The
lifespan of a thatched roof depends on many things. I will discuss the
lifespan of thatched roofs with water reed here although most arguments
will count for other materials as well.
In general: the dryer the roof , the longer the lifespan will be .
The following
factors are crucial: the slope of the roof
The slope and the craftsmanship of the thatcher are by far the most
important factors which will determine what the lifespan of a roof
will be. In general every thatched roof should have a slope of at
least 45 degrees. The lifespan is depending on the slope so much that
you can give the expected lifespan as funtion of the slope:
25 degrees
up to 15 years
30 degrees 10-20 years
45 degrees 25-45 years
50 degrees 45 years and longer
the dormer window is quite flat so it is the first item to be renewed.
Because the lifespan of a thached roof so clearly depends on the slope
the question how flat the roof can be made is mainly a conscientious
one. Builders and architects often dare to construct a flatter roof,
thatchers tend to be more cautious. The mimimum slope also depends
on the shape and length of the roof surface. The Dutch Federation
of Thatchers works with the following standards as to minimum measures,
they are:
For round shaped dormer windows 25 degrees (water can find its way
out sideways as well)
For short roof surfaces 30 degrees. (up to 2,5 meter, flat from ridge
to bottom )
For other roof surfaces at least 35 degrees.
If the roof surface can be more steep it should always be made so
!
The thatchers
craftsmanship
A thatched roof, applied properly and kept in shape will last for
decades.Mimimum lifespan is 25 years.But 40 years or longer certainly
is not an exception, provided the former named slope angles are observed
and the roof is apllied according to craftsmanship.
Most occuring faults deal with the execution of the thatching itself.
Too often the client compares prices and then chooses the cheaper
bidding thatcher, not realizing that his roof may have a shorter lifespan
(10 to 15 years probably).
How to select a thatcher ? selection criteria
Recipe to a long
lifespan:
(in order of succession)
1- Make the
roof as steep as possible.
2- Choose your
thatcher with care.
3- Keep the
roof free of algea and mosses. ( see also:
maintenance )
4- Use only
first class reed.
5- Provide
surroundings with much wind, little shadow, large trees should not
be standing in the direct environment of the house.
6- Small defects
should be repaired immediately.
Note
There are two kinds of lifespan: functional and esthetic.
Functional: how long will the roof stay waterproof(on average more
than 45 years)
Esthetical: a new roof looks better than an old roof
Many thatched roofs in the Netherlands (on cottages and country-houses)
are replaced because of esthetical reasons. Hence the normal lifespan
of 45 years will not be obtained.
On farms and sheds the functional lifespan is more decisive and so
a 50 years lifespan is no exception.
