Recoating & Stripping of Thatched Roofs
Why does the thatch on some roofs seem so much thicker than on others?
This is indeed the case and is due to what is called ‘recoating’ or ‘spar coating’ which means the new thatch is fixed over the old thatch which is left largely intact. It’s most commonly done with straw roofs, although in Ireland flax roofs are thatched in this way and in Scotland marram roofs (also known as bent).
If this recoating is carried out every time a roof is re-thatched then unsurprisingly the resulting thickness of thatch can amount to several feet.
Please click on pictures to enlarge
Roof in Northumberland before removing the thatch
After removal of thatch
So why is recoating done and will it affect the quality of the thatch?
The most common reason is because so many thatch roofs are on old buildings and it is often the case that the roof timbers are also very old.
This is what we found under the thatch
If the thatch was to be stripped completely then these timbers would also need to be repaired or sometimes replaced leading to a more costly job for the thatch owner. Ceilings which lie immediately on the underside of rafters may also be cracked or more seriously damaged.
The second reason is that for many Thatchers who work on their own or with a labourer, having to strip maybe 5 coats of thatch is an enormous undertaking and so it’s understandable why they would choose not to do this. Sometimes however the sheer weight of thatch means some stripping is necessary.
The third reason is that many that work with the conservation of old buildings do not want to see these old coats of thatch stripped. They argue that such historical layers are part of the buildings historical development and should be preserved for future generations. They also believe that removing too much thatch will destroy the character and look of the building.
Finally, roofs thatched in the shorter marram or flax which cannot be laid to a great thickness in one coat and especially on the slacker pitched west coast roofs of Ireland and Scotland require thatching every 2-5 years and it is necessary to build up a good thickness of thatch through which driving rain will not penetrate.
As regards quality issues, as long as the thatch is securely held with the fixings at the right depth onto a firm and level base coat then on steep roof of 50 degrees or more, there is no reason why a 12” spar coated straw thatch should not last as one fixed directly to the roof timbers.
Some may be asking at this stage if the roof timbers are in bad enough shape to need repairing or replacing then shouldn’t this be done? The answer many Thatchers give is that if the timbers have survived this long then why disturb them – almost a case of if they’re only partly broke why fix them?
These roof timbers were repaired
Aside from structural roof considerations, there are other issues with spar coating that need to be addressed.
The first is that constant recoating will change the outline or the silhouette of the roof. Gables that were once showing a foot of thatch thickness may now show 4 feet. Chimneys that were once 5 feet above the thatch may now be barely 18inches and ridges may become very rounded and not shed water as quickly. The sharp crisp outline of a window in the thatch may be turned into a dumpy rounded non-descript shape. In some ways, it is ironic that some conservationists want to see these layers retained because they will also know the true original profile of the roof is more authentic than the one that exists today. In addition, it goes without saying that historic layers are never externally visible and only the underside of the very bottom layer may be seen from the inside of a property, if there is a loft.
However, there is a much more serious implication of having multiple layers of thatch and that is the more recent trend of so many roofs being lost to fire. Unfortunately, the growing popularity of wood burners has dramatically had a devastating impact on many of our old multi layered roofs. Chimney related fires are the biggest cause of all thatch fires and with many only one brick thick and in a poor state of repair and which have remained hidden under layers of thatch, they are just not up to coping with the tremendous heat that wood burners produce. Chimneys’ tops which were once high above the thatch are often barely high enough to be able to ensure any sparks and debris are safely ejected.
Despite these concerns the stripping of thatch is often frowned upon and it’s not only conservationists that are against it; there are also some Thatchers that take the same view. Generally, removal of all the thatch will only happen when the thatch has deteriorated to such an extent that water is getting into the property and there is no other choice or when the roof is structurally unsound.
Roof in Northern Ireland which has been left too long and will now need new roof timbers
Sometimes this decision is also taken away from the Thatcher when thatch owners will seek permission to remove not only the thatch but also the roof timbers because they want to incorporate fire barriers or open up bedrooms to have vaulted ceilings.
In Northern Ireland, we have recoated many historic roofs such as The Andrew Jackson Centre and the Cross Keys Public House and at least 16 other such historic roofs. There have been other roofs where we have repaired roof timbers and added scraw or turfs such as at Ballymena and Crossgar.
My philosophy is that if a lot of historical thatch roofs are not to be lost for good then sticking to a rigid policy must never be allowed to exist and dialogue should take place between Thatchers and other professionals who make decisions about thatch roofs. Only in this way can their future be safe guarded.
Stripping old roof in Northern Ireland
After new timbers were fitted we fitted scraw or turfs