Roof Gutters

Of the membrane roofing work Scie Construction Ltd undertake in each year, approx. 20% of our work is lining or relining large internal roof gutters. Some of these are as part of a flat roof system, otherwise as part of a metal roofing system, mostly on commercial buildings such as warehouses, factories and schools.

Internal roof gutters handle approx 95% of the water which falls on a buildings roof area, the other 5% evaporates very quickly from the roof surface after rain, especially on Mineral surfaced roofing systems.

It is therefore critical for trouble free operation that; the roof gutters are built with adequate falls,  the gutter membrane has perfect joints and that they are cleaned out as part of a regular maintenance program.

In NZ the standard gutter lining for the last 20 years has been butyl rubber, which is very easy to lay in long lengths. The biggest cause of failure, that we have seen over the years in these linings, is the breakdown of the few joints which may be required and the finish of the outlets. In every case the failure of a joint has led to major water leakage into the building below.

Other types of lining may include Nuralite or Zinc. Same problem.

We have been using Torchon membranes for lining roof gutters for many years without any problems, mainly due to the perfect bonding between the overlapping joints, bitumen to bitumen, welded by hot air or flame torch method.

There has been is a tendancy to avoid flame applied membranes for gutters, mainly for the obvious reason of risk of fire during the application. For this reason these membranes are not suitable for every situation, and due care does always have to be taken, especially when working near metal roofs with flammable building paper underlays.

In new work, Torchon membranes do not pose such a fire risk, as they are applied before the metal roofing is fixed, and although the Torchon membranes cannot be laid in lengths of more than 3 metres at a time without the risk of poor overall contact adhesion between the membrane and the substrate,  the perfect bonding of the joints and the heavy thickness of the membrane (usually 3mm) compensates for this in the long term.

It is possible in new work to pre plan the joint layout and chisel / router out the width of the overlapping sheet joint and dress the edges of one end of the sheet membrane into the groove/channel and overlap the next sheet over, thus providing a level overall run for the waterflow to the outlet.