Insulation thickness is a simple way to choose insulation based on the depth of the space you need to fill. This allows you to select the most appropriate material or product range to deliver the performance you need for that required depth. That makes it easier to match the insulation to structures and cavities without forcing or compressing it.
Insulation by thickness means selecting an insulating material that matches a required depth. The required depth typically depends on the size of timber or steel framing members. It is also determined by UK Building Regulations and target U-values, as well as existing construction constraints that cannot be altered.
To work properly, insulation must fit the space for which it is designed. If it is thinner than the void, heat can escape around it. If fibrous insulation is over-compressed, the trapped air structure is reduced, leading to a drop in performance. So thickness matters just as much as the material itself.
This approach applies to all insulation types. Mineral wool slabs, glass wool rolls, blown fibre, phenolic foam, PIR, EPS, XPS, and aerogel products are all installed to set depths, and so they can be used correctly in different parts of a building.
Insulation comes in these common depths:
Insulation Wholesale stocks insulation thicknesses from 2mm right up to 200mm. Manufacturing constraints and performance requirements determine the depth ranges for each material.
Typical available ranges include:
This wide range allows insulation by thickness to work across refurbishments, extensions, and new builds without structural redesign.
You can buy insulation by thickness from Insulation Wholesale. We stock multiple materials across a full depth range, so you can choose the material that best fits your construction build-up, without compromising. Our team helps match insulation thickness to your application, whether for floors, walls, roofs, or specialist applications. We supply UK stock and support both trade and DIY customers with clear advice and reliable delivery.
There is no single “best” insulation thickness. The right choice depends on the space available, the target U‑value, and the material used. A thinner high‑performance foam can outperform a thicker fibrous product, while deeper mineral wool can give better sound control and fire resistance. Choose the thickest insulation that fits without compression while complying with UK Building Regulations.
Yes, you may combine materials - as long as they are compatible and correctly detailed. You can combine a rigid board layer with mineral wool of the same depth to improve thermal control and sound absorption, for example. The key is to maintain continuity with no air gaps. Do a full vapour control and condensation risk assessment before combining materials.
100mm Isover Acoustic Partition Insulation Roll is a glass mineral wooldesigned to reduce sound transmission between walls and floors, creating quieter and more comfortable spaces.
100mm Isover CWS 32 Cavity Wall Slab offers excellent thermal insulation for cavity walls, effectively reducing heat loss and boosting energy efficiency. Lightweight and easy to install, it delivers reliable, long-lasting performance.
100mm Isover CWS 36 Cavity Wall Slab offers excellent thermal insulation for cavity walls, effectively reducing heat loss and boosting energy efficiency. Lightweight and easy to install, it delivers reliable, long-lasting performance.
100mm Acoustic Insulation Roll from Knauf is a Glass Mineral Wool roll, designed for use in internal wall and floor applications, to offer sound absorption and noise reduction properties.
100mm ODE Insulation Acoustic Roll is designed to reduce sound transmission, making it an ideal solution for creating quieter indoor environments. Its flexible and simple-to-install design effectively absorbs sound, making it perfect for both residential and commercial spaces.
100mm Rockwool Flexi has been designed as a multi-use, dual-purpose acoustic and thermal mineral wool insulation with a unique flexible edge along one side. It is suitable for use all over the home, in pitched roof rafters, framed external walls, internal partitions, intermediate floors, separating walls and floors, and timber suspended ground floors.
100mm Rockwool RW3 Slabs can be applied to an array of general building applications for acoustic, thermal and fire protection of partition walls, ceilings, floors and roofs.
100mm Rockwool RWA45 has been developed for thermal, acoustic and fire performance in a range of construction types. It is suitable for applications on partition walls, ceilings, floors and roofs.
Acoustic Roll 12 is a lightweight, non-combustible glass mineral wool insulation roll. The product is designed to provide thermal and acoustic insulation for several applications, including internal floors and partitions. Manufactured at a minimum density of 12kg/m3.
125mm Isover CWS 32 Cavity Wall Slab offers excellent thermal insulation for cavity walls, effectively reducing heat loss and boosting energy efficiency. Lightweight and easy to install, it delivers reliable, long-lasting performance.
125mm Isover CWS 36 Cavity Wall Slab offers excellent thermal insulation for cavity walls, effectively reducing heat loss and boosting energy efficiency. Lightweight and easy to install, it delivers reliable, long-lasting performance.
140mm Rockwool Flexi has been designed as a multi-use, dual-purpose acoustic and thermal mineral wool insulation with a unique flexible edge along one side. It is suitable for use all over the home, in pitched roof rafters, framed external walls, internal partitions, intermediate floors, separating walls and floors, and timber suspended ground floors.
150mm Isover CWS 32 Cavity Wall Slab offers excellent thermal insulation for cavity walls, effectively reducing heat loss and boosting energy efficiency. Lightweight and easy to install, it delivers reliable, long-lasting performance.
