Repairing Concrete Floors

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

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.

Staircases

Filed Under: Do it yourself, Home repair, Redecorating, Remodeling    by: ITC

Staircases are often taken for granted yet they are complex pieces of carpentry which give many years of trouble-free use. They rarely need replacing: just as well, since they are often tailor-made to fit. Even so you can buy ready made versions, which cater for common storey heights and these can often be easily adapted to fit exactly.

A staircase comprises a number of steps fixed between two long boards which are fixed to the joists of the floors they connect. These boards are called strings, the horizontal surfaces of the steps are called treads and sometimes they have vertical boards between them known as risers.

Strings can be in two forms: closed and cut. With the former the ends of the treads and risers are housed in shallow slots cut in the face of the string and held there by wedges driven in from behind and below. The risers are fixed to the treads below with housing joints or screws, and to the treads above by triangular blocks glued and nailed in place. The top edge of a cut string is shaped to provide horizontal ledges to which the treads are fixed. Sometimes both foul’s of string will be used in the same staircase, the closed string being fixed against a wall with the cut string on the outside.

Further support for the steps can be provided by a beam that runs below the treads and risers parallel to the strings. This is known as a carriage.

There are two basic types of staircase: the closed tread and open tread. Of the two, the former is most common, having treads and risers in a boxed-in construction. The underside of the strings are usually clad with lath and plaster or gypsum board or there may be a closet below the stairs. The latter is preferable since it allows easy inspection and repair. The open tread staircase has no risers and is completely exposed.

In a closed tread staircase the treads are about lin thick and will overhang the risers by a similar amount, their leading edges or noses being rounded off. A decorative molding is often fitted below the nose. An open tread staircase will tend to have thicker treads because they are not supported by risers, although sometimes a batten will be set on edge immediately below them to stiffen the tread.

All staircases must have at least one handrail and if wide they must have one on each side, depending on the requirements of your local code. The handrail forms part of the balustrade, the other parts of which are the newel posts and balusters.

The newel posts fit at each end of the stairs with the handrail running between them. Not only do they support the handrail but often the strings as well which will be slotted into them and fixed with wooden dowels. Further support for the handrail is provided by the balusters which fit between it and the strings.

Though straight staircases are common, where space is limited it is often necessary for the stairs to change direction on the way up. A small quarter landing is used to provide a 90° change of direction and a half landing will turn the stairs back on themselves.

If there is not room for a half or quarter landing a turn can be put into the stairs by inserting triangular treads called winders. Winders are also used in spiral staircases which can be great space savers. Unfortunately they are not very practical since carrying furniture and other bulky items up them is difficult.

Covering Roof with Asphalt

Filed Under: DIY Outdoor, Do it yourself, Home repair    by: ITC

The method used for constructing a flat roof is outlined in the following way; the joists usually being laid along the length of the extension from the house to the end wall. At the house end, the joists may either rest on top of a wooden wall plate, being toe-nailed in place, or be nailed to metal hangers which are also nailed to the wall plate. The ends of the wall plate are set in sockets built into the extension side walls.

At the end of the extension, the joists can simply rest on top of the end wall and be nailed in place or, if there is a window in the end wall, a second wooden beam can be fitted to span the opening and support the joists.

Tapered furring pieces are nailed to the tops of the joists to create the right fall. For felt covering the fall should be 1 in 60, but for asphalt it should be 1 in 80.

Sheets of exterior grade plywood are used to provide a roof decking and are nailed down through the furring pieces into the joists. The sheets should be staggered so the joints between their short edges do not coincide.

Although a felt-covered roof is the cheapest and easiest to construct, a much more durable finish can be obtained by having it covered with asphalt. This material is heated until it melts and is then spread over the roof to provide a solid, impervious layer when it cools. It is a job that requires a great deal of skill and is one that you should get a building, contractor to do for you.

