Wooden houses and roofs have been built for long time. I'd be more worried about leaking plumbing. If you bring piece of wood indoors and let it dry, it's wate

Wooden houses and roofs have been built for long time. I'd be more worried about leaking plumbing. If you bring piece of wood indoors and let it dry, it's water content will drop to about ~17%. If you take it outside and hang it somewhere so that it catches rain and then dries, it's moisture content will average about ~20% in most places on earth. Wood has evolved to do capillary action. This means it's very good at drying, but it's also very good at staying wet if there is moisture around. https://en.wikipedia.org/wiki/Capillary_action https://en.wikipedia.org/wiki/Capillary_action Most wood eating fungi need moisture content of at least 30%. And this has to be long term, wet week doesn't do anything. But there is fungus called dry rot, that can cope with 20%. This leaves you practically no buffer, as the indoors natural is 17%. The catch here is that dry rot needs certain minerals to ever start growing. Cement and mortar have these minerals. If you build effective barrier between cement and wood structures and keep the moisture below 30%, you don't have to worry about rot ever. Insects are another problem. But it's rare that you get insects if you didn't get rot first. In those rare occasions, there has been some visible defect in the surface of the wood. Or alternatively some very infested thing nearby. Regular paint goes long way. UK has traditionally had lots of problems in build quality. Mostly because they didn't take into account dry rot. Source: Deterioration and preservation of timber in buildings. G. A. Scott 1968. And no, this info has not dated since 60's.