On the face of it, knocking a hole through an internal load bearing wall is quite a daunting task. It conjures up visions of accidental structural damage and consequent high cost of putting things right. But if you approach the job properly, there’s no reason why it should cause any problems.
Improving access between rooms or creating a larger living area are probably the main reasons for breaking through a wall from one room to another. But you need to use similar techniques if you simply want to make something like a serving hatch between a kitchen and dining room, for example.
Whatever the reason for the building work and whatever the size of opening you require, the principles are the same. The most important point you have to remember is that you must provide some form of support for the structure above the opening.
The exact positioning of the opening in your wall will depend on a number of factors. Make sure it allows you enough remaining wall to accommodate any items of furniture there may be nearby — it’s infuriating to have something like a sideboard that’s just frac tionally too long for the wall you want to stand it against. If the opening is to be a doorway, it must be conveniently sited for the normal traffic flow within the house. And don’t forget the proximity of electrical accessories with their wiring, and also pipework for your water supply or central heating. If possible, position the opening so that you won’t have to reroute cables and pipes.
If you’re removing a complete wall to turn two rooms into one, you must leave enough of the wall at each end to provide adequate supports (called ‘bearings’) for the beam. If you cut too close to an adjoining wall, you may weaken the entire structure; leave at least two bricks’ width of the old wall at each end. This will allow you to cut bearings of the minimum required size (150mm 225mm). Similarly, leave enough of the original wall above the opening to be able to insert the beam and the needles above it.
But if you’re making a new doorway, remember that readymade doors and frames come in a range of standard sizes. You’d be wise to choose the size of door first then make the opening to suit, unless you really want to go to the trouble of making your own door and frame.
Before you can choose the type of beam to use you’ll have to find out whether the wall you plan to open is actually loadbearing. As a basic guide, a nonload bearing wall —which offers no support to the building —usually runs parallel to the joists in the floor or ceiling above. A loadbearing wall usually runs at rightangles to the joists, and supports them. If you are in any doubt assume the wall
is loadbearing. You will have to gain the approval of the building inspector before proceeding and the inspector will advise you if you aren’t sure.
Even if a wall is not loadbearing, in the sense that it is not carrying the joists, if it extends to an upper storey, you must arrange to support the weight of the wall itself over the new opening.
Choosing a beam
A rolled steel joist, or RSJ, is suitable for spanning an opening of any size. But longer lengths get very heavy and RSJs require special preparation before plastering.
Galvanized steel box beams are much lighter and will accept plaster directly, but they are much more expensive. They are available in lengths up to 5. 4m.
For openings of up to 3m, the kind of beam you choose depends largely on convenience. Both reinforced and prestressed concrete beams are available, but for a given strength the prestressed variety is much lighter and for this reason alone is preferable.
Whatever you do, before you start work, you must consult your local building inspector and get approval for what you plan.
Alterations to the structure of the house must comply with the building regulations which ensure the work is carried out safely and that the finished job is sound. So don’t do anything until you get official written consent.
Obviously, removing a wall will produce a lot of rubble and debris: so to minimize disposal try to reuse as much as you can.
Where possible, remove whole bricks as you make the opening; these may prove useful for other projects and it’s always handy to have a few bricks around for use in the garden. Broken masonry can be used as hardcore. However, if you don’t see any need for the material you’ll have to dispose of it. You could bag the rubble in stout polythene sacks, and ferry it to your local dump, but it’s much better to hire a rubbish skip.
Tools and equipment
Although you might consider this a fairly ambitious project, the tools you need are quite basic.
For marking out the opening, and the. Holes for the needles, you’ll need a tape measure, pencil, straightedge and spirit level.
A bolster chisel (preferably fitted with a mushroomshaped hand guard) and club hammer will be necessary to chop out the masonry.
For mixing mortar, equip yourself with a piece of flat board and a spade, and have a bucket handy to carry the mortar to the opening.
You also need a bricklayer’s trowel, and a plasterer’s steel float and hawk for finishing.
Most important is a suitable number of adjustable (Acrow) props to support the wall and floor above the opening, and these can be hired from any good toolhire company.
Even if you’re only making a doorway, you will want some form of platform to stand on whilst chopping out the slot for the lintel and the upper courses of bricks from the opening. An ordinary pair of stepladders will do for a narrow opening, but for something wider, a scaffold board between two pairs of steps or a section of scaffold tower would be better. If you don’t have such equipment, it can be hired from the same source as the props.
