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Photograph of  really worn out asphalt roof shinglesThatch Roof Types, Inspection, Maintenance Guide

  • THATCH ROOFING - CONTENTS: Thatch roof inspection, failures, repairs. Brief history of types of thatch roofing. Books & Articles on Thatch Roof installation, repair, history, & archaeology. Contemporary thatch roofing designs, products, product sources.
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Thatched roofing guide:

This article describes types of thatch roofing used on buildings, with a brief history of thatch and a focus on contemporary use of this roofing method. Thatch roofing is not only a very old and well established (though high labor) roof covering method used in many parts of the world, it is also used on a wider variety of types of buildings than you might expect.

Our page top photo illustrates a palapa roof beneath which the author both hosted visitors and slept in Mexico in 1976. In the article below we illustrate types of thatch roofing from around the world.

Thatch roofing is still in active use in many countries making use of local grasses, hemp, straw, palms, or other materials as well as using synthetic thatch made from a variety of materials including recycled waste plastic materials. This website provides un-biased articles about many common roofing materials, installations, inspection, defects, roofing repairs, and products.



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Thatch Roofing Installation, Properties, Fire Safety, Maintenance, Research

Thatch roofed home in Wolvercote, England, U.K. (C) Daniel Friedman

[Click to enlarge any image]

At above is a thatched roof home in Wolvercote, Oxford, England, U.K. The Wolvercote thatch roof is covered with netting, most likely to make the thatch roof less inviting as living space for birds or other pests.

Kon Tiki Raft Roof (C) Daniel Friedman

At above right is the a palm leaf thatched roof used on the shelter mounted on Thor Heyerdahl's 1947 Kon Tiki Raft. (The Kon Tiki and its shelter are preserved at the Kon Tiki museum in Oslo, Norway.) At below left is a thatch roofed windmill in Holland showing thatch used on a very steep sloped roof surface.

Thatch roofed windmill, Holland

Article Contents:

Traditional thatch roofing was constructed of straw, combed wheat, longstraw, broom, sod, and water reed (Phragmites australis). But other plant materials have been used depending on what was readily available in various parts of the world, including palm leaves and plant fragments. Thatched roofs were typically installed on steep sloped roof structures in order to shed water rapidly (rather than absorbing it).

Life Expectancy of Thatch Roofs

Our photos (below) show the exterior and also the interior structure a traditional Mexican thatch roof used at the visitors' center of el Charco, an environmental park in San Miguel de Allende, Guanajuato, Mexico (2004). The interior photo (below right) shows how the thatch roof skylight window was constructed. A close up of this window seen from outside is provided below in this article.

Thatch roof el Charco, San Miguel de Allende Mexico (C) Daniel Friedman

Water reed thatched roofing can last up to 50 years. Combed wheat reed typically has a life expectancy of 25 - 35 years, and long straw 15 - 25 years. For all of these traditional thatch roof types, re-ridging is needed about every 10 - 15 years.

Thatch roof el Charco, San Miguel de Allende Mexico (C) Daniel Friedman

The life of a thatch roof varies considerably depending on the roof slope (shallower or lower pitch thatched roofs are more likely to leak, absorb water, and have a short life), and on the geographic area where the roofed building is located. The typical slope of a thatched roof structure is 50 degrees. But as we explain next, the slope of the roof structure is not the same as the slope of the thatch itself.

The life of a thatch roof is also significantly affected by the thickness of the thatch, since a thicker thatch results in a less-steep angle of the individual reeds or straws. A less steep reed or straw angle results in a shorter roof life. A 9-15" thickness is recommended for a water reed thatch roof and a 9-12" thatch is recommended for wheat reed and longstraw thatches.

