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I've spotted water damage in my roof space

John Conlin / 24 January 2019

Chartered surveyor John Conlin explains what could be causing condensation and water damage in the roof space.

Roof space


Having recently bought a 1970s house I went to put some boxes in the loft and worryingly saw that several of the timber supports along the underside of the roof slopes appeared water stained, and in several places there were little beads of water on the black fabric beneath the tiles. Is there any way to waterproof the roof without major expense?


The droplets of water are likely to be condensation and the staining to the timber rafters is, similarly, likely to be due to long term absorption of the moisture collecting on the underside of the tile underlay.

It is a common problem due to lack of ventilation often caused by loft insulation being packed into the eaves cutting off air circulation. Draw back the insulation so that the eaves are unobstructed and check there are adequate vents in the underside of the eaves. More recent buildings include these as standard.


I think the felt beneath the roof tiles has started to leak as I have seen drops of water on the underside of the felt when I have been in the loft. Is there any way to stop this without stripping all the tiles and laying new felt?


You will be relieved to hear that it is unlikely that the felt is leaking. I have seen water droplets on the underside of felt lining to tiled roofs on dozens of occasions. It is condensation due to poor ventilation of the roof space. A common cause is the packing of insulation into the eaves cutting off natural ventilation.

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The opinions expressed are those of the author and are not held by Saga unless specifically stated.

The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.