Roof Mortar Torching – an explanation

This is the huge loft-space of a 1930s semi-detached house we recently surveyed.

roof mortar torching visible in large loft space of house

You’ll notice the white material that appears between the timber battens. This is a mixture of lime mortar and horsehair. This is what is known as roof mortar torching and was packed in between roof tiles and battens as a water-proofing measure.

The practice became outdated in the late 1930s as bitumen under-felt began to be used instead.

If you are buying a house and the torching is as good as this example, then you should have another five to 10 years left in the roof – so long as you keep foot traffic off the tiles!

Of course, we always recommend you arrange a full building survey on any property you are interested in buying.


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