Superior Firm Foam Sheet 42H — 42kg/m³, 240N Hard, Crib 5 (HR40 250 / RX42/250)
Regular price
£33.99
Sale
Our firmest and densest upholstery foam — 42 kg/m³ density, 240 Newton firmness, Crib 5 fire rated, cut in the UK. The longest-lasting grade we make.
The top of our upholstery range. At 42 kg/m³ it is the densest polyurethane foam we sell for seating, and at 240N the firmest. Suited to high-quality furniture, dining chairs, and to caravans, boats and camper vans where a cushion takes constant use and needs to hold its shape for years.
It is also the only grade we offer down to 1/4" thickness, which makes it useful for thin firm pads where a softer foam would simply bottom out.
Specifications
| Foam grade | 42H (HR40 250 – RX42/250) |
|---|---|
| Density | 42 kg/m³ (high density) |
| Firmness | 240 Newtons (ILD at 40% compression) — hard feel |
| Fire behaviour | Crib 5 (BS 5852 Ignition Source 5) |
| Colour | Blue |
| Material | Polyurethane foam |
| Sheet sizes | 230 x 200cm (90.5" x 78.7") · 230 x 100cm (90.5" x 39.3") |
| Thicknesses | 1/4", 1/2", 1", 1.5", 2", 3", 4" |
| Manufactured | United Kingdom |
What this foam is for
- Dining chairs and upright seating — firm support in a thin pad
- High-quality sofas and armchairs where a firm sit is wanted
- Caravan, motorhome and campervan seating in constant use
- Boat and yacht cushions (interior, dry use)
- Thin firm pads — the 1/4" option suits applications a softer foam would bottom out on
Questions about this foam
Is this too firm for a sofa?
It may be, depending on what you want. At 240N this is a genuinely hard foam — it gives an upright, supportive sit with very little sink. If you like a sofa you settle into, choose the 41M (150N) instead. If you have back problems, or you dislike sinking, this is likely the one you want.
Why is it the longest-lasting foam you sell?
Density. At 42 kg/m³ there is more material per cubic metre than in any other seating foam we make, which directly resists compression set — the gradual permanent flattening that makes an old cushion feel dead. Density predicts lifespan; firmness predicts feel. This foam happens to be high on both.
What does Crib 5 mean?
Crib 5 is BS 5852 Ignition Source 5 — the UK furniture fire test required for contract and commercial seating. It is a different standard from Class 0, which is a building regulations rating for walls and ceilings, not furniture. Note that BS 5852 is a composite test: certification applies to the foam and cover fabric together, so the finished cushion’s compliance also depends on the fabric you use with it.
For the full explanation of density, firmness and fire ratings, see our foam FAQs. To compare every grade side by side, see our foam grade comparison.
Cut to order in our own UK factory. Next working day delivery is available to most of the UK — see our delivery page for timings to your area.