High Density Foam
High density foam is polyurethane foam with a tightly packed cell structure, giving it more weight per cubic metre than lower grade foam. That extra material is what makes it more durable and better at holding its shape, which is why it is the standard choice for sofa cushions, chairs, seat pads and other seating. GB Foam Direct cuts every grade below to your exact size and shape, with next working day delivery available.
- All of our indoor upholstery foam is high density. The grades in the table below range from 31.4 to 43 kg/m3.
- Density decides how long foam lasts. Hardness, measured in newtons, decides how firm it feels. You need to choose both.
- For sofa seat cushions we recommend GB 39H up to 4 inches thick and GB 41M above that. Use GB 39S for back cushions.
- We have been cutting foam since 1976, work to ISO 9001 quality standards and back our foam with a 5 year guarantee against faults in manufacture.
- Orders placed before 11am Monday to Thursday are eligible for next working day delivery.
What Is High Density Foam?
High density foam has a compact cell structure that makes it dense, durable and long lasting. That structure lets the foam conform to the shape of the user while still providing support and springing back to its original form. Unlike lower density foam or fibre fillings, it resists sagging and keeps its shape over time.
It is used wherever a cushion needs to stand up to regular use, including sofa and chair cushions, bay window seats, dining chairs, caravan and camper van seating, boat seating and mattresses.
How Foam Density Is Measured
Density is the weight of a piece of foam divided by its volume, expressed in kilograms per cubic metre (kg/m3). For example, a 1 m3 block that weighs 35 kg has a density of 35 kg/m3. Higher density foams generally offer better support and a longer working life than lower density foams.
Each of our upholstery foams has a technical datasheet that gives its apparent piece density, tested to BS EN ISO 845, along with its hardness, tensile strength, compression set and fatigue classification. You can download the datasheets from our upholstery foam sheets page.
Density Is Not the Same as Firmness
A common mistake is to assume that high density means hard. It does not. Density tells you how much foam material is packed into each cubic metre and therefore how long the foam will last. Hardness tells you how firm it feels when you sit on it, and it is measured separately in newtons to BS EN ISO 2439.
GB 39S and GB 39H are a good example. Both have a density of 37 to 41 kg/m3, so both are premium high density foams. But GB 39S has a nominal hardness of 100 to 140 N and feels soft, while GB 39H has a nominal hardness of 180 to 220 N and feels firm. Choosing the right foam means picking the density grade for longevity and the hardness for comfort.
Our High Density Foam Grades
These are the upholstery foam grades we cut to size, with the figures taken from each grade’s technical datasheet.
| Grade | Density (kg/m3) | Hardness (N) | Fatigue Class (BS 3379) | Best For |
|---|---|---|---|---|
| GB 33S (Average Soft) | 31.4 to 34.7 | 100 to 140 | S (severe) | Sofa back cushions and general use |
| GB 33M (Average Medium) | 31.4 to 34.7 | 115 to 155 | S (severe) | Seat cushions 5 inches (12.7cm) or thicker, replacing fibre filled cushions |
| GB 33H (Average Hard) | 31.4 to 34.7 | 160 to 220 | S (severe) | Sofa and upholstery seat cushions, boats, caravan seating, dining chairs, camper vans |
| GB 39S (Luxury Soft) | 37 to 41 | 100 to 140 | V (very severe) | Sofa back cushions and general use |
| GB 39H (Luxury Hard) | 37 to 41 | 180 to 220 | V (very severe) | Seat cushions up to 4 inches thick, boats, caravan seating, dining chairs, seat pads, camper vans |
| GB 41M (Luxury Medium) | 39 to 43 | 130 to 175 | V (very severe) | Seat cushions 4 inches (10cm) or thicker, replacing fibre filled cushions |
| GB 42H (Superior Hard) | 38 to 42 | 220 to 300 | V (very severe) | Heavy use seating, boats, caravan seating, dining chairs, camper vans |
We also stock a Superior range, GB 50M (medium) and GB 50S (soft), made as an ideal replacement for feather cushions. It combines the comfort of feather with the durability of foam, with instant recovery after use. All grades are available in thicknesses from 1/2 inch (12mm) to 4 inches (100mm). See the full range on our upholstery foam sheets page.
Which High Density Foam Should You Choose?
| Application | Recommended Grade | Why |
|---|---|---|
| Sofa seat cushions, 1 to 4 inches thick | GB 39H | A firm foam with just enough give to provide support and shape retention on thinner cushions |
| Sofa seat cushions, over 4 inches thick | GB 41M | A medium feel foam that gives comfort and shape retention for years on thicker cushions |
| Sofa back cushions | GB 39S | A luxury soft foam that suits backs but is too soft for seating |
| Replacing sagging fibre filled cushions | GB 41M or GB 33M | Medium feel foams designed as a replacement for fibre filled cushions at 4 inches or thicker (GB 41M) or 5 inches or thicker (GB 33M) |
| Dining chairs, boats, caravans and camper vans | GB 33H, GB 39H or GB 42H | Hard seating grades suited to everyday use, with GB 42H offering the greatest longevity |
If you are not sure which grade suits your project, our guide to what foam to use for sofa cushions explains our recommendations in more detail, or you can call our team.
