Boat House Renovation Benefits From “Intuitive” A. Proctor Group Membranes

A chemical engineer’s retirement project to convert a former fishing bothy is taking advantage of the benefits of two different membrane products from the A. Proctor Group: Facadeshield® UV and Proctor Air.

The former boat house, complete with double doors leading directly onto a slipway to the beach, has been bricked up for a decade. Now, it is being renovated by David Gibson into a two-storey beach house, fulfilling a long-held ambition.

Facadeshield UV provides short-term protection to exposed walls

The existing boat house structure provided a tight footprint, being only 3.5m wide by 8m long. David took the  existing walls down to around one metre in height, and then began the process of erecting the timber frame that would sit behind. All of this allowed him to use the existing sleeper foundations.

Originally, he planned to use an open-jointed timber cladding as the finish above the retained brickwork. He therefore chose the A. Proctor Group’s Facadeshield UV membrane, which combines UV resistance, water resistance, and high vapour permeability. Designed specifically for open jointed cladding, Facadeshield UV is also dark in colour to provide a shadow effect in the open joints. Ultimately, David had to amend his timber cladding specification to a closed system. The boat house sits right on the boundary of his property, and fire safety regulations necessitated a change in approach.

Nevertheless, the qualities of Facadeshield UV still proved useful. As David is carrying out the work himself, progress can inevitably be slow – especially if weather conditions are not favourable. The wall membrane was left exposed for three months before the timber cladding was completed in January 2025, but it has protected the OSB sheathing and timber frame well in that time.

Maintaining a traditional appearance

On the roof, David chose Proctor Air as an air permeable, low resistance (APLR) membrane, for use below a traditional slate finish. Maintaining a traditional appearance as part of the conversion work is important to David, given the building’s history of use.

The monopitch roof design made ventilation provision tricky, as David was specific in how he wanted to detail the ridge and keep it secure in the coastal location in Carnoustie. Selecting Proctor Air removed any such concerns, as it provides a uniform flow of air that effectively ventilates the roof space and removes any risk of condensation.

A tile or slate roof finish is the first line of defence against the weather. As water can get into the space below the tile or slate, the chosen underlay must also be capable of resisting water ingress. While not waterproof, Proctor Air has a W1 water resistance, and can be left exposed to UV for up to three months.

“Installing both membranes has all been quite easy and intuitive,” said David, before adding, “as long as it isn’t windy!” Although carrying out as much of the work by himself as possible, he did seek some help in getting the roof membrane installed, acknowledging “that it would be tricky for one person.”

Having an understanding of heat loss and dew points, David was happy to carry out U-value and condensation risk calculations himself. He has been grateful for the support available during the project so far: “I swapped a few emails with the A. Proctor Group technical team to check things were okay,and Building Control have been really helpful on site as well.”

At the time of writing, most of the external works to the boat house are complete. David will move on to the internal works, where he plans to use the company’s Reflectatherm® Plus to the internal side of the timber frame. https://proctorgroup.com

Pitched Roof Ventilation and Solar PV

The increased adoption of solar photovolataics (PV) on pitched roofs has led to the introduction of new and updated guidance to ensure roofs continue to perform as intended. However, as Pamela Howat, Senior Technical Advisor at A. Proctor Group, explains, the terminology used in the updated guidance is causing confusion about the types of underlays that can be installed on roofs featuring PV panels.

Permeability is a term used in relation to two distinct parts of a pitched roof build-up: the underlay and the external roof covering. The permeability of a pitched roof underlay – installed over the rafters and below the external covering – impacts on the provision of ventilation to the roof space. The permeability of the roof covering itself impacts on whether there is a requirement for a ventilated batten & counter batten cavity below it.

Updates to industry guidance, like the NHBC’s revised technical standards for 2024, now list integrated solar PV panels as a type of impermeable roof covering. As a result, the A. Proctor Group technical team has received enquiries about the suitability of our Proctor Air® as an underlay in roofs featuring solar PV. 

Standards and guidance already referenced impermeable roof coverings, including tightly-jointed slates and tiles, and metal sheets. With these finishes it is already common practice to include a ventilated batten and counter batten cavity. The air movement removes moisture from the area below the roof covering, preventing condensation from occurring. 

