: Underlay choices by floor type (and how cheap underlay ruins floors)
Underlay isn’t just for comfort. It affects:
- sound
- stability
- click system lifespan
- moisture resistance
- how “solid” the floor feels
Decent trade building merchants can advise on the right underlay thickness for your subfloor.
Laminate underlay basics
Good for:
- minor imperfections
- impact sound reduction
- stabilising the click system
Bad underlay causes:
- bouncing
- joint separation
- “drummy” hollow sound
- broken locking edges
LVT underlay basics (more sensitive than people realise)
LVT needs a flatter base than laminate.
- click-LVT has more tolerance
- glue-down LVT needs near-perfect prep
Too-soft underlay can make LVT feel spongy and can stress the joints.
Moisture barriers (don’t skip on concrete)
If you’re laying over concrete, moisture protection matters even in “dry” rooms.
A damp issue on concrete doesn’t always show up as visible wetness — it shows up later as:
- lifting
- mouldy underlay
- musty smell
- warped joints
Step 7: Acclimatisation and expansion gaps (this is where creaks begin)
A lot of DIY floors creak because they’re pinned tight and have nowhere to move.
Acclimatisation (don’t rush it)
Leave flooring in the room before fitting so it reaches room temperature and humidity.
Skipping acclimatisation can lead to:
- boards expanding after installation
- tight edges
- buckling
- noisy movement
Expansion gaps: non-negotiable
Your floor needs a gap at the perimeter (and sometimes at thresholds). If you push laminate tight to walls, it will push back.
Typical pain points:
- tight fits around door frames
- tight cuts at radiator pipes
- skirting not allowing movement
- thresholds forcing boards to pinch
You want the floor to float. If it’s trapped, it creaks and lifts.
Step 8: Cutting tips for clean edges around frames and pipes
Messy cuts aren’t just ugly — they can cause tight spots that create noise.
Door frames and architraves (the clean method)
Don’t try to scribe boards around frames freehand.
Instead:
- undercut the frame slightly
- slide the flooring underneath
- keep the expansion gap hidden
A small handsaw or multi-tool makes this far easier.
Pipes (the method that doesn’t crack boards)
- drill a hole slightly larger than the pipe
- cut a neat wedge out to fit around it
- glue the wedge back in place (depending on floor type)
- cover with a pipe collar
Trying to force boards over pipes is a common way to split click joints.
Step 9: Avoid these common mistakes (the ones that create creaks)
1) Damaging the locking system
Click joints are precise. If you:
- hammer edges too hard
- angle boards incorrectly
- force warped boards into place
…you’ll weaken the joint and it’ll click/squeak later.
2) Fitting edges too tight
Floors expand. Tight edges = pressure points = noise.
3) Laying over an uneven subfloor “because the underlay will fix it”
It won’t. Underlay masks tiny imperfections, not dips and movement.
4) Skipping primer under leveller
Leveller without primer is one of the most common DIY failures.
5) Poor room planning
Plan your direction and your first row. A bad start makes the whole job harder.
Final step: The “walk test checklist” after installation
Before you put furniture back and call it finished, do this:
Walk test checklist
- no squeaks in traffic areas
- no clicking at joints
- no bounce or hollow feel
- no tight spots around frames and pipes
- expansion gaps still present at perimeter
- thresholds fitted without pinching the floor
- the floor feels consistent in every direction
- no visible gaps opening along long runs
If something feels off now, fix it before skirting, trims and heavy furniture hide the evidence.
Tools and Trade Building Supplies worth having from day one
If you’re doing this properly, the tools matter almost as much as the flooring.
Tools
- spirit level / straight edge
- tape measure + pencil
- jigsaw or circular saw (cleaner long cuts)
- multi-tool or fine handsaw (door frames)
- tapping block + pull bar (for laminate/click LVT)
- spacers (for expansion gaps)
- vacuum (dust ruins prep)
- mixing bucket + paddle (for leveller)
Materials
- levelling compound
- screed/leveller primer
- suitable underlay (correct type + thickness)
- moisture barrier (if required)
- flooring screws (for timber subfloors)
- thresholds + trims
And yes, trade building supplies like primer and leveller aren’t exciting, but they’re the difference between a floor that lasts and one that becomes a constant irritation.
Finishing touches that stop creaks long-term
The last 5% is where floors get ruined.
- Don’t trap the floor with skirting or trims
- Fit thresholds that allow the floor to expand
- Leave correct gaps at walls, pipes and frames
- Keep the room stable for the first few days (avoid big temperature swings)
If you’re unsure about underlay thickness or moisture protection, trade building merchants are genuinely useful here, getting the right product combination up front is far easier than diagnosing a creaky floor once it’s installed.