Only a handful of thatched houses remain on Tiree and here is a picture of one of them. They are usually thatched in marram grass or bent (Ammophila arenaria).
As with the Blackhouses on Lewis the walls are very wide (see our Scotland page on the website) and consist of an inner and outer wall. The roofs are all hipped and their shape (no sharp angles) means they are able to cope with even the strongest winds; the walls also have a role to play in deflecting the wind upwards and away from the roof. The thatch eaves are also protected because they sit on the inner wall.
The second picture shows the typical alignment of roof timbers. The main timbers – rafters or couples are about 150mm in diameter and are very closely spaced. On top of the rafters there are two or three sets of purlins and the ridge plate consists of several pieces of wood which makes the apex more flat and rounded than most other roofs.
Turfs are then laid over the rafters before the marram grass is fixed into and on top of the turfs. The turfs can be seen in the second photo. Finally on some of the roofs stones secured to ropes are laid around the eaves to help keep the thatch from moving in the wind.
Unfortunately the marram needs to be renewed every 2-5 years and it is probably for this reason and also the difficulties in obtaining local marram that the number of cottages has declined despite grant funding from Historic Scotland who wish to see the continued use of marram.