Wear old clothes, safety goggles to protect your eyes from flying fragments of brick, and stout gloves to protect your hands.
Because so much dust is produced, cover all furniture nearby with dust sheets and roll back any floor covering. It would be better to remove the furnishings from both rooms completely if you can. A stout polythene sheet should be spread on the floor to collect the debris.
As for materials, you’ll need lengths of 100mm X 75mm timber for needles, and scaffolding planks to support ceilings and stand the props on. For mortar, you’ll want a quantity of soft sand and Portland cement to provide a bed for the lintel and any brickwork at the sides you have to replace. You’ll also need Carlite browning plaster and finish plaster, and either readymade metal corner beading or timber battens for thickness guides when plastering the corners of the reveals.
PROVIDING TEMPORARY SUPPORT
The weight carried by a loadbearing wall in your house can be considerable. On no account should you attempt to cut an opening in such a wall without first providing support for the wall and ceiling above.
It’s essential to use adjustable props and timber needles or planks to support the load when making an opening. The needles should be about 1. 8m long and the props should be positioned about 600mm from the wall. The props should be placed so that the needles they support are immediately above where the lintel is to be placed.
One needle should be, at least, at each end of the slot unless the opening is very narrow — less than 1m — when one can be placed centrally. With wide spans they should be set at 1m intervals as well.
Where the ceiling joists run at rightangles to the wall, planks can be used on either side to support the ceiling. Props should be set at lm intervals along the plank, under a joist. In both cases, the base of the prop should rest on a plank running at right angles across the joists of the floor — for safety sake, pull up a floorboard and check the direction in which they run.
Props offer both coarse and fine adjustment. The approximate height is set up inserting the locking pin in one of the adjustment holes. Fine adjustment is performed by turning the threaded collar.
You’ll need someone to help you as props should be extended simultaneously so that the needle or plank can be set level. Check this with a spirit level.
A certain amount of self-support is provided by the interlocking pattern of brickwork. For small openings in a nonload bearing wall, the area at risk is a 45° triangle immediately above the opening. This must be supported until after the
lintel is in position. On wider spans the area at risk is a rectangle the width of the opening to the top.
Left unsupported, such an area could be disastrous
REMOVING THE BRICKWORK
Using a bolster chisel at a shallow angle, start removing the plaster within the outline of the opening.
With the plaster removed, start work on the masonry itself, starting at the course immediately below the lintel. Cut into the vertical mortar joints first, then into the horizontal joints to lever out each brick in turn. You’ll need to hit the chisel really hard with the hammer to cut into the masonry — a rubber or plastic hand guard fitted to the shank of the chisel is useful in case the hammer head slips.
As you chop out the masonry, you’ll find that you will have to remove parts of bricks in alternate courses at the edges due to the overlapping bonding pattern. Cut each as you come to it, striking directly into the face of the brick in line with the edge of the opening so that it splits cleanly, then lever it out from below. Bag up rubble as you proceed down the wall to ease clearing up later and to give you an uncluttered work area.
Forming the opening is a matter of chopping out the masonry bit by bit with a hammer and holster. Damp down the dust with water.
BUILIDING THE PIERS
The whole purpose of fitting a lintel is to bear the weight safely, so it must be strong enough for the job and must be firmly. Fixed. The building inspector will want to be sure not only that you are using a suitable beam, he will also want to be sure that it’s properly supported at each end.
The primary requirement is that the beam overlaps its supports by at least 150mm at each side. After ordering the beam large enough to cope with this, the supports themselves can be made in a variety of ways. The most convenient is where the wall at right angles to the beam is made of two layers of brick. Here it may be sufficient to chop out a hole to take the end of the beam, allowing the weight to be taken on the existing foundations. This supposes that the walls are in good condition, and that the building inspector can be convinced that there is no need to build new foundations in the affected area.
In older houses the mortar may be perished and this is enough to create a problem. The very least required is that the joints be raked out and pointed in fresh mortar to consolidate the brickwork and prevent further deterioration. Where you are dealing with a large span, the building inspector will almost certainly require that you build proper brick piers with their own foundations. He will want to take a look to be sure that everything is satisfactory, from the condition and type of subsoil, through the hardcore to the padstone or whatever is going to carry the weight of the beam. You will have to lift the floorboards so that the inspector can look underneath.
