Builders in London

Builders in London

Fixing for solid walls

builder drilling wall
Solid walls are generally made of either brick, concrete, or lightweight cellular or aggregate building blocks. Attaching objects to brick and concrete is usually straight forward, and a secure fixing can be made with masonry nails or any of the standard types of plug and screw fixings in the case of cellular blocks, an adequate fixing can be made by simply drilling and driving in a screw. Care is needed, however, when fixing to aggregate blocks as these do not provide as secure a bedding as the other materials.

Masonry nails
These can be used to fix such things as shelving battens, picture rails, skirting boards and studs for wall panelling to most types of solid surface in the home. They are tempered to prevent bending and can be nailed straight into the wall with a hammer. Special cartridge tools which fire the nail into the wall can be obtained. These are particularly useful where large quantities of nails need to be driven. Two types of nail are available. One has a straight shank and the other a twisted one, which improves penetration into hard materials and helps keep the nail firmly in place. When nailing, always drive the nail in at right angles to the wall and ensure that the nails are long enough to penetrate at least 13mm and not more than l9mm in into the masonry. If the wall is plastered add the thickness of the plaster to the length of the nail required. To prevent them from snapping, nails with straight shanks should be gently driven into the wall with light hammer blows aimed to hit the head of the nail straight on. With twisted shanked nails, start the nail off with light hammer blows, and then use heavier blows to drive the nail home they are stronger than straight shanked nails and will not break so easily if possible, wear goggles as protection from flying chips of masonry or broken nails.

Wall plugs

Most household objects can be firmly attached to solid walls with one of the many types of plug and screw fixings available. They all require a pre-drilled hole, which can be made with either a hand boring tool or a tungsten carbide-tipped masonry drill. To make a hole with a hand tool, first tap the tool with a hammer through any plaster and then use firmer blows when the masonry is reached. Twist the tool slightly after each blow to ensure a neat hole and to stop it jamming. Once the required depth for the plug has been reached, remove the tool and blow out any dust. If you are using a masonry drill, you must use either a hand brace or an electric drill with a speed reducer. With some drills this is built in but an attachment is available to reduce the revolutions of a fixed speed drill. As you drill, press firmly so that the bit bites into the masonry. Remove it from the hole a few times and clear away any debris. Take care to keep the drill steady or the hole will become larger than required. If this does happen, you will have to pack it with a suitable filler. A percussion drill is desirable for use with concrete as it saves time and wear on the drill bit. This can be hired but, again, an attachment for converting an ordinary drill is available.

Second, the screw shank must never be allowed to enter the plug; this would weaken the fixing and the masonry. If the thickness of the article to be secured is less than the length of the screw shank, sink the plug further into the wall. When the hole has been made, first insert the screw a couple of turns into the plug and then push the plug into the wall. Then tighten the screw until the shank is about to enter the plug. Withdraw the screw, attach the fixture and then screw it up tight. Plastic wall plugs are also available and come either as strips which you cut yourself, or in pre-cut lengths. They have the advantage of being rotproof and waterproof, and are colour coded for size.

Aggregate blocks
The main problem encountered when attaching objects to walls made of aggregate building blocks is obtaining a firm anchorage for the fixing. Although light objects can often be adequately fixed with standard plugs and screws, it is safer to use one of the many nylon plugs designed for the purpose. These have ‘teeth’, or ridges, which grip the surrounding material, and ‘fins’ which prevent the plug rotating while screwing. They will also take screw shanks with little distortion, and can be used in normal masonry. Another device that is useful for fixing to aggregate blocks is the’Rawlnut’. This has a rubber sleeve which, when the bolt is tightened, expands and compresses against the surrounding material. lt can also be used for fixing to other types of masonry and is suitable for hollow surfaces.

Lathing ceilings

Lath can be used as an alternative to plasterboard as a base for ceiling plaster. Various types are available, but the most common are ‘expanded metal lath’ and ‘K-lath’. Wood lath has largely been replaced by these. Expanded metal lath is a metal diamond shaped mesh which is fixed in position with galvanised clout nails, screws or staples. It comes in 2.7m 600mm sheets and can be cut with tin snips. When fixing to the joists, stagger the sheets to avoid long joins, and overlap each about 13mm. Wire any unsupported joins with galvanized wire at frequent intervals. K-lath consists of a mixture of metal wire and paper. It is also cut with snips and fixed with galvanized nails or staples. Wood lath is made up of strips of timber about 1.2m x25mm x6mm. The strips should be nailed about 6mm apart across the joists, and the joints should be staggered wherever possible.

