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Orangery Roof Design
This article will seek to explain the differences between the three main types of orangery roof and the advantages and disadvantages of each. The options considered here are:
- Flat Roof
- Box Gutter
- Perimeter Gutter
Other types do exist, including the “mock orangery”, which is essentially a conservatory roof with a false ceiling. Our preferred method is the “Flat Roof” as shown below. These are illustrated with a traditional timber orangery, but the same principles apply for modern aluminium styles.
Flat roof
Advantages
- Most visually attractive
- Most reliable
- Most durable
- Ability to walk on flat roof area
- Any size lantern can be fitted
- Possibility of multiple lanterns
Disadvantages
- Minimal falls must be used, some standing water possible. Not a technical problem, but potentially a psychological issue.
- Time consuming and costly to construct
Falls
Whilst described as a “flat roof”, there will be falls as shown in the diagram below.
On this type of roof, the slope of the roof is hidden behind the fascia, this means we have very little height in which to achieve the falls.
Normally it’s not desirable or possible to have too many outlets and downpipes, so often the water has a long way to travel. The recommended falls are between 1 in 40 and 1 in 80 and we lay the roof deck on pre-made firring timbers which are within this range.
The outlets need to be sited on a flat section of roof and this is often at the convergence of different planes which complicates matters further. This is the area where water is most likely to pool, however it can occur anywhere particularly on larger orangeries with fewer outlets.
We use a Sarnafil single-ply roofing membrane, click here for more information, which is unaffected by standing water.
Box Gutter
Advantages
- Potentially cheaper
- Potentially quicker to install
Disadvantages
- Not able to walk on roof
- Joints in box gutter not most reliable
- No choice of lantern size
- Box gutter is totally level, i.e. no falls. Not a technical problem, but potentially a psychological issue
- Requires frequent cleaning
Falls
A box gutter is level, with no falls.
Whilst some box gutters can be laid to falls, those used on most orangeries or conservatories are not. This in itself is not a problem, but the main disadvantages of the box gutter are listed above.
Perimeter Gutter
Advantages
- Most effective drainage
- Ability to walk on flat roof area
- Any size lantern can be fitted
- Possibility of multiple lanterns
Disadvantages
- Arguably least visually attractive option
- Aluminium gutter joints less reliable and durable than flat roof material
- Requires frequent cleaning
Falls
An orangery with a perimeter provides for optimum rainwater dispersal
With a perimeter gutter the water is readily moved across a short area to the gutter. We would use an aluminium gutter with internal fixings so that a decorative timber moulding can be fitted below. Seamless aluminium gutters don’t really stand up to close scrutiny when used at low-level, so we use a sectional system which is visually attractive.
Being “sectional” it does have joints which are a weak point. Whilst these joints are external to the building, any leakage through them would adversely affect the decorative mouldings below over the long term.
The overriding factor is the aesthetics, and we’ve found that the vast majority of clients prefer the “flat roof” orangery with the fascia that hides the flat roof.