Laying your EPDM around obstacles & angles

Some tips when laying your EPDM in some atypical situations.

On occasions, laying your EPDM will not be straightforward. You may need to lay your EPDM around one or more skylights, pipes, vents, angle changes & more. Here are some tips on laying your EPDM in some more awkward situations.

Bonding your EPDM when you have skylights on your Flat Roof (or other large roof protrusions).

Step 1: To make your installation simple, do not fit the skylight kerbs until the EPDM membrane has been fitted. 

Instead, first fit some temporary boarding in your skylight openings (safe to walk on), flush with the main deck.

Step 2: You can then bond your EPDM in one piece as seen in Laying Your EPDM, taking care to not glue to the temporarily boarded area, or the area where the kerbs will secure to.

Once bonded, cut your EPDM as shown (right), by cutting from each corner towards the corner at a 45 degree angle, folding back ready to install your skylight kerbs.

You can now remove your temporary boarding. A seamless install with no seam joints!

Alternate Steps: If your skylight kerbs are already fitted, you must complete your installation differently. Unfortunately it is not as simple as β€˜lifting’ the laid out EPDM over them – this can cause creases which can be difficult get out.

Instead, you need to cut the EPDM & wrap around the skylight, or install in two pieces & seam together.

Step 1: Fold your EPDM back as you usually would, then adhere it to your deck with your water based deck adhesive, right up to your skylight kerb (or any roof protrusion). 

To make sure the EPDM is positioned correctly before bonding, you may need to measure your folded back section, & double check it will reach the roof perimeter with the required overhang.

Step 2: Mark out the skylight size on your folded back EPDM, with the correct length & width. Chalk straight lines from one corner to the other, making an X. 

Also mark from one of the two furthest corners (see image), in a straight line to the edge of your EPDM, as shown on the picture (right).

Then cut these lines.

Step 3: Now your EPDM is cut, you can fold it appropriately so that it can be wrapped around your skylight when ready to bond.

You can then bond the remaining EPDM to your decking, leaving the triangular cuts to bond up your skylight kerb (or any roof protrusion) as seen in Bonding Your EPDM to Walls & Verticals

Step 4: As you now have a cut in your EPDM, you will need to join this together once your EPDM is bonded to your deck.

You can't use you 3'' Seam Tape here, as there isn't any excess EPDM to overlap itself.

Instead, you must 5'' Flashing Tape. 

Use a straight edge & your chalk/crayon to mark a neat line, 75mm either side of your cut in the EPDM.

Note: You will flash the corner of your skylight where your cut begins from separately & after this stage.

Step 5: Using your Quickscrub Pad & Handle, apply an even layer of Quickprimer Plus, leaving no pooling.

Once touch dry, starting at one end, carefully mate your 5 inch Flashing Tape, peeling the tape as you go, as smoothing with your other hand.

Take care not to have air pockets. You can help this by keeping the flashing taut whilst applying but not stretching.

Pipes & other Vertical Protrusions:

When you have other vertical roof protrusions, your EPDM will need to bond to these also, unless you can install them after - therefore allowing your EPDM to be bonded in one piece as previously mentioned. 

Step 1: As before bond your EPDM all the way up to the pipe or protrusion.

Mark the area to be cut, as well as a line from the furthest edge, to the end of your EPDM.

Proceed to cut.

Step 2: Bond your EPDM around the protrusion as previously described & bond with your 5 inch Flashing Tape, also as previously mentioned.

You can also apply a continuous neat bead of Firestone Elevate Lap Sealant on all flashing edges to improve the seal, taking care to not have your bead too proud, creating a lip stopping water run-off.

See EPDM Pipe Sealing for tips on sealing around pipework.

If you have multiple Skylights, Vents or Pipes on your Flat Roof, you will need to plan multiple folds & cuts appropriately.

Alternatively, you can install your EPDM in two or more pieces, causing less cuts to fold around you roof protrusions. 

Be sure to allow an overlap of EPDM on each piece to allow you to bond the pieces together as seen in Bonding your EPDM with 3 inch Seam Tape.

Bonding your EPDM around corners, such as an L-Shape Roof.

if your L-shape reveal is relatively short, you can install your EPDM in one piece, allowing for some off-cut. Follow step 1 for this.

If your L-shape reveal is quite large or long, you should consider installing in 2 separate pieces, as the off-cut would be quite larger. Follow Step 2 for this.

Step 1: Bond your EPDM as previously outline, all the way up to the point where EPDM will then need to continue around the corner.

Then cut your EPDM from the corner, at a 45 degree angle back towards yourself.

You can then continue to Bond the EPDM to the remaining L-shape, & seal your External Corner if applicable.

Step 2: Install your EPDM in 2 pieces, one one the larger square or rectangular section, the other on the L-shape reveal.

Be sure to allow at least 100mm of overlap between the pieces of EPDM.

You will then need to seam the EPDM together as seen here