Catering for Drain Pipes

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

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.

Building an Extension

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

A ground floor extension can be purpose-designed and built to suit your needs exactly, or it can be constructed from a number of standard prefabricated components purchased from an extension manufacturer. Which type you choose depends on what you will use it for. The former is ideal for bathrooms, kitchens, bedrooms, living rooms; the latter is more suited to laundry rooms, sun rooms, children’s play rooms, work-shops and so on, and includes simple metal-framed, full-glazed conservatories.

The most important parts of the structure of your new extension are the foundations, which support the walls and spread the load evenly across the ground. Consequently, their design is quite critical and should be carried out after consulting your local Building Code which will specify the type of foundations required for the job and the depth to which they must be dug, based on local ground conditions.

To be effective, foundations must lie on firm, stable sub-soil, and depending on the soil type this may mean digging to a depth of 3ft or more. The type of soil will also dictate the type of foundations needed, as will the method of construction of the extension.

For a purpose-built extension with brick or block walls, it is usual to lay concrete in a trench and build the walls on top but for lighter constructions, such as prefabricated buildings, a slab of concrete known as a “raft” is more common.

The most common form of foundation is the “strip” type. With these a layer of concrete at least 6in thick is spread along the bottom of the trench, leveled off, then the walls built on top. Normally, a width of 18in is quite adequate, but at depths below 3ft or on certain types of weak soil a width of 30in or more is preferable — often with steel reinforcement added.

The trench-fill foundation is filled with concrete to within 6in of the ground level and the walls begun.

The concrete for this type of foundation should be at least 20in deep and about 6in wider than the width of the wall. The sides of the trench must be vertical to prevent any possibility of the load above causing the foundations to topple.

The walls of a habitable extension to your house must be of cavity construction; that is comprising an outer leaf of bricks and an inner leaf of bricks or. more usually, concrete insulating blocks with a 2in Pit- gap in between giving a wall thickness of 1 lin, although the cavity may be 3in wide to accommodate polystyrene slab insulation and still leave an air gap.

Even if the main part of your house has solid outer walls, the Building Code specifies that your extension must be of cavity wall construction.

Working on the Interior

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

Wearing protective clothing, (especially the goggles), carefully cut away the plaster from within the lintel outline to expose the masonry below. Remove the bricks or blocks by cutting through their mortar joints and lifting them out. If any above the slot should drop, remove these and keep them for replacement later. Retain any whole bricks from the slot for possible reuse.

Lift the lintel into place, bedding it on mortar (3 parts soft sand: 1 part masonry cement) laid on the “bearings” at each end of the slot. It is best to get the help of an assistant with lifting the lintel, especially when lifting weights above the head. Make sure the lintel is level and, if necessary, pack it out below the ends with tiles or slates.

Finally, fill any spaces around the lintel with more mortar and replace any bricks or blocks that may have dropped out at the slot-cutting stage. If the wall is constructed of blocks, bring the lintel up to the height of the adjacent blocks by laying a course of bricks on top, and mortering them in place.

Leave the mortar to set for at least 24 hours, and preferably 48. Then remove the needle and wood supports. Fill the needle holes with brick offcuts and mortar. Lever off the baseboard and place it to one side for cutting down later.

Remove the plaster inside the outline of the opening to expose all the masonry below. Using a light sledge hammer and bolster chisel, cut this out by chiseling through the mortar joints, carefully working down the wall one course at a time. Because of the bonding pattern used, you will find that on alternate courses you will have to cut through bricks at the sides of the opening. Do this as you come to them. driving the chisel into their faces and levering them out from below to leave a straight edge to the opening. Remove all the bricks from the opening.

Trim off the masonry flush with a solid floor, or jus: below a wooden one. In the latter case, join the tv,-: floors by screwing battens to the joists then fit a piece of plywood or short pieces of floor-board on top neaten and close the gap.

The frame can be held in place with either galvanized metal ties mortared to the wall, or by screws and wall plugs. If ties are to be used, you need three per side. Cut recesses in the sides of the opening for the ties. If you intend screwing the frame to the wall, drill screw clearance holes in it and offer it up so these can be marked on the wall. Drill and plug the holes.

Set the frame in place, packing out the sides as necessary with wood offcuts to set them vertical. Then either fill the tie recesses with mortar and brick offcuts or insert the screws.

Fill in the gaps round the frame with more mortar and offcuts and trowel a thin layer of mortar over any exposed masonry at the sides and top before refinishing the plaster.

Finally, nail lengths of molding around the frame, mitering the corners, and trim and refit the base boards to the base of the wall.

Bridging Openings

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

The way you tackle the job of making an opening in a wall or removing the wall completely in your house, depends on the type of wall it is and its construction.

A load-bearing wall contributes to the strength of the house by supporting some of its structure: a floor/ceiling, an upstairs wall or part of the roof.

A non-load-bearing wall is simply a dividing partition and its complete removal will have no effect on the rest of the house.

Inspect the floor space above it for signs that it supports the joists, or an upstairs wall. Look in the attic, too, to see if any of the roof framework rests on the wall in question.

All external walls are load-bearing and in general any wall at right-angles to the joists will be load- bearing too. Walls that run parallel to the joists are probably non-load-bearing.

Walls may be of brick, concrete blocks or be wood framed. All three types of construction are used for both load-bearing and non-load-bearing walls.

When you make an opening in a wall, no matter how narrow or wide, you must insert a supporting beam or lintel across the opening to take the load of the structure above, even if it is a non-load-bearing wall. The problem is that even by removing a narrow row of bricks or blocks to make room for the be will put the structure at risk.

For a narrow opening like a door, the bond in pattern of the bricks or blocks will tend to make the wall above the opening self-supporting (or self-corbelling) and only a small triangular section of masonry will be at risk. This can be removed, the lintel fitted and the masonry replaced.

With a very wide opening, the self supporting tendency will disappear and a wide area of the wall will be liable to collapse. To prevent this happening. you must support the wall (and sometimes the ceiling on either side) temporarily with heavy wood and adjustable props.

Openings in walls may be spanned by lengths of concrete, steel or wood. Those for fitting over small openings like doors and windows are called lintels; those for spanning wider gaps are called beams. The following are common: Steel Joist — a heavy I or L-shaped girder for spanning very wide gaps in load-bearing walls; Reinforced Concrete Lintel — for internal or solid brick external walls in spans of up to 10ft.

Heavy to lift and often cast on the job site, is the Pre-stressed Concrete Lintel — lighter than reinforced concrete lintels but not suitable for load- bearing walls, except in upper floors. For spans of up to loft, the wood lintel is used in wood framed walls.