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Prep your sub-floor.
Level, dry and sound — the bit that decides whether laminate, tile or LVT lasts 10 or 25 years.
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Costs, timelines, pitfalls and the right questions to ask before any flooring starts on subfloor Preparation.
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Itemised quotes from up to 3 local floorings on subfloor Preparation — so you can compare like-for-like, not lump sums.
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Top tips
Hiring a flooring, without the regret.
Four moves that separate a smooth job from a nightmare.
Floor laid on damp concrete
Wood and laminate cup within 6 months. Always test moisture.
Unfilled dips
Bumps and dips telegraph through laminate as hollow sounds and click failures. Self-level to 3mm in 2m.
Insufficient ply over timber
6mm minimum for tile; 18mm structural ply for stability over springy joists.
Hidden rot or beetle damage
Always lift and inspect existing timber subfloors. Treat or replace damaged boards.
Costs & timeline
Know what it costs. Know when it ends.
Indicative UK ranges and what affects price.
Cost range
By job type
Inc. VAT · 2026
Source: NMT quotes
Source: NMT quotes
Self-levelling 3–5mm per m²Concrete subfloor
£10–£25/m²
Self-levelling 5–10mm per m²Heavier dips
£15–£35/m²
Ply-lining (6mm) per m²For tile-on-timber
£12–£25/m²
WBP ply (18mm) per m²Structural overlay
£20–£40/m²
Liquid DPM epoxy per m²Two-coat moisture barrier
£15–£30/m²
Board fixing & repair per m²Loose boards screwed down
£8–£20/m²
!
Quote spread is typically ± 18% — always get 3 quotes.
At a glance
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Flooring explained
A flat, dry, sound subfloor is the foundation of every successful floor install. Skipped or rushed subfloor prep is the single biggest cause of premature floor failure in UK homes. Expect to pay £8–£40 per m² for proper subfloor preparation depending on the work needed.
What Does the Work Involve?
The fitter checks the existing subfloor for: flatness (3mm in 2m for most floors; 1mm for large-format tile or LVT), moisture (max 3% CM for concrete; 18% for timber), soundness (loose boards or cracks fixed), and damp ingress. Common remedies: self-levelling compound (3–10mm thick to smooth concrete), ply-lining (6mm tile-backer or 18mm WBP over timber joists), DPM (liquid epoxy moisture barrier on damp concrete).
Typical Costs
| Item | Low (£) | High (£) | Notes |
|---|---|---|---|
| Self-levelling 3–5mm per m² | 10 | 25 | Concrete subfloor |
| Self-levelling 5–10mm per m² | 15 | 35 | Heavier dips |
| Ply-lining (6mm) per m² | 12 | 25 | For tile-on-timber |
| WBP ply (18mm) per m² | 20 | 40 | Structural overlay |
| Liquid DPM epoxy per m² | 15 | 30 | Two-coat moisture barrier |
| Board fixing & repair per m² | 8 | 20 | Loose boards screwed down |
| Moisture meter test | 0 | 50 | Free with most quotes |
How Long Does It Take?
Self-levelling 20 m²: 4 hours work, 24 hours cure. Ply-lining 20 m²: 1 day. DPM epoxy: 1 day. Total prep often 1–2 days before the finish floor goes down.
DIY or Professional?
Self-levelling is DIY-able with care. Moisture testing and DPM application are professional — moisture content is critical and easy to get wrong.
Choosing the Right Tradesperson
The flooring fitter normally handles subfloor prep. Always insist on a moisture test before any wood or vinyl floor is laid — cheap fitters skip this step and the floor fails. Get the moisture reading in writing.
UK Regulations
No specific regulations. Manufacturer warranties on flooring are usually void if substrate prep doesn't meet their spec.
Common Problems
- Floor laid on damp concrete: Wood and laminate cup within 6 months. Always test moisture.
- Unfilled dips: Bumps and dips telegraph through laminate as hollow sounds and click failures. Self-level to 3mm in 2m.
- Insufficient ply over timber: 6mm minimum for tile; 18mm structural ply for stability over springy joists.
- Hidden rot or beetle damage: Always lift and inspect existing timber subfloors. Treat or replace damaged boards.
Frequently Asked Questions
How flat does a subfloor need to be?
3mm in 2m for laminate, vinyl, carpet. 1mm in 2m for LVT and large-format tile (600 × 1200mm+).
Can I self-level my own floor?
Yes — Ardex, Mapei or Sika compounds are user-friendly. The trick is mixing to the right consistency and finishing the edges.
What's a DPM?
Damp-Proof Membrane. Either a plastic sheet under the slab (during construction) or a liquid epoxy applied to existing concrete to block residual moisture.
How do I test moisture?
Concrete: pin-type moisture meter or hygrometer test (best). Timber: pin-type meter. Or hire a Tramex CME4 from local hire shop.
Will the floor fail if I skip subfloor prep?
Yes — within 6–18 months typically. Wood cups, laminate joints fail, vinyl bubbles, tile cracks. Subfloor prep is the most important step.
Do I need ply-lining over chipboard?
For tile and LVT yes — chipboard moves too much. For laminate and carpet, sound chipboard is fine.
This guide was written with AI assistance and is intended for general information only. Prices are estimates based on UK averages and may vary by region. Always get at least three quotes and consult a qualified professional before starting any work.
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