EPDM under tiles

A step-by-step guide to sealing your EPDM under tiles when your flat roof meets a pitched roof.

We cover some of the preparation of this area in more detail Flat Roof Preparation Advice. Be sure to check it out.

Note, if there is a vertical before the EPDM meets your tiles (such as a course of bricks). You will need to bond to this first, see EPDM to verticals.

Step 1: Carefully remove the tiles & batons, enough to expose 30cm in vertical height above your roof deck. Place these to one side, ensuring no nails damage your EPDM.

If the base of a β€˜gable-end’ or valley also meet your flat roof, you may need to carefully remove some cement in order to dress the EPDM underneath this area. This will need recementing later.

Bonus tip: If you are moving multiple battens, slates or rosemary tiles, it may be worthwhile noting the spacing or location, ready for refitting.

Step 2: Gently fold back the pitched roofing membrane, you can lip it under the tiles held above hold it, out the way.

You will likely need to clean this area as there will be a natural build-up of debris from over the years.

Step 3: If these is no lay-board already there, you will need to install some. Lay-board is a layer of timber, typically 11mm OSB or plyboard, which you secure to the base of the rafters, approx. 200mm-250mm width. Your EPDM will be bonded to this to ensure it doesn’t sag between rafters, allowing ingress.

Ensure lay-board joints meet on a rafter.

Step 4: Using a tape measure and chalk/crayon, measure the amount of EPDM which will be bonded to your lay-board then mark this depth on your rubber.

Using your Firestone Elevate Bonding Adhesive, spray an even coverage to the EPDM within your chalked area, as well as onto your layboard.

Step 5: Once touch-dry, mate the two together, starting at the centre and bottom of the join, smoothly working up and outwards. Don’t stretch the EPDM. Work in with your Silicon Rubber Roller.

If your EPDM meets a valley, your EPDM will need to be dressed under the lead or fibreglass valley tray also, as well as under your cement soffit board on a 'gable-end'.

Step 6: Carefully resecure the battens & refit the tiles. 

If you removed any cement, you will need to redo this, using a 3:1 mix of sand & cement, pointing to a neat finish, paying attention to the correct colour mix if visible.