Plastering on lath

Before the normal floating and setting coat, a ‘rendering’ coat has to be applied directly to the lath. If you are using a lightweight finish coat, a plaster such as Carlite Metal Lath should be used. If using this plaster, however, you must use the same material for the floating coat. Using a sanded mix is more complicated, but it does enable you to use a slower-setting finish plaster. To mix a sanded rendering coat, first prepare a lime mortar by mixing three parts of sand and one part of lime with water (use a bucket as a measure). Hair, or a special nylon fibre made for the purpose, should be added to this mix to strengthen the finish mortar. As a guide, if you have used three bucketful of sand and one of lime mix in about one handful of hair or fibre.

Allow this mix to stand for about 24 hours, then mix six parts of it to one part Portland cement. Add water, but only enough to make the mix fairly stiff. When applying the rendering coat, press it on firmly with the laying trowel so that the plaster firmly ‘keys’ with the lath. If you are plastering over wood lath always apply the plaster in the direction of the joists, so that you plaster across the ‘run’ of the lath. Once the lath has been covered to a depth of about 6mm, key the surface well and leave it to set. Now mix your floating coat and lay screeds around the edges of the ceiling with the laying trowel. Rule them in with the featheredged rule. Divide the ceiling into manageable sections with further screeds if required.

Then proceed to fill in the sections and rule them flush with the screeds. Smooth over and key the surface with the devil float, and clean out the corners with the laying trowel. When dry, skim on a thin layer of finish plaster with the steel trowel. Go around the edges first and then apply strips from one side to the other. Follow up with the wood float, using strokes in the same direction. Then put on another layer, this time crossing the previous strips at right angles. With the steel trowel, lay on a final coat and then smooth all over. Clean out the corners where the ceiling meets the walls with the angle trowel and, finally, wash down adjacent plasterwork if required.

Plasterboarding ceilings

plasterboarding ceilings
Red plasterboards are fire rated
Plasterboard consists of a gypsum core sandwiched between paper liners. Various types are designed to take plaster, and it is advisable to read the manufacturer’s instructions regarding fixing and plastering before you start work as there can be small variations to the instructions given below. Most plasterboards, however, have square edges and these need ‘scrimming’, or reinforcing, after the boards are placed in position. Most can also be plastered with one ‘thick’ (about 5mm coat of finish plaster.

The plaster must be a hemi-hydrate. Various sizes of boards are available and it is sometimes useful to obtain a variety to minimize wastage. But as it is easy to cut, one of the standard sizes, say 1.2m x 2.4m (4ft x 8ft) is a convenient size to work with. Plasterboards also come in two thicknesses 9.5mm and 12.5mm. The first is suitable for most situations, but where the distance between the centres of the ceiling joists exceeds about 350mm, the latter should be used. Some ceilings are very uneven and it may be necessary to counter batten them to provide a new level surface on which to nail the plasterboards. The first battens are nailed at any convenient, spacing and are used to form fixing points for a second set of battens which are then fixed at right-angles to the first ones. This second set of battens are fixed at centres to suit the width of the plasterboard and they are levelled by driving thin wooden packing pieces between the battens where necessary.

The ends of the boards can be butted up to the walls or the plaster can be chipped away so that the boards can go right up to the brickwork. In the former method jute scrim is applied to the angle to reinforce the plaster. When flxing the plasterboards to the joists do not use ordinary galvanized clout-head nails as these large, flat heads cut the paper covering of the boards.

If you are not using plasterboard screws, use only the proper plasterboard nails which have a slight bevel underneath the head rather like a countersunk screw head. These small-headed galvanized nails should be 30mm long for 9.5mm thick boards and 40mm long for the 12.5mm boards. Place the nails 12.5mm from the edge and at 150mm centres.

