Water ingress may damage your property or cause wet and dry rot. Nick King from Klober explores the reasons behind choosing lead-free flashings for maintaining a watertight roof, and outlines the installation
considerations to be aware of
The roof is often overlooked in the early stages of a self-build project, resulting in last-minute decisions on critical components that can make a big difference. Flashing is one of those areas.
ROOF FLASHING
Breakpoints could leave a property vulnerable to water ingress if they are not sufficiently waterproofed. This often happens through tiles’ vulnerable intersections, such as chimneys or valleys. If these intersections are inadequately sealed, moisture may enter your home or building. This is where a roof flashing detail is essential.
Roof flashings can be installed to cover over profiled tiles and slates, closing off dry valleys, sealing solar panels, rooflights, for changes in roof pitch, on abutments and chimneys. The main purpose of installing flashing is to maintain a watertight roof.
LEAD-FREE
Its durability and waterproofing properties make lead a popular choice for roofing solutions on residential and commercial properties. You’ll often see it on the roofs of historic buildings and in conservation areas to preserve appearance. While lead has a place in certain areas, there are numerous benefits associated with choosing lead-free flashing for other applications.
In terms of safety, the use of lead-free is less likely to be a health hazard for those working with this material because it is non-toxic. What many don’t realise is that specification requirements can vary from one roofing job to the next. Lead-free flashings can offer a significant point of difference here. For projects which do not specify traditional lead, lead flashing substitutes made without lead can offer a great alternative.
Over the years, lead-free has become more popular for a few reasons. The first is that, despite recorded lead-theft declining, the threat still remains. When it happens, this leaves the roof vulnerable, as well as being inconvenient and costly to replace. However, there is no scrap value to lead alternatives so would-be thieves won’t look twice at a roof with this solution.
Secondly, the speed and ease of installing lead-free flashings is another major benefit. This is in part because they are extremely malleable and easy to manipulate, shape and form by hand. They can be stretched over details while dressing to give a smooth, neat and premium lead-like appearance, allowing easy application for a wide range of details.
What’s more, lead-free flashing does not require bossing like lead does, so it is quicker to install. While lead components typically require a lead specialist to be subcontracted, opting for lead-free alternatives eliminates this added time and cost as the installation process does not depend on specialist skills or tools.
It is important to note that if lead-free flashings are incorrectly installed, water ingress could still occur. That’s why competent installation is necessary.
INSTALLATION TIPS
Ahead of installation, it is key to ensure all surfaces are dry and free from dust, oil and moss, before laying the flashing. It is also crucial that self-adhesive lead-free flashings are not used on bitumen or tar surfaces. Some superior lead flashing alternatives have a perforated release paper on the back which allows direct application onto the tile surface once removed. If installed in lower temperatures or applying flashing to damp surfaces, specialist glue can also be used to ensure strong adherence to the roof.
The best practice when turning into brickwork joints or chasing in, is to allow a minimum of 30 mm. When it comes to sealing, flashing sealant should be used for brickwork joints. Strips of flashing which are folded into wedges are a good way to hold the flashing in place in the brickwork joint, prior to sealing. Under no circumstances should silicone-based sealants or adhesives be used.
For long runs, self-welding flashings can simply be overlapped, although with available lengths of up to 10 metres it may not even be necessary. Some products are flexible and able to stretch in both directions, which allows the product to move without the use of an expansion joint or consideration of a maximum length. When using self-welding flashings, overlaps should be no less than 50 mm, using a roller to apply pressure. Any gaps must be supported to prevent sagging and water build-up.
ADDITIONAL CONSIDERATIONS
To get the best results, roofers should follow the manufacturer’s guidance because not all lead-free replacements will be the same. Superior lead-free alternatives have unique properties that allow them to overlap by up to 50 mm and form a weld due to their flexibility, whereas, other more economical lead-free products would require a welt detail.
You may also wish to look for quality products that hold third party accreditation, when choosing roofing components, to give additional peace of mind. For example, if a product holds BBA certification, product performance has been verified based on rigorous testing and standards. On top of this, checking the product guarantee and opting for flashings with long promises of assurance is advisable.
AND FINALLY…
Roofers should also not neglect primary on-site safety procedures. It’s essential to take safety precautions, especially for pitched roofing work. Those installing roofing components must be competent in using the latest techniques, standards and materials and training should include safe working practices.
Thanks to advancements in lead-free flashings along with best practice installation methods, it is clear that roofing contractors can complete high-performance roofing projects with ease when they decide to go lead-free.
Nick King is portfolio manager at Klober