Preparing a floor for tiling

A tiled floor can transform the appearance of any room, and for the most part the job is straightforward and quick. Badly-laid tiled floors can be an eyesore, but you can prevent this by taking a little extra care at the planning and preparation stages.

Vinyl floor coverings are by far the most popular choice, especially for kitchens and bathrooms, and it is not difficult to see why. Vinyl tiling is available in various forms and a seemingly infinite range of colours and designs. And although various types of fixing methods may be used, none presents a problem. The techniques of laying vinyl tiles are covered in the next part of this course.

Cork has some splendid characteristics which make it well-suited for use as a flooring material, and is almost as easy to lay and finish. And of course there is nothing to match the quality and durability of quarry or ceramic tiles. Laying these tiles is covered in a later part of the decorating course.

You can tile a floor only if the surface is sound, firm and level. Loose floorboards, damp or uneven concrete, old linoleum and pitted asphalt are typical floor conditions that need to be checked and corrected before laying vinyl or any other form of tiling. Bumps and high points quickly cause wear or cracks in floor coverings.

Preparing wood floors

Nail or screw down any loose boards and drive in or remove insecure nails and screws. Wood floors should be covered with plywood or hardboard.

Vinyl flooring may be laid directly on chipboard used in place of floor-boarding provided the chipboard is of flooring grade and has a minimum thickness of 18mm. Be sure to remove any existing floor covering first.

Suspended wooden floors at ground level must always remain well-ventilated if damp and rot are to be avoided. A vinyl or tile floor covering will not allow timbers beneath to ‘breathe’ and this can only aggravate any borderline condition that may be present. Check that air bricks in the outside walls are not blocked and take the additional precaution with old, damp properties of raising a floorboard here and there to check for both dry and wet rot.

Preparing concrete floors

Provided concrete floors are dry, clean, level and free from anything which could conceivably react with the overlay (particularly grease and solvents which can have a marked affect on vinyl), they form an ideal base for flooring whether in tile or sheet form.

The most common problem is dampness, particularly on concrete floors laid directly on top of earth that have not been provided with a permanent damp-proof membrane. Even if a concrete floor looks dry, try a simple test to check whether or not it is so. Place a rubber mat, piece of cooking foil or plastic sheet on the concrete and tape the edges down as best as possible. Turn on the heating at a setting a little higher than normal, then, after 24 hours, peel off the test sheet. The presence of any moisture on the underside indicates a damp floor.

If the floor is damp, it must be treated with waterproofer before being overlaid with flooring of timber, cork or any other material that could be affected by moisture. A wet floor may have to have its surface relaid and a waterproof membrane inserted (regardless of the floor covering used).

A damp floor can be treated with waterproofing compound—usually an epoxy coating or a rubberized bitumen material.

Pitting and general unevenness can be rectified using what is known as a self-levelling compound. Pour this over the floor area to a minimum depth of about 4mm, following the maker’s instructions closely as these may vary. You cannot, however, lay sheet material over some damp-proofing compounds—so check this point with your floor covering dealer.

To fill larger holes, make up a mortar mix of three parts soft sand to one of Portland cement. Add just enough water to make the mix male-able and a little plasticizer to minimize shrinkage during drying.

Damp the holes with water and apply the mortar with a bricklayer’s trowel. Tamp it down with the end of a piece of timber and slice off any surplus with a timber straightedge.

Floors with a surface which is powdery but otherwise sound can be coated with a latex-based sealer before being overlaid by tiling.

Other floors

It is possible to lay vinyl and cork flooring over existing quarry or ceramic tiling provided that the gaps between the original tiles are filled with self-levelling compound. This is to prevent the old tile pattern from working through—a particular problem near doorways and other areas subject to continuous wear.

Also, take particular care to remove grease, dirt and grit: perhaps harmless to the original tiling but often damaging to vinyl and cork. A good wash with household detergent and hot water is normally sufficient.

