Flat roofs can be finished in different ways depending on the termination type. Trims can be useful in helping to complete this detailing.
How do you fix the edges of an EPDM flat roof?
How you fix the edges of an EPDM roof will depend on the type of termination you have. Typically, there are 4 types or termination on a flat roof; under tiles, at a parapet, up a wall and a standard drop-down perimeter.
Where a rubber roof meets tiles, you would not normally use a trim, but remove the bottom few rows of tiles, fix the EPDM in place and refit the tiles over the top. If you have a parapet, the rubber would run up the wall and be sandwiched under the capping stones. Where the flat roof meets the wall of the building, the rubber would run up the wall by around 150mm up, and be finished with a cover piece, either trim or lead flashing. The drop-down outer perimeter of a roof is where it is best to use trim to tidy and protect the EPDM.
Why trim the edges of an EPDM flat roof?
Using a roof trim to complete your EPDM roof has several benefits.
- If you use the correct rubber roof trims, they can help to direct water landing on your roof (rain) in the right direction, so you don’t get puddling or overflows.
- The trim provides a clean, smart finish to the edge of your roof similar to a facia board on a traditional roof. From ground level, this trim is what you will see rather than the EPDM on the roof.
- EPDM roof trims help to stop water from getting behind the rubber and causing issues with your roof.
- Trims are a good way to hide any cut edges or folds in the EPDM roof.
EPDM roof trim materials
There are two main types of rubber roof trim:
- Metal roof trim: Metal roof trims are the cheaper option. They are usually formed in metal and plastisol coated both to protect the metal and to provide a better aesthetic. Metal roof trims are usually pretty simple, require drilling for fixing holes on site and may need additional work doing to the roof prior to the EPDM being installed to make them work (e.g. for kerb edges). Metal trims are very easy to use and can be cut using snips to bend them around corners. Their slim profile makes metal trim especially useful when finishing your rubber roof up a wall.
- Plastic roof trim: Plastic roof trims are the more expensive and higher quality option. These trims are specially designed for either kerb edges or drip edges, and often have a range of corners, clips and matching pins to complete the installation. The quality of these trims varies between manufacturers, the best roof trims come predrilled with fixing holes, are of solid construction (usually thicker in profile rather than a thin piece of plastic), have foam sealing tape pre-attached and are supplied with all the fixings required. Once installed, plastic roof trims provide a smart, clean finish to your EPDM.
Which type of EPDM roof trim do I need?
- Kerb edge: Kerb edge trim is for the outer perimeter of your roof where you don’t want the water to overflow, but to be pushed back onto the roof. Plastic roof trims are designed with an integrated upstand to achieve this. Metal roof trims are the same for both kerb edges and drip edges. To use these as a kerb edge trim, you would need to fix a tanalised batten around the perimeter of your roof and fit the rubber up and over this to create an upstand.
- Drip edge: Drip edge trim is for the outer perimeter of your rubber roof where you want the water to flow over into the gutter. Plastic roof trims usually come as a two-part system with a backplate and front facia. The EPDM rubber is sandwiched between these pieces to provide a watertight seal. Metal trims are fitted to the edge of the roof, over the EPDM. Any water will flow over the top of the trim and into the gutter.
- Wall trim: Wall trim is usually made of metal and is designed to provide a protective finish where the EPDM roof membrane is finishing part way up a wall. A channel is chased out of the wall and the trim inserted to create a cover over the cut top edge of the EPDM. This trim is used in conjunction with flashing tape and lap sealant to ensure a watertight seal.