Question 1

1. What’s the difference between non-breathable and breathable roof membranes?

Accepted Answer

Non-breathable roof membranes are waterproof barriers that prevent moisture vapour from escaping, potentially causing condensation and dampness inside the roof. In contrast, breathable roof membranes allow moisture vapour to escape while blocking water from getting in. This reduces condensation, mould, and rot, and provides better indoor air quality and roof longevity.

Question 2

2. What’s the best breathable membrane for roofs in the UK?

Accepted Answer

If you’re looking for the best breathable roofing membrane in the UK, you’ll want one with a high level of water resistance and excellent vapour permeability. You’ll also want to look for a membrane with proven durability, ease of installation, and strong moisture control. Tyvek, Klober and Proctor all offer membranes tested to BS EN 13859-1 and widely used in UK roofing projects.

It’s also best to choose a product that’s appropriate for the job in hand. Different roof types will suit membranes with different levels of breathability, and local climate and weather conditions can also be important. For example, in sheltered or drier area, a standard breather membrane might be enough, whereas in wet or coastal areas higher water resistance may be better.

Question 3

3. What is the difference between a ‘vapour control layer’ and ‘breather membrane’?

Accepted Answer

A vapour control layer (VCL) is a semi-permeable film designed to restrict moisture vapour from entering roof or wall cavities, helping to prevent condensation and dampness. Meanwhile, a breather membrane is a highly permeable material that allows moisture vapour to escape from within the building while providing excellent weatherproofing. Essentially, a VCL controls internal moisture, whereas a breather roof membrane manages external moisture and airflow.

Question 4

4. Is a breathable roof membrane waterproof?

Accepted Answer

A breathable roof membrane is water-resistant but not fully waterproof. It stops wind-driven rain and snow from entering the roof structure but still allows vapour to pass through. For complete weather protection, it should be used with an external roof covering like roof tiles or shingles.

Question 5

5. What’s the lifespan of a roof breather membrane?

Accepted Answer

Most quality breathable roofing membranes last 30+ years when installed correctly and protected beneath the roof covering. Prolonged UV exposure before covering can reduce this lifespan however.

Question 6

6. Can breathable roofing membranes be used for both warm and cold roof designs?

Accepted Answer

Yes - they suit both warm and cold pitched roofs, although they work differently in each. In warm roofs, they sit above insulation and may need a separate vapour control layer. In cold roofs, they manage moisture in the loft void.

Make sure you choose a membrane with the right level of breathability for how the roof is constructed:

In warm roofs, less vapour passes through because insulation is above the rafters, so a standard breathable membrane is often enough.
In cold roofs, more vapour can reach the membrane, so you may need a high vapour-permeable membrane to avoid condensation.

As a rule, the more moisture that could reach the membrane, the higher its breathability rating should be.

Question 7

7. Do breathable roof membranes come in different colours, and does it matter?

Accepted Answer

Yes. Breathable roof membranes are available in colours such as grey, blue, and black. A black breathable membrane absorbs more heat, while lighter colours reduce glare and keep roof spaces brighter during installation. However, other than this, the colour doesn’t affect vapour permeability, durability, or water resistance. It’s mainly a manufacturer choice.

Question 8

8. Is breathable roofing felt the same as a breathable roof membrane?

Accepted Answer

Yes. The term breathable roofing felt is often used on site to describe modern breathable roof membranes. Traditional roofing felt was bitumen-based and non-breathable, relying on ventilation to manage moisture. Modern breathable ‘felt’ is a synthetic, vapour-permeable membrane that allows moisture to escape while resisting rain.

Breathable roof membranes

Tyvek Supro Breather Membrane Felt Underlay 1m X 50m (50m2/roll)

Tyvek Supro Breather Membrane Felt Underlay 1.5m X 50m (75m2/roll)

A.proctor Roofshield Breather Membrane 50 X 1m X 0.75mm

UltraPerm Lite 92gsm Roof & Wall Breather Membrane / Underlay - 1m x 50m (50m2)

Tyvek® Supro Plus, With Integral Tape, Breather Membrane 1.5m X 50m

Wraptite Detailing Tape 150mm

Wraptite Detailing Tape 300mm

1500mm X 50m Primaguard Breathable Membrane 115GSM

Easy Trim Ultra Breather Membrane 50m X 1m

Easy Trim Grafter Breather Membrane 50m X 1m

Easy Trim Ultra Breather Membrane 50m X 1.5m

Cromar Vent 3 High Performance Breathable Membrane 50M x 1M Grey

Procheck FR200 1.6 x 50m