Insulating Value of Thatched Roofs

Insulating Value of Thatched Roofs is generally about R-11 for a typical 9-12" thick thatch. The Dorset Building Control Technical Committee (cited below) notes the following U values for Reed and Straw thatch:

In order to achieve a ‘U’ value of 0.2w/m2K for thatched roofs, the following was taken from CIBSE Guide A3:

Reed = thermal conductivity 0.09 and a resistivity of 11.1

Straw = thermal conductivity 0.07 and a resistivity of 14.3

This gives a ‘U’ value of 0.2/m2K for 450mm of reed and 350mm of straw. On this basis ceilings may require additional insulation. - op cit.

Example of Traditional Method for Preparing Palm Thatch

Palm thatch roof in La Manzanilla, Mexico (C) Daniel Friedman 2011 Palm thatch roof in La Manzanilla, Mexico (C) Daniel Friedman 2011

Above and below we illustrate palm thatch roofing in current use in La Manzanilla on the Pacific coast of Mexico. Local owners told me that the life of a palm thatch roof may be as short as five years. Individual palm leaves used in thatching at Barra de Potosi cost about 5 pesos which may sound inexpensive, but thousands of palm leaves may be required for a larger roof, and that is of course a cost before labor is added.

Palm thatch roof in La Manzanilla, Mexico (C) Daniel Friedman 2011

The preparation of roof thatching material varies considerably around the world depending on the plant used for thatching. Our example below quotes drawings and text from US Patent US7900415 B2 by original inventors Carlos Armando and Azcué García whose patent application for a procedure to produce (synthetic) palm roof tiles for rustic roofs includes twenty illustrations of the traditional thatch preparation methods described just below. The patent citation is given in detail below.

Quoting from the Armando Garcia patent:

[Click to enlarge any image]

Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2

Comments from the cited patent explain the use of the palm to produce thatch for a Mexican type palapa.

FIGS. 1 to 6 correspond to the plant called Brahea dulcis, which has simple leaves like a fan, green in the fascicle and pale in the back, divided into 40 to 60 segments that measure 40 to 50 cm in length; the leaves 1 are concentrated in the top end of the stem and going down there are some fallen leaves 1. The leaves have marginal teeth 2 2.4 cm in length; the palm leaf presents hanging inflorescence in a raceme shape, which are 1 to 3 m in length.

Brahea dulcis is the most abundant species of the Arecaceae family and can be found in many calcareous soils located from 900 to 1900 m above sea level. Popular names include “hat palm”, “sweet palm”, “fan palm”, “common palm”, “apache palm”, “pochitla palm”, and “soyal” or “soyate”.

When the leaves 4 are ripe they have a fan shape and after they are cut they shrink.

To avoid shrinking a stone or other heavy object 5 is put on them.

FIG. 1 is a conventional inferior view of a palm plant B. dulcis with some inferior leaves fallen.

FIG. 2 is a conventional superior view of the plant shown in FIG. 1.

FIG. 3 is a view of plant B. dulcis showing hanging inflorescence in a raceme shape.

Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2

FIG. 4 shows a ripe palm leaf in a fan shape.

FIG. 5 shows a palm leaf that contracts after being cut.

FIG. 6 shows a palm leaf that was cut and has a heavy object on it (e.g., a stone) to avoid shrinking of the leaves.

Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2

FIG. 7 shows the traditional fastening or fixing of the pressed leaves onto crosspieces. FIG. 7 shows how roofs are traditionally constructed using pressed palm leaves, where they are individually tied, knitted over the crossbars 6 overlapping its collocation 7. As demonstrated in FIG. 8, by contrast, using self-supporting palm tiles 7 according to the present disclosure, being previously knitted, are hooked onto the crossbars 6 staying firmly fastened.

