Updated: Dec 6, 2022
Thatching is building a roof with dry vegetation and it is one of the oldest roofing techniques in existence. Its history goes back hundreds of years on the European and Asian Continents, and America's first settlers lived under thatched roofing as well. A variety of grass like vegetation can be used for thatching such as water reed, straw, sedge etc. Palm leaves are also a popular thatching material in tropical climates.
A well-maintained thatched roof will easily last 50 years and more with proper care. It is a very effective weatherproof coating, and an excellent thermal and acoustic insulator; its eaves will shed rainwater without the need for gutters.
Thatch is a sustainable material, which has little impact on the environment throughout its life cycle. Requires no mechanical processing and can be fixed using hand tools. At the end of its life, it can be composted and returned to the land.
The average depth of a water reed thatch is between 30-35 centimeters, or 11-13 inches, and weighs about 34kg/sq.m. or 7lbs/sq.ft., compared to slate and conventional asphalt shingle roofing, thatched roofing is lighter but sheds water and snow just as effectively and absorbs very little moisture.
Thatch is not as flammable as many people believe. Due to its tight construction, it burns slowly, like a "closed book". Its flammability can be further reduced with modern fire retardant treatments, making it comparable to conventional roofing.
The U-value for a thatch at this depth is about 0.22W/(m2K), some sort of insulation under the thatch is required in most states to meet building regulations. Roof pitch should be at least 45 degrees, but 50 degrees and above should be achieved where possible.
A thatched roof can help in attaining LEED Certification as it is 100% compostable.
Although they are rare in North America, and outlawed in a few states, a small number of homes with a thatched roof can be found in New York, New Jersey and Connecticut,
If you are considering a property with a thatched roof, remember to NEVER attempt to walk on it. Inspecting a thatched roof is best left for the professionals.