£43.92
In stock
9999 in stock
Create a strong and dependable base layer for a built-up felt roofing system with this SBS Glass Fibre Torch-On Roofing Felt Underlay, supplied in a generous 15m x 1m roll.
Designed specifically for use as a roofing underlay, this membrane combines an SBS-modified bitumen construction with a stable glass fibre reinforcement to provide a practical base sheet beneath compatible roofing cap sheets.
The upper surface is finished with fine sand, while the underside is protected with a plastic foil film suitable for torch application. The membrane can also be installed using a compatible cold roofing felt adhesive, providing installers with additional flexibility depending on the roof specification.
With a 2.2mm thickness, 15m roll length and stated 10+ year life expectancy, this roofing underlay is a practical choice for professional flat roofing, garages, extensions, outbuildings and other suitable bituminous roofing systems.
A roofing underlay forms the important lower layer beneath the final weather-facing cap sheet.
Its job is to help create a continuous waterproofing system while providing a suitable base for the upper roofing membrane.
This product is particularly relevant for customers searching for:
Each roll measures approximately 15 metres long by 1 metre wide, providing around 15m² of roofing membrane before overlaps and cutting are taken into account.
The long roll size is particularly useful for:
Actual installed coverage will be lower than 15m² because allowance needs to be made for side and end laps.
At approximately 2.2mm thick, this membrane is designed specifically as a roofing underlay rather than the final exposed cap sheet.
The underlay forms the lower waterproofing layer beneath a compatible mineral-finished or other suitable roofing cap sheet.
A properly designed system may typically include:
The membrane uses SBS — Styrene Butadiene Styrene — modified bitumen.
SBS modification improves the flexibility of bituminous roofing materials compared with more basic oxidised bitumen membranes.
This can provide benefits such as:
The membrane incorporates a glass fibre reinforcement, providing dimensional stability within the bituminous sheet.
Glass fibre roofing membranes are particularly well suited to underlay applications because the reinforcement helps the membrane maintain its shape while creating a dependable waterproof layer.
Benefits include:
The upper surface features a fine sand finish.
The sanded surface provides a practical finish for an underlay membrane that will subsequently receive another roofing layer.
This differentiates it from mineral cap sheets, which are designed to remain exposed as the final weather-facing roof surface.
The underside of the membrane is finished with plastic foil.
This surface is designed to work with torch-applied installation methods.
When heated correctly during installation, the underside allows the bitumen layer to bond to the prepared substrate.
Installation using a gas torch should only be carried out by a competent person familiar with torch-on roofing systems and appropriate fire-safety procedures.
This underlay can be installed using the traditional torch-on roofing method.
During torch application, controlled heat is applied to activate the underside of the bituminous membrane before it is bonded to the roof surface.
Correct torch application can create a strong bond across the membrane.
Torch-on installation requires:
The current specification also permits installation using a compatible cold felt adhesive.
Cold application can be useful where flame application is unsuitable or where the chosen roofing specification allows an adhesive-bonded system.
Benefits of cold-applied installation may include:
Always ensure the adhesive is compatible with the membrane and intended roof system.
This product is specifically intended as an underlay, not as the exposed final roof finish.
It should normally be covered with a compatible cap sheet as part of a complete bituminous roofing system.
A cap sheet provides the final weather-facing layer and may feature:
Using the correct underlay and cap sheet together helps create a more complete and durable waterproofing system.
It is important that customers understand the difference between the two main layers.
Roofing Underlay
Roofing Cap Sheet
This 15m x 1m product is the underlay layer.
SBS roofing felt is widely used within suitable flat and low-slope roofing systems.
Potential applications include:
Always ensure the complete roofing system is suitable for the particular roof pitch and building design.
Higher-performance torch-on felt systems are commonly used on roofs where greater waterproofing durability is required compared with basic shed felt.
Typical applications can include:
The complete roof build-up should always follow the project specification.
The membrane can be used as part of a new built-up roofing installation over an appropriate substrate.
Before installation:
Correct preparation is essential for achieving a dependable bond.
This roofing underlay may also be used as part of appropriate roof refurbishment systems.
Potential projects include:
Existing roofing materials should be assessed before applying a new system.
Good surface preparation is critical for both torch-on and adhesive-applied roofing.
The roof substrate should generally be:
Any existing defects should be corrected before the roofing membrane is installed.
For many torch-on roofing systems, a suitable bitumen roofing primer is applied to compatible substrates before the underlay.
Primer can help:
Always follow the requirements of the roofing system and primer manufacturer.
Successive sections of roofing felt need to be correctly overlapped.
Proper overlaps help prevent water from reaching the roof deck through joints.
Particular attention should be paid to:
Poorly sealed laps can become weak points in an otherwise sound roofing system.
Roofing membranes are normally laid so each higher section overlaps the membrane below.
This allows water to flow naturally:
from the higher roof area → over the lap → towards the drainage point
rather than being directed into the joint.
Although each roll contains approximately 15m² of material, the finished coverage will be lower after allowing for laps and detailing.
Allow additional material for:
For complex roof shapes, additional allowance may be required.
The current Felt Products specification states that the membrane does not have to be rolled out prior to use.
This can help make installation more convenient on site, particularly when compared with roofing materials that need time to relax before application.
The live specification lists low-temperature flexibility at approximately 0°C.
This is useful information when planning storage and installation conditions.
As with all torch-on roofing materials, installation should be carried out within suitable environmental conditions and in accordance with the relevant roofing system requirements.
Felt Products currently states a 10+ year life expectancy for this roofing underlay when correctly installed as part of the intended roofing system.
Long-term performance depends on factors including:
This membrane is particularly useful as a component of a built-up felt roofing system.
Using multiple compatible layers can provide greater waterproofing security than relying on a single lightweight membrane.
A typical system may consist of:
Torch-on roofing involves the use of an open flame, creating a significant fire risk if carried out incorrectly.
Torch application should only be undertaken by competent installers with suitable equipment and fire-safety procedures.
Particular care is required around:
Where open flame presents an unacceptable risk, a compatible cold-applied roofing system may be more appropriate.
Choose SBS Glass Fibre Torch-On Roofing Felt Underlay 15m x 1m for a stable, dependable and versatile base membrane suitable for professional built-up roofing systems.
Thank you for visiting and shopping at www.feltproducts.co.uk. Following are the terms and conditions that constitute our Shipping Policy.
We only deliver to mainland UK excluding the Scottish Isles. All other areas, please call for pricing.
All orders are processed within 2-3 business days. Orders are not shipped or delivered on weekends or public holidays.
If we are experiencing a high volume of orders, shipments may be delayed by a few days. Please allow additional days in transit for delivery. If there will be a significant delay in shipment of your order, we will contact you via email or telephone.
Shipping charges for your order will be calculated and displayed at checkout.
| Shipment method | Estimated delivery time | Shipment cost |
| Standard | 3-5 business days | As specified at checkout |
Delivery delays can occasionally occur.
You will receive a Shipment Confirmation email once your order has shipped containing your tracking number(s). The tracking number will be active within 24 hours.
Felt Products Northern Ltd is not responsible for any customs and taxes applied to your order. All fees imposed during or after shipping are the responsibility of the customer (tariffs, taxes, etc.).
Felt Products Northern Ltd is not liable for any products damaged or lost during shipping. If you received your order damaged, please contact the shipment carrier to file a claim.
Please save all packaging materials and damaged goods before filing a claim.
We currently do not ship outside the UK.
Our Return & Refund Policy provides detailed information about options and procedures for returning your order.
