The traditional Bermuda Roof has been used as the preferred roofing system in Bermuda for nearly 400 years. In fact the first Bermuda Roof was installed on Carter House, St. George’s, Bermuda (see Bermuda Vernacular Architecture
) in 1640 (nearly 400 years ago) and the original roof is still intact today. How many roof products in Hurricane regions can make this claim? (see Bermuda’s Architecture
The Bermuda Roof has always been built over an open-batten structure (see photo) and material used has always been limestone cut into 18”x12”x1” slate. The slate is bedded in mortar and each row of slate overlaps the previous row by half (9”), therefore all the way up the roof there is approximately 3” of roof material.
Once installed the Bermuda Roof becomes a monolithic structure and as such there is nothing for the wind to grab onto.
Our manufacturer, Kaidisen
, does not take credit for developing the Bermuda Roof but does take credit with modernizing and improving the performance of a proven and time tested roof system. Kaidisen has replaced limestone with autoclaved aerated concrete (AAC) (click to see Wikipedia definition of AAC
) which is a man-made light weight, fire resistant material that has properties that are very similar to limestone.
The Kaidisen product has a significantly lighter installed weight (approx. 13lbs/ft2) compared to limestone (approx. 28lbs/ft2). The uplift threshold of the Kaidisen product, however, is superior to that of the limestone roofs due to the addition of a fastener (screw or PVC clip).
Hurricane Fabian, a Cat 3 Hurricane hit Bermuda on September 3, 2003, while there was some damage reported to the limestone roofs, there was NO UPLIFT reported on roofs built using the Kaidisen product.
After the Hurricane had cleared, Mr. Mark Bove, Senior Research Scientist - Meteorologist with Munich Re America Catastrophe Management went to Bermuda, surveyed the damage caused and prepared a Catastrophe Report
and in his report this is what he said regarding the Bermuda Roof:
“Homes in Bermuda performed very well during Hurricane Fabian, largely due to strict building codes and the unique method of constructing roofs on the island.”
“...the style of roof construction in Bermuda is probably the biggest reason why residential damage was minor.”
“Traditional Bermudian roofs, designed to catch rainwater for consumption, are usually hip roofs, one of the more wind-resistant roof styles. They are built with a framework of cedarwood beams and laths, which are covered by limestone tiles about 1 inch thick and 12 to 18 inches square, joined together by mortar. The tiles are then covered with cement coating, than whitewashed using lime or paint. This all results in a very strong, heavy and monolithic roof, sealed from the elements and difficult for wind to penetrate.”
Also see Roof damage by hurricane force winds in Bermuda authored by Mr. Mark Rowe of the Bermuda Department of Environmental Protection (click here
You can view Bermuda Roof installation details as aired on the television series This Old House in an episode entitled This Roof Resists Hurricanes, Collects Water