Walk On Glass Rooflight
The Duplus walk on flat glass rooflight is designed to be flush with surrounding flooring, typically on roof terraces with decking (see indicative drawing below). As with all Duplus rooflights an upstand is required for this product, the rooflight should be fitted first with the decking completed around the rooflight in order to achieve a flush finish. With a walk on product it is essential that the correct loading standards are considered and imperative that products are fully backed up with structural calculations to prove that they are safe to use. With this in mind and following extensive structural glass calculations we utilise a minimum walk on glass thickness of 25.5mm toughened laminated glass for our smaller rooflights and 31.5mm – 33.5mm for our larger rooflights.
Diagram above shows typical walk on glass rooflight installation with decking either side
Building Regulations and Applicable standards
In order to calculate the thickness of the glass for our range of walk on rooflights, we have considered the requirements of the Building Regulations which in respect to the amount of load the glass is required to withstand, require compliance with the imposed loads set out in Eurocodes BS EN 1991.
BS EN 1991-1-1:2002 places the use of buildings, for example, residential, social or commercial properties into different Categories with different uses within those buildings placed into further Sub-categories.
Duplus stock walk on Rooflights have been designed to meet the imposed load requirements of BS EN 1991 Subcategories A1, A2, A3 and A5 meaning that they are capable of withstanding a uniform distributed load (UDL) of 1.5kN/m2 to 2.5kN/m2 and a concentrated load of 2.0kN and as such are suitable for use in in the following applications:-
All usages within self-contained dwelling units ( a unit occupied by a single family or a modular student accommodation unit with a secure door and comprising not more than six single bedrooms and an internal corridor) – Minimum UDL requirement 1.5 kNm/2, Concentrated 2.0 kN
Balconies in single family dwelling units and communal areas in blocks of flats (with not more than four self-contained dwelling units per floor accessible from one staircase) – Minimum UDL requirement 2.5 kNm/2, Concentrated 2.0 kN
Communal areas, including kitchens, in blocks of flats (not more than three storeys in height and with not more than four self-contained dwelling units per floor accessible from one staircase) – Minimum UDL requirement 1.5 kNm/2, Concentrated 2.0 kN
Bedrooms and dormitories (except those in hotels and motels) – Minimum UDL requirement 1.5 kNm/2, Concentrated 2.0 kN
Please ensure before purchasing your Duplus glass walk on rooflight that the project you are intending to use our product in, falls into one of the sub-categories listed above.
For projects started after the 1st October 2013 the loads listed above are the minimum level permissible under the Building Regulations. Lower imposed loadings were given in the now withdrawn standard BS6399-1:1996. However, these loads now only apply to projects which began on site or were subject to a building notice, full planning application or initial notice submitted before 1st October 2013. For new projects started after 1st October 2013, walk on rooflights stating only compliance to the lower loads defined by BS6399 ( 1.5KN per square metre and 1.4KN concentrated load ) should be avoided.
All Duplus walk on glass rooflights incorporate double glazed units with a centre pane u value of 1.2 W/m2k. Our products overall true U value and Ud values are available upon request.
Duplus walk on glass roof lights have been designed such that no unexpected stresses will be seen by the double glazed unit spacer bar or the inner pane of glass, no loads are transferred to the inner pane of glass.
Independent glass consultants have undertaken extensive finite elemental analysis on our behalf in order to determine the actual stress and deflection of various thicknesses of glass across our product size range.
Diagram above shows typical stress and deflection structural calculation results using finite element analysis
From these calculations and as you might expect, as the size of walk on rooflight increases, so does the thickness of the glass you will be walking on.
Our smallest walk on rooflights are manufactured using a 25.5mm toughened laminated outer pane of glass, however in the main, our walk on products utilise a 31.5mm or 33mm toughened laminated outer pane.
Surface roughness and safety
It is most desirable for glass used as a floor panel to remain dry and to ensure as far as is reasonably possible that the soles and heals of all shoes will be dry by the time they come into contact with the glass. In order to aid slip resistance, Duplus walk on glass rooflights are available with either a Sandblast external decorative finish or our Avant Garde finish at an additional cost, both finishes meet BS7976-2, details are given below.
Duplus Sandblast finish BS7976-2 Av.DRY 65 Av. WET59
Duplus Avant Garde Finish BS7976-2 Av. DRY 72 Av.WET 61
It should be borne in mind that it is never feasible to ensure that glass will not break under sufficient abuse. Any damaged glass should be replaced immediately and the walk on unit should not be used in the meantime. When activities are to take place where damage to the glass can be foreseen, the glass should be protected.