25mm Isover Acoustic Partition Insulation Roll is a glass mineral wooldesigned to reduce sound transmission between walls and floors, creating quieter and more comfortable spaces.
25mm Acoustic Insulation Roll from Knauf is a Glass Mineral Wool roll, designed for use in internal wall and floor applications, to offer sound absorption and noise reduction properties.
25mm ODE Insulation Acoustic Roll is designed to reduce sound transmission, making it an ideal solution for creating quieter indoor environments. Its flexible and simple-to-install design effectively absorbs sound, making it perfect for both residential and commercial spaces.
25mm Superglass Acoustic Partition Roll (APR) is a lightweight, non-combustible glass mineral wool insulation roll. It is suitable for the following applications: internal walls and floors, timber and metal stud partitions, drylining systems and separating walls and floors. Manufactured at a minimum density of 10kg/m³.
50mm Isover Acoustic Partition Insulation Roll is a glass mineral wooldesigned to reduce sound transmission between walls and floors, creating quieter and more comfortable spaces.
50mm Acoustic Insulation Roll from Knauf is a Glass Mineral Wool roll, designed for use in internal wall and floor applications, to offer sound absorption and noise reduction properties.
50mm ODE Insulation Acoustic Roll is designed to reduce sound transmission, making it an ideal solution for creating quieter indoor environments. Its flexible and simple-to-install design effectively absorbs sound, making it perfect for both residential and commercial spaces.
50mm Rockwool RWA45 has been developed for thermal, acoustic and fire performance in a range of construction types. It is suitable for applications on partition walls, ceilings, floors and roofs.
50mm Superglass Acoustic Partition Roll (APR) is a lightweight, non-combustible glass mineral wool insulation roll. It is suitable for the following applications: internal walls and floors, timber and metal stud partitions, drylining systems and separating walls and floors. Manufactured at a minimum density of 10kg/m³.
75mm Isover Acoustic Partition Insulation Roll is a glass mineral wooldesigned to reduce sound transmission between walls and floors, creating quieter and more comfortable spaces.
75mm Isover CWS 36 Cavity Wall Slab offers excellent thermal insulation for cavity walls, effectively reducing heat loss and boosting energy efficiency. Lightweight and easy to install, it delivers reliable, long-lasting performance.
75mm Acoustic Insulation Roll from Knauf is a Glass Mineral Wool roll, designed for use in internal wall and floor applications, to offer sound absorption and noise reduction properties.
75mm ODE Insulation Acoustic Roll is designed to reduce sound transmission, making it an ideal solution for creating quieter indoor environments. Its flexible and simple-to-install design effectively absorbs sound, making it perfect for both residential and commercial spaces.
75mm Rockwool RWA45 has been developed for thermal, acoustic and fire performance in a range of construction types. It is suitable for applications on partition walls, ceilings, floors and roofs.
100mm Knauf Insulation Rocksilk RS45 is a Rock Mineral Wool slab, designed for use in multiple thermal and acoustic applications. It is non-combustible with the best possible Euroclass A1 reaction to fire classification.
100mm Rainscreen Duo Slab is dual-density insulation specifically developed for use within ventilated cladding systems, as well as sealed systems such as curtain walling. Once installed, the robust outer surface of the slabs, in combination with a factory applied water-repelling agent, acts to resist rain ingress during construction.
100mm Rockwool RW4 Slabs can be applied to an array of general building applications for acoustic, thermal and fire protection of partition walls, ceilings, floors and roofs.
100mm Rockwool RW5 Slabs can be applied to an array of general building applications for acoustic, thermal and fire protection of partition walls, ceilings, floors and roofs.
125mm Rainscreen Duo Slab is dual-density insulation specifically developed for use within ventilated cladding systems, as well as sealed systems such as curtain walling. Once installed, the robust outer surface of the slabs, in combination with a factory applied water-repelling agent, acts to resist rain ingress during construction.
140mm Knauf Insulation Rocksilk Flexible Slab is a Rock Mineral Wool slab, designed for use in multiple thermal and acoustic applications as well as the fire protection of a loft conversion floor. It is non-combustible with the best possible Euroclass A1 reaction to fire classification.
150mm Rainscreen Duo Slab is dual-density insulation specifically developed for use within ventilated cladding systems, as well as sealed systems such as curtain walling. Once installed, the robust outer surface of the slabs, in combination with a factory applied water-repelling agent, acts to resist rain ingress during construction.
180mm Rockwool Flexi has been designed as a multi-use, dual-purpose acoustic and thermal mineral wool insulation with a unique flexible edge along one side. It is suitable for use all over the home, in pitched roof rafters, framed external walls, internal partitions, intermediate floors, separating walls and floors, and timber suspended ground floors.
180mm Rainscreen Du Slab is dual-density insulation specifically developed for use within ventilated cladding systems, as well as sealed systems such as curtain walling. Once installed, the robust outer surface of the slabs, in combination with a factory applied water-repelling agent, acts to resist rain ingress during construction.