How To Insulate Walls


If you can see both headers and stretchers on the outside of your house, your walls will probably be solid and therefore rather more difficult to insulate. Before you try to insulate them you must be sure that they are protected by a damp proof course. If you cannot find one or if you are doubtful, it is worth obtaining a free survey and quote from a damp proofing firm; for addresses see under ‘Damp Proofing Contractors’ in the Yellow pages. A good firm will offer a guarantee of their system, and your local authority may give you an improvement grant to cover half the cost. The local authority environmental health department, which deals with improvement grants, may suggest some names of reputable firms, or you can try asking other people for their experiences.

You will have to chip off the damp plaster before the damp proofing is carried out, but if you plan to insulate do not replaster as the insulation can be put over the unplastered wall. If you qualify for a grant this will contribute towards the cost of replastering, or of the battens and plasterboard if you insulate the walls after the damp proofing. Only when the wall is successfully damp proofed can you think of insulating it.

Cavity wall insulation is a job for the professional. But when it comes to solid external walls which let a lot of heat escape, DIY insulation is a practical proposition.

Lining the wall with polystyrene in 5mm roll form is cheap and simple, but although it reduces condensation, it won’t cut the heat loss dramatically. But other similar methods can do so very effectively.

Dry lining: Modern technology has brought this well within the scope of the home handyman by introducing simpler methods and materials to the DIY market. Boards and battens have largely been superseded by various thermal boards which fix directly to the wall.

Gyproc thermal board, for example, is attached to the wall with 863 Gyproc adhesive and comes in standard 1200mm widths, three lengths and several thicknesses of insulation.

1. To use Gyproc thermal board, first remove wallpaper or sand down paintwork with a coarse grade paper then brush off any dust.

Remove any skirtings and anything else attached to the wall surface.

2. Alternatively, fix the boards directly above existing skirtings by removing a section of polystyrene backing. Apply in the following way before attaching new skirting boards to the wall lining.

Light and plug sockets will have to be relocated to accom-modate the new lining and wooden window sills should be extended to accommodate the thickness of the wall board. If the existing sill has a curved edge. Plane it square and glue and pin a new piece of wood to the edge.

Next draw out the board sections on the wall. Start from a door or window and remember to allow for the thickness of the board which will line the window or door recess. Add 2mm to the overlap to allow for the thickness of the adhesive.

3. Cut the boards to size with the wallboard surface upper-most.

Use a fine tooth saw and cut at a shallow angle.

Mark the first board. Lay the board on the floor and place a spare piece of wood under the board to prevent damage to the floor sur-face from the drill bit, before drilling for screws or nailable plugs. Use either method to fix boards to the old wall surface.

Put the board against the wall and get someone to hold it in position while you mark the fix-ing points on the wall through the drill holes. Take the board away and drill the holes in the wall using a masonry bit if you intend to use screws. Now cut sections out of the board for switches or sockets.

5.Apply adhesive to the wall —in bands 200mm wide with a trowel. Spread with an applicator.

6.Place the board in its position against the marked wall, making sure the vertical edge is plumb

Fixing procedure for each board is a combination of heavy duty adhesive available from the board manufacturer and screws or special ‘plugged’ nails.

Drill nine holes at the points shown for the secondary fixings and tamp it firmly into place. Put in the secondary fixings — nailable plugs or screws.

The sides of the window and door recesses should also be lined with the board. If the exposed framework of the window or door is not wide enough to accommodate the thickness of the board. The existing plaster should be removed from the recess and the back- ground thoroughly cleaned.

It will be necessary to remove the polystyrene from the wall panel where it overlaps the recess in order to allow the plaster edges to meet. Fix the lining with adhesive and provide support for the top piece for 24 hours to allow it to dry.

When all the boards are in position, fill in between the joins with a joint filler — fill the screw heads too. The method is the same as that used for jointing ordinary taper edged plaster-board.

Use jointing tape to cover the filled joints. This comes in 150m rolls. 53Mm wide.

About an hour after applying the filler and tape, apply Gyproc joint finish — stir 5kg into two litres of cold water or amounts in the same proportions, spread in a broad 200mm wide band down the joint, feathering out the edges slightly with a damp sponge or cloth.

To finish the job apply a coat of dry wall topcoat over the boards and refix the skirting.

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