Hints & tips on laying your first hardwood floor

Solid wood makes an attractive and practical flooring. It is always in fashion, and costs around the same as a quality carpet but is more hard-wearing.

Since 1985, County Hardwoods have specialised in supplying hardwood flooring of all types. Initially specialising in solid oak, ash and elm, we now offer a wide range of oak flooring products - both engineered and traditional oak planked flooring in random widths. 

Laying an oak floor is quite straightforward providing you observe the following guidelines:

• Timber is hygroscopic. It may expand and contract (it will absorb or give out moisture) depending on the ambient conditions when it is laid and seasonal changes thereafter.
• Always make sure that new concrete/screed is fully dry.
• Avoid using newly tanalised battens to fix down to. We would recommend that plywood battens are used instead.
• If you are laying into a conservatory, with perhaps excessive summer temperatures, consider using one of our engineered products which will be more stable.

Type of sub-floor

Traditional plank flooring can be fixed down to either joists, battens or sheet materials (flooring grade chipboard), nailed down over an existing wooden floor (lay crosswise), or glued to suitably prepared concrete/screed subfloor.

Concrete/screed base

If using chipboard or battens, prior to fitting either we suggest that you lay a 1200g polythene membrane on top of the concrete to help reduce any possible ingress of moisture from the subfloor. 

Then proceed with the installation of flooring grade chipboard (this will be T & G and WBP – waterproof). Builder’s merchants can supply in 18 or 22mm thick and sizes 1200 x 600mm. Please do not economise by using non-WBP grade, as it is likely that regular chipboard will absorb moisture like a sponge, swell and distort.

Chipboard can be screwed to the concrete or the tongue and grooves can be glued and left as a floating floor.

For installations involving battens, these should be approximatley 70mm wide (to allow the meeting of cut ends), a minimum of 25mm thick and at 350mm centres. We always recommend using plywood battens. If this is not possible, make sure that tanalised battens are fully dry before fitting the oak flooring.

If using battens, you may also want to lay sheet polystyrene insulating slab, e.g. Jablite, between the battens. This will help to deaden sound as well as provide extra insulation.

Where head height is limited the use of adhesive is invaluable. 

In the case of a concrete/screed subfloor, it is recommended that the moisture content of the slab be no more than 35% RH or 2% - 2.5% moisture by volume. In practice, however, it is very unusual for a concrete base to achieve a moisture content that low. Therefore, the use of a liquid epoxy damp-proof membrane is generally advised to prevent the moisture causing a problem with the oak flooring.  We stock Rewmar MB/DPM, which is a two part two coat operation. Once fully cured, this makes for an ideal surface in which to glue. 

The Rewmar MS Polymer adhesive is fully flexible, allowing for the natural expansion and contraction of the oak flooring. It is also compatible for use with water-based underfloor heating and with our engineered oak flooring products.

The Rewmar MS Polymer is applied directly to the newly laid DPM surface using a 6mm notched trowel, sufficient for approximatley two rows at a time.  The flooring is fitted to this, making sure that the glue does not over spill into the tongue and groove section (which would prevent the oak boards from naturally expanding and contracting).

Using the glue down method will increase your wastage.  As boards which are "sprung" not flat and straight cannot be pulled in as with nailed down installations.  These boards are not considered to be defective and are with out a manufacturing fault.  We would therefore suggest that these boards are cut and used at the ends of rows to help reduce on site wastage.

For further information regarding installations using any of the Rewmar products please either contact the office or access the following web site: www.rewmar.co.uk.

Height difference between rooms

Adding a wooden floor may bring about a difference in height between rooms at the threshold. No problem: they can be “lost” in the doorways by using a purpose-made solid oak threshold. Our workshops will be happy to machine these.

Site conditions

The site must be dry, weather tight, wet trades finished and plaster dry and subject to season and with the heating on.

It is essential that the sub-floor is totally dry. If wishing to lay over new concrete, allow at least 1 day per 1mm of thickness of concrete.  Please refer to your builder/site manager as there are many other factors which will extend the drying time of your slab.

When your solid oak flooring arrives unwrap and store it in the room that it will eventually be fitted please do not store in out buildings or garages as these areas often have more moisture and the flooring will absorb this.  Store the oak flooring on well supported battens off the ground and stack so that the air can circulate. We would suggest a minimum period of two weeks for acclimatisation however longer is always better if time permits.

The acclimatisation period for our engineered flooring is considerably less.  We would suggest two or three days.

If site conditions are not ready please consider changing delivery dates. 

Underfloor Heating - Water based

For this type of installation our oak engineered flooring really comes into its own.

It will offer greater stability and will speed up installation as there is no requirement for laying the flooring out loose over the subfloor with the under floor heating running to help further the acclimatisation of solid oak flooring.

General Advice and Recommendations (Hot Water Pipe Systems)

The radiant heat system must not exceed 8 watts/sq ft heating capacity, and the running water temperature should range between 38-48°C.

The sub-floor temperature should not exceed 27°C.

To preserve the integrity of the multi-layer hardwood flooring, the room temperature must not vary more than 10°C between seasons. The humidity must be maintained between 40 and 65% relative humidity throughout the year. A humidifier should be used to maintain relative humidity if necessary.

