Why underlay matters more than people think
Underlay is the part of the job nobody sees and everybody feels. It cushions the carpet backing from the floor, stops the pile crushing flat under footfall, adds warmth and sound insulation, and evens out small imperfections in a timber or concrete sub-floor.
Put a mid-range carpet on good underlay and it will feel better and last longer than an expensive carpet on cheap foam. It's the single best place to spend a bit extra on a flooring job.
8mm, 10mm or 11mm — which to choose
Density matters as much as thickness. A thick, soft, low-density underlay squashes flat quickly; a high density one at the same thickness keeps supporting the carpet for years. That's why I recommend the 11mm high density for main living areas.
- 8mm — a good, economical choice for bedrooms and quieter rooms, or where a door clearance is tight and you can't gain height.
- 10mm — the everyday all-rounder. Comfortable underfoot in lounges and bedrooms without lifting the carpet too high at thresholds.
- 11mm high density — the most comfortable and hardest working of the three. Same roll size as the 8mm and 10mm, £60 per bag. Best in lounges, hallways and anywhere that takes daily traffic.
Room-by-room recommendations
- Lounge and dining room — 11mm high density for comfort and longevity
- Bedrooms — 10mm, or 8mm on a budget
- Hallway and landing — 11mm high density; it takes the heaviest traffic in the house
- Stairs — firm, dense underlay cut into pads per tread
- Over concrete — good underlay plus the right damp precautions makes a cold floor feel far warmer
Gripper, door bars and thresholds
Underlay works as part of a system. New gripper is fitted around the perimeter, the underlay is taped and stapled or bonded down inside it, and the carpet is stretched onto the gripper. Where the carpet meets another floor covering, a door bar finishes the join neatly and protects the edge — those are £6 each.
Gripper and tape are included in my fitting price. Underlay is charged by the bag, and I'll work out how many bags your rooms need at the free measure.
Common questions
What thickness of carpet underlay is best?
For most homes 10mm or 11mm high density underlay is the sweet spot — noticeably softer underfoot and it protects the carpet from flattening. 8mm is fine for bedrooms and lower-traffic rooms or where door clearances are tight.
How much does underlay cost?
Underlay is sold by the bag. 11mm high density is £60 per bag, with 8mm and 10mm in the same roll size costing less. One bag covers a typical bedroom, and I'll tell you exactly how many bags your job needs at the measure.
Can I reuse my old underlay?
Usually not worth it. Old underlay compresses, holds dust and often crumbles when the carpet comes up. New underlay is the cheapest way to make a mid-range carpet feel and last like an expensive one.
Do stairs need different underlay?
Stairs take the most punishment in the house, so a firmer, denser underlay works better than a very soft one — it holds its shape on the nosing instead of squashing flat. I cut pads per tread rather than running a single length down.
Want a price? Send me the room sizes.