Bill
You emailed us asking about the construction of thatched roofs at Pendon Museum.
The basic material used for thatching is plumber's hemp also known as tow. It is a fibrous material which is normally supplied in large hanks and used by plumbers to seal screwed pipe fittings. The hemp is cut into small bundles about 1 inch long and about 0.25 inches thick. These bundles are glued (using PVA glue) onto the card base of the roof in rows working up the roof and overlapping each row. This is similar to the way that real thatch is laid, although it isn't glued! When the apex is reached, more bundles are laid over the ridge and glued in position top form the ridge capping. Real thatch is typically about 2 feet thick so in model form should be 0.25 - 0.5 inches thick (all dimensions are given for OO scale 1:76).
When the glue has dried, trim the thatch using a small pair of scissors, cutting with the blades pointing up the roof to avoid putting straight lines into the thatch. Liggers (the hazel spars used to tie the thatch down) are made using brown cotton soaked in PVA glue to stiffen the cotton. The liggers are pegged down using small pieces of fuse wire bent into a V shape, by pushing the wire peg into the thatch with the cotton trapped under it.
The thatch is then given a wash of colour using either acrylic or oil based paints. An earth brown colour usually works well, but thin the paint well before applying it and allow the paint to soak in. Finally, weathering is added - typically, mosses and lichens grow in the thatch and these can be represented by thin washes of green paint. For a very heavy mossy appearance add a little plaster to the paint to thicken it and put blobs of paint/plaster onto the thatch.
Hope this helps you to create a thatched cottage.
Malcolm Smith
Development Director
Pendon Museum