Flat roofs can often suffer from condensation when moist air passes through the ceiling from the rooms below and cools on contact with the underside of the roof — particularly with bathrooms and kitchens and when the atmosphere is damp.

Leaving ventilation gaps behind the fascia and insulating the roof will help, but the best idea is to either use foil-back gN,:psumboard for the ceiling – which will stop the moist air passing through – or staple a separate polyethelene vapor barrier to the underside of the joists before nailing the gypsum- board in place. Once the extension has been weatherproofed by glazing the windows and fitting the doors, the room can be finished. Before plastering the walls and ceiling, lay in the necessary electrical cables, mount accessory boxes and run in any pipe work for hot and cold water or central heating.

Directions

1 Nailing the roof joists into hangers attached to the main beam; toe-nail through the top of the roof joists into the main beam also.

2 Nailing furring pieces (narrow end over the front wall) to the tops of the roof joists to set a 1 in 80 fall for the roof

3 Nailing the plywood roofing sheets over the furrings: stagger the joints between the short edges.

4 After pouring hot asphalt onto the roof. smoothing it out to a layer about 3/8in thick.

Fitting an Attic Ladder

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

When you want to get into your attic there is no reason why you should not use an ordinary ladder, provided it is secured to the opening in some way – by hooks and eyes perhaps, but whatever you do, never use a pair of step ladders. In trying to climb out of the attic and groping for the top of the steps with your foot, you could easily knock them over, leaving you stranded, or worse you might fall with the ladder causing physical injury.

One drawback to using a normal ladder is that you will need somewhere to store it and you will have to go to the trouble of digging it out of storage every time you want to get into the roof space — or it may be in use elsewhere in the house.

A much more satisfactory solution to the problem of climbing into your attic is the proprietary extendable attic ladder. This sits just above the trapdoor on hinges or pivots screwed to the inside or top of the opening frame and can be pulled down whenever you need it. Such a ladder, with its own built-in storage, makes your attic much more usable and accessible.

Purpose-made attic ladders are usually produced in aluminum with 2 or Sin wide treads. Most have two or three sliding sections with a safety catch that must be released before they can be extended. Some are linked to the trapdoor by a special bracket so that they come immediately to hand when you open it up.

When closed, the ladder lies across the tops of the joists next to the trapdoor, but it swings upwards over the opening before it can be pulled down, so it is essential that there is enough height above the opening for this.

Another important factor is the size of the opening itself which must be large enough to allow the ladder to pass through. This is not usually a problem if you are making a new opening, but if you want to fit the ladder to an existing opening, you will have to take some careful measurements. You will also need to know the distance from the floor of the attic (not the ceiling) to the floor of the room below.

For extremely limited attic space, there is a concertina attic ladder that folds up compactly rather than sliding.

Attic ladders can be simple or complex in design with risers and balustrades just like a proper staircase. Most come with some form of automatic trapdoor catch operated by relatively light finger-tip pressure on the door itself.

Obviously, the method of installing an attic ladder varies from one make and model to another, but usually it is quite a simple procedure. Often all that is necessary is to screw the hinges or pivots to the framework of the opening (on the same side as the trapdoor hinges) and fit the automatic catch to the other side of the opening. There may also be travel stops to adjust on the ladder and a bracket to fit to the trapdoor to hold the ladder so that it is easily reached.

Fitting a New Ceiling

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

Gypsum board for ceilings comes in two thicknesses: 3/sin and 1/2in, the former being suitable for use where the joist spacing is no more than l8in and the latter where the joists are up to 2ft apart. The standard sheet sizes are 8 and 10 x 4ft. You may find the smaller sheets easier to handle and you can cut them in half to make them even more manageable. The edges should meet on the joist centerlines, so you will probably have to trim them slightly anyway.

The first job is to nail lengths of 2in sq or 2 x Sin wood along the walls parallel with the joists so that its lower edge is level with the undersides of the joists. Then fit more short lengths of wood to the walls between the ends of the joists to provide support for the edges of the boards.

