When you are looking to build a polycarbonate or glass Lean To roof you have two main choices when you are looking for the Glazing bars.
Glazing bars fall into two main categories. These being rafter supported glazing bars or Self supported glazing bars.
These terms refer to how the bar is supported which is then essentially how your glazing material is supported.
Rafter Glazing Bars
Rafter supported glazing bars are generally used on timber frameworks or rafters. These wooden rafters will fall from the higher to the lower part of the roof. Rafters create the structural strength of the roof and support the glazing you have chosen. Rafter glazing bars screw down into these wooden rafters along its length at regular centres.
The glazing bar has no inherent structural strength of its own and has two main purposes:
1. To securely fix the glazing material to the rafter
2. To provide a water tight seal to your roof
These glazing bars generally have a snap down PVC cap or a screw down aluminium one.
They are more cost effective than self supporting glazing bars but you have to factor in the extra time and expense in creating the wooden support framework.
Self support glazing bars
These bars are structural in their own right and do not need rafters along their length. They are generally fixed at the top and bottom of the bar.
When using self supporting bars you need to take into account what centres you can have between them. The bigger the projection of your roof, the narrower these centres become in order that the structural strength is maintained. All self supporting roofs will have a spanning table or ‘bar snow loading’ table that shows you how far apart your bars can be over different projections. You will also need to take into account the glazing material you are using e.g polycarbonate or glass.
These self supporting glazing bars have a bigger and stronger aluminium core which allows them to achieve set spans without the need for support. This makes them a cost more than rafter bars but there is much less work needed on site.
Self support bars have three main purposes:
1. They are the structural beams that support your glazing
2. They hold the glazing material in place
3. They provide a water tight seal to your roof
These bars generally have a knock down PVC cap which secures the glass or polycarbonate sheets. They also often have a PVC underclad to finish off the bar aesthetically underneath.
If you need further advice which Glazing bars to use on your roof please give us a call on 01536 446395 and will be very happy to talk this through with you.