Indy Total Construction

An important consideration when building an extension is the position of any drainage pipe run — either an existing one from the house or any new waste pipes from fittings in the new extension. You must sort out the route the pipes will take before the walls are built since they will pass through them below floor level, and openings must be left in the walls as they are built.

Lintels will need to be incorporated to support the wall above the openings. If the extension is to have trench-fill foundations, ducts should be made in the concrete to allow the passage of pipes. A simple method is to set slightly larger pipes in the concrete as it is poured and then run the pipes through these round openings later.

The positions of the inner and outer leaves of the walls should be marked centrally on the concrete of the foundations with chalk. The center lines of the wall and foundations being within lin of each other.

As the walls are built, stringlines are stretched between the corners to make sure each course of bricks or blocks is laid in a straight line.

Although you can use brick for both inner and outer leaves of the wall, in practice it makes more sense to use lightweight concrete blocks for the former since these will provide a certain amount of insulation — a requirement of the Building Regulations.

With this type of construction, the inner leaf is the load-bearing part of the wall, carrying the weight of any floors and ceilings so lintels must be fitted across doorways and windows. Steel boot lintels are best since they are relatively lightweight and their shape ensures that any water that penetrates the outer leaf of the wall is prevented from reaching the inner leaf and is channeled out over the toe of the boot.

The two leaves of the wall should be constructed simultaneously, laying a few courses of each at a time. As construction proceeds, the two leaves must be linked together with metal or plastic wall ties to prevent them leaning away from each other.

Ties are designed to prevent water running across them to the inner leaf but they must still be set in the mortar joints so that they slope downwards slightly towards the outer leaf. Ties should be set about 18in apart vertically and 3ft apart horizontally, the positions in each horizontal row being staggered with those above and below. At door and window openings, ties should be set one above the other at 12in intervals.

Water penetration must also be prevented from below and this is achieved by inserting a flexible bitumen damp-proof course (DPC) in a horizontal mortar joint around the base of each leaf, at least two courses of bricks above ground level.

When the floor is laid, a damp-proof membrane (DPM) is taken up the walls and tucked under the DPC. Strips of DPC must be fitted in the vertical mortar joints where the inner leaf is turned to close off the cavity at windows and door openings, and below the threshold of the door, linking to the DPC in the outer leaf.

The walls must be toothed into the existing house walls at alternate courses to ensure permanent stability.

Having set the new lintel in place and re-finished the brickwork of the inner leaf above it, you can cut out the brickwork at the sides of the opening and, if necessary, across the base. First, draw the outline of the new opening on both sides of the wall, making it about lin wider and deeper than the actual frame dimensions to give a fitting tolerance.

External walls comprise two layers of bricks; each layer should be treated separately, working in from each side of the wall.

If the wall is a solid one produce a square edge along the opening outline on the inner layer by cutting through bricks where necessary. Always remove complete bricks even if they project beyond the outline. This gives a toothed effect to the edge.

If the base outline runs through the center of a course of bricks, remove the course completely; you can make up the difference later.

Replace the outer layer at the sides of the opening by mortaring cut bricks into the toothed sections so that their cut ends are innermost.

Next, replace the area of wall above the window, laying the bricks on the lintel and copying the original brickwork bond for strength and appearance. In a solid wall, you can create a curved, self-supporting soldier arch by setting a wooden framework in the opening on which the bricks of the arch are laid. Then the surrounding courses are fitted round the arch and the mortar left to set for a couple of days before removal of the formwork.

The frame must sit squarely in the opening; if it is twisted, you may have problems in opening and closing the window and the glass will be under stress and may shatter at the slightest vibration.

In a solid wall you can set the frame: flush with the outer face with its sill overhanging the edge; in the center of the opening with narrow reveals on each side; or flush with the inner face with a sub-sill at the bottom to throw water clear of the wall.

When the frame is set forward in the opening, the sides and top of the reveal are plastered and a wooden or tiled window board set across the bottom. When set at the back, it is normal to trim around the inside of the frame with molding

The simplest method of securing the frame is with frame fixings, a hefty screw and long plastic wall plug, but you can also use conventional wallplugs and screws, wooden wedges or metal frame ties. With each type, wedge the frame in the opening with wood offcuts so that it is set squarely in place, while the fixings are marked and made.

With screws and plugs, clearance holes must first be drilled in the frame and the hole positions on the wall marked through these. The holes are drilled and plugged and the frame fitted.

Wooden wedges are tapped into slots cut in the mortar joints and the frame nailed to the wedges. Metal frame ties also fit into slots in the joints, being screwed to the frame and mortared in place.

In all cases, you must leave a’/sin gap between the top of the frame and the underside of the lintel to allow for any settlement of the structure.

Leave the packing pieces in place. and fill the gaps at the sides with mortar, leaving it about 1/sin below the level of the frame face. Fill this gap with caulk when the mortar has set. Use caulking to fill the gap between the lintel and frame also. If there is a gap below the frame, fill this with bricks and mortar, splitting the bricks lengthways if necessary.

Make a sub-sill from wood screwed or nailed in place, or a double layer of tiles set on a sloping bed of mortar.