Fixing to the ceiling

plasterboarding ceiling

Plasterboards over which you intend to plaster can normally be nailed either across or along the joists. For large areas it is often desirable to position them in both directions so that long joins, which may cause cracking, are avoided wherever possible. It is particularly important to ensure that the joints are adequately nailed to the joists. You should leave an 3mm gap between the boards for scrimming. Before starting work, it is a good idea to draw a plan of the ceiling and work out roughly how your boards will be placed. This will help you to arrange them to minimize cutting, and also to ensure that they are sufficiently staggered.

If you are working alone you will need the help of a ‘dead man’s hand’ in addition to the normal tools and working platform. This is simply a long piece of straight-edged wood, about 50mm x 25mm to which is fastened a cross piece about 600mm wide. The bottom of the batten rests on the floor and the cross piece is wedged against the plasterboard to hold it in position. Your hands are then free to nail or screw the board to the joists. The easiest way to cut plasterboard is to score the face side deeply with a knife along a straight edge and then lay the board, with the cut side uppermost, over the edge of a table or bench so that the cut is in line with the edge. Snap the core by pressing down sharply, turn the board over and cut the paper on the other side along the crease. Alternatively, you can use an old saw, but this is slower and more tedious.

Plastering

Repairing cracked plaster sometimes turns into a much bigger job than expected: you find a whole wall that needs replacing. Plastering a complete wall or ceiling is a fairly ambitious job and some skill is required to produce a true, flat surface. If you doubt your ability, it would be a good idea to experiment first on a suitable ‘hidden’ surface like a garage wall or ceiling or get a Plastering Company to do it for you.
Plastering Company London

Plastering a wall

It is unlikely that your wall will be perfectly flat and upright, so the first job is to find the high spots and determine whether or not the wall is out of true.

To do this, hold a spirit level on the back of a long straight-edged rule and move it systematically over the wall. Once you have prepared your surface, taking particular care to ensure that it has a good key, mix your mortar floating coat and start to lay ‘screeds’ on the wall. These are strips of plaster about 200mm wide which act as depth guides. They also break up the wall surface into easily manageable sections. With the steel laying trowel, lay the first screed a little over 13mm deep, from the floor to the ceiling on one side of the wall. Take it right up to the end of the wall. If this is a reveal corner, and you are using a length of angle bead to make a neat edge, place the bead in position before you lay the screed. If you are using the more traditional method, leave the reveal until you have floated the whole wall.

When you have laid the first strip, use a straight-edged rule about 1.8m long to rule it off. Hold the rule vertically and move it gently up and down from the outer edge of the screed inwards. Test for plumb with the straight edge and spirit level, and adjust, if necessary, with a little more careful ruling. Add more mortar if required. The ruling should reduce the thickness to about 13mm if the surface is good. A screed similar to the first one should then be laid on the other end of the wall. You should lay a minimum of two vertical screeds although, for ruling off later, it will help you to lay additional screeds at about 1.5m intervals. Now lay a horizontal screed about 50mm from the floor to join the vertical ones. Use the latter as guides when ruling off this screed. Another horizontal band should now be laid about 1.5m from the floor and ruled in the same way. The final screed should be laid across the top of the wall, flush with the ceiling, and ruled.

The screeds should now be smoothed with the plastic float. The sections between the screeds are then to be filled in flush. Deal with one section at a time and apply the floating mortar with the laying trowel. Rule off each section using the screeds as guides. Fill and re-rule if necessary. The 50mm strip at the bottom of the wall can be left if skirting board is to be used). When the whole wall is covered, clean the internal angles with the laying trowel, and wash down any adjacent surfaces smeared with mortar. Finally, go over the entire surface with the devil float to flatten any small bumps and to key the surface.

If you are using a sanded floating mix, allow it to dry for 24 hours; a lightweight plaster will take about four hours. If you are using the traditional method, any reveals in the wall should now be plastered with both the floating and the setting coat. Before applying the finish plaster, it is wise to test the surface for suction. Brush water on to a small section of the wall and watch what happens. If it is ‘sucked’ straight through, there is excessive suction. As this can have a disastrous effect by weakening the final coat, it will have to be remedied. Throughly dampening the wall will be sufficient in many cases, but if the suction persists, brush on a weak mixture of water and pva bonder-one part bonder to six parts water is about right-arid follow up immediately with the setting coat. When you are ready to apply the setting coat, mix up some finish plaster in a bucket and pour it on the spot board. Then clean out the bucket and fill it with clean water so that it is ready for another mix. Start to skim on the plaster with the laying trowel. First skim a band, about a trowel width, along the top. Then skim over the whole wall in vertical strips, up to the band already laid.

