Buy Knauf Loft Roll Online: 44 Combi-Cut Thickness, Sizes and Delivery in England
Knauf Insulation Loft Roll 44 Combi-Cut is a glass mineral wool roll made for laying between and over loft joists. This guide covers the thickness you need, the roll sizes we stock, how many rolls a typical loft takes, how to fit it safely, and how delivery works if you are buying Knauf loft roll online in London, the Midlands or Yorkshire.
Quick answer
- Aim for around 270mm total depth of mineral wool in a cold loft. With Knauf Loft Roll 44 the neat way to get there is 100mm + 170mm.
- Lay the first layer between the joists and the second layer across them at right angles (cross-laying).
- Prices are from £31.29 ex VAT per roll. We deliver across England, and delivery is free on insulation orders from £400 ex VAT.
Why 270mm is the standard depth for loft insulation
Building Regulations set a U-value target rather than a thickness, but for mineral wool laid at ceiling level in a cold loft, 270mm is the figure most commonly recommended (for example by the Energy Saving Trust). Heat rises, and the loft is one of the biggest routes for heat to escape, so a deep, unbroken blanket makes a real difference. Going deeper than 270mm still helps; going shallower leaves savings on the table. Our guide to what thickness of loft insulation you need explains where the figure comes from.
The "44" in Loft Roll 44 is Knauf's name for the roll's thermal conductivity class (0.044 W/mK). A lower figure means better insulation per millimetre, so check the datasheet on the product page when comparing rolls from different makers.
How to layer 100mm + 170mm (and other combinations)
Most older lofts have joists about 100mm deep, so a 100mm roll fits snugly between them. The second layer goes over the top and covers the joists, which would otherwise let heat bypass the insulation.
| Between joists | Across joists | Total depth |
|---|---|---|
| 100mm | 170mm | 270mm |
| 100mm | 200mm | 300mm |
| 150mm | 150mm | 300mm |
| 150mm | 200mm | 350mm |
| 170mm | 100mm | 270mm |
If your joists are deeper than 100mm, choose a first layer that fills them without being squashed, then top up across the joists to reach at least 270mm. Topping up over existing insulation? Measure what is already there, check it is dry, and add the difference.
Knauf Loft Roll 44 Combi-Cut roll sizes
All four rolls are 1140mm wide. The "Combi-Cut" part means the roll is perforated lengthways so you can tear it, without a knife, into 2 strips of 570mm or 3 strips of 380mm, to suit different joist spacings. Use it full width over the top of the joists.
| Product | Thickness | Coverage per roll | Price |
|---|---|---|---|
| Knauf Insulation Loft Roll 44 Combi-Cut 100mm | 100mm | 13.89m² | from £31.29 ex VAT per roll |
| Knauf Insulation Loft Roll 44 Combi-Cut 150mm | 150mm | 9.18m² | from £31.29 ex VAT per roll |
| Knauf Insulation Loft Roll 44 Combi-Cut 170mm | 170mm | 8.01m² | from £31.29 ex VAT per roll |
| Knauf Insulation Loft Roll 44 Combi-Cut 200mm | 200mm | 6.84m² | from £31.29 ex VAT per roll |
Because each roll costs about the same, the thicker rolls cover less area, so the cost per m² rises with thickness. That is why the sensible plan is to match the thickness to the depth you need rather than over-buying.
Worked example: how many rolls for a 6m × 5m loft?
- Loft floor area: 6m × 5m = 30m².
- Add about 10% for cutting and waste: 30 × 1.1 = 33m².
- First layer, 100mm: 33 ÷ 13.89 = 2.4, so 3 rolls.
- Second layer, 170mm: 33 ÷ 8.01 = 4.1, so 5 rolls.
That is 8 rolls for 270mm total depth. At from £31.29 ex VAT per roll the rolls come to about £250 ex VAT. Rolls are sold whole, so you may have a little left over, which is handy for patching round pipes and hatches. For larger lofts, or several jobs at once, free delivery applies on insulation orders from £400 ex VAT. You can also use our free insulation calculator.
