Today the most widely used materials for thatching are;
See Sections below for more details.
The exact lifespan of a thatched roof is impossible to predict precisely since it depends on so many variables and factors that can change over time, however, there are things that can determine thatched roof lifespan such as;
It is generally accepted that a water reed roof can be expected to last longer than combed wheat or long straw roof. As a rough guide any ridge will probably need replacing every 10 to 15 years; a combed wheat or long straw roof may last 20 – 30 years and a water reed anything from 30 – 50 years. This not an exact science as as there are examples of combed wheat lasting for 50 years or more.
Maintenance and repair of any damage will help to achieve maximum life span.
The risk of a thatch fire is much less than often most people imagine.
For a new build the architect or planning authority will often specify the installation of a physical barrier beneath the layer of thatch, of which there are many different suitable products on the market.
Houses already thatched do not have this option unless the old thatch is being completely stripped off. Liquid fire retardant products available that can be sprayed onto the thatch, however there is concern that chemicals may change the basic behaviour of the material and affect the roof’s performance.
Chimneys: Since most thatch fires start from a problem with the chimney or fireplace it is critical to keep the chimney in good repair and swept regularly. It is important that the correct size of wood burner is fitted and that liners are fitted correctly. Also taking care what is burnt - using dry seasoned wood is best.
When a house is re-thatched it is traditional for the old thatch to be stripped down to a firm base into which the new thatch can be fixed. In some circumstances water reed is fixed onto a base layer of wheat reed. In some cases, for instance if the roof has been so neglected that the roof structure itself needs to be repaired and it is necessary to strip the entire roof.
With all materials the thatch is laid in the same way – in courses, upwards from the eaves to the ridge, the fixings of each course covered by the course above.
The thatch is fixed in place with a variety of materials dependant on individual circumstances – for example: hazel spars; steel thatching crooks; stainless steel screws and wires; mild steel rods or tied on with tarred twine or sisal.
Wiring is used to prevent birds from pulling out straw from a roof. It is usually fitted to the ridge only of a water reed thatch or the entire roof of combed wheat and long straw. Each vertical drop of wire should be laid side by side and not overlapped; the two sides should be joined by sewing the seams – twisting the two seams at intervals of about 6 – 8” apart. This leaves a neat finish.
Ridges are an important part of the roof they protect the coat work and prevent water damaging the top courses. The ridge will need to be replaced ever ten to fifteen years and will give a good opportunity to dress up the coat work and repair if required. We use various styles and patterns which usually will depend on the property, or what the customer desires. You can see examples in the gallery. Straw Block cut ridge, Straw flush ridge used traditionally on long straw, Sedge ridge usually used on water reed.
Water Reed is traditionally grown in Norfolk. There was a time when Water Reed was grown all over the country but sadly this is no longer the case. Due to the high demand most reeds are now imported from abroad. Water Reed roofs are usually stripped down to the timbers. This gives a good opportunity to inspect timbers and fit a fire barrier required. Water Reed is the hardest wearing material and usually lasts in excess fifty years.
Straw is used all over the country and is traditional to lots of older properties. Straw roofs usually have several layers of straw. One Layer is removed, then a new coat thatched on top, fixed with hazel spars. While this can be a practical solution for some roofs it is not a good idea to allow the straw to get too thick - there comes a point when it is prudent to re-thatch. One issue with allowing roofs to get too thick is in the (unlikely) event of the roof catching fire, it will be very difficult for the fire brigade to extinguish.
This style goes back before the combing machines where around. Prior to the straw being thatched on the roof it will need to be placed in along bed. After several buckets of water have been throne over the bed. Straw is then drawn out - this action straightens and leaves most of the rubbish in the bed. The straw is then gathered up in thin wedges and made into yelms. Long straw roofs have a shaggy appearance and have extra pattern work around the eaves and gables. Traditionally finished with a flush ridge. Long straw roofs last about twenty five years, sometimes more.
This is top quality straw that has been though a comber ready for the roof. The life span is about thirty five years, some times more. Combed wheat roofs have cleaner dressed finish than long straw with softer and rounder gables than water reed.