You will have to dig out to a specified depth and put in a good bed of hardcore, well consolidated with a sledge hammer or similar tool. On to this you pour a layer of concrete to the required thickness. When this has cured, you will be able to commence the brickwork from the footings up to floor level. At floor level a dampproof course must be inserted, and if you have a solid ground floor, measures must be taken to ensure the continuity of the new DPC with the existing one.
The bond in the brickwork will vary with the size of pillar. It should be tied into the existing brickwork; this is best done by cutting out and allowing one in three bricks to interlock the adjacent wall.
In some cases engineering bricks can be used to form the DPC in the pillar. They should also be used at the top of the pier as they will take the weight of the beam without crumbling. If engineering bricks are not available, you can cast a padstone on top of the pillar in strong concrete or use steel plates. The building inspector will sort out these details with you.
In most cases the pier can be built before anything else is disturbed, keeping the demolition down to the minimum needed to give you working room.
This, in turn, will minimize your hire charges for the props, and leave the structure undisturbed until the last possible moment.
POSITIONING THE LINTEL
If your lintel is heavy, you will find it much easier to lift it up to an intermediate platform before placing it in the slot. Good step ladders will do, but even more essential are enough people to bear the weight.
Once the lintel is in its slot, cut a spare prop under each end.
Adjust the props to bring it hard up under the wall or floor that needs supporting.
Where there is a gap between the beam and its bearings, it should be filled as tightly as possible. It is not enough to cement it in and hope for the best, cement shrinks. Wedge in engineering bricks, tiles or slate in such a way that they bear the weight directly. Any gap between the lintel and what it is supporting must be wedged. Too. In the case of a beam supporting the floor joists directly above, hardwood wedges with a large surface area can be used. Doublecheck the lintel with a spirit level to make sure it is level.
1. Put a layer of mortar on top of the piers or bearings, then lift the lintel into place. You will need an assistant
2. Two more props are required at this point. Jack the lintel hard against the bricks or joists above. Wedge and level it
3. Pack out between the lintel and the piers with bricks, slate or tiles so that the piers bear the weight directly
PLASTERING AND FINISHING
Making good and finishing a knockedthrough wall is straight forward. But there are a few extra points you will come across.
Concrete beams will accept plaster directly and box beams have a mesh finish which takes lathing plaster directly. But an RSJ has to be boxed in with plasterboard mounted on a softwood frame, then finished normally using angle beads.
Galvanized metal angle beads should also he used on the piers or on the reveals of the doorway. They have strips of mesh to straddle the angle and a rounded nose which should he left ex posed to form a metal knockresistant corner.
The beading is attached to the angle with nails or dabs of plaster. True it up before allowing the dabs to harden, then apply the first float coat.
Rule off the next layer with a batten held across the nose of the beading and another guide that you can fix temporarily.
Then use your float to draw the plaster down so as to make room for a thin coat of finish plaster. This is applied using the nose of the beading as a guide, but take care to keep the bead clear of plaster at the very edge.
At the bottom of the opening. The way you finish off depends on the type of floor you have. If it’s solid, simply level off the wall flush with the surface of the floor on each side. If there is any uneveness, level it with a mortar screed.
If the floor is suspended, remove the masonry to just below floorboard level — but not too far below in case you damage the dampproof course. Fill the gap between the two sections with an extra floorboard supported on battens fitted between the joists.
If there’s a considerable difference in the floor levels on either side of the opening, you’ll need to make a step by attaching a piece of floorboard to the remaining strip of wall at the bottom of the opening.
Alternatively, you could cast a concrete step, using plywood formwork. This will contain the concrete while it cures and can then be knocked away.
If you have made only a narrow opening and are going to put in a door which will open into the area with the lower floor, the step should be made to project by about 400mm.
If the door frame is to sit proud of the reveal, make a reveal guide from a piece of batten.
Cut a notch at one end to rest on the frame so that when the batten is placed between the frame and the beading nose its edge will be parallel with the reveal. This will allow you to draw the plaster off to the correct depth.
If you have made a wide opening and want to fit concertina or sliding doors to close it on occasion, check carefully to see how the track should be fitted before you make good around the opening. You will almost certainly need to line the masonry with a timber frame.