Indy Total Construction

A solid floor often consists of concrete rag that has been laid on top of a layer of hardcore in the ground. This is then covered by a damp-proof membrane, which may in turn be protected by a thin layer of mortar called a screed which is leveled out arid topped by the flooring. But not all solid floors are laid directly on top of the ground.

You may find solid floors in flats and houses, at first floor level and above, as an alternative to framed floors which are supported by beams and structural walls and are usually floorboards mounted on joists.

How are solid floors constructed? You’ll only find the concrete floor surface laid directly on the soil in the oldest houses. And even then you’re more likely to find a heavy concrete slab beneath the surface flooring. If your floor is old, it will probably consist of hardcore with up to 150mm (6in) of concrete on top.

Surface finish, such as a 25mm (1 in) terrazzo screed, quarry tiles, floorboards on slim joists or wooden block flooring like parquet. Was then laid on top.

With this older style of construction little consideration was given to rising damp. Parquet blocks were sometimes bedded in bitumen, but only if the surface of the floor came below soil level would any systematic damp-proofing be used. In that eventuality, the structural slab was covered with asphalt, which was in turn covered with a further 75mm (3in) of concrete.

The design of a modern solid floor slabs allows for a much more rigorous approach to damp proofing. A 100mm (4in) structural slab is laid over a damp-proof membrane that protects the walls as well in order to provide complete protection. On top of the structural slab may come a mortar screed suitable for carpet or vinyl laying or a direct surface finish? Damp proofing is vital because although well-laid concrete. Basically water proof, it still may allow damaging water vapor to pass through without the membrane.

Cracks are the most common fault in solid floors – and are usually due to drying shrinkage or thermal movement. But, provided the cracks are no wider than 6mm (I/4in), you can repair them quite easily yourself. Minor surface damage such as roughness and unevenness is also simply repaired.

If, however: the cracks are wider than 6rnm (‘/4in), that means that something more serious is wrong with your floor – probably a crack going all the way through the slab as well as the screening – so you should call in a builder or surveyor to advise you. A still more worrying problem, especially in a direct-to-earth floor, is rising damp. If a damp-proof membrane already exists and there is still evidence of damp, the damp is likely to be localized: the result of a small break in the membrane.

This may show up only after the old porous floor surface has been replaced with some more modern flooring. The original surface would have let damp through, so avoiding damage, but as the modern ones don’t let water vapor evaporate. It tends to build up underneath and attack both the adhesive and the flooring.

So. If you are going to fit new flooring on an old solid floor, first of all check that it’s damp proof (see Ready Reference). If you do have damp. Then you can put up with your existing flooring: replace it with a new flooring of the same

All you do is slightly widen the crack by using a club hammer and cold chisel, going down to a depth of 12mm (1/2in), undercutting the surrounding floor a little. This is very important as it allows the mortar to get a much better grip on the surface than it would if you were attempting to fill a crack with smooth, feathered edges.

Clean out any dust or debris before brushing on a coat of PVA adhesive, smoothing in the mortar with a small trowel and finishing it off level with the surrounding floor. The chances are that the crack will open up again at some stage. Especially if the floor on one side of it has pushed either up above or down below the rest. The only really permanent solution is to have the floor completely replaced before you lay your new floor surface.

Inserting a damp-proof membrane the simplest way to do this is to remove the skirting boards and strip off the plaster on the walls to a point 50mm (2in) above the wall’s damp-proof course. If at this stage you find your walls don’t have a damp-proof course. It is advisable to get one put in before going any further.

Various forms of damp-proof membrane are used, ranging from thick polythene (often known as ’1000 – gauge’ or ‘sheet 1000′), PVC, butyl rubber or polyisobutylene for large scale work (where the sheets are loose laid or bonded to the structural slab with water-resistant adhesive), to bitumen emulsion for smaller scale jobs.

These sealants are sprayed or painted on the slab in two coats. With the second one being brushed at right angles to the first to prevent thin spots and pin holes where damp could come through. To protect your room completely against rising damp you should link the membrane into the damp-proof course.

