Heating & energy
Loft insulation cost calculator
Loft insulation is the cheapest, easiest and fastest-payback job in the house, and a perfect first project. You just unroll mineral wool in the right places. Aim for around 270 mm total depth.
- Full DIY
- £240
- Smart Hybrid
- £240
- Full Trade
- £370
Typical mid-range job, Midlands rates. Yours updates below.
Updated November 2026. Estimates based on typical UK prices.
Cost calculator
Price this job three ways
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Smart Hybrid saves £130 against a full trade job.
Smart Hybrid
You take on what you can, a trade handles the rest.
£240
- Materials
- £240
- Labour
- £0
- You take on: lay loft insulation.
- Everything else stays with a trade.
Turn this into a plan
Get the order of work, who to book and a budget tracker, all editable.
Order of work for this job
A typical order. Always confirm timing with whoever you book, since some steps can overlap.
- 1
Finishing touches
- Lay loft insulationYou · ~0.6 days
How we worked out the materials›
- Loft insulation£24024 m² × 2 crossed layers (to 270mm recommended depth) = 48 m²
Estimates only, based on regional averages. Always get 2 to 3 written quotes from local trades.
The price
What affects the cost?
- 1
Loft area
Cost scales with the floor area of the loft you are insulating.
- 2
Existing insulation
Topping up needs less than starting from bare joists.
- 3
Material
Mineral wool is cheapest. Sheep wool and recycled fibre insulation cost more.
- 4
Access and storage
Loft boarding or a restricted hatch makes the job slower.
- 5
Doing it yourself
Fitting is quick, so DIY saves labour but not materials.
Be honest with yourself
Can you do this yourself?
You can do
- The whole job: it is the most beginner-friendly job in the house
- Boarding a section for storage
- Insulating the hatch
Leave to a pro
- Spray foam or blown insulation (specialist)
- Loft conversions
- Anything involving damp, wiring or a leaking roof
The rules
No regulations apply to topping up insulation. Do not cover downlight hoods, recessed lights or electrical cables carrying heavy loads without checking ventilation and heat.
DIY guide
How to insulate a loft, step by step
Tools you'll need
- Gloves, long sleeves and a dust mask
- Torch or head torch
- Knife or scissors
- Boards or planks to kneel on
- Tape measure
Materials
- Insulation rolls (100 mm and 170 mm layers)
- Loft hatch insulation
- Boards or loft legs for a walkway
- 1
Check the loft first
~0.25 daysLook for roof leaks, damp, vermin and old wiring. Check the existing insulation depth, and make sure any ventilation at the eaves is clear.
Never step on the plasterboard ceiling between joists. Stand only on joists or a board.
- 2
Buy enough and plan the layers
~0.25 daysCalculate the loft floor area. For a loft with no insulation, plan for two layers: about 100 mm between the joists, then 170 mm laid across the top to reach about 270 mm.
- 3
Lay the first layer between the joists
~0.5 daysUnroll the insulation between the joists, cutting to fit. Do not squash it, because the air trapped in the wool is what insulates. Keep it clear of the eaves so air can still flow.
Tip: Wear gloves and a dust mask. Mineral wool is itchy but harmless once laid.
- 4
Lay the second layer across the joists
~0.5 daysRoll the second layer crossways over the first and the joists, which covers the cold bridges the timber would otherwise create.
- 5
Work round pipes and lights
~0.25 daysInsulate cold water tanks and pipes in the loft, but leave the space below tanks uninsulated so warmth from the house stops them freezing. Keep insulation clear of recessed lights unless they are rated to be covered.
- 6
Insulate the hatch
~0.25 daysFix a piece of insulation to the top of the loft hatch and add a draught seal round the edge so heat does not escape through it.
Learn from others
Common mistakes to avoid
- Squashing the insulation and losing its effect
- Blocking the eaves ventilation, which can cause damp
- Covering recessed lights that are not rated for it
- Insulating below a cold water tank so it freezes
- Forgetting the loft hatch, a big heat leak
Frequently asked questions
How much does it cost to insulate a loft?
For a typical 6 × 4 m loft insulated from bare joists to the recommended 270mm depth, expect from around £240 doing it yourself to £370 with a contractor. It’s one of the cheapest and quickest home improvements there is, and often pays for itself in a couple of winters.
How much does loft insulation cost per m²?
Mid-range mineral wool insulation costs around £5 per m² per layer. You need two crossed layers from bare joists to reach the recommended depth, or one if you’re just topping up existing insulation.
Can I fit my own loft insulation?
Yes — it’s widely considered the easiest DIY job in the house. Roll it out between and then across the joists, wear a mask and gloves, and use a loft board or plank to spread your weight rather than standing directly on the insulation.
How thick should loft insulation be?
The UK-recommended depth is 270mm of mineral wool, which usually means two 100–150mm layers laid crossways to cover the joists themselves. If you already have some insulation, you may only need to top it up rather than start again.
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