The procedure to manufacture palm tiles is as follows:

a) Collect the palm leaves manually directly from the tree holding the leaf with one hand and cutting and separating the petiole P with the other (see FIG. 9).
b) Dry the leaves by exposing them directly to the sun rays (see FIG. 10) or by a mechanical dehydrating process using a dehydrator (not shown).
c) Cut the excess of petiole manually or mechanically down to the base (see FIG. 11).
d) Cut or tear the leave lengthwise into two parts (see FIG. 12) using a punching object or a mechanical instrument.
e) Select the leaves by size (see FIG. 13) so they have a uniformed presentation.
cf) Place and arrange the leaves two by two (see FIG. 14) in a mold 8 which can be of any size but designed to avoid deformations of the palm tile when it is sewn.
g) Sew, glue, staple, fasten or tie up the leaves using a strap 16 where the fan begins taking advantage of the natural union of the lamina and the petiole.
h) At this stage of the process (or later) the hooks are fixed 9 (when used) onto the finished tile 10 by setting the threads 11 for sewing perpendicularly.

FIG. 8 illustrates the collocation and fastening of a palm tile onto crosspieces.

FIG. 9 shows how leaves are collected.

Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2

FIG. 10 illustrates the drying of the leaves outdoors with the help of sun rays.

FIG. 11 shows the cutting of the petiole.

FIG. 12 shows the lengthwise cut of the palm leaf.

Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2

FIG. 13 shows the hanging of the leaves to select sizes.

FIG. 14 illustrates the collocation and arrangement of the selected leaves pair by pair in a mold. FIG. 14 shows a mold 8, which in this particular embodiment is a rectangular table 12 with a crossbar 13 intermediate and an extreme crossbar formed by a crosspiece 14, two lower 15 crossbars and a strap 16 with orifices 22 and screws 21 extending therethrough as shown to screw and tighten it with butterfly nuts 17 to press the leaves between strap 16 and lower cross-bars 15.

FIG. 15 shows the mold with the leaves set and fixed and screwed with a crossbar to prevent movement. FIG. 15 shows the mold 8 as a rectangular table 12 with the leaves set and fixed and screwed with a crossbar to prevent movement.

Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2

FIG. 16 shows the sewing of the tile, which is in the mold.

FIG. 17 shows the hooks or clips, whichever are chosen. FIG. 17 shows the hooks or clips 9, fixed onto the finished tile 10 by threads 11.

FIG. 18 shows a finished tile. FIG. 18 shows a finished self-supporting palm tile 10 removed from mold 8 after forming.

Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2 Palm thatch preparation illustrated by Armando_Garcia_US7900415_B2

FIG. 19 shows a hook shaped attachment to fasten to the crossbars. FIG. 19 shows a hook 9, that has two loops in its body 18 and 19 that are used to hold to the threads for sewing the tile and the hook is held to a crosspiece or “strap” to the structure of hut or palapa fixing the tile. These hooks 9 can be of diverse materials, the most common ones are plastic and wire, their shape and size depend on the crosspiece but the purpose is the same, to hang and to set the tile to form the palm roof.

The leaves and/or the tiles, whether in process or finished, can have a chemical or natural treatment to preserve the color, avoid infestation by plagues or/and delaying or inhibiting fire and/or different finishing measures or special accessories that facilitate the fixing or placement in the structures of huts or palapas that hold them.

The disclosure of every patent, patent application, and publication cited herein is hereby incorporated herein by reference in its entirety.

While this invention has been disclosed with reference to specific embodiments, it is apparent that other embodiments and variations of this invention can be devised by others skilled in the art without departing from the true spirit and scope of the invention. The appended claims include all such embodiments and equivalent variations.

- Azcué, Armando Carlos García. "Procedure to manufacture palm roof tiles for rustic roofs and the obtained product." U.S. Patent 7,900,415, issued March 8, 2011.

Palm thatch roofing, Oxaca Mexico (C) Daniel Friedman

The palm thatched roof above and below is on a structrure forming part of a hotel restaurant on the Pacific coast of Mexico.

Palm thatch roof, Oxaca Mexico (C) Daniel Friedman

As I show below, some of these palm-thatched roofs on the Pacific coast are covered outside by a wire mesh net, perhaps to reduce wind damage.