This is easy if the dip is above the floor, but it is possible that it’ll be below the level of your floor. If that’s the case then you will have to dig a small channel round the floor so you can gain access – Then all you do is paint bitumen. Either up or down the wall or fit the poly-sheets with more water resistant aches.

Some solid floors are not laid direct. Some of them are cast in situ around reinforcing steel and some are precast concrete floorboards that are locked together_ others, which are made of hollow terracotta blocks that are linked together with Meta Rods and that have the gaps filled in with concrete, are also technically known as solid floors.

You can create a damp-proof membrane by using two coats of bitumen emulsion and applying them over the concrete slab and the exposed brickwork. The second coat should be brushed on at right angles to the first.

Finishing an Imperial ceiling with a coat of plaster is carried out in a similar manner to finishing off a drywall partition. However, when working above your head (which often presents difficulties of its own) it is best to apply small amounts of plaster at a time to avoid tiring your arms.

Deal with the joints first, spreading a thin layer of plaster down the center of each one and pressing lengths of 2in wide nylon mesh or paper tape into the wet plaster with your trowel. Lightly trowel over the tape then apply another thin layer of plaster on top.

Divide into handy bays; fill in each bay with a thin layer of plaster, but not over the joints. Hold the trowel blade at 30° to the surface of the ceiling; the back edge about 1/Gin clear of the board to provide an even layer. Reduce the blade angle as the plaster spreads and pinch the back edge in as you complete the stroke to stop the plaster falling off. Work away from you to avoid flicking plaster into your face.

When you have filled in all the bays, go over the entire ceiling with another thin layer of plaster. Rule it off with a long metal straightedge to remove the high patches and show up the low spots, which should be filled with a thin coat of plaster.

How you treat the angle between the ceiling and walls depends on whether you are replastering the walls at the same time or not. If not, simply run the corner of the trowel blade along the angle from the ceiling and wall sides to cut out the angle neatly. If you are replastering the wall as well, lay on the floating coat then tape the joint between the wall and ceiling before applying the finish coats. Finish the corner as normal.

Finally, polish the hardened plaster with a clean, wetted trowel blade.

If you intend papering or painting directly over the drywall, the joints must first be made to “disappear”. For this you will need drywall joint compound, paper jointing tape and joint finish (see below).

First spread a layer of compound down the seam and, with a taping knife, press the tape into it. Apply another layer of compound over the top, feathering the edges by going over them with a damp sponge.

When the compound has dried, apply a finishing layer, feathering its edges in the same way. Treat the nail head depressions with compound and finish in the same manner.

At the angles between wall and ceiling, fill large gaps with compound; then apply compound to both wall and ceiling and press a creased length of tape into it. Apply two more layers of compound to wall and ceiling, feathering the edges of each one.

While the upper floors of a house will always be constructed of wood, the ground floor may be made of wood or it may be of solid concrete.

All wood floors are based on the same method of construction with minor differences. They all have a supporting framework of wooden beams called joists onto which are nailed wooden boards or plywood panels and may have a plain or decorative finish.

The joists of wooden ground floors are supported at their end — and sometimes at one or two points in between — or additional wood beams known as “wall plates”. These, in turn rest on the tops of low brick “sleeper” walls.

These are not solid, but are laid in honeycomb fashion with spaces between the bricks to allow the air to circulate below the floor to prevent condensation and rot forming. For the same reason, vents are usually fitted at the base of the external walls and must always be kept clear. Slates or strips of flexible flashing material are laid between the wall plates and sleeper walls to prevent damp attacking the wood.

Sometimes the joists are laid on top of individual bricks set on the ground. Upstairs, the joists are also supported by wall plates but these are held by metal brackets called joist hangers, which are cemented into the walls. Sometimes the joist ends may be set in sockets between the bricks, with a metal plate below to spread the load through the wall.

Most modern houses have solid ground floors. These comprise of a layer of compacted gravel on top of which is a 4in layer of concrete called the subfloor. A damp-proof membrane bitumen or thick plastic is laid next and is carried up and down the wall to link with the flashing around the base of the house.

