RoofTX® Maxi Vapour Permeable & Air Barrier Underlay by Don & Low
Designed for use in both pitched roofing systems and external cladding installations, this lightweight RoofTX® Maxi underlay by Don & Low is a reinforced, vapour‑permeable underlay and wall breather membrane that helps protect buildings from moisture and air leakage. Offering excellent resistance to water penetration, it supports effective condensation control across roofing and wall applications where long‑term weather protection is essential.
With a robust weight of 170 g/m2, the membrane delivers an ideal balance of strength, durability, and ease of handling on site.
About RoofTX® Maxi Vapour Permeable & Air Barrier Underlay by Don & Low
Whether you’re installing a new metal roof or cladding an external wall, managing moisture correctly is essential for long‑term performance. RoofTX® Maxi is designed to support both roofing and cladding installations, helping protect the building envelope from external weather while allowing it to breathe.
This lightweight, three‑layer vapour‑permeable membrane allows moisture vapour to escape safely from the structure, while resisting air penetration and water ingress from outside. Installed beneath roofing materials, such as metal roof sheets, or behind external wall cladding, RoofTX® Maxi helps reduce the risk of condensation and supports a more durable roof or wall build‑up. During installation, it also offers temporary protection against wind, rain, snow, and dust until the primary covering is in place.
Suitable for UK wind zones 1-5. In the most exposed locations (wind zone 5), additional taping and sealing may be required in accordance with the manufacturer’s installation guidance.
Benefits of RoofTX® Maxi Vapour Permeable & Air Barrier Underlay
- Supports moisture control in both roofing and wall constructions
- Allows vapour to escape while acting as an effective air barrier
- Provides excellent resistance to water penetration
- Reinforced structure improves durability during roofing and cladding installation
- Suitable for use as a roofing underlay or wall breather membrane
RoofTX® Maxi is designed to perform across a wide range of roofing and cladding systems, making it a versatile choice for mixed‑use building envelopes. It is suitable for use in:
- Warm, non‑ventilated pitched roof systems
- Cold, ventilated roof systems
- Non‑ventilated pitched roofing constructions
- External walling and cladding installations requiring a vapour‑permeable breather membrane
Manufactured under BS EN ISO 9001, it is well‑suited to both fully supported and unsupported cold and warm roofing systems.
Specification
- Size: 50 x 1m
- Lap line: 150mm
- Fabric weight: 170g/m2
- Colour: Black (top) / Grey (bottom)
- Tensile strength (machine direction): 400N
- Tensile strength (cross direction): 260N
- Water penetration: Class W1
- Reaction to fire: Class E
- Wind zone compatible: 1-5 (installations in wind zone 5 will require taping)
RoofTX® Maxi is CE compliant and independently certified to recognised European and UK standards. It holds approval from the NSAI (National Standards Authority of Ireland), is certified by the BBA (British Board of Agrément), and carries KOMO certification, providing reassurance of consistent quality and performance.
Fixing Guidance
The following guidance is provided for general information purposes only. Customers should always refer to and follow the manufacturer’s official installation instructions and relevant building regulations before installing RoofTX® Maxi.
For general roofing installations, the membrane should be unrolled horizontally across the roof with the coloured side facing upwards. It should be dressed down over the proprietary eaves carrier by a minimum of 150mm.
The membrane is then fixed directly to the rafters or boarded sarking. Each subsequent course should overlap the previous run by 150mm, ensuring water is shed safely out and down the roof slope. Where adjacent rolls meet, a 100mm side lap should be maintained.
For general walling installations, fix RoofTX® Maxi directly to timber sheathing, ensuring the base timbers are covered and vertical joints are staggered. Secure with stainless steel nails or staples at max 500mm centres. Maintain 100mm horizontal and 150mm vertical laps, return 300mm at external corners, lap over cavity barriers, and neatly detail into openings to ensure effective weathering.
Please note: once RoofTX® Maxi has been installed, the primary roof covering should be installed within one month.
Order A Sample Pack!
Download our printable installation guide (1).
