How to Prepare a Subfloor Properly Before Laying Anything

Nearly every flooring failure traces back to the surface underneath it, not the product on top.

Check flatness with a long straightedge

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Lay a 2m straightedge across the floor in several directions. Most manufacturers allow around 3mm of deviation over 2m. Anything worse and you will get flex, gaps and eventually broken locking joints.

Test the moisture content

Concrete slabs hold moisture far longer than people expect — roughly a month per 25mm of thickness in decent conditions. Laying wood or vinyl over a damp slab is the most common route to a floor that has to be lifted within the year.

Level with the right compound

Self-levelling compound handles broad dips; a patching compound handles local defects. Priming first is not optional — it stops the slab drawing water out of the compound and cracking it.

Let everything acclimatise

Wood and laminate need 48 to 72 hours in the room where they will be installed, still boxed, at normal living temperature. Skipping this step is why boards gap in winter and buckle in summer.

Written by

Kushal E

Senior Writer — Garden & Kitchen

Kushal E covers gardens, kitchens and the parts of a home where daily use decides whether a design was any good. He came to writing from horticulture, and he still keeps a working balcony garden in Bengaluru that doubles as a test bed for most of what he publishes — which is why his plant guides tend to mention the things that failed as well as the ones that worked. On the kitchen side he focuses on modular layouts, storage that survives real cooking, and the honest maintenance cost of the surfaces everyone falls in love with in a showroom. He is happiest writing the article that saves someone from an expensive, good-looking mistake.