According to the international building code the typical built up flat roof that uses tar or asphalt goes by the guideline that for every foot 12 inches of a flat roof a minimum of inch must step up or down.
Positive pitched flat roof.
Pros of a pitched roof extension.
One of the biggest factors when deciding between a pitched roof extension and a flat roof extension is cost.
It is a significant renovation if you are converting from flat to pitched.
Flat roofs require constant maintenance of their drainage systems to avoid leaking.
The materials used are generally more weather resistant and durable though with more robust materials being introduced into the flat roofing market this gap is starting to close.
This is a generalization that depends a great deal on the type of roofing material you install but is a good guiding principal.
Pros of a pitched roof.
A pitched roof is more expensive.
A 900 square foot flat roof in the san francisco area made of concrete tiles costs.
The pitched roof makes it easier to reuse rainwater than flat roofs.
This is especially true is the roof is covered in high quality natural slate with a lifespan of over 100 years and no need for any maintenance.
Pitched roof extensions typically cost more simply because they involve more work and take longer to complete.
Anything pitched 3 and 12 or less is considered a low sloped roof.
If you have a high rise building converting your flat roof to a pitched one may not be applicable.
To get rid of ponding water problems.
Flat roofs also don t last as long.
This is the basis for calculating the angle which is approximately a 1 19 degree slope.
While pitched roofs are more expensive cheaper and less frequent repairs compensates for this.
Flat roofing systems come with benefits and drawbacks.
It was all done by me and a carpenter friend who did the fram.
According to improve net s online roofing calculator a flat roof is significantly cheaper than a pitched roof.
Pitched roof extensions afford a more traditional look and that means they blend in better with the style of many houses.
However flat roofs require much more aggressive and consistent maintenance than a pitched roof.
This shows how my flat asphalt roof was dug up and converted to a tiled pitched sloping roof.
When we roof a flat or low slope roof we use a membrane system to cover it.
When it comes to the disadvantages some property owners are being pestered by leaks.
Pitched roofs are anything 4 and 12 or above.
This is a factor that planning departments tend to look on favourably.
Unlike sloped roofs flat roofs are susceptible to ponding water.
Pitched roofs are generally less expensive to install and last longer than low slope roofs.
This is because shingle systems are easier to install than membrane systems and shingles cost less.