EPDM Through Wall Outlet

A step-by-step guide to when your rainwater exits through a wall via an outlet.

Firstly, the size options for your through wall outlet are 100mm, or 150mm. Where possible, plan your outlet hole size to be very slightly larger than the most suitable one for your project. This will allow a neater finish to the exterior of your wall, also reducing the cavity space around the through pipe.

Secondly, & similarly to β€˜Set-up tip 1’ in EPDM Internal drain. The thickness of your through wall outlet & subsequent flashing will cause a natural β€˜hump’ or β€˜kick’ on your deck, which even with a good fall, can cause a small amount of water ponding (won’t leak if installed correctly).

Where possible, our team use 11mm OSB (instead of 18mm OSB) on the area to be flashed, and chamfer the change in timber height. This way, once you have fitted & flashed your outlet, there is no (or less) kick for better water dispersal.

Step 1: Ensure your EPDM is bonded to your timber decking, & to your vertical wall first. Then cut out the through hole. 

Ensure area is clean & dry.

You can see Laying your EPDM & Bonding your EPDM to Verticals for some more guidance.

Step 2: Apply a continuous bead of Bond & Seal to the back face of the through wall outlet, at least 20mm from the edge. Carefully slide the outlet into the opening, compressing the sealant. Ensure there is no excess sealant.

Step 3: Using your washers & fasteners, secure the outlet in place.

Step 4: You now need to flash your outlet. Your Quickseam flashing must overlap onto your EPDM at least 75mm all the way around the outlet. Cut a piece of flashing to size for this purpose. 18’’ Quick Seam Form Flash will be suitable for this.

If you need to flash your outlet in 2 or more pieces, be sure to allow 75mm overlap onto adjoining flashing pieces.

Step 5: Using your Quickscrub pad and holder, apply an even coverage of your Quickprimer plus to the face of your outlet, & around 85mm past & onto your EPDM. (allows a 10mm buffer around your 75mm flashing overlap).

Step 6: Once touch-dry & tacky, carefully apply your flashing, starting at the deck, working towards & up the wall, smoother out as you peel & go. Work in with your Silicone Rubber Roller & Penny Roller.

Step 7: Neatly cut out the through hole & place into position your Leaf Guard.

As an extra precaution, you can apply a bead of Lap Sealant to the exposed edges of your flashing. Be sure to not apply an unnecessarily thick bead, causing pooling water.