When the wall is covered, use the wood float to put on another thin application, again with vertical strokes. Work systematically from the left to the right (if you are right handed) and keep the seams well pressed down. Now, still using the wood float, Put on another thin application, but this time use horizontal strokes. At this point use the feather-edged rule to rule out the internal angles. Any seams still visible should be smoothed over with the wood float. If you are using an anhydrous plaster such as Sirapite, a little water will help for this, but do not use any at this stage if it is a hemihydrate. The final application of finish plaster should now be put on the wall. Use the steel trowel and lay a ‘tight’, or firm, coat with long vertical strokes. Then wash the trowel and sprinkle a little water over the plaster. Quickly follow up with the trowel and smooth over the whole area. Use the angle trowel to finish the internal angles and, finally, scrape any unwanted plaster off the floors, adjoining walls and the ceiling before it sets.

Building an extra room in the garden

Do you need an extra room?

If you are short of living space,especially if you live in London, you may wish to treat a small back garden primarily as an extra living room, or as an extension of a kitchen-dining room, especially in warm weather. In this case a glazed (or better still, double-glazed) door into the garden gives a sense of extra space and continuity where a conventional wooden door would act as a view-stopper. Sometimes it is possible to use flooring to add to this sense of continuity. Quarry tiles on the kitchen floor can be continued outside to form a small patio, and possibly link up with cobbles and brickwork to make a patterned garden floor.

Extra room in the garden London

The mini-garden that is used as a ‘room’ has to provide several of the functions of a real room. Warmth, privacy and shelter can be given by high walls or palings. For a verandah effect, cover a third or half the garden with a pergola or some other roof structure. This can be glazed, fitted with pull down slatted wooden or canvas sun blinds, or twined with climbing plants. If there is sufficient shelter, outdoor cooking may be possible. This could be on a brick barbecue built along one wall, or on a simple brick or tiled counter top fitted with outlet sockets for various plug-in appliances, (Remember to use special outdoor plugs and sockets installed by professional and qualified electricians.) In an extra ‘room’ of this kind, seating is important.

interior extra room garden london

Mini-gardens often belong to smallish houses so that, while there is plenty of attractive garden furniture available, finding somewhere to store it is a problem. An alternative to the white-painted iron seat, or teak bench, that can be left out all year round, is built-in seating. A brick or concrete block bench down the length of one wall can be softened with a scatter of gingham cushions for impromptu outdoor meals, and double as a parking place for glasses if you have a small drinks party-or even, since your outdoor room is still a garden, as a table for plant pots !

before building the extra room
The outdoor room being built
outdoor room being built by builders london

London Builders Robuild can provide you with a free Design and Estimate for your building project.The outdoor rooms can be used as offices, gyms, etc.We also build Garden office and Garden Gyms to high standards.

Concrete mixes & Mixing concrete

Mixing concrete

cement mixer

All preparatory work on the sub-base should be completed before the concrete is mixed. If you are mixing by hand, rather than using a concrete mixer, mix on a clean, smooth surface. An old sheet of plywood or hardboard is excellent. Alternatively, you can work on a section of path or patio, protected if need be with a heavy layer of polythene sheet. Blend the cement/aggregate until the pile is a uniform colour with no patches of sand or cement. Make a well in the middle of the pile and pour in a little water.

With a shovel, work the inside walls of the well into the water until the water has been absorbed; then add more water and continue until the mix is just wet enough to place and compact. An easy way of checking this is to pat the surface a few times with the bottom flat of the shovel; after this compacting, the surface should be smooth and close-knit. Avoid using too much water, as this will weaken the concrete and cause shrinkage as it hardens. But the mix must be workable enough to be put in the moulds and compacted without leaving air-holes, which will result in honeycombing and loss of strength.

