Lofts are usually dark, dirty places, so it’s advisable to wear some really old clothes, preferably ones you can throw away afterwards. Blanket insulation, especially glass fibre, can cause irritation to the skin, so you must wear rubber gloves when handling it.
It is also sensible to wear a simple mask to cover your nose and mouth as the insulation material is not only unpleasant but dangerous to inhale. Loose-fill is a dusty material and you’d be wise to wear a pair of protective goggles — as well as a mask-when laying this. You can buy a mask, with replacement lint filters, and the goggles, all of which are available from most DIY stores. You’ll need a good light to work by; a fixed loft light is best, but if there isn’t one, you could rig up an inspection lamp or even a table lamp.
Don’t, however, use a torch: you’ll have enough to contend with without having to carry and aim a light. Don’t use a naked flame because the risk of fire is high in the enclosed space of the loft. Be careful where you tread. The space between the joists-the ceiling of the floor below – is only plasterboard or, in older houses, lath and plaster, and neither will support your weight. Rather than balancing on the joists – especially when you’re carrying rolls or bags of insulation – it’s better to have a short plank or piece of chipboard to stand on, but make sure that both ends are resting on a joist without overlapping, or it could tip up under your weight, with disastrous consequences.
Before you start to lay the insulation you should remove any boxes or other items you have stored in the loft to give you plenty of room to manoeuvre: if there’s too much to take down from the loft you can shift it up to one end of the loft, lay the insulation in the free area, then move the boxes back again and lay the other half. Clean up the spaces between the joists using a vacuum cleaner with a nozzle attachment to enable you to reach awkward corners. If you don’t have one you can use a soft bristled broom or a hand-brush and a dust-pan, but you’ll stir up a lot of dust in the process. Use small pieces of the insulation material to block up any holes made in the ceiling for pipework to and from storage tanks.
Laying the insulation
Laying the blanket type of insulation is simplicity itself: all you do is to start at the eaves and unroll the blanket between the joists. On widely-spaced joists it’ll just lie flat on the loft floor but if the joist spacing is narrow, or irregular, you can tuck it down and allow it to curve up the sides of the joists. Cut or tear small pieces of blanket from the roll to fit very small nooks and crannies.
Butt up new rolls and allow for extra material at beams and pipes that are set at right angles to the joists. Cut the insulation and tuck it under the obstruction, then butt up the next piece to it. Don’t insulate under the cold water tank, which will be mounted on timber bearers at right angles to the joists: heat rising through the ceiling immediately beneath the tank will help to prevent the water freezing in very cold weather. The tank itself should be insulated, with glass fibre blanket or expanded polystyrene sheets all round and on top, or you can use a proprietary tank lagging kit, available from DIY stores.
If your tank is mounted high above the loft floor — usually to enable you to get a sufficient head of water for a shower unit – you can insulate underneath it. The whole tank should, in this case, be lagged. Cut a square of blanket to cover the top of the loft hatch cover and tack it in place, leaving an overlap to stop draughts getting into the loft space. If you’re laying one of the loose-fill materials you’ll have to stop it from falling into the wall cavity at the eaves. Place a few bricks on edge, or a panel of chipboard, between the joists near the eaves, to contain the granules. Empty out the bags between the joists, starting at the eaves, and use a specially shaped timber spreader (see Ready Reference) to spread it to the correct thickness. The loft space will be much colder after you’ve insulated it, so it’s particularly important that you lag any water pipes that pass through the loft
TYPES OF ROOF INSULATION
There are three types of loft insulation you can lay yourself:
• blanket insulation consists of rolls of glass or mineral fibre matting, 80 or 100mm (3 or 4in) thick by about 6 or 8m (20 or 26ft) long. It’s unrolled between the joists
• loose-fill insulation can be a granulated mineral called vermiculite, expanded polystyrene granules, mineral wool fibre or cellulose fibre, available in bags. It’s tipped between the joists and spread out to an even thickness -100mm (4in) forfibre types, 125mm (5in) for granular materials
• sheet insulation is either expanded polystyrene between the joists or rafters, or fibreboard, which is laid across the joists with loose-fill or blanket insulation underneath.
LEVELLING GRANULAR INSULATION To lay granular materials to the correct depth -100mm (4in) – make a timber ‘spreader’ from anoffcut of chipboard, which you draw along the joists. Ensure:
• the body of the spreader just fits between the joists
• the arms rest on the joists • the depth of the body is 100mm (4in) above the loft floor. If your joists are only 100mm (4in)deep, lay the material flush with the top of the joists.
HOW MUCH INSULATION
To work out how many rolls of blanket insulation you’ll need: • multiply the length by the width of the loft to get the number of square metres
• allow a little extra for insulating tanks and pipework.