The sheets of gypsum board must be fitted with their long edges at right-angles to the joists. Toe-nail more lengths of batten to act as bracing between the joists so that the inner edges of the sheets will fall on their center lines. A length of batten marked with the board width will help position them accurately.

Finally, mark the position of each joist on the walls as a guide for nailing the sheets in place.

To cut sheets to size, use a utility knife and steel straightedge. Cut down through one face of the board, snap back the waste against a batten and run the knife blade down the crease from the other side.

If you intend plastering the ceiling, fit the gypsum- board gray side down. For painting or papering directly over the top, leave the ivory side showing.

Holding large sheets of board against the ceiling for nailing can be difficult so nail lengths of 2 x lin batten together to foiiu T-shaped props with which a helper can support it while being nailed in place.

Nail the first board in place, working from the center outwards and spacing the nails at 6in intervals. Drive them home so that they just dimple the surface; to be filled later. Use 11/4in gypsum board nails for thinner sheets and 11/2in for thicker kinds.

Continue in this way, working across the ceiling. Keep any cut edges up against the wall, but if this is not possible make sure they meet on a joist with a slight gap in between for filling; stagger the joints.

When you have clad the entire ceiling, seal the joints between the sheets and, if you prefer, apply a thin skim coat of plaster.

Removing an Old Ceiling

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

Taking down an old lath-and-plaster ceiling is an extremely dirty and dusty job, so before you start you must take the necessary action to protect both yourself and the other rooms in the house.

Protective clothing is essential and you will need to wear overalls, safety goggles, a facemask and thick gloves. But the most important item is a construction worker’s hard hat, which you can rent or buy. Hopefully the ceiling will come down under your control, but it is as well to be prepared for unexpected falls.

Because so much dust will be flying about, strip the room of all furnishings and seal the connecting doors to other rooms with plastic sheets or old blankets. It is a good idea to spread a large, thick plastic sheet across the floor to make collecting the debris easier, and you should have a good supply of thick plastic sacks to hand for bagging up the rubbish. If the ceiling is very large, it may be worthwhile renting a small container to dispose of the old ceiling.

You need to be able to reach the ceiling easily so that you can lever sections of it away from the joists. For simplicity, place a scaffold board between two step ladders so that your head will be about 6in from the ceiling — a ladder on its own is not suitable. An alternative is to rent sections of scaffold tower to make small access platforms, but this is probably only worthwhile if the job is large.

Any ceiling-mounted lighting fittings must be

removed (after turning off the power at the service panel or removing the appropriate fuse). Pull the supply cable back above the ceiling if you can get to it; if not tape up the ends and leave it hanging.

If the ceiling is immediately below the roof space, check that there are no other electricity cables lying across the top of the ceiling which you may snag as you remove it. Clip these to the joists.

Any dirt and dust above the ceiling should be removed with a vacuum cleaner.

Many attics are insulated with various materials laid across the top of the ceiling and obviously, these must be removed. Roll up glass fiber mat insulation and put into plastic garbage bags stacked in an unaffected part of the attic until it can be replaced. Loose-fill insulation should be scooped up and poured into garbage bags; or suck it up with an industrial vacuum cleaner before bagging it.

You can use a large claw hammer or a flat chisel and hammer to remove the old ceiling, although you might find the former easier as the latter will mean holding both arms above your head, which can be very tiring.

Hack into the plaster, levering pieces away until you have exposed a large area of laths. Prise these from the joists, always working away from yourself so that any falls will not be on top of you.

Continue working across the room until the entire ceiling is removed. Using pincers, pull out all the lath-fixing nails from the joists. Work round the edges of the ceiling with a chisel to clean up the plaster on the walls.

Repairing an Old Ceiling

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

There are two types of ceiling construction, depending on their age. Early ceilings were made by nailing thin strips of wood (laths) to the joists so that there were narrow gaps between them. Plaster, often reinforced with animal hair, was then spread over the laths and forced through the gaps in between. The ridges so formed are called “nibs” and these hold the ceiling together.