Benefits of High Density Foam
- Durability and longevity. The compact cell structure gives a long lifespan, which makes high density foam ideal for mattresses and seat cushions that see long term use.
- Resists sagging. It holds its shape and support far better than lower density foam or alternative fillings, giving consistent support over time.
- Comfort and support. It conforms to the user while returning quickly to its original form.
- Suitable for heavier users. It can handle greater pressure without losing comfort or support.
- Fire safety compliant. The upholstery grades in our range comply with the Furniture and Furnishings (Fire) (Safety) Regulations 1988.
Buy High Density Foam Cut to Size
You can order any grade cut to the measurements you provide. Here are some of our most popular shapes, and you can see the full selection on our foam cut to size page.
Looking for something specific? Our replacement sofa cushions, caravan cushions, boat cushions and campervan foam pages are set up for those projects.
How to Order Custom Cut High Density Foam
Choose your foam shape. Pick one of our existing shapes or select the custom shape option and provide your own template.
Measure and enter your size. Enter your dimensions in millimetres, centimetres or inches. Our guide to measuring foam cushions will help you get accurate measurements.
Choose your foam type. Select the grade and firmness that suits your project using the tables above.
Select any extras. We can add Dacron and stockinette to your foam for an additional charge. See our Dacron and stockinette guide for what each does.
Place your order. Orders placed before 11am Monday to Thursday are eligible for next working day delivery, and Saturday delivery is also available.
Why Buy High Density Foam from GB Foam Direct?
GB Foam has been converting foam in High Wycombe since 1976, originally for the town’s furniture industry. Our factory combines CNC cutting technology with experienced freehand foam cutters, and we work to ISO 9001 quality standards. Our foam carries a 5 year guarantee against faults in manufacture, and we cater to everyone from one-off retail customers to large manufacturers ordering daily.
Speak to Our Team
If you need help choosing a grade, call us on 01494 441177, email sales@gbfoam.com or fill out our contact form. We are in the office from 9am to 5pm Monday to Thursday and 9am to 3pm on Friday.
High Density Foam FAQs
What is high density foam?
High density foam is polyurethane foam with a compact cell structure, which gives it more weight per cubic metre than lower grade foam. That extra material makes it more durable and better at holding its shape, so it resists sagging and keeps providing support over long periods of use. All of our indoor upholstery foam is high density.
How is foam density measured?
Foam density is the weight of a piece of foam divided by its volume, expressed in kilograms per cubic metre (kg/m3). A 1 m3 block weighing 35 kg has a density of 35 kg/m3. Our technical datasheets give the apparent piece density of each grade, tested to BS EN ISO 845.
Is high density foam firm?
Not necessarily. Density and firmness are separate properties. Density affects how long the foam lasts, while hardness, measured in newtons, affects how firm it feels. GB 39S and GB 39H share the same density range of 37 to 41 kg/m3, but GB 39S is a soft foam at 100 to 140 N and GB 39H is a hard foam at 180 to 220 N.
What is the best high density foam for sofa cushions?
For seat cushions 1 to 4 inches (2.5 to 10cm) thick we recommend GB 39H, a firm foam with enough give to provide support and shape retention. For seat cushions over 4 inches (10cm) thick we recommend GB 41M, a medium feel foam. For sofa back cushions we recommend GB 39S, which is too soft for seating but ideal for backs.
How long does high density foam last?
That depends on the grade and how often the foam is used. Higher density grades resist sagging and hold their shape for longer, and our upholstery foam comes with a 5 year guarantee against faults in manufacture. Grades rated V (very severe) under BS 3379 have been tested for heavy-use seating, so they are a good choice for furniture that gets daily use.
What is the difference between high density foam and memory foam?
High density polyurethane foam springs back quickly when you stand up and gives firm, resilient support, which suits sofas, chairs and seat pads. Memory foam is a slow recovery foam that moulds to the body and returns to shape gradually, which suits mattresses and comfort layers. We cut both to size, and you can combine them in the same project.
Can I order high density foam in a custom shape?
Yes. You can choose from our range of foam shapes and enter your own measurements, or select the custom shape option and send us a template. The template can be physical or digital, and our foam cutters will follow it to produce your piece.
Is your upholstery foam fire retardant?
The upholstery grades in our range comply with the Furniture and Furnishings (Fire) (Safety) Regulations 1988. If you would like more detail on the fire safety specification of a particular grade, call our team on 01494 441177.
Cameron has emerged as a key marketing expert since joining GB Foam Ltd in 2017. A graduate of the University of Winchester, with a professional background in Public Relations; he has combined his content writing and brand awareness expertise with an in-depth knowledge of foam products and foam conversion technology to enhance the company’s marketing strategies and industry presence. Cameron has led numerous marketing campaigns, in both B2B and B2C segments, to further brand recognition and open up new business avenues worldwide.