You can also lay some types of vinyl and cork tile over existing linoleum and vinyl flooring where removal poses problems. Again, make sure the surface is clean and that all edges on the old tiling are stuck down properly. Where possible, do remove all old tiling as this helps avoid problems both in laying the new tiling and later. Old tiling must be removed if quarry or ceramic tiles are being used.

Laying hardboard

On an old, rough wooden floor, laying hardboard or plywood over the entire surface is often the only way of easily achieving a smooth surface on which to lay tiles. Concrete floors sometimes require the same treatment but usually this is not essential, although you may prefer the additional insulation this underlay provides.

Standard-sized hardboard comes in sheets 2440mm X 1220mm, and for this job select the 6.4mm thickness.

Hardboard sheets have to be conditioned prior to use otherwise buckling may occur through localized shrinkage or expansion after they have been laid. Temper the boards by brushing the.rough side with water and lay the sheets flat, smooth sides together, overnight or longer so the moisture is fully absorbed. The idea is that the sheets will dry out after being laid, in the process shrinking slightly to form a very tight, level surface.

The hardboard is laid rough side upwards as this gives a better key for any tile adhesive used. Stagger the joints to reduce the likelihood of strain at any particular point—which could lead to cracks or wear in flooring placed above—and avoid coinciding the hardboard joins with those of floorboarding below for the same reasons.

On a wooden floor, use 25mm hard-board pins to nail the board at 150mm spacings over the entire surface and at 100mm spacings along the edges. On a concrete or cement floor you have to glue the board in place using a suitable adhesive such as neoprene thixo-tropic. When sticking anything to concrete, check whether or not an initial coat of primer is required as concrete can very easily absorb some other types of adhesive.

Few rooms are truly square and you will need to use wedges and strips to fill the small gaps left after trimming the boards as they are laid. If these gaps are very small, it is worth using filler paste instead.

When you have laid the boards, allow them to dry out before overlaying vinyl tiles or sheet—a day or so is normally long enough. Spend the time correcting any tight-fitting doors which open into the room. Normally the gap between the base of the door and the floor is sufficiently large enough to accommodate a layer of thick floor covering or, in this instance, a layer of plywood or hard-board—but only rarely both together. So check the gap beneath the door both before and after laying covering boards.

If necessary, lift the door off its hinges and trim (by planing or sawing) 6mm or so from the base. You may find it easier to replace the existing hinges with rising butt hinges.

Where board laying continues through a doorway into an accompanying room, ensure that draughtproofing aids such as a threshold bar are removed. Sheet edges should be tightly butted here—and then covered with the threshold bar again if further draughtproofing measures are necessary, which seems likely.

Laying plan

Once the floor preparations have been completed, some idea of the lie of room is necessary for planning a design and for choosing tiles or tile sheeting.

In theory, all designs should radiate or progress from the centre of the room. Find this by measuring off the centre line of two opposing walls. Stretch a chalked string between the two and snap this against the boards on the floor. Repeat this for the two remaining walls so that another chalk mark is made: where they cross is the centre, point of the room. This is a simple enough job for a normally-shaped room.

Border walls

Although any design is based on the centre of the room, border walls must be considered if an even pattern is to be achieved. Also, the tile direction should be square, or perfectly symmetrical, to the main doorway of the room. You would base the tile pattern on either door 1 or door 2 in preference to door 3 even though the tile pattern falls at 45° to this, which is visually acceptable.

To mark out guide lines for laying, produce a chalked mark at right angles to the doorway , far enough for another chalked mark to be made across the room and coinciding with the centre point.

Make another chalked line at right angles to the second line, again passing through the centre point. This line is of course parallel with the first. The resulting cross you have chalked on the floor is now used for the exact planning of a pattern, and also provides a guide for the tile-laying sequence which follows.

When, later, you have chosen your tiles and have designed a pattern for these, follow the cross-lines in a ‘dry laying’ sequence to check how the tiles finish off at the edges. Ideally the border round the room should be even and although this is not always possible as far as the pattern is concerned, it is certainly possible to rearrange the position of the chalked cross so that tile widths are even on each pair of opposing walls.

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