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Insulation project planning

Preparing your loft before you start

Clear the loft of any obstacles and clutter

This makes working in your loft much safer and allows you to work out what you need to buy.

Check that your loft is properly ventilated

Ventilation prevents problems like damp occurring in your loft. There will either be an opening at the eaves where the pitched roof meets the external wall or proprietary ventilators in the pitch of the roof. If neither are present then ventilation must be installed and specialist advice should be sought.


Calculate how much you need

Check what insulation is already in place

If you have insulation between ceiling joists already, ensure it finishes level with the top of the joists. If not, you will need to top it up. Building Regulations recommend a minimum of 270mm thickness, comprising of a 100mm bottom layer between ceiling joists and a 170mm top-up layer above. However, a 200mm layer cross-laid on top will give you even more energy efficiency. This should be laid at a 90º angle to the bottom layer to ensure coverage of the timber ceiling joists.

Measuring for loft roll

It’s better to buy too much than too little loft roll, as any left over can simply be laid over the top as an additional layer to provide extra energy efficiency.

  • Determine the area of your loft by multiplying the length by the width. You can measure the floor below instead if it’s the same size on you floor plan
  • Deduct 10% from the area for a 100mm roll to allow for joists
  • Divide the area by the loft roll pack coverage to get the number of rolls required

The table below will give you a good guide.

How much loft roll?
2 Bed Semi/Terrace 50m2 3 Bed Semi/Terrace 60m2 3 Bed Semi 80m2
Coverage Approximate number of loft rolls needed
100mm bottom layer 11.08m2 5 6 8
170mm top layer 6.47m2 8 10 13
200mm super top layer 5.61m2 9 11 15

Insulating your cold water tank and pipework

Your cold water tank and pipes need to be insulated with specific tank and pipe insulation. Insulating your loft makes the space much cooler as it’s no longer warmed by heat escaping from the rooms below. This increases the likelihood of pipes and cold water tanks freezing in colder weather.

Insulation for your cold water tank

It’s better to buy too much than too little loft roll, as any left over can simply be laid over the top as an additional layer to provide extra energy efficiency.

Tank capacity Width Length Insulation needed
4 gallon (18 litre) 305 mm 457 mm 4 gallon Tank Jacket
25 gallon (114 litre) 559 mm 737 mm 25 gallon Tank Jacket

Pipe insulation

Measure the length and diameter of any uninsulated water pipes that run through your loft. Pipe insulation is available to fit both 15mm and 22mm pipes and is sold in 1m lengths.

Downlight covers

You will need to fit a downlight cover for every recessed downlight you have in the ceilings below your loft. This will prevent warm air leaking into your loft through the downlight but also protect from overheating and fire risk. To fit them properly, you will need silicone sealant. One tube should be enough for an average loft.

Calculating materials for new storage space

Decide the area of space you want to create using the table below, remembering that space with little headroom will be less useful. How many loft legs and screws you need will depend on the distance between your joists.

Size of storage area 5m2
Approx. area of kingsize bed
10m2
Approx. area of transit van
15m2
Approx. area of single garage
Loft storage panels
Pack of 3 (1.17m2)
5 5 9 9 13 13
Ultra gold screws
4.0 x 30mm. Pack of 200
2 2 3 3 5 3
Loft legs
Pack of 12
6 4 9 7 12 9