What is the best flooring for an extension with underfloor heating?

Porcelain tile conducts heat best, so it gives the most efficient output from underfloor heating, while LVT is nearly as good and feels warmer and softer underfoot. Engineered wood works but lets through less heat, and thick carpet or laminate is a poor choice over UFH.

Is LVT or laminate better for an extension floor?

LVT is the better choice because it is fully waterproof and stable over underfloor heating, whereas laminate lets water into the joints and swells once the core gets wet. For only marginally more per square metre, glue-down LVT gives far better water resistance and UFH performance.

Should you lay flooring before or after the kitchen units?

It depends on the material. Floor tiles are usually laid across the whole room first so the units sit on a continuous surface, while LVT and other floating coverings should not sit under heavy units, so the kitchen goes in first and the floor runs around it.

Why is engineered wood used instead of solid wood over UFH?

Solid wood expands and contracts too much through heating cycles and will warp, cup, or gap. Engineered wood bonds a real hardwood layer to a stable plywood or softwood core, so it stays flat over underfloor heating.

Do you need a movement joint where an extension floor meets the house?

Yes. The extension and the original house are separate structures that settle at different rates, so a flexible movement joint is needed at the boundary or rigid coverings like tile will crack along the join.

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Phase 7 · Second Fix · Task 05 of 07

Flooring for Your Extension: Options, Costs, and Timing

LVT, porcelain tiles, or engineered wood for your extension? Costs from £50 – £75 per m2 to £50 – £120 per m2/m², plus the moisture test that controls everything.

9 min readUpdated 2026Premium

Decision flowchart showing extension flooring options filtered by UFH compatibility, water resistance, and comfort, with cost ranges for each material type

Prerequisites

Complete these first

The floor is the biggest surface in your new room, and the one your eyes (and bare feet) land on every day. Get it right and a run of large-format porcelain or warm engineered oak pulls an open-plan extension together and makes it read as one calm, generous space. Get it wrong and it's the finish you notice every morning, and the hardest one to change once the kitchen is sitting on top of it.

Two things decide whether you get it right. The first is choosing a material that suits how you actually live and works with your underfloor heating. The second is not laying a single plank or tile until the screed underneath is genuinely dry. The first is the enjoyable part. The second is the one that catches people out, so this guide is honest about both.

What this guide covers

01The moisture test that gates everything
02Your main options
03UFH compatibility: the number that matters
04Tiles first or units first?
05Floor levels: plan this during construction, not after
06What it costs
07Extending flooring beyond the extension
08Before your installer arrives

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