Lee Griffiths, technical sales manager GBI at Dakea explains what is required to ensure a safe and secure roof window installation.
Installers will often be working across residential projects and will need to know how to correctly fit roof windows. It is an important job, poorly fitted windows can become problematic, causing condensation, build up and leakages. To this end, there are a number of things you must remember to achieve a correct installation.
Regardless of the technique you use, the first step when installing a roof window is to ensure the roof aperture is at least 50mm wider and 45mm taller than the external frame size of the window. If necessary, this might require you to remove the roof’s rafters. If this is the case, then it is essential to take great care to preserve the roof’s structural integrity. Once access has been achieved, cut the underlay and envelope it around the support trimmers, stapling it into place. Next, determine the correct height of the window and fasten a batten to support the frame – be sure to position it level and 80mm above the tiles.
Once this is completed you can begin to fit a membrane collar around the window frame. Fitting a collar prevents water or air passing through the un-insulated gap that exists between the rafter and the back of the window frame. However, if this is incorrectly repaired, then the interior surface can become damaged, which will adversely affect the energy efficiency performance of the property. Additionally, failing to get this part of the installation right could lead to a violation of Part L1B of the Building Regulations.
To resolve the problem, many installers like to secure the gap using rigid foam, cutting the piece to fit from larger, premium priced sheets. Whilst this is a sure-fire method for achieving a secure and tight fit around the frame it is also a time-consuming solution. Furthermore, using this technique results in on-site debris and wasted foam. As such, we advise installers to consider utilising a more efficient, alternative method.
At Dakea, we fit our roof window range with an Insulating Foam Collar (IFC). The rebated foam profile is manufactured to perfectly fit the window frame without the need for onsite cutting. The collar helps to significantly reduce installation time, which can be achieved in three minutes. What is more, once installed the solution provides excellent insulation performance.
Installing the IFC is relatively straightforward. To begin with, ensure the brackets have been secured to the frame with the provided screws. Afterwards, clean the outer frame and stick the IFC to its outer side. It is important to pay particular attention to the corners and edges of the frame, which tend to attract the most dirt. Next, pass the frame through the opening onto the support battens and check the alignment. Insert the sash to test that it can be opened and closed sufficiently.
Once the sash can be opened and closed without any issues, the next step is to replace the roofing membrane. Taking this additional step helps to further restrict water and air ingress around the frame. Once again, there are many ways to handle the task and some installers will choose to cut and secure the membrane themselves. Unfortunately, achieving a water and airtight seal requires accurate cutting, so choosing this technique can become time-consuming on larger projects.
Thankfully, Dakea has developed an Underfelt Foil Collar (RUC) to make the process easier. The innovative solution comprises a single piece of stretchable, highly tear-resistant polypropylene, non-woven fabric with a vapour permeable polyurethane coating. As a result, the flexible fabric can be stretched around the frame and fixed to the outer edge with staples or tape. To complete the installation, the flashing and covers need to be fixed to the bottom, sides and top of the frame, while the roof tiles just need to be replaced and the sash re-fitted.
Whether new to the game, or a time-served veteran, domestic roof window installations can be tricky but must be handled correctly. Making a mistake can allow the ingress of water and outside air, which in turn can affect the roof’s structural integrity. However, by working with an innovative manufacturer like Dakea, installers can overcome the challenge. The company’s roof windows can be installed correctly and effectively without the need to create a bespoke membrane. In turn, this can help installers to save time on-site and reduce waste.