A flooring installation succeeds or fails on preparation far more than most people expect. The actual fitting is often the easy part. Getting the room, the subfloor, and the material itself into the right condition beforehand is what determines whether the floor stays flat and gap-free for decades, or starts showing problems within the first year.
Room Temperature Matters More Than You'd Think
Installation should happen in a room at a normal, stable temperature, ideally around 20°C. This isn't an arbitrary number, it reflects the conditions the floor will actually live in day to day, so installing it in a room that's unusually cold or hot sets up a mismatch that shows up as movement once the room returns to normal temperatures.
Getting Humidity Right
Humidity is one of the most commonly overlooked factors, and it's worth checking properly rather than guessing. A moisture meter, widely available from builders' merchants, gives an accurate reading rather than relying on how the air simply feels.
The figures worth aiming for:
- Room relative humidity: roughly 30% to 50% is the range flooring manufacturers generally recommend for both installation and long-term performance.
- Wood moisture content: most timber flooring performs best installed at around 6% to 9% moisture content, though this varies slightly by species and product, so it's worth checking the manufacturer's specific guidance.
- Below 30% humidity is generally too dry for installation and increases the risk of excessive shrinkage and gapping once the floor settles in.
If the room is running too dry, a humidifier ahead of installation day can bring it into range before you start.
Measuring Up Properly
Before ordering material, calculate the exact area of the room, then add roughly 10% extra, around 3 to 4 square metres for an average room, to account for cutting waste and offcuts that can't be reused elsewhere. Running short partway through a job, particularly with a specific batch or colourway, can be a genuine headache if matching material isn't readily available afterward.
Acclimatising The Flooring Before You Start
New flooring shouldn't go straight from delivery to installation. Leaving it in the room where it will actually be fitted for at least 48 hours beforehand allows the material to adjust to the room's specific temperature and humidity, reducing the amount of movement that happens after installation rather than before it. Skipping this step is one of the more common causes of early gapping or unevenness in an otherwise well-installed floor.
Checking The Subfloor Itself
The subfloor needs to be smooth, clean, and dry before anything goes on top of it, and its moisture condition matters just as much as the room's:
- Concrete subfloors should generally read within the range specified by the flooring manufacturer, commonly a low single-digit percentage, before it's considered safe to install over. Newer concrete can take considerably longer to dry out fully than people expect, so this is worth checking properly rather than assuming enough time has passed.
- Wooden subfloors have more tolerance but should still be checked, with most manufacturers specifying an upper moisture limit before installation.
- If either reading comes back too high, addressing the moisture source, or in some cases using a damp-proof membrane, is necessary before installation rather than proceeding and hoping for the best.
Underlay Isn't An Afterthought
The right underlay affects comfort underfoot, sound performance, and how well the floor handles minor subfloor imperfections. Different underlays suit different flooring types and different priorities, acoustic performance in a flat, moisture protection over concrete, or simple comfort in a quiet bedroom, so it's worth matching the underlay to the actual room rather than defaulting to whatever's cheapest.
Tools You'll Actually Need
A basic but genuinely necessary kit for a fitting project includes:
- A tapping block, used to knock planks firmly into place without damaging the edges.
- Expansion wedges, placed around the perimeter of the room to maintain the gap that allows the floor to expand and contract naturally.
- A board puller, useful for the final rows where there's no room to use a tapping block directly.
- A pencil, hand saw, and measuring tape for marking and cutting boards accurately as you go.
Missing even one of these can turn a straightforward job into a frustrating one, particularly the expansion gap tools, since skipping that step is one of the more common causes of buckling later on.
Frequently Asked Questions
What humidity level is best for installing wood flooring?
Roughly 30% to 50% relative humidity in the room, with the wood itself ideally sitting around 6% to 9% moisture content, though this varies slightly by product and species.
Why does flooring need to acclimatise before installation?
It allows the material to adjust to the room's actual temperature and humidity before it's fixed in place, which significantly reduces the amount of movement, and the risk of gaps or unevenness, that happens after fitting.
How much extra flooring should I buy beyond the room's exact measurements?
Around 10% extra is the general rule of thumb, to account for cutting waste and offcuts, particularly around the room's edges and any awkward corners.
Can I install flooring over a concrete subfloor that's still slightly damp?
It's not recommended without addressing the moisture first. Installing over a subfloor that hasn't dried sufficiently is one of the most common causes of early flooring failure, and in some cases a damp-proof membrane is needed before work can proceed safely.
Call us on 020 7036 0625 or request a free site visit and we'll assess your room and subfloor properly before recommending the right installation approach.
