Hardwood Floor Settings

Preparations to Set.

The most dangerous enemy of hardwood floor is moisture. Wherever you are planning to set your floor all other materials (concrete, plaster and timber) must be dry. The room in which the floor is to be laid must have been settled to the ambient conditions of temperature and humidity that will usually prevail at that time of year.

Any timber – existing flooring, joinery or battens – should have a moisture substance of no more than +2% above the moisture substance of the new floor. It as advisable, when laying on to existing timber, to ensure this is treated against fungal or insect attack.

Concrete or screed should contain a moist proof membrane and have a moisture substance of no more than 5%. This is, in practice, almost impossible to achieve and so additional precautions should be taken to prevent moisture reaching the new floor.

However it is worth remembering that any new concrete or screed will take about 1 day per mm thickness or 1 month per 25mm of thickness to dry naturally to a moisture substance of 5%. The thicker the slab, the longer the period, for example a 150mm slab will probably take 10-12 months to dry back to a safe moisture level. (Please contact Millennium Hardwoods for advice on how to shorten this time.)

At the time of laying the ambient conditions in the room should lay somewhere in the range of 40-50% humidity and a temperature of 15 to 25oC. Only set up the floor when you are ready to lay it. Under no conditions, store it in a room that is wet or outside, or even in a garage where it could pick up moisture.

Bring the floor into the room in which it is to be laid in the optimum working conditions and let it to adapt to the temperature etc for a minimum of 48 hours. True acclimatisation will take a couple of weeks and this is best done after the floor has been laid (assuming correct tolerance has been made for enlargement of contraction).

Allowing for expansion

All wood floors will expand and contract over the course of the year. Usually they will expand across their width during the summer since the air becomes more humid and the boards take in moisture, and shrink during the winter when heating dries out of the air and removes moisture from the boards.

Kiln drying to 8-10% moisture content will minimize excessive motion.
Tolerance for expansion should be left around the edge of the floor – a gap of 15-20mm is usually sufficient.

However, a floor laid in winter that will expand in the summer may require extra expansion to be allowed for across the width of the floor.

Recommended fitting methods

Millennium Hardwoods recommend that all our floors be set up by hidden nailing to timber (either an existing floor or battens or plywood laid over concrete). The advantage of this method is that boards can be fitted tighter together for a better fit. In addition, the mechanical fixing of boards is a long established technique that allows the boards to expand and contract whilst remaining firmly fixed down.

Gluing immediately to concrete is becoming an established method of fixing providing that the screed is completely smooth and level. Where this is discovered as the preferred option we would still recommend the laying of plywood over the concrete and the floor being glued and pinned to the plywood. (Millennium stock Sika glues.)

Any board that is more than five times wider than its thick is more prone to bowing and cupping. Therefore any board over 140mm wide should be nailed additionally across its width either by screwing and pelletting, face nailing or using adhesive material on the back of the board.

Fitting to concrete floors

We do not recommend immediately to ground floor joists because this may cause the floor to cup. This happens typically when the air below the floor is dampish and causes the underside of the board to expand whilst the air above the floor is dry (usually due to heating) causing the topside to contract.

Millennium Hardwoods would recommend the laying of 18mm exterior grade moisture resistant plywood overlaid with a non-polythene vapour barrier on the hardwood floor hidden nailed to the plywood.
On second floor joists where the problem of differential moisture is unlikely to occur, the hardwood floor can be hidden nailed directly to the joists (assuming they are at centres no wider than 400mm). An additional vapour barrier is not required.

Fitting to existing floors

A new solid hardwood floor can be fitted to an existing floor whether it is old floorboards, sterling board, plywood or chipboard (though chipboard does not hold a nail as other floor types).
When fitting to existing floorboards these should be well fixed down, any high points sanded out and all nails punched below the surface. On a ground floor we recommend overlaying with a non-polythene vapour barrier. The new floor is then hidden nailed at 90? or 45? to the direction of the existing floor.

Where, for aesthetic reasons, it is desirable to lay the new floor in the same direction as the old floor. A layer of 6mm exterior grade plywood can be firmly fixed down and the new floor hidden nailed with a long enough nail to penetrate the plywood and into the old floor. The plywood serves to stop the expansion and contraction of the softwood floor from affecting the new floor. The plywood can be laid as sheets or as strips at 300mm centres.

Under no circumstances is it recommended to accommodate a solid hardwood floor to a floating chipboard floor, because it is not rigid enough.

Underfloor Heating

When laying a floor where Underfloor heating has been set up, it is important to follow these guidelines:

1. We recommend an Engineered Board instead of a solid floor
2. The heating has been on at least 3 weeks prior before laying the floor
3. Make sure there is no water leaking and the concrete is dry. This means no more than 3% moisture, full depth of screed
4. The concrete copes with all the requirements for Underfloor heating
5. The surface temperature of the ground cannot exceed +27oC
6. We advise that the heating is switched off 48 hours prior to the laying of the floor

Engineered Floors

Engineered boards are ideal for Underfloor heating. Always apply an rug pad with a damp proof membrane when floating the boards. In large or odd shaped rooms, engineered boards should be glued and not floated.

Pre-Finished Floor (Finished)

Our automatic process sprayings lacquer on to ALL edges of the board completely sealing it to keep all moisture away.

Finally a catalytic infra red drying system then dries any chosen finishing and expels any smell promptly and efficiently. With some suppliers this process is accomplished on installation, we prefer any smell to be in our factory – not your home.

Finishing a Millennium Hardwoods floor

Before applying any finishing to your floor, the surface should be flat, smooth and clean. On new wood floors this should be accomplished using first medium grit sandpaper (60-80 grit) followed by fine grit (100-120 grit) to ensure a smooth surface. Alternatively Millennium Hardwoods can supply boards pre-sanded to a 100/120 grit finishing to save the work of sanding.

When complete, all dust should be removed (including ledges and skirting) prior to applying finishings. A wide range of finishings are available. Those we recommend are:-

Granglaze Satin – An oil based seal which presents a deep colour to wood similar to an oil finishing. It is especially good on oak tree floors.

Application – All these finishings can be applied using a 12″ applicator & Pad or a good quality brush. Rollers are not recommended. After thorough shaking and pouring into a suitable tray, the product should be evenly applied along the grain of the wood. When dry, the surface should be softly sanded using fine sandpaper (160 – 180 grit) to remove raised grain.

After removing dust further coats are applied as directed. Three or four coats are usually required although heavy traffic areas may require extra costs.

When the last coat is dry the floor should be left for a minimum of 24 hours in domestic and 48 hours in commercial premises prior to light use.

The floor will remain susceptible to scratching until the full curing time is reached (approx 7 days). The floor should not be cleaned or covered with rugs for this period.

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