The more modern method of constructing a ceiling is to nail sheets of gypsum board to the joists and cover them with a thin skim coat of plaster.

Cracks are the most common form of damage found in a ceiling and if they are only fine they can be filled with a filler compound. However, if they are wide and cover a large area of the ceiling the structure will be dangerously weak and should be replaced.

If a plasterboard ceiling sags it is probably because the fixing nails have loosened. Refix the affected area by renailing with 2in drywall nails spaced 6in apart.

If plaster has fallen away from the laths but they appear to be in good condition, replaster them after cutting back the original plaster to make a regular shape and reach sound plaster. Undercut the edges of the plaster and make sure there is no old plaster left between the laths. Then treat the area with an adhesive.

When plastering always work across the laths, spreading on a thin coat of bonding plaster first and keying it with a scratch comb made by knocking a row of nails into the edge of a short batten. Apply another coat of bonding plaster and key this with a devilling float, pressing it down to allow for two thin finishing coats. Polish these when hard with a wetted steel trowel.

Casting a Solid Floor

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

The first job is to remove the old floor and dig out the ground below to at least 12in below the final floor level. Lever up an old wooden floor and saw through the joists for easy removal. Then demolish the dwarf walls. Break up a concrete floor: the best way is with a rented jack hammer. Keep the rubble for use as a bed for the concrete later. Wear stout boots, thick gloves, overalls and safety goggles.

Find the flashing in the walls; it may be a layer of slate or bitumen, or one or two courses of engineering bricks. If necessary, chip away the plaster to find it.

If the floor in the next room is of suspended wood, lay plastic drain pipes between any airbricks and the inter-connecting door threshold, setting them in place with bits of stone or brick: this is vital to provide ventilation throughout the floor. Build a retaining wall across the threshold with concrete building blocks.

Next make up some datum pegs from 2 x tin sawn softwood marked with the depths of the bed and concrete subfloor layers: 6in and 4in respectively. Cut a point on one end of the pegs then drive a peg into the ground near a given reference point, to indicate the surface of the floor. Drive the other pegs in at 3ft intervals, checking that their tops are level with the first.

Put down the brick and stone bed, leveling it with the marks on the pegs and compacting it well with a purpose-made tamper. Spread a layer of damp builder’s sand over the top to fill any voids.

The concrete for the subfloor should be of 1 part cement: 21/2 parts concreting sand: 4 parts gravel.

Lay the concrete so that it is level with the tops of the pegs, tamping it down well and drawing a stout batten across the tops of the pegs to level it. Fill any hollows with more concrete then tamp again.

When the concrete has cured, lay the cleavage membrane. With bitumen emulsion apply about three coats, taking it up the wall to the flashing. If plastic sheet is used, tack it to the walls above the flashing. Fold the corners and overlap the sheets by 8 to 12in, sealing the join with building adhesive.

Use 1 x 2in battens to divide the floor into 3ft wide bays for the finishing screed. Set them in place with dabs of mortar, level if necessary by packing offcuts underneath: check with a spirit level.

Fill the bays with a 3:1 mortar mix and draw it off level with a straight-edged batten held across the tops of the dividing battens. When two bays have been completed, lift out the batten in between and fill the resulting slot with mortar. Then trowel both bays smooth with a metal trowel. When the mortar has stiffened, give it a final polish with a wetted trowel.

Relaying Floor Boards

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

Buy boards at least two weeks before starting work and stack them in the room in which they will be laid. This will allow them to dry out properly, preventing shrinkage later. Ideally, choose tongued-and-grooved boards (T&G), but if you are just replacing odd boards, square-edged ones would be better. In the latter case, make sure you get the right size: 4in and 6in are common widths and the usual finished thickness is 3/4in. but thicker boards are available.

