With SkanDek’s roofing elements, skylights can be placed nearly anywhere as long as the main support beams bearing capacity is not compromised. Maximum width is typically 1500mm. The ends of the skylight apertures are closed off with framing bulkheads of galvanized steel. In cases where the aperture is smaller than that of beam span, extra supportis placed between the skylight transverse reinforcements, though to a maximum length of 3000mm.
SkanDek’s roofing elements consist of few load bearing rafters (box beams) making installation of large or wide skylights in existing constructions matter of course. The skylights are, as usual, mounted on the outside of the steel roofing elements according to the manufacturers specifications.
The normal number of beams in a roof box section is 3 – 4 beams, however, in constructions of larger width combined with greater load or distortion requirements, up to 8 beams can be installed. The main body of the SkanDek beam is 250mm, whilst the overall width is 294mm because of the two clinched edges on each side of the beam, which acts as a joint for the top and bottom flanges of the SkanDek beam, this is normally made up of a 22mm secondary space board screwed onto the casing. The factory installs damp course, laid under the roof membrane, as a temporary measure under transport and installation procedures. The damp course can later be cut as required and re-sealed to the architects or manufacturers specifications. The skylight can also be delivered with painted finishing panels for the aperture.
Above: Typical installation of a skylight between two SkanDek beams. In this illustration the light panel dimension is 24mm smaller than the aperture as finishing panels of 12mm are installed on both sides. Space blocking boards of 22mm can also be seen for the clinch curbing.
Below:Cross section of roof elements with 3 and 4 beams respectively. Note the curbing rafter against the roofing elements and stabilizing wall
Checklist for planning skylight projects
As a useful aid, we have compiled a list of items which should be taken into account whilst drawing and planning skylight installation
- Calculate the necessary area for smoke ventilation (fire vents) and luminosity, sketch these requirements on the plan blueprints. Distance between fire sections should also be considered.
- Coordinate placement and size of the skylights with the consulting engineer undertaking the statical analysis of the roofs in-plane actions (diaphragm action), with regards to the norms for steel construction EN1993/Eurocode 3, as well as light gauge sheet metal norms DS 446.2000. It is important that the skylights do not obstruct the in-plane action of the roof.
- Sketch the coupling details between the SkanDek elements and the skylights so that the aperture measurements of the roof boxing units coincide with the aperture panel and frame measurements
- Coordinate the final positioning of the skylight units with SkanDek regarding roof elements geometry and modular width.
Links and downloads:
- Download skylight details as PDF or DWG.
- Skylight and in-plane action in light gauge sheet metal constructions.
- SBI (government building research institute) specifications paragraph 5.5.2regarding angular flame spread and eve-end and rafter tail fire proofing
- With regard to smoke vent dimensions we advise referral to DS428 and the Enterprise and construction authority.