Screening a solid floor

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

Screening your floor gives vital protection to a new layer of damp proofing and is an essential preparation before replacing floor covering.

It can be done in two ways. If the unevenness is slight, or you want to cover the existing flooring without lifting it, the best method to use is a self-leveling flooring compound. Make sure your floor is clean, dry and dust-free. If it is at all dusty, you should treat it with a proprietary concrete sealer before applying the flooring compound.

Mix the compound with water until it has a creamy consistency, and then pours enough on the floor to cover an area just under 1 sq m (1sq yd). Using a steel float smooth it out so that nowhere is the layer thicker than 3mm (Vain).

Then move onto the next square. Remembering that the compound will level itself out, so removing float marks and producing an acceptable finish. Leave it for a week or longer before laying the flooring. A second application, to smooth out slight lumps and bumps, can be applied after two or three days, but no more than three coats should be used otherwise there will be a risk of cracking at a later date.

The second method of leveling, using a mortar screed, is slightly more arduous but it does give the damp-proof membrane greater protection. Working from the far end of the room towards the door, divide the flood into strips about 1m (3ft) wide using 50 25rnrn (2 x line) softwood battens, and use more battens around the walls. Make sure that they are level with a spirit level, and if they aren’t, pack them out with scrap wood.

It is vital that you get all the battens level because they serve to guide you when you start laying the screed. If you don’t have them level, then your screed won’t be true and that’ll cause more problems when you come to lay the final surface. Cover the floor. a section at a time, with a 1:3 cement to sharp sand mortar, mixed with the minimum of water to the consistency of brown sugar_ Using a stiff board, scrape jt level with the battens and tamp it slightly as you go, using a steel float to give it a smooth finish.

To get the best finish to your screed keep the blade damp to stop the surface from dragging, but don’t make it too wet. When you complete each section remove the guide batten furthest from you and fill in the resulting channel before tackling the next section.

If you lay a screed during a warm dry spell it’s advisable to lay a plastic sheet over it for at least three days. This stops the mortar drying out too quickly and lets it cure properly. Even in milder weather it’s still best to sprinkle water gently over it twice a day for a few days. If the mortar dries out too quickly it will be below strength and will probably crack as it dries. Finally make good the walls and replace the skirting.

The big drawback with this method is that it raises the level of the floor by 25mm (1 in). Strictly speaking you should dig out the existing floor to the required level before starting, but this carries the risk of damaging any existing damp-proof membrane. One way of accommodating the extra thickness is to trim the bottom of the doors and build up any existing external doorsteps.

Do make sure that you don’t reduce the floor/ceiling height below the Building Regulations minimum of 2.3m (7ft 6in) and remember to do something about the change in level at the door thresholds: a shallow ramp is better than a shallow step.

There is another option, and that is not to lay a membrane at all. Instead you select flooring that can be laid using cement-based flooring adhesive. The former lets the damp through. so you should choose material that won’t be harmed by it, and the latter acts as a sort of damp-proof membrane itself.

But. as it is a makeshift solution. it will not always work and there is nothing to stop the damp rising through the walls. The floor will therefore be attacked from the edges. which can be just as harmful and the result will be that the whole floor will eventually have to be replaced, not only giving you extra work but also further expense.

Finishing Plasterboard

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

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.

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.

Plastering Wallboard

Filed Under: Do it yourself, Remodeling    by: ITC

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.