A thin layer of mortar can be laid on top of the membrane which will provide a level surface for most types of flooring.

Over the years a wooden floor can suffer considerably from wear and tear. The joists may warp or sag, boards may shrink to open up gaps through which draughts whistle, or they may become loose or damaged. The whole structure may be further weakened by woodworm or rot. Fortunately, many of the minor problems can be cured easily, although serious rot or insect attack may mean complete replacement and should be dealt with by a specialist.

Probably the most common fault with a wooden floor is creaking floorboards due to the fixings working loose. The cure is simple: either drive the nails back in or replace them with longer nails or screws. Punch nail heads below the surface and countersink the screw heads.

Gaps of less than 1/tin can be filled with papier-mdché, which you can make yourself. Half fill a bucket with small pieces of torn, soft white paper, gradually adding boiling water while you pound the paper into a thick paste. Allow it to cool and stir in enough cellulose wallpaper paste to make a thick mixture. Add wood stain to match the color of the boards.

When the papier-mâché is quite cold, force it between the boards with a filling knife, leaving it slightly proud of the surface. Leave it for at least 48 hours then sand smooth.

Fill wider gaps with softwood fillets: cut the fillets fractionally wider than the gaps they are to fill, using a backsaw. The fillets should be fractionally deeper than the floorboards: that is, about lin. Plane the fillets so that they taper slightly at the bottom then tap them into the gaps with a hammer and block of wood. Use a plane to shave the top edges of the fillets flush with the tops of the floorboards. Make sure the ends of fillets meet on a joist: secure them to the joists with brads.

Damaged boards

Damaged sections of boards should be cut out and replaced, or a new board fitted if the damage is substantial. First check that there are no pipes or cables running below the damaged section, otherwise you will have to remove the entire board in case you cut into them by accident.

To cut out a section of board, first find the edges of the joists at each end. Do this by sliding a knife blade along the gap between the boards. If the boards are tongued-and-grooved, you will have to cut through the tongues by drilling a starting hole and using a keyhole saw or with a circular saw set to the depth of the board.

Drill a starting hole for the saw just in from the edge of each joist and cut through the board at each end in line with the joist edges.

Lift out the damaged section; if it is nailed to intermediate joists, lever it free using a masonry chisel and a stout length of wood. Lever the board upwards at the fixings with a chisel until you have lifted the end enough to be able to slide the wood below it, while resting it on the tops of the boards on each side. Pushing down on the end of the board will spring the fixings from the joist. Continue in this fashion until you have freed the board. A complete floorboard can be removed in the same way.

Screw or nail lengths of 2in sq batten to the sides of the joists flush with the undersides of the old boards. Then nail a new section of floorboard to the tops of the battens.

Sagging joists

On wide, unsupported spans, the joists may sag in the centre of the floor, giving it a slightly “dished” surface. To overcome this, add packing pieces to the tops of the affected joists.

Lift the floorboards and place a straightedge across the joists at several points. Measure any gap between the tops of the joints and the straightedge and use the measurements to mark out lengths of softwood batten. These must be the same width as the joists. Plane the battens to size and nail them to the tops of the affected joists. Finally, re-lay the floorboards.

You need only apply two very thin finishing coats directly over the drywall.

The plaster needed for the job is sold ready mixed or in a powder form requiring only the addition of water. It is mixed in the same way as other plasters and has a creamy texture.

Because you are only applying a finishing coat to the drywall board there is no need for thickness guides, except at any external corners.

It is a good idea to practice scooping the plaster from the hawk on to the trowel first, using a spare piece of drywall to try your hand at spreading the plaster and making it stick to the board_ The technique is to hold the hawk in your left hand (or right if you are left handed) so the top is level and set the trowel blade on edge, so it is at right angles to the top of the hawk. Use the trowel to push some plaster towards the edge of the hawk, scooping it off at the same time as tilting the hawk towards you. The whole is done in one smooth movement.

The first job is to seal the joints between the individual panels of gypsum board, reinforcing them with perforated paper tape or nylon tape to prevent the plaster cracking. The standard paper tape is available in 2in wide rolls of 50-500 feet.