Another way is to cast a concrete sill in situ, making up a wooden formwork “tray” nailed to the wall. The sill should overlap the edge of the bricks by no more than in and you can form a drip channel (to prevent rainwater trickling under the sill) along the bottom edge by pinning a length of waxed cord (sash window cord will do) in the bottom of_ the tray. The top of the lintel should slope downwards so angle the sides for this. Also provide reinforcement by setting steel rods in holes drilled in the brickwork.

Mix the concrete from 4 parts sand: 1 part cement and pour it into the form. Agitate the mix to compact it and remove air bubbles and draw it off level with the top of the form. Leave the concrete for at least 24 hours before removing the foiinwork.

The frame fixing is much simpler to use and is ideal for securing wooden members to masonry. It comprises a hefty screw and a long plastic wallplug.

To use, wedge the frame in its opening and drill holes for the fixings right through it and into the wall. Without removing the frame, tap the plug and screw combination through the frame and into the wall, finally tightening the screw for a secure fixing.

Frame fixings are supplied in various lengths to hold wood thicknesses up to 33/sin. Another development of this is the hammer fixing, which is used in the same way, but set by driving a ridged, countersunk pin into the expanding plug.

With the wall above the window opening supported by stout wooden needles and adjustable jacks, and the old window frame taken out you can remove the old lintel and brickwork from above the opening.

Remove the bricks from the outer layer first. These may be laid in horizontal courses across the lintel or they may be set vertically. If the house is old, they may form a self-supporting segmental arch.

Cut through the mortar joints with a bricklayer’s chisel to remove the bricks, making a gradually tapering, stepped opening up to the level of the wooden needle above. This will prevent any brickwork from falling while working on the opening.

Removing the bricks from the outer leaf of the wall will expose the face of the load bearing lintel set in the inner leaf. You should remove this next.

From inside the house, hack off the plaster above the window opening to expose the inner face of the lintel and the brickwork above it. Again, cut out the bricks to foam a stepped opening up to the level of the needle. Then cut into the mortar joints at each end of the lintel, working along the top, ends and underneath. Use a stout bar to lever the ends of the lintel upwards to finally release them. Then get some help to lift the lintel from its bearings in the wall.

the thickness of the wall. It may lodge and form a bridge for moisture to cross from the outer skin to the inner and cause damp patches on the inner wall.

Measure up the new lintel and draw its outline on the inside of the wall centered over the new window position. Remember, the new lintel should be at least 6in wider at each side of the window opening to provide decent-sized bearings. Also, allow an extra lin at each end and on the depth to provide enough space to manoeuvre the lintel into position.

Cut straight down through the plaster along the outline with the bricklayer’s chisel to provide a cutting guide and then hack off the plaster within the outline.

Go on to remove the bricks exposed by the removal of the plaster, again cutting through the mortar joints in an effort to keep as many bricks in one piece as possible. Clean up the bearing openings and make sure their surfaces are flat and level.

Whether you are using a steel or concrete lintel, you will need some help to lift it into place.

Trowel a layer of mortar onto each bearing and lift the lintel into place, setting it centrally over the opening. Check that the lintel is flush with the inner face and outer layer of the wall.

Hold a level against the underside of the lintel and check that it is horizontal. If necessary, correct this by packing pieces of tile or slate beneath the ends. When level, fill the gaps round the ends of the lintel with more mortar and brick offcuts, pointing the joints neatly flush with the surrounding brickwork.

In remodeling your living space you may wish to enlarge a window, either to let in more light or ventilation, by installing an opening window to replace a fixed one.

Window types and materials

Modern windows come in a wide choice of styles in wood metal or plastic. They can be simple fixed panes or they can open with either top-hinged, side-hinged, pivotting, horizontally-sliding or vertically-sliding sections. The tendency is to go for large, uninterrupted panes of glass, but if your house is old you can still buy windows made up of small panes to give it a period look.

Despite the fact that it needs regular maintenance, wood is the most popular material for window frames and offers the widest choice of styles and sizes.

Steel windows are functional in appearance but can suffer considerably from rust if not looked after. Aluminum windows, too, can suffer from corrosion due to the atmosphere, especially in coastal areas.

On the face of it, plastic would seem to be ideal for window frames, being largely maintenance free. However, it is not easy to paint (and is intended not to be), which means that you are stuck with the manufacturer’s color, and if this is white you may find it yellows with age.

Assuming that you are going to fit a larger window frame in place of the original, you must provide temporary support for the wall (with needles and jack posts) while you remove the old frame and lintel. This should be either concrete or steel so that both leaves of the wall are supported. For a solid wall, fit a concrete lintel to the inner leaf and, at the same time, form a curved soldier arch over the top of the window in the outer leaf.

With the lintel in place, cut out the brickwork for the larger frame. Prepare the edges of the opening, prop the frame in position and nail, screw or cement it in place. The final job is to seal around the edges with mortar and caulk.

To make the frame lighter and easier to handle, first remove any opening sections and then carefully remove all the glass.

Cut out the mortar seal at the edges of the frame with a flat chisel and run a screwdriver round the gap to locate the fixings. Cut through them with a saw inserted in the keyhole.

Having cut through or released the fixings, lever the frame out with a stout bar or knock it out with a length of wood and a light sledge hammer.

Wooden window frames are normally held in place by galvanized metal ties cemented into the brickwork at the sides of the opening, by nails or screws driven into wooden wedges set in the brickwork, or by screws and wallplugs. Metal-framed windows may be held by metal brackets or be fitted to hardwood frames, which in turn are screwed into the opening.