Building movement: Steel framed buildings

We have all stood on a roof of a steel framed building and thought… “This is moving” – even the action of surveying a roof, walking along its length, can make us aware of minute movement.

Typically, steel framed buildings are formed from heavy section steel portals bolted together with light weight steel cold formed purlins and rails to form bays usually between 6m and 7m centres. The steelwork design incorporates bracing beams and anti sag rods or bars to limit structural movement but in periods of high winds, snow and extreme weather, loads are created forcing twisting and lateral movement into the building. This stresses all the roofing and cladding and gutter components. Obviously the longer or higher the building, the greater the stresses induced.

Over time, the purlins spanning between portals supporting the roof covering tend to sag; this is especially visible at gutter level. Steel gutters are typically bolted together with a butyl or silicone seal between the joints at 3m centres. Therefore at least 1 gutter joint is in a location between portals.

Gravity outlets are usually installed adjacent to portal locations. This allows the downpipes to be secured to and be protected by the upright part of the steel frame. Inadequate falls and the sagging between the portals lead to poor drainage. Standing water tends to collect between drainage points and this effectively puts the gutter joints between portals under water promoting substrate failure.

Consider for the following factors:

Misaligned gutter sections, constant water, poorly installed flexible seals, steel corrosion, bolt corrosion, building movement inducing gutter joint stresses, freeze and thaw expansion. Factor in loadings caused by foot traffic during maintenance, or even lack of maintenance to the point where outlets are blocked, there’s additional debris and foliage growth and it becomes obvious why joints fail over time, leading to leaks.

It’s in response to the demands of this hostile environment that Sharmans designed its unique, BBA approved, 25 year guaranteed, seamless and non-bonded Plygene Gutterline system for gutter refurbishment.