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Laying Loft Insulation - Step By Step

Any amateur DIYer can easily insulate their loft

Laying Loft Insulation - Step By Step


Laying loft installation is not a complicated job.

Any amateur DIYer can easily get it done and this page is intended to give you a detailed guide on how to lay loft insulation as long as you are fit enough to get up into the loft space.

There are however some potential dangers that you should consider. Time taken at the preparation stage will save you valuable time and effort when you actually come to do the job.

Lofts can be hazardous

Lofts can be poorly lit, dirty/dusty places packed with junk.

They are also where you will find electric cables and water/heating pipes so it’s crucial that you survey your loft and take proper safety precautions to prevent an accident or injury.

If you do not have sufficient lighjting in your loft space you may want to consider hiring some portabel lighting. It's almost impossible to lay insulation whilst holding a torch at the same time.

Do Your Homework

Do Your Homework

  • Calculate the amount of insulation youre going to need. Measure the size of the loft (and the depth of the current insulation if any, to determine the thickness you will need to bring it up to 270mm)
  • Measure the loft hatch opening so you know you'll be able to get the insulation packs into the loft
  • Ensure the loft is properly ventilated with either spaces at the eaves where the roof meets the floor, or from ventilators in the roof. If you can't locate these then you will need to address this to prevent condensation in the roof space which could cause the timbers to rot
  • If youre filling the gaps between the joists, measure the gap between the joists to determine the width of insulation you need. If laying on top of existing insulation, the choice of width is less important
  • Check for any water/heating pipes as these will need to be lagged to prevent freezing as your loft space will be a lot cooler once you have the insulation in place. pre-formed pipe insulation is available to buy different in different lengths
  • If you have a water tank in the loft you may want to consider buying a tank jacket. They come in various sizes so measure the size of your tank.

Getting Prepared

Getting Prepared

  • Identify any potential dangers such as electrical wires or loose boards. Remove any boxes and other items so the space is completely clear (Its a good opportunity to have a clear out!)
  • Get some wide planks or boards to walk on. Try to use ones which are a minimum of one metre long (This way they should span at least three joists.)
  • Wear suitable protective clothing; gloves, dust proof breathing mask etc. Glasswool fibres can irritate the skin. Some insulation is eclosed to prevent this. See which is virtually itch free
  • You might need a knife to cut the insulation. (Be careful when cutting to avoid any electric wires running through the loft

Laying Your Loft Insulation

Laying Your Loft Insulation

  • IMPORTANT! Only stand on the joists if you have to, but never in-between them, or you could put your foot through the ceiling or even fall through it.
  • Start at the farthest corner from the loft hatch. Tuck the end of the roll into the eaves but don't totally block them - It's important to leave a gap of at least 5cm to allow enough airflow to prevent condensation
  • If there is no insulation already between the joists, start by laying 100mm between the joists
  • Lay a further 170mm across this first layer at right angles to the joists. At this stage take extra care, working across the loft in a line. As you cover the joists be sure not to lose your footing as you move about
  • You may need to cut the insulation to fit round pipes or route cables. Butt the ends together around the obstruction. This will avoid the risk of overheating and possible fires in the loft. Do not bend or pull wiring out of the way
  • Lag any pipes as you lay the insulation. Doing this,as you come across them will mean you don't have to walk across the loft once you've finished laying the insulation
  • If you have a cold water tank, dont put insulation underneath it. Fold insulation up around the sides of the tank at the bottom and then wrap the tank jacket round the tank and over the top of the ends of the insulation to form a draught proof seal
  • If there are hoses for extractor fans or recessed light fittings protruding into the loft space, trim the insulation around them, leaving a gap of approx 15cm round them
  • Lastly the loft hatch. Just nail or staple some insulation onto the back and you're done.

Watch The Loft Insulation Video

Watch how easy it is to insulate your home and start saving energy and money.




The products used in this video are the 100mm Knauf Earthwool Loft Insulation and the 200mm Knauf Earthwool Loft Insulation which are laid at right angles to each other to acheive a total of 300mm of insulation which is 30mm more than the government recommendations and inline with what a lot of new-build properties are being built with.