Cavity formers for Windows and Doors are typically made from high-density foam, and they are used to create a space or cavity between the window frame and the surrounding masonry. The primary purpose of a cavity former is to use the cavity closer bar lengths (that were typically installed after the apertures were formed) to close off the cavity to form a 3- or 4-sided frame that can be installed into the external wall make-up as the walls are being built.
This predetermines the sizes of the Windows and Doors that will be installed at a later date.
The Windows and Doors can then be manufactured ahead of time (whilst the external envelope of the building is still ongoing) instead of waiting to measure the existing apertures, then signing off an order and waiting 8–9 weeks. In theory, you should be able to have the Windows on site the same week you need them, helping ensure the build process is on time and running smoothly, which in turn saves on cost.
Fire-Rated Cavity Formers
Fire-rated cavity formers are also available, combining a 60-minute cavity fire barrier and cavity closer former into one product.
How To Install Cavity Formers
- Check that the closer is level and square.
- Prop the former to ensure it remains plumb, and build up the course work around the former by one course.
- Insert a brick tie into the former, rotate it by 90°, and bed it into mortar on both inner and outer courses.
- Continue to build the coursework up around the frame in the normal manner, ensuring that the frame remains plumb. Brick ties should be inserted every third outer course and every other inner course (a minimum of three per vertical).
- Build the inner and outer courses up to the lintel height. The lintel should be set 5mm over the former. Locate the lintel in position and bed it into mortar. Allow the mortar to set before removing the props and brace.
Mumford & Wood's Cavity Formers
The benefit of our cavity formers is the quick lead time from order to delivery, enabling openings to be quickly and accurately formed on-site. This then allows the scheduling of external joinery to be taken off the critical path. Windows and Doors can be ordered quickly, knowing they will fit precisely into the pre-formed openings. There’s no need to wait for the openings to be built, measured, and then ordered, potentially saving weeks on site.
The standard cavity former order process is incredibly straightforward. Just specify the cavity size and whether it is ‘in-line’ (brick and block lining through) or ‘in-check’ (set behind the face brickwork).
Important Note
The closure frame must be periodically checked throughout the building operation to ensure it remains true and square. Any movement or twisting in the frame could result in a poor Window fit. We recommend using tape and a spirit level to ensure the frame is correctly installed.
Looking for a Trusted Partner?
If you’re looking for a leading partner for your next building or construction project, Mumford & Wood has got you covered with high-performing timber Windows and Doors that stand the test of time. We take great pride in working with homeowners, developers, architects and builders nationwide to provide beautifully crafted windows and doors that boast an array of benefits and features.
For further information on our range of products, download the Mumford & Wood brochure or request a physical copy online. Additionally, you can view our range up close by visiting us at our showroom or requesting a factory tour!
