When constructing a canopy over a front door, it is important that thought is given to how it will be supported. It is important that all timber used in a canopy is treated with preservative. Ensure that timber is treated with two heavy coats of preservative.
Canopies can either be cantilever supported, supported by struts, or supported by full-height posts. The aforementioned methods apply to simple canopies of simple construction. Fixing for more complex and larger canopies should be detailed by an engineer who is qualified by examination, in private practice, and possesses professional indemnity insurance.
Diagram D70 - Typical configurations for canopies
Diagram D71 - Canopy support to external wall with floor joists
With a cantilever canopy, the canopy is fixed to the wall and supported by the first floor joists as shown above. This method can be used for both hollow block and cavity wall construction. The method can only be used when the floor joists are perpendicular to the external wall.
It is also possible to secure a cantilever canopy by using galvanised straps that are a minimum of 30 mm x 2.5 mm x 800 mm to securely fix the rafters to the wall plate at every rafter location as detailed in the diagram below.
Diagram D71(a) - Self supporting canopy detail
Fix straps such that the 600 mm minimum length of the strap is fixed to the slope of the rafter. Fix the wall plate through the external wall by means of at least 4 stainless steel bolts/threaded bars of minimum diameter 12 mm. This method can be used for both cavity wall and hollow blockwork construction.
When using this fixing method for canopies the back plate can be located on the inside face of the outer leaf of the masonry.
If brackets containing struts are used to support the canopy, ensure that the strut is fixed using appropriate stainless steel fixings with each fixing terminating at a back plate.
Diagram D72 - Typical fixing details for canopies
The diagram above shows a typical detail for bracket support. It should be noted that these details also apply to hollow blockwork construction.