Including solar PV alongside established impermeable coverings has caused people to read the guidance afresh. The 2024 NHBC Technical Standards, for example, say: 

“Where arrays of integrated solar roof panels are installed, forming the roof covering, then the roof covering should be treated as air impermeable and the whole roof ventilated accordingly, unless the panel manufacturer is able to demonstrate their system is air permeable … Solar roof panel manufacturers may also require a ventilated space beneath the panel, to increase ventilation and cooling of the panel.”  The clause in bold is our emphasis. As people get to grips with the new guidance, it is leading to confusion over the acceptable permeability of underlays as well. 

An extra factor to consider is that ‘impermeable’ solar PV is often being installed as part of roofs with a traditionally air permeable covering. Traditional slates and tiles, by their nature and often irregular sufaces and edges, are generally considered to be air permeable, ie the use of them on a roof allows vapour to pass through the joints in the tiles. More modern roofing materials and manufacturing processes can produce very close fitting tiles or slates, such as fibre cement slates and metal sheets and tiles. 

These can be advantageous to use, due to availablility and the fact they can often be used to provide primary weather hold out at lower pitches, but the lack of permeability through the joints can mean that vapour can build up in the batten cavity, between the top of the underlay and the underside of the outer covering. If this vapour cannot escape you have an increased risk of moisture related issues, such as timber rot and corrosion of fixings. 

Use of a counter batten and below tile ventilation, can easily resolve these potential problems. 

Of course, the relationship between air movement and moisture vapour in the roof space, and air movement and moisture management below the roof covering, very much depends on the type of underlay used.

Traditional bitumen felt is a high resistance (HR) underlay. It is impermeable, allowing the passage of neither moisture vapour nor air from the roof space into the area below the roof covering. The roof space must be ventilated in accordance with relevant technical guidance, when using a HR underlay. 

Low resistance (LR) membranes are vapour permeable, and come in two types. The majority of ‘breather membranes’ are airtight and allow the passage of vapour only. Air permeable LR underlays, as the name suggests, allow the passage of both vapour and air into the batten space, and then through the outer covering, depending on its permeability. 

It’s not hard to see how wording like, “the roof covering should be treated as air impermeable” could lead specifiers and installers to think that the underlay specification is included. We can provide reassurance that only the external covering is included in that statement. 

LR membranes, of either type, can therefore continue to be used in conjunction with integrated solar PV panels. When using an airtight LR underlay then the appropriate guidance in the NHBC documentation must be considered, ie this could include both batten and loft space ventilation. 

When using Proctor Air, an APLR underlay, then there is only a requirement to provide ventilation into the batten/counter batten cavity as is currently the case with close fitting outer coverings – even if only part of it features integrated solar PV.  The slating and tiling must also be carried out in accordance with the relevant clauses of BS 5534:2014, BS 5250:2021 and the tile/slate manufacturer’s instructions.

Using Proctor Air means that no additional ventilation into the roof space is required, and compliance can be achieved by using a ventilated batten and counter batten space. This complements potential cooling requirements for the PV Panels as well as allowing vapour to disperse the roof construction. A ventilated batten and counter batten space means roofs can still benefit from the extra advantages offered by an air permeable LR underlay like Proctor Air®. 

Proctor Air permits the passage of both air and moisture vapour through the roof construction, to the under-tile or ventilated batten space, and then to the outside. It reduces the risk of issues occurring in roof spaces due to poorly installed VCLs or ventilation, since neither is needed – even where the external covering is considered impermeable. 

In fact, Proctor Air provides a more uniform flow of air than normal vents, helping to prevent ‘dead’ areas of poor ventilation in complex roofs.  A. Proctor Group is a 4th generation family business with a history of technical innovation, promoting good practice, and developing products that roofing contractors want to use. We have applied this wealth of experience to creating the next generation of air permeable LR membrane.

By choosing and installing Proctor Air, specifiers, contractors and building owners/managers can enjoy the confidence that comes from a high-performance product doing its job without intervention. All of this is backed by our unique 15-year warranty, offering peace of mind even in the face of an uncertain future climate. 