Palm thatch roof, Oxaca Mexico (C) Daniel Friedman

Simulated or Synthetic Thatch Roofing

Synthetic thatch roofing material including plastic products made from plastic waste has applications not only as a replacement for natural materials on building roofs but interestingly in other applications such as use of synthetic thatch for temporary shelters (Golden 2005) and even for producing a synthetic ski slope (Wehr 1963).

Thatch eave member design for synthetic thatch roofing - Huber US Pat US7117652 B2 Thatch eave member design for synthetic thatch roofing - Huber US Pat US7117652 B2

Illustrated above are designs for a thatch eave member explained by Huber in their patent as follows: [Excerpting]

... the invention relates to such roofing members known as thatching, which are used to create what are termed thatch roofs, wherein the term thatch is taken to include both natural and synthetic materials. Even more particularly, the invention relates to discrete thatch members in the forms of shingles or rolls that are applied in multiples to the roof to provide the appearance of a natural thatch roof.

Thatch roofing has been used to create shelter from the elements of sun and rain for thousands of years. The type of thatch roofing often varies by region, with roofing in the Caribbean and South Pacific typically formed of grasses or palm fronds and presenting a generally loose or random appearance, while thatch roofing in Europe is typically formed of straw and reeds and presenting a more controlled or dressed look. Thatch may be made from natural elements such as straw, grasses, reeds, palm leaves or the like, and in modern times is also made from artificial or synthetic elements, typically composed of plastic, which are formed to present the appearance of natural thatch material. The modern thatch roofing members which incorporate artificial material are more durable, typically easier to construct and apply, and are more resistant to mold, mildew and other forms of degradation or weathering. The overall appearance of the roof is more easily controlled.

Because the aesthetics of a thatched roof are unique, thatch roofing is gaining in popularity. Natural thatch is typically highly combustible, and therefore cannot pass building codes in many jurisdictions. Natural thatch is also very susceptible to rotting and degradation due to high humidity and moisture, and presents natural nesting material for insects, vermin and birds. Furthermore, natural thatching requires skilled artisans for the construction of the individual thatch members and for the installation of the roof—a skill which is rapidly disappearing. The development of synthetic or artificial thatching has lessened or obviated some of the these problems. The artificial thatching is typically produced in the form of rolls or shingles which are properly disposed on the roof to form a waterproof surface with a pleasing exterior. An example of artificial thatch elements is shown in my U.S. Pat. No. 6,226,949, the disclosure of which is incorporated herein by reference.

Since natural thatching consists of individual reeds, palm fronds, etc., multiple layers of such materials are necessary to form a water impermeable covering. Because of this necessity, the exposed ends or faces of the thatch elements along the eaves of the roof are relatively thick. In modern construction where artificial thatch elements are utilized, an underlayment of water impermeable sheet material allows the covering members to be produced as thin elements, thereby lowering manufacturing costs and easing application to form the roof. However, the use of thin shingles or rolls of synthetic thatch presents an undesirable appearance along the eaves of the building, since the entire thickness of the lowermost thatch shingle or roll is exposed to the observer. Since natural thatch roofs are by requirement relatively thick, this exposed thin edge indicates that the roof is not a true thatched roof, detracting from its appeal. - Barry Ray, and Abram Huber. "Thatch eave member." U.S. Patent 7,117,652, issued October 10, 2006.

Synthetic Thatch Roofing Patents of interest:

Platic stalk thatch roof design by Friedhelm Houpt US Patent US5333431 A Platic stalk thatch roof design by Friedhelm Houpt US Patent US5333431 A

[Click to enlarge any image]

Shown at above left, Golden's synthetic thatch tiki shelter, and at above right, Friedhelm Houpt's synthetic thatch plastic stalk roof segment patented roof design cited below.