Concrete mixes

Although an average concrete mix could be used for most purposes, certain types are more suitable for particular projects, and the proportions of sand and cement must be adjusted accordingly. The mixes shown here are suitable for different kinds of concrete work outdoors. Where strength or resistance to wear is important, it is best to use mix ‘A’. Where a lower grade will do, mix ‘B’ could be used. Mix ‘C’ is a fine concrete suitable for very thin sections or for bedding mortars. Mix ‘D’ is for bedding paving stones. All proportions are by volume.

A 1 part cement, 2 of sand, 4 of coarse aggregate. Suitable for paths, pools, steps, fencing and edging.

B 1 part of cement,2,1/2 of sand, 4 of coarse aggregate. Suitable for foundations, garage floors, drives, filling for garden rollers, and thick walls.

C 1 part of cement, 3 of sand. For formal or crazy paving less than 50mm thick. This is also the mix for brick laying mortar if soft sand is used.

D 1 part of cement, 5 of sand. A stiff mortar mix for bedding paving.

Pre-mixed concretes

Many London builders make up their own concrete mix, although for small jobs it is more usual to buy a bag of dry mixed ingredients that requires only the addition of water. Dry mix can be bought from a builders’ merchant or DIY shop and is usually sold in 50kg bags, although some places sell bags as small as 3kg. As the cement in the mix deteriorates with storage, buy only enough for the job in hand. The dry mix is sold in a variety of proportions to suit different work, so when you order make sure you specify exactly what you are using the mix for.

For large jobs, such as for the foundation of a house extension, garage or for a long driveway, ready mixed concrete is the answer. This has the correct amounts of cement aggregate and water mixed in a central plant, and is delivered, ready to lay, in special agitator lorries. Ready-mix can be ordered in most places through a builders’ merchant and, in theory, can be obtained in any quantity. But in practice, quantities of less than 4 cubic metres (4 cubic yards) is uneconomical for the supplier.

concrete foundation ready mix cement

A quantity of ready-mixed concrete can be delivered when it is most convenient, so that a large concreting job can be done in stages. And if there is access to the site, the agitator lorry can place the concrete directly into the formwork or trench, thereby saving a lot of back-breaking labour. If you do order ready-mixed, have your site ready before the concrete is due to arrive. And make sure that you have sufficient labour to handle the job quickly, 1 cubic meters of concrete weighs about 2 metric tonnes (2 tons) and in warm weather it may become unworkable in as little as an hour.

Setting and curing

Fresh concrete should not be allowed to dry out too quickly. If this happens, its strength will be reduced and cracking and ‘dusting’ will occur. Keep concrete damp after laying by covering it with a polythene sheet for 24 hours as soon as setting has completed sufficiently to prevent marking. Concrete goes through two stages before reaching its maximum strength. The first stage is ‘setting’, which is the initial reaction caused by the activation of the cement by water. In normal weather, setting takes about seven days, but hot weather could shorten the time to four days, and cold could extend the period to ten days.

concrete foundation london house extension

It is easy to see when setting has completed because the concrete turns ‘green’, and literally takes on a greenish tinge. When this happens the concrete is starting to ‘cure’. When curing is complete, the concrete loses its green tinge and is said to have reached maximum strength, although it will actually go on getting stronger for up to 20 years. The complete cycle for setting and curing takes about 28 days. The formwork could be removed once the concrete has set, but if possible leave it in place until curing has completed. If it is unavoidable, you could start building on, or using, the concrete before it has cured. But it might crack badly if the maximum weight it is intended to carry is used during this time. Avoid laying concrete during frosty weather. Water in the mix will expand on freezing, and this is likely to make the concrete break up.

london bricklayers building

Paving with concrete

Concrete usually conjures up impressions of towering skyscrapers and similar giant constructions, but the very qualities that make concrete so valuable in large scale projects are just as useful to the any builder for home improvements. The durability of concrete is only one of its qualities. In terms of weather resistance it is virtually indestructible, and it is impervious to most kinds of chemical attack. But concrete’s greatest asset is its versatility. Its range of uses includes drives, garages, paths, fencing, patios, walls and even complete buildings. And all can be produced in a wide range of coloured, textured and profiled finishes for infinite variety.

cement mixer concrete mortar rendering

Composition of concrete

Concrete is made from cement, aggregate (sand, gravel, pebbles, crushed stone) and water in varying proportions. Sand is described as ‘fine aggregate’ and should be the ‘sharp’ variety, as distinct from the ‘soft’ bricklayer’s sand used in bricklaying mortar. Gravel, pebbles and crushed stone are described as ‘coarse aggregate’, and consist of particles varying in size between 5mm and 19mm. The cement most often used is Portland, which is light grey in colour. Also popular is white cement, which can be used on its own or with a colourant to provide a wide range of colours.
There are also many cements of a more specialised nature, such as quick setting cement, and masonry cement, which sets slowly and is used for certain types of brickwork.