For more information visit: https://proctorgroup.com/products/proctor-air 

A. Proctor Group Collaborates with Park Home Manufacturer to Deliver Fire Safety

The introduction of the Building Safety Act 2022 was focused around higher-risk residential buildings, defined as being above a certain number of storeys or a certain height. But a culture of taking fire safety seriously applies to buildings of all types – and park homes designed for short-term holiday rentals are no exception.

For Lissett Homes, a manufacturer of premium park homes and lodges, one customer’s request to use a different style of cladding had ramifications beyond the aesthetic appearance of the building. It meant their design team reviewing all of the product specifications and detailing to ensure the necessary performance was achieved – and making use of manufacturer expertise where needed.

Minimum heights and distances are a key feature of fire safety regulations, and it is no different for park homes and lodges. “The Caravan Act requires a six-metre gap between buildings,” said Chris Close, Design Director at Lissett Homes. “It can be possible to build closer than that, but it depends on the fire classification of the products used in the build-up.”

For Lissett Homes, a significant challenge is not having control over how buildings are sited once they leave the production facility. For the two ‘Bainland’ homes under construction, they could make no assumptions about how the buildings would ultimately be positioned.

As Chris explained: “We suspect the customer will site these lodges six metres apart, but we can’t be sure. Also, one large group might rent both buildings at the same time, so the customer might install a timber deck – rather than a paved surface – bridging between the two. That creates an additional fire risk, so we had to make sure the specification was capable of dealing with any eventuality.”

The typical Lissett Homes specification features A. Proctor Group’s Proctorwrap Reflect® behind the timber cladding. However, that is based on the external cladding achieving a classification of Class 3 when tested to BS 476-7:1997 Fire tests on building materials and structures. Method of test to determine the classification of the surface spread of flame of products.

For the new ‘Bainland’ homes, the customer requested a type of vertical cladding, treated with linseed oil, which only achieves Class 4 when tested to the same standard. Combined with the uncertainty over the siting of the buildings, Lissett Homes opted to “design and build for the worst-case,” in Chris’s words. That meant looking at incorporating a fire-rated vapour permeable membrane behind the cladding. “I’ve worked with A. Proctor Group for seven or eight years,” said Chris, “so they were our first port of call and together we found the right solution.”

In wanting peace of mind that the new specification could offer the right level of fire safety performance, Lissett Homes benefitted from A. Proctor Group’s high level of technical support.

That support started with a recommendation to use Fireshield®, a vapour permeable membrane offering Class B-s1,d0 reaction to fire when classified in accordance with BS EN 13501-1:2002 Fire classification of construction products and building elements. Classification using test data from reaction to fire tests.

U-value calculations and condensation risk analyses were then carried out to show the wall build-up – based on an OSB-faced structural insulated panel (SIP) – offered the same thermal and moisture management performance as one featuring Proctorwrap Reflect.

Despite the change in membrane specification, “we were able to maintain the exact same wall structure and panel thickness,” Chris confirmed.

Swapping from typical horizontal cladding to a vertical cladding might sound like a relatively simple aesthetic change. For Lissett Homes, working with vertical cladding for the first time, it also meant reworking a host of details, such as around window openings and at soffits.

That reworking included making sure Fireshield was securely fixed so as to not create a hidden fire risk, and here A. Proctor Group were again able to support with compatible tapes and detailing advice. For Chris and Lissett Homes, the experience of developing this new specification gives them something new to offer to other customers: “There has been a lot of work on this project, but now we’ve done it once we’ll be adding it to our range of solutions.”

As a 4th generation family business with a history of technical innovation and promoting good practice, A. Proctor Group has a reputation for bringing new ideas to the market.

Fireshield is a vapour permeable walling underlay with an intumescent coated surface, installed and fixed to the substrate in the same way as standard breather membranes. Fireshield is suitable for all walling applications including those in higher-risk buildings, and its intumescent coating helps protect the substrate by reducing the risk of fire taking hold.

Find out more at https://proctorgroup.com/products/fireshield