Cut strips of tape to run the length of each joint, including any horizontal ones, before you begin plastering. They must be exactly the right length and should not overlap or be folded, otherwise the plaster will not grip the wall properly.

To seal the joint, spread a thin layer of plaster, about 4in wide, along it from bottom to-top. Hold the trowel so that the blade is at an angle of about 30° to the wall, reducing it as you move up the joint and the plaster on the trowel thins.

While the plaster is still wet, press the tape into it. The easiest way to do this is by draping one end over the blade of the trowel and pressing this into the plaster at the ceiling. Then gently slide the trowel down the plaster, positioning the tape with your other hand. Once the tape is in place, run the trowel carefully up the plaster to make sure it is bedded properly. Treat all the other joints between the panels in the same way.

When the taped joints have dried — which should take about 11/2 hours — fill in the areas between them with more plaster. Work upwards from the floor, spreading the plaster in thin vertical strips and being careful not to build up ridges at the joint positions. Stop just short of the ceiling and work downwards from there to get a clean, sharp angle.

Unless you are working on a very small area, by the time you have finished putting on the first coat, the area you started on will be ready for the second coat. This should be about 1/sin thick and applied with long, sweeping strokes to eliminate ridges. Start at the bottom corner of the wall and work upwards and along to make one continuous coating.

Allow the plaster to set slightly and then go back over it with a clean trowel to smooth off the surface. Finally, when it has hardened fully, “polish” the surface by splashing clean water on to it with a paintbrush (about 4in wide) then sweep the trowel back and forth lightly. This will give a smooth, matt finish ready for decoration.

Before laying the blocks it is as well to carry out a dummy run on the first two courses, so you will know how best to arrange them to keep the number of cut blocks to a minimum. Set them out along the layer of mortar in line with the scribed mark, spacing them a finger-thickness apart.

If the partition is to have a door in it, now is the time to position the frame. Nail battens across the corners of the frame and across the bottom to hold it square and prop it up with a batten nailed to the top.

Now begin laying the blocks properly. It is best to build up about four courses of blocks at each end of the partition first and then stretch a stringline between them as a guide for the blocks in the middle.

Trowel a layer of mortar onto the original thin layer and “butter” the end of the first block with more mortar. Set the block in place against the scribed line and against the wall to form a neat mortar joint. Tap the block level and upright with the handle of the trowel. Repeat the procedure for the next block in the course and lay two or three more before working back towards the wall with the second, third and fourth courses. Collect the mortar that is squeezed out from between the blocks for reuse.

Make sure the blocks butt up to the guide batten and check them every now and again with a mason’s level to ensure that you are keeping the courses upright and level. Tie each alternate course to the wall with galvanized metal wall ties. Similarly secure the door frame to the blockwork; build up the center of the partition.

If you need to cut any blocks, do this with a bricklayer’s chisel and hammer. Measure up the block and scribe a cutting line on all four sides with the end of the chisel. Then tap gently along this line with the chisel. Finally, lay the block face up, set the chisel in the center of the cutting line and strike it a sharp blow which will separate the two halves of the block.

Directions:

1. Dry-laying to check for fit; allow a finger-thickness between blocks for mortar. Vertical battens give support until the mortar hardens.

2. Spreading the mortar bed on the floor; scribe the line of one face of the wall in the mortar with the point of the trowel.

3. “Buttering” one end with mortar before laying the block; place this end against the previous block.

4. Laying the block on the mortar bed, flush with the scribed line.

5. Tamping the block level with the adjacent block using the trowel handle; check each block as it is laid with a spirit-level.

6. Securing a metal frame-clamp to the side wall; tie alternate courses in this way.

7. Checking the face of the blockwork for alignment; use a long spirit-level or straight-edge and check in a number of directions.

8. Nail temporary “strainer” battens across a door-frame to keep it square and support it in an upright position with a plank nailed to the top.

9. A door-height opening needs a lintel above it to support the blockwork; a course of bricks on top will align with the blockwork.