18mm Solid Wood Flooring
18mm solid wood flooring is the classic thickness for a traditional solid oak floor: boards of solid hardwood that are thick and strong enough to be secret-nailed straight to joists in many homes, and that can be sanded and refinished many times over their life. 18mm solid oak flooring has been laid in British homes for generations, and with care it lasts for decades and can be renewed again and again.
Solid oak flooring 18mm thick comes in narrow, standard and wide boards, rustic to prime grades, and every finish: natural and white oils, lacquers, smoked and grey tones, and unfinished solid wood for finishing on site. For a thicker board, see 20mm solid wood; for a slimmer one, 15mm solid wood. Every solid oak is in solid oak flooring.
For concrete floors, kitchens and underfloor heating, 18mm wood flooring in engineered form is usually the better choice: see 18mm engineered wood. See all solid wood flooring, or read our solid wood guide.
Not sure which floor is right? Order free samples and see them in your own light, or call our team on 020 3287 6206 for honest, no-pressure advice.
Aurea Golden Hand Scraped Distressed Oiled Rustic Solid Oak Flooring 18 x 125mm
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Aurea Golden Hand Scraped Distressed Oiled Rustic Solid Oak Flooring 18 x 125mm
Why 18mm?
- Joist fixing: many 18mm boards can be secret-nailed directly to joists at the right spacing, replacing old floorboards.
- Long life: the wearable thickness above the tongue can be sanded many times.
- Solid feel: heavy and quiet underfoot.
- Height matching: lines up with traditional floorboards in period homes.
How 18mm solid wood is fitted
Secret-nailed to joists
Boards are nailed at an angle through the tongue into each joist, so the nails are hidden. The joists must be level, sound and at the spacing the maker allows (often no more than about 400mm centres). This is the traditional method over suspended timber floors.
Nailed to a timber subfloor
Over plywood or existing floorboards laid at right angles.
Glued down
To a dry, flat concrete or plywood subfloor with a solid wood flooring adhesive, after a moisture test. Wide boards are often glued as well as nailed.
Solid wood is not usually floated, and most solid boards are not recommended over underfloor heating.
Where solid wood is not the right choice
- Underfloor heating: choose engineered wood approved for heating.
- Damp or new concrete: moisture causes solid boards to swell and cup.
- Kitchens and conservatories: large changes in humidity and heat; engineered is safer.
- Bathrooms: never real wood.
How to choose
Width: narrow and standard boards move less; wide boards look grand but need gluing as well as nailing. Grade: rustic hides wear; prime looks refined. Finish: oil is natural and repairable; lacquer is low maintenance; unfinished boards are sanded and finished in place for a perfectly level surface.
Acclimatisation and moisture
Solid wood must be acclimatised in the room it will be laid in, at normal living temperature and humidity, for the time the maker states. Check the moisture of both boards and subfloor before fitting. Most problems with solid floors come from moisture.
Living with a solid floor
Solid wood moves with the seasons: small gaps can open in dry winters and close in damp summers. Keeping indoor humidity steady limits this. Door mats, felt pads and a pH-neutral wood floor cleaner keep it looking good, and oiled floors are refreshed with maintenance oil.
Fitting tips
Leave an expansion gap at every wall, finish with oak skirting or beading, and use an experienced fitter for nailed or glued floors. Our installation guides explain the methods.
Comparing samples at home
Order free samples of two or three options and put them on the floor of the room where they will be laid. Look at them in daylight and in the evening under your own lamps, next to the walls, skirting, units and furniture they will sit with. Colours and textures look different in every room and on every screen, so a few minutes with real samples is the best way to avoid a costly mistake. Stand back as well as looking close up: a floor is mostly seen from standing height and from the doorway.
Common mistakes
- Nailing to joists that are too far apart or uneven.
- Laying on damp concrete or over underfloor heating.
- Skipping acclimatisation and moisture checks.
- Laying boards tight to the walls, with no room to expand in a damp summer.
Replacing old floorboards with 18mm solid oak
In many period homes, the old pine floorboards are lifted and new solid oak boards are nailed straight to the same joists. Before you do, check the joists are sound, level and at a spacing the new boards allow; pack or plane uneven joists, and add noggins where needed. Insulate between the joists on ground floors over a void, and leave the void ventilated. This is skilled work, so most homeowners use an experienced fitter.
FAQs on 18mm Solid Wood Flooring
Many 18mm boards can be secret-nailed to joists at the maker’s stated spacing. Check the product.
Many times over its life, depending on the thickness above the tongue and how deeply it is sanded.
Usually not recommended. Engineered wood approved for heating is the safer choice.
Solid is traditional over joists; engineered is more stable and suits concrete and underfloor heating.
Yes, glued down to a dry, flat slab after a moisture test. New or damp concrete is not suitable.
Solid wood shrinks in dry winter air and swells in damp summers. Steady humidity limits gaps.
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