Laying a concrete slab

A concrete floor slab-cast on site, without digging foundations-is a straightforward job even for the inexperienced. The technique is the same whether you are laying a drive, a path, or a foundation for a small building. You begin with a mould formed by laying planks or other sheets of timber (the form work) round the edges of the area to be concreted. The formwork is held in place by stakes driven into the ground, and protruding up to the top of the formwork. The interior of the mould or formwork is then filled with a concrete mix that is allowed to set before the timber is removed. The choice of materials for formwork is dictated by the shape of the concrete slab required. If the edges are to be straight, or angular, as is usually the case with drives and foundations for buildings, the formwork can be laid in simple timber planking.

house extension foundation

But if curved edges are required, and for paths this usually gives a more pleasing outline then the formwork will consist of strips of flexible plywood, or even hardboard that can be pegged into a curved shape. Concrete should not be laid in frosty weather.

Drilling metal

The action of drilling metal is to remove material from the hole in the form of two spiral sections and filings. It depends on the type of metal whether these spiral sections are removed as a continuous coil or as fine metallic particles. Soft brass, for example, when drilled leaves two wire strips. Iron and steel, on the other hand, are usually too brittle to assume this form, and so is thrown up as fine lumps. This waste material is known as swarf. The swarf is formed by the drill point being pressed into the metal while in rotation.

Metalworking Techniques

Occasionally you will have to tackle a metalworking job which calls for more advanced techniques. Here basic instructions are given for sawing metal bars and hardening and tempering home made tools, together with all you need to know about drill bits, screw thread taps and dies. The first consideration is how to cut the material. Before this can be done it must be supported firmly. Here a good solid bench vice is vital. Don’t be tempted to use a carpenter’s woodworking vice-you will spoil the jaws and damage the screw-but use a solid metalworkers’ bench vice. As a rule, always buy the largest, biggest and best you can afford since it will make your work so much easier. The weight of a large vice will help to prevent the work juddering during sawing and provides a perfect support. A tight grip on the metal you are to cut is very important; if the metal slips while you are cutting it, at the very least you may break the hacksaw blade and you may also bruise and skin your knuckles at the same time.

Cutting metal

robuild builder cutting metal

The hacksaw is the best tool for sawing metal, but remember that a hacksaw is not a universal tool. It is only a frame into which you can fit a variety of blades. These blades come in two basic types-ordinary carbon steel and high-speed steel. The latter are more expensive but, used with care, last perhaps three times as long as the more brittle carbon blades. Blades are also described by the number of teeth they have to the inch. The fewer the number, the coarser the blade, and you must select the right one to suit the job. A good guide is that, whatever you are cutting, there are a minimum of three teeth of the blade in contact with the metal at any moment. This is important when cutting narrow sections because if the blade is coarser than this, the teeth will straddle the metal and chip off. For cutting large sections of steel, the coarser the blade (within reason) the better since the wider gaps between the teeth will allow plenty of clearance for the tiny chips of metal which the teeth remove as they are pushed across the metal.

When you fit a blade into a hacksaw frame, always make sure that the teeth point forwards, and keep the blade tight by screwing up the adjuster on the frame-a slack blade is easily broken. Working with a hacksaw is simple providing you use the correct technique. Hold the saw firmly in both hands with your forearms horizontal. Push the saw forward and pull it back with a smooth, steady movement. Don’t saw too quickly-one forward stroke per second is ideal. Do not apply pressure on the back stroke-this does not cut and you will only blunt the tips of the saw teeth. With practice you will automatically develop the correct sawing technique. When you do you will be able to work with a hacksaw for long periods without fatigue. If you have to make a long cut through a narrow section, you can turn this blade through 90 degrees in the frame so that the bow of the frame is well clear of the metal.