Thatched Roof Fire Safety

Remains of a plapa afterr a thatch roof fire in Mexico (C) Daniel Friedman Remains of a plapa afterr a thatch roof fire in Mexico (C) Daniel Friedman

In the U.K. the Dorset Building Committee (cited below) notes that

Statistics show that 70% of fires in thatched homes are caused by solid fuel burning appliances. The installation of a woodburner or a multi fuel appliance requires great caution due to the extreme temperatures generated over prolonged periods. - op. cit.

But any spark or fire or heat source can start a fast-spreading thatch fire. Our friends who live in San Miguel de Allende, Guanajuato, Mexico enjoyed a thatch roofed palapa atop their home until the thatch roofing was set afire in 2010 by misguided fireworks set off by a neighbour. The resulting fire ignited and burned rapidly and hot. Heat and fire not only destroyed the palapa but damaged ceramic tiles and glass block components of the structure below. Keep fires, fireworks, or other spark soruces at least 100 meters from your home or expect trouble.

Remains of a plapa afterr a thatch roof fire in Mexico (C) Daniel Friedman

Measures to improve the fire safety for thatched home

Watch out: depending on where you live, thatch roofing may not be permitted at all. Check with local building department and fire department officials.

The above was adapted and expanded from:

Treatments for Thatch Roofing: pesticides, fungicides, fire retardants

Thatched roofs present special concerns for both fire safety and insect or rodent infestation for which there are centuries of experience and modern solutions.

Thatch roof at Alberque Bosque Esquinas in Costa Rica (C) Daniel Friedman Thatch roof detail, Chaco del Inginero, San Miguel de Allende, Mexico (C) Daniel Friedman

At above left is a large thatch roof at the Alberque Bosque Esquinas in Costa Rica. At above right and at below left are details from a thatch roof at el Charco del Inginero, San Miguel de Allende, Mexico.

at below right is the thatch roofed Anne Hathaway Cottage, actually a twelve-room farmhouse, where Anne Hathaway, wife of William Shakespeare, lived as a child on Newlands Farm in Shottery, Warwickshire England, near Stratford on Avon, England, U.K. (Daniel Friedman 1969). The earliest parts of this house were constructed before the 15th century.

Thatch roof detail, Chaco del Inginero, San Miguel de Allende, Mexico (C) Daniel Friedman Thatch roof on Ann Hathaway Cottage, Stratford on Avon (C) Daniel Friedman

Thatch Roof Treatment Research & Patents of Interest:

Because product descriptions and patents are a helpful source of understanding of the issues faced by roofing products we include the following:

Books & Articles on Thatch Roof Inspection, Installation, Repair, Maintenance, & History

Closeup of el Charco's thatch roof (C) Daniel FriedmanThe books listed below can be found by using the "Roofing" link at the InspectAPedia Bookstore.

Quick Comparison of Typical Roof Costs, Life Expectancy, Characteristics

Synethetic Thatch Roofing exampleAt left is a plastic synthetic thatch roof produced by Chinese roofing supplier kebagm.com. OPINION: the chemistry of some synthetic roof materials, while avoiding historic health concerns such as those arising from mosquitoes or other insects may present health or environmental questions needing investigation.

Here is a quick comparison of common roofing materials. Our roofing inspection, diagnosis, repair and installation articles listed at left and below provide roof inspection, roof leak or problem diagnosis, roof installation, and roof repair information as well as details about the factors that affect the life of any roof. We include roof warranty and claim information and links to roofing product sources.

Below at left are several thatch roofed structures on the Pacific Coast of Mexico and at below right, contrasting with the 1976 beer-drinking festival hosted by the author and Steve Coursey below the thatch roof photo at page top, the author enjoys coffee below a thatched roof in La Manzanilla, Mexico in 2011.

Thatch roofed buildings, La Manzinilla, Mexico Pacific Coast viewed from the water (C) Daniel Friedman 2011 Daniel Friedman with coffee, thatched roof La Manzanilla Mexico (C) Daniel Friedman 2011

...


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