Removing the old boards

Lift the second board in from the wall. Then use a length of stout wood to lever up the others. Take care along the walls, since the boards are likely to be tucked under the baseboard. Tidy up the joists by pulling out any remaining nails and fitting packing strips if necessary.

Fitting the boards

Fit four or five boards at a time, keeping any end joints between them to a minimum. Where joints cannot be avoided, make sure the boards meet at the center of a joist and that their ends are cut square. Use up offcuts when you can and stagger the end joints so they do not all fall in a line.

Mark and cut the first board to clear any obstructions and fit it up against the wall. Force a chisel blade into the top of the joists and use it to lever the board tight against the wall while you drive two nails through it into each joist. Use cut floor brads at least twice the length of the depth of the board.

If you are using T&G boards, the groove of this first board should face away from the wall and be nearer the joist than the top. Set the next four boards in place and push them tightly together using wooden wedges or floor cramps.

In the former case, nail a length of wood temporarily across the joists and fit pairs of opposing wooden wedges between it and the boards. Tapping the wedges together will force the boards tight up against each other. Floor cramps clamp to the joists and when tightened exert great force against the edges of the board, (you should be able to get them from a good tool rental company).

In both cases, cut short offcuts of floorboard to fit between the edges of the boards and the wedges or cramps to protect the board edges. With the boards cramped tight, nail the outermost one down. Then remove the wedges or cramps and nail the remainder.

Continue in this way across the room. Where there are pipes or cables below the floor that you might want to reach in the future, screw the boards down. Cut off the tongues of T&G boards to make lifting easy.

The final boards

Stop within the width of two boards from the far wall since you will not be able to cramp these last boards. To fit the final boards, first lay a full board up against the last one to be nailed down. Lever it tight up against this board with a chisel. Next, take a short offcut of floorboard and hold it against the base so that its other edge overlaps the full board. Hold a pencil against the edge of the offcut and run it along the full board to mark the profile of the wall on it.

Cut the board along the pencil line and then refit it, but this time along the wall, springing in a full board between it and the others at the same time. Nail both boards down.

Renewing Floor Joists

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

You may find that a problem floor is simply due to one or two joists having become twisted and this can be cured by toe-nailing tight fitting wooden struts between them. However, if the wood is being eaten away by insects or rot, you will have no option but to replace every affected piece.

Lever up a sufficient number of floorboards to get at the affected joists, using a claw-headed hammer with a wooden batten to help leverage. Pull out all the nails and stack the boards so that you can replace them in the same order.

If only a small section of a joist is damaged, the affected area can easily be sawn out and replaced. However, for safety, make sure that the cuts are at least 24in beyond the damage.

Removal of a complete joist will mean levering it from its wall plates at each end, and also any intermediate wall plates. If the ends are set in sockets in the wall, cut through the joist just short of the wall and pull the stubs out. Brick up the sockets, cementing metal hangers into the top joints.

If only a section of joist has been removed, cut a new piece of joist to the same size plus extra wood so that it will overlap the ends by at least 18in. Bolt this to the old joist with two carriage bolts at each end.

If a complete joist is to be fitted, trim back its ends to a taper so that there is no chance of it touching the external walls. Toe-nail the joist to its wall-plates.

If the wall plates themselves are affected, replace them at the same time, simply laying them on top of the sleeper walls. Make sure you prevent contact with the masonry by laying a strip of flexible flashing along the wall first. It is recommended that pressure treated lumber be used for replacement sections.

Something to watch out for are pipe and cable runs below the floor. Pipes are usually set in shallow-cut notches in the tops of the joists and cables pass through holes drilled in them.

Always remove the fuse, or flip the circuit breaker, controlling any underfloor electrical circuit before work begins. Cut the cable out of the old joist by making two saw cuts down to the hole. Make similar cuts in the new joist and glue the offcut back for added protection. Alternatively, disconnect the cable from the nearest fitting and thread it through the holes.