How to fit Knauf loft roll
- Prepare the loft. Clear the floor, check for damp or leaks, and fix any damaged cables or pipes first. Use boards or a crawl board to stand on, never step between joists.
- Lay the first layer between the joists. Unroll the 100mm roll and tear along the perforations if the gap is narrower than 1140mm. Butt the ends together with no gaps.
- Lay the second layer across the joists. Work at right angles to the first layer so it covers the tops of the timbers. Use full-width 1140mm sections here.
- Finish round obstacles. Cut neatly round pipes and the loft hatch, and insulate the hatch itself.
Our guide to installing loft insulation has more step-by-step detail.
Safety tips
- Wear protection. Gloves, long sleeves, goggles and a dust mask (FFP2 or better) make handling mineral wool far more comfortable.
- Don't compress the rolls. Squashed insulation loses thickness and performs worse. Let the roll expand, and do not pile stored items on top.
- Keep the eaves clear. Leave a gap so air can flow into the loft at the eaves; use eaves ventilators if needed.
- Keep clear of recessed lights and hot flues. Unless a downlight is rated to be covered, leave clearance round it and follow the manufacturer's guidance.
- Take care with electrics. Lay cables on top of the first layer where practical and do not bury or crush them. If in doubt, ask a qualified electrician.
Delivery of Knauf loft roll across England
We deliver across England, and delivery is free on insulation orders with a minimum of £400 ex VAT. Prices are shown ex VAT. Rolls are bulky, so for the best value it is worth ordering everything for the job in one go, including your top-up layer.
Knauf loft roll delivery in London
Ordering for a London home? We deliver to London addresses. Loft joist spacing varies from house to house, so measure yours first: the 570mm and 380mm Combi-Cut strips suit narrower gaps, and the full 1140mm width suits the top layer. Think about access and where the rolls can be left safely, and see our delivery information.
Knauf loft roll delivery in the Midlands
Ordering for a Midlands home? We deliver across the Midlands. Measure the insulation you already have and top up to around 270mm, working out each layer separately with the worked example above, or use our insulation calculator.
Knauf loft roll delivery in Yorkshire
Ordering for a Yorkshire home? We deliver across Yorkshire as part of our delivery service across England. Check your joist depth and spacing, choose your two layers, and order everything for the job together so you reach the £400 ex VAT minimum for free delivery.
Frequently asked questions
What thickness of Knauf loft roll do I need?
For most lofts, aim for 270mm in total. A 100mm roll between the joists plus a 170mm roll across them gives exactly 270mm.
What does Combi-Cut mean?
The roll is 1140mm wide and perforated so that it tears into 2 strips of 570mm or 3 strips of 380mm. That helps it fit between joists at different spacings.
How many rolls do I need for my loft?
Divide your loft area (plus about 10% for waste) by the roll coverage for each layer and round up. For a 30m² loft that is 3 rolls of 100mm and 5 rolls of 170mm.
Can I lay new loft roll over old insulation?
Yes, provided the existing insulation is dry and in reasonable condition. Lay the new layer across the joists.
Is delivery free?
Yes, on insulation orders with a minimum of £400 ex VAT. We deliver across England.
How can I contact you about an order?
Call 03330 908479 (Mon–Thu 8am–5pm, Fri 8am–12pm) or email sales@insulationwarehousedirect.co.uk.
Buy Knauf loft roll online
Choose your rolls: 100mm, 150mm, 170mm or 200mm, from £31.29 ex VAT per roll, or browse the full loft insulation collection. Questions? Call 03330 908479 or email sales@insulationwarehousedirect.co.uk.
Coverage figures are from our product listings. Thickness recommendations are indicative; confirm your specification with your designer or building control body. Correct at the time of writing (18 October 2026).