Pre-Installation Requirements

Before installing the multi-layer hardwood flooring, radiant heat slabs must be activated to normal living temperatures for a minimum of 21 days. This will help to ensure that the slab is dry. However, the use of a hydro-metre is advised to determine the exact moisture percentage of the slab prior to proceeding with the installation. During this period, the temperature should be gradually increased until the maximum recommended temperature is reached. The maximum temperature should be maintained for at least a week.

Heating pipes must be covered with 30mm of concrete or minimum 3mm below bottom side of plywood sub-floor. In addition, for plywood sub-floor, heat transfer plates or insulation boards must be under pipes.

Prior to the installation date - approximately 3 days, switch the heating unit off following the manufacturer's heating units guide-lines. This ensures that at the time of installation, the sub-floor temperature is between the recommended range of 18-20°C.

The installation can now be carried out.

After installation, the temperature of 18-20°C should be maintained for 3-4 days before the heating unit is turned on. Then gradually increase the temperature over a further 3-4 days until the recommended surface temperature of 24-27°C is reached. Whatever the season, this temperature should be maintained for a further 3-4 days.

During the heating period, small hairline cracks might appear. These hairline cracks are generally evenly spread and are not cause for concern. They may also eventually appear under rugs and furniture.

Allowing for wastage

Allow 10% extra if laying onto joists, battens or gluing down, just 5% if onto sheet materials.

If you’re economical, then you can use many of the short bits up in corners when laying onto chipboard, though you will lose the ability to use the tongue and groove on the ends in some cases. This is not good practice when fixing to joists or battens.

Setting out

Before commencing installation, spread the short and long lengths equally over the area and work out of serveral packs. This ensures an even look to the floor and also helps to stagger the end joins.

It is usual though not essential for the flooring to run lengthways in room. Aesthetic considerations apart, movement in wood occurs across the width and the effects of this will be minimised.

For the average room you can start laying the boards adjacent to the longest wall, leaving an expansion gap of 12mm around the entire perimeter of the floor.

Face nail the first row (ie vertically drive the nails, sinking with a nail punch and filling the depression) with the tongues pointing towards you back into the room. Alternatively, glue the first row and allow it to set hard.

If the room is irregular draw your datum line more in the centre and work outwards towards the walls. If boarding out a lounge then the fireplace will be the most important feature. It is important to make sure that the planks line up with that, so we suggest you start from there.

Care should be taken to ensure that a balance is maintained when laying out the floor. Any boards which are suspect should not be laid.  Remember your floor fitter will be last person to see the boards so ultimately the job of checking prior to fitting will be their responsibility. 

Nailing

We would strongly urge the use of a nail gun - either hiring from us, if available, or any hire shop. This will drive in a flat serrated brad of suitable length in the correct position - a great time saver, since each brad will be set at precisely 45º through the tongue (sometimes called secret nailing). Nail at 250mm intervals on chipboard and to each batten and/or joist.  Do not glue the tongue and grooves together - it will prevent even distribution of movement.

Beat the next plank tight up against the tongue by hitting a rubber mallet against a scrap of T & G reversed.

The last planks will be too tight against the wall to use the nail gun, so use normal ovals drilling at an angle if thought appropriate. The final row can either be again face nailed and filled, or, if left with a narrow plank and your subfloor is chipboard, gluing to this will be sufficient.

Measure twice, cut once

Most flooring will now be laid onto sheet materials or concrete/screed base, where you can safely use up scrap lengths in corners without a tongue on one end.

You may find sawing easier by hiring a professional circular saw and make up a simple measuring jig. This can be a simple home-made MDF guide exactly measuring the width of the oak flooring purchased. First measure the gap needed for the saw and clamp the plank and guide together on the workbench. The saw is then simply brought up to the guide and pressed firmly against it while running the saw through the plank. Perfect cut every time.

Finishing

If you have not ordered a pre-finished flooring, you will need to sand the floor.

Sanders can be hired from most hire shops - however, as with the portanailer, we also hire a Golia sander. This is a rotary sander not a drum sander.

A small edge sander is also useful as you will not be able get up tight against the walls with the big sander. It is also ideal for sanding back undulation.

We also recommend reserving some of the sanding dust since it can be used with Lecol 7500 binder to make a filler. This then can be used to fill small gaps and cracks, which is particularly useful for rustic and character grades. A small tin (800g) will go a long way. Do this before the final sanding.

Mind the gap

To hide the gap round the walls, use a solid oak skirting board or a matching oak quadrant or scotia which we can supply.

Alternatively, a cork strip can be used to fill the expansion joint. This is extremely useful when used against stone walls and fire hearths where there is no provision for skirting.

If you have an existing step then we can machine a T bar strip to conceal the gap.

Sealing

 For an excellent hard-wearing low-maintenance finish we recommend OSMO Poly-X Hardwax Oil, a natural mixture of oils and waxes.

This gives a lovely subtle satin finish. It requires just two coats applied with a brush, with no rubbing down between coats. A major advantage of the Hardwax oil is that it can be used to touch in heavy wear areas, such as inside an entrance door, without re-sanding an entire area. 

Before application brush and hoover several times to clear all traces of dust.

A separate leaflet is available on request for the OSMO products.

Maintenance

The flooring can be cleaned by sweeping through and then using a solution of OSMO Wash & Care and warm water immerse a mop head wring out well and using this damp mop, mop the area.

Occasional applications of  OSMO Liquid Wax Cleaner will preserve the lustre and beauty of your floor.