Floor Fitting

Preparation

As with any job, the key to success is in proper planning and preparation.

One of the main things to consider is the relative humidity of the air in the room where the floor is to be installed/stored. Ideally this should be between 50 & 65%. All our floors are kiln dried to a moisture content of about 10% and then stored prior to despatch/collection in our temperature controlled factory. This means that they are ideally conditioned for a normally centrally heated environment and will require little, or no acclimatisation before laying.

However, timber is a hygroscopic material, i.e. it will absorb or lose moisture to ‘try’ and reach equilibrium with its environment. As it does so it will move; expand or shrink.

In all but under floor heated environments the problems with relative humidity’s are that they could be too high. So, dealing with this first, below are possible reasons for this and suggested courses of action.

i) Moisture

Insufficient or defective damp proofing can cause moisture to track through sub floors, moisture vapour to rise up from below or water to soak through walls.

You don't need to actually see water for moisture to be present and a problem.
If there is any doubt professional advice should be sought and proper readings taken.

ii) New Building

We all know how much water is used in the preparation of concrete and plaster. That water has to go somewhere as it dries out. It is imperative to ensure that everything is fully dried out and relative humidity within the room has reached acceptable levels prior to installation. Under normal conditions concrete screeds can take one month per inch to dry out and traditional base and top coat plaster several weeks.

Also, new sub floors such as chipboard can become very damp due to water from plastering, plumbing works etc.

De-humidifiers can speed up the drying process but again, professional advice should be sought and proper readings taken prior to installation.

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Fitting

There are three ways of fitting a hardwood floor; i.e. mechanical fixing, glueing and floating.
The principles of these three methods are set out briefly below;

i) Mechanical fixing

This is the usual way of fitting a hardwood floor and arguably the most successful as it is the way that floors have been fitted for years. Mechanical fixing means nailing or screwing the floor down onto joists, battens, sub floor or existing floorboards. Although there are several ways of achieving this such as pre drilling and screwing or face nailing, by far the most popular method is to secret nail. Here, a special nail gun is used to drive a nail at between 33 degrees and 45 degrees through the side of the tongue.

ii) glueing

View the Lecol MS250 Technical Data Sheet, suitable for solid hardwood floors here .
View the Lecol 5500 Technical Data Sheet, suitable for engineered and parquet floors here .

This method is used particularly when fitting over a solid sub floor such as concrete. Ensure that the subfloor is fully dry & that a continuous Damp Proof Membrane is installed.

iii) Floating

Floating a floor means that it is not fastened down to the sub floor below. We would only
ever recommend the use of adhesive floor fitting foam to create a floating floor.
ON NO ACCOUNT should floorboards be glued together and floated. Again, floor fitting foam is usually only needed over a solid sub floor.

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Procedures

The procedures for these three methods are as follows;

i) Secret nailing

If the floor is to be nailed down then obviously there has to be something under the new floor that is capable of taking a nail such as joists, battens, chipboard subfloor or existing floorboards.

The following preparation work is recommended;

a) Joists

Pin a layer of visqueen, overlapped at the joints, on top of the joists. This is particularly advisable at ground floor level. Moisture content of the joists should be comparable to the
floor i.e. 10%.

b) Battens

If fastening over concrete a layer of visqueen should be placed over the concrete prior to fitting the battens. Insulation can then be placed between the battens if required. A further layer of visqueen or a layer of building paper can then be pinned to the top of the battens. Again, the moisture content of the battens should be about 10%.

The recommended centres for both joists and battens is 400mm (16”).

c) Chipboard/Plywood/OSB Board

When laying over concrete the sub floor should be of flooring grade quality, tongued & grooved all round.

The correct fixings must be used to ensure a good 'hold' when using chipboard.

Firstly ensure the concrete base is sound. Cover in a layer of visqueen, overlapped at the joints by 150mm (6”) and taken up the side walls by 100mm (4”).

Then lay out the sub floor material in a brickwork design so that the joints are not lining through. Glue with PVA glue along the joints. Leave a 12mm ( ½ ”) gap all round the outside.

The hardwood floor can then be fitted by secret nailing or screwing.

If the sub floor is already in place over joists then check that it is securely fastened down. Any points of movement can be rectified by screwing down on to joists.

d) Existing Floorboards

Existing floorboards should be sound and securely fastened to the joists beneath.
If not make good any defects or overlay with plywood. Again, pin a layer of building paper over the whole floor, particularly at ground floor level.

Once the sub floor has been prepared then you can start to nail the hardwood floor down. You should always allow for an expansion gap all around a hardwood floor.
It is important to understand that any movement that may occur will be across the width of the boards and not in the length. Bear this in mind when planning the run
of the boards. Also we usually recommend that, when fitting over existing floorboards, the new boards run at 90 degrees to the old ones. The expansion gap should be about 12mm ( ½" ). How you are going to cover this gap will dictate what space you allow. There are four ways of doing this namely;

i) Leave ½" expansion gap from the wall and cover with skirting boards (diagram 1). This is the neatest option but entails removing existing skirtings and re-fitting or replacing.

ii) Leave a 1" expansion gap from the existing skirting and cover with low profile bead (diagram 2). This is an easier option and is still neat as the beading is unobtrusive.

iii) Leave ½" expansion gap and cover with either quadrant or scotia bead (diagrams 3 & 4). This is the cheapest option but the beading does 'ride up' the skirting by ¾" which may be a problem, particularly on shallow skirtings.

