A low pitch roof system will often require internal gutters or a gutter under a parapet that will be lined with a membrane to fulfil weathertightness and building code requirements.

The position and selection of outlets and penetrations in the gutter takes some investigation, and can have an effect on things such as location and interaction of downpipes and overflows once they enter the building envelope, or pass through the parapet to atmosphere or a rain water head.

Once the roof drainage design and downpipe size has been selected the consideration toward outlet specification will be required. Bronze or PVC base? Stainless steel, bronze or ABS plastic for the ring and grate?

A bronze outlet will always be seen as the premium componentry for securing the penetration of the membrane. The CNC machined bases and fixings provide superior durability, great adhesion properties for the membrane and provide a classic aesthetic to visible installs.

If you are considering where your products come from and the manufacturing process that goes into them, the Sureflow and Vinylrite roof system cannot be overlooked. Made in Auckland at a family owned business that is utilising the latest moulding methods including recycled materials and up to 50% of self sourced solar energy to produce the fittings cannot be ignored. Not to mention compared to overseas manufacturing which adds carbon miles to get pre-made products to site.

The PVC based systems manufactured by Allproof Industries are at the leading edge of solution-based design. Vertical or 90 degree outlets will help with the interaction of the downpipe with structure and other mechanical services inside the building envelope. A 90-degree outlet will allow the downpipe the least possible invert (fall) along the run that the engineer may thank you for going forward.

The PVC bases have been tested and approved for use with all membrane systems, adhesive, heat applied and asphalt based product can all be laid into the Sureflow base.

Recent feedback from site that Allproof received was that the longrun roofing running into the channel was spilling into the overflow outlet causing the soffit penetration to weep onto the entrance patio below. To counter this, Allproof can now supply all overflow outlets with a one piece fabricated stainless steel overflow with integrated cowl to protect the penetration from atmospheric rain, or spillage from roofing run off. This cowl, or hat, acts like an umbrella to protect the penetration from above while allowing the overflow to activate via perforations in the side of the riser. Another example of this company working with industry to make things better.

The sole purpose of an overflow is to provide “early, conspicuous warning to the building occupier that maintenance is required” (E1 Surface water Chapter 5.5) so therefore these must be tracked outside the building to atmosphere and not connected to the downpipe system. To cover the visible outlet, Allproof’s soffit overflow cover in stainless steel, or now PVC can be bought through the building wrap and past the cladding with confidence as the whole system is glued removing any risks of water weeping.

So when thinking of the roof outlet, the full system from design to manufacture must be considered for the best solution that works alongside other building elements, is functional and also aesthetically pleasing