Download the datasheet for RoofTX® Maxi Vapour Permeable & Air Barrier Underlay by Don & Low
| Type | When? | Cost? | ||
|---|---|---|---|---|
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National Delivery | Orders under £1,000 | Est. 5 working days* Roofing items 7-10 working days* |
£192.00 |
| Orders over £1,000 | Est. 5 working days* Roofing items 7-10 working days* |
£96.00 | ||
| Orders over £1,500 | Est. 5 working days* Roofing items 7-10 working days* |
FREE | ||
| Scotland Delivery | Postcodes: PA, PH, DD, AB, IV, & KW | Est. 15 working days* Roofing items 7-10 working days* |
£360.00 | |
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Millboard Delivery | Orders under £2,000 | Est. 5 working days* | £192.00 |
| Orders over £2,000 | Est. 5 working days* | FREE | ||
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Parcelforce Standard | (Small Parcels) | 3-5 working days* | £10.30 |
| (Large Parcels) | 3-5 working days* | £31.80 | ||
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Sample Packs via Courier | 5 working days* | FREE | |
*Please allow for public holidays and weekends (non-delivery days)
Some of our products are available for collection from our warehouses in Okehampton (Devon) and Andover (Hampshire) - This option will show at checkout, when available.
Standard collection lead time is 3-5 working days, this may vary depending on the product. If you would like to collect your order after 2 hours, please choose this option at checkout.
Please note that collections are only available from Monday-Friday, 08:00 - 17:00 & Saturday, 08:00 - 12:30 (Note: this IS the cut off time for collections, despite our closing time of 13:00)
Please Note The Following Prior To Collection:
Vehicles we can and cannot load
Cladco Profiles® will only load flatbed lorries and flatbed trailers for insurance purposes. If the appropriate vehicle is not available, two people would be required for a collection.
Cladco Profiles® will NOT load any vehicles with roof racks, horse boxes, cattle lorries or fixed-sided trailers. Cladco Profiles® has the right to refuse loading a vehicle for any reason.
Before arranging a collection, please read our Customer Collection Notice below.
Our Okehampton HQ and Warehouses (Devon)
Our Andover Warehouses (Hampshire)
Customer Collection Notice
Please ensure you have pre-booked your collection slot before travelling to site.
When arriving to collect your order, please report to a member of our Warehouse Team who will register your arrival and locate your goods. Once ready, your items will be picked and brought to your vehicle loading area.
During busy periods, there may be a short wait while our yard team assist other customers or complete other loading tasks. We always do our best to work within your booked collection time.
We respectfully draw your attention to the following important points:
- Loading is ultimately the customer’s responsibility. While our team can assist with mechanical loading using forklifts, we cannot handball items into enclosed vehicles. Customers must ensure their vehicle is suitable and that goods are safely loaded and adequately secured before leaving the premises.
- Sharp sheeting, metal goods, and long/heavy items may pose additional handling risks. Please come prepared with high-quality protective gloves, and any appropriate protection materials to avoid damage to your vehicle or restraints (e.g. ropes or straps). The edges of roofing sheets and metal products can be extremely sharp, and care should be taken when handling.
- We strongly recommend that customers bring their own straps, ropes, or other securing materials, as we are unable to provide these at the point of collection.
- If you are unsure of your vehicle’s load capacity, we can advise the approximate weight of your order in advance. It is your responsibility to ensure your vehicle is suitable for transporting the goods safely and legally.
- Cladco will not be held liable for any damage to your vehicle or goods once they have been loaded and leave our premises. Loading assistance is provided entirely at the customer’s own risk.
Click & Collect – Pre-Booking Required
You are welcome to collect your order from either our Okehampton (Devon) or Andover (Hampshire) site. All collections must be pre-booked in advance so your items can be picked, packed and ready for you.
Please do not travel to site without a confirmed collection time, as we cannot guarantee your order will be available.
Once your items are ready, you will receive an email with a link to book your collection slot. Please note, same-day collections are not available and bookings must be made at least two hours in advance.
When you arrive, please bring your order confirmation and follow the signage to the collection area where a member of our team will assist you.
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