Once you have set out for the expansion gap then the first line of boards can be set. Choose the wall that you want to start from, this will usually be the longest wall.

The first one or two rows of boards will have to be face fixed, i.e. vertically. First pre drill a fine hole, nail through into the sub floor, sink the nail head with a punch and fill. Be careful that the nails used are suitable flooring nails and that they will not penetrate further than the sub floor. A guide to what nails to use where is given below;

Floor Thickness	Angle of nail	Method of nailing	Nail Length
			1 ¼”	1 ½”	2”
15mm	90	Face fix into 18/20mm sub floor
15mm	45	Secret nail into 18/20mm sub floor
15mm	90	Face fix into 25mm sub floor
15mm	45	Secret nail fix into 25mm sub floor
15mm	90	Face fix into joists
15mm	45	Secret nail into joists
20mm	90	Face fix into 18/20mm sub floor
20mm	33	Secret nail into 18/20mm sub floor
20mm	45	Secret nail into 18/20mm sub floor
20mm	90	Face fix into 25mm sub floor
20mm	33	Secret nail fix into 25mm sub floor
20mm	45	Secret nail fix into 25mm sub floor
20mm	90	Face fix into joists
20mm	45	Secret nail into joists

Some nail guns have adaptor shoes to vary the nail angle between 33 and 45 degrees.

As you start to secret nail the boards down take care to ensure that the joints are completely random. Try not to line joints through or set the floor out brickwork style i.e.

Also, if you have a floor that has a variegated pattern such as brown oak, ash, coloured maple or fumed oak ensure that you open several packs at a time in order to ensure an even mix.

Nails should be at 6 to 8" centres with a nail a couple of inches either side of joints.

Once you reach the far wall you will need to face nail the last one or two lines of boards as before.

Whilst fixing the floor a few points should be borne in mind:

i) The boards should fit up snugly together, if not there is a good chance that there is some debris in the groove or a tongue is damaged. Clear this before nailing.

ii) Flooring should not be scribed around areas like architraves and casings. These should be undercut by hand or with a jamb undercut saw so the flooring can neatly slide under. Remember to leave some gap for expansion. Refer to picture above.

iii) When fitting around radiator pipes a 20mm hole (for 15mm pipes) should be drilled in the floor to allow for expansion. The floor should then be cut out as below;

How to fit around a radiator pipe
Carefully mark the position of the pipe.	Drill a clearance hole.	Mark out out a 15° wedge.
Cut neatly down the lines with a fine tooth saw.	Push the wedge back in and file to circle again.	Slide back over the pipe and glue wedge in place.
	The finished job should be neat with no visible gaps.
Fit a pipe cover in a matching timber.

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If, after following all the procedures above, you are still concerned about the moisture vapour emissions from the floor then a concrete sealer should be used. Once the concrete is sealed the floor can be laid onto a full screed of adhesive. Both of these products, application tools and full details on testing for moisture vapour emissions and methods of use are available from British Hardwoods. The principles about laying the floor are the same as for nailing down as above.

iii) floor fitting foam

When using floor fitting foam first lay a full layer of visqueen over the whole floor overlapping on the joints by 8" and running slightly up the walls.
Roll out the floor fitting foam at 90 degrees to the run of the new floorboards with the plastic coated face uppermost.

Leave a slight gap between rows of floor fitting foam.
On the wall where you intend to lay the first board peel back approximately 500mm of the plastic top film exposing the glue. Onto this glue apply a spare sheet of the plastic top film and fold it towards you with the fold to the wall. Onto this separate piece place the first few rows of flooring, locked tightly together and leaving the proper expansion gap as detailed above.

Carefully, pull out the loose piece of plastic sheet and affix the boards firmly to the floor fitting foam. Once this is done, lock in the next row of boards and then peel back the main plastic sheet by 75% of the width of the board (to allow the next row to be laid without sticking), continue to do this across the room, see diagrams below;

Whilst laying the floor, the floor fitting foam can be slightly stretched before sticking down the boards. So, if the boards shrink slightly they will tighten up to avoid gaps.

Again, the general principles for laying the floor are the same as for nailing.

Relative humidity	Values for the equilibrium moisture content of wood
85%	18.1	18.0	18.0	17.9	17.5	17.1
80%	16.2	16.0	16.0	15.8	15.5	15.1
75%	14.7	14.5	14.3	14.0	13.9	13.5
70%	13.2	13.1	13.0	12.8	12.4	12.1
65%	12.0	12.0	11.8	11.5	11.2	11.0
60%	11.0	10.9	10.8	10.5	10.3	10.0
55%	10.1	10.0	9.9	9.7	9.4	9.1
50%	9.4	9.2	9.0	8.9	8.6	8.4
45%	8.6	8.4	8.3	8.1	7.9	7.5
40%	7.8	7.7	7.5	7.3	7.0	6.6
35%	7.0	6.9	6.7	6.4	6.2	5.8
30%	6.2	6.1	5.9	5.6	5.3	5.0
Temperature in °C	10°	15°	20°	25°	30°	35°
Chart showing equilibrium moisture content in relation to temperature & relative humidity

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