Due to start our loft conversion on Monday in a victorian property. The roof is slate, unfelted, do we need to fit a breathable membrane?

yes you do ,but this company should have told you before they won the contract ,i wonder if other companies had quoted included this but they looked to expensive ,this happens often ,honest companies spend time issueing a fully detailed quotation only to lose the contract to these companies who FORGET lol to add these costs at quote stage then hold you to ransom once job starts ,they will end up the most expensive beware

Substructure is bang on with his comments.Surely one of the things that a loft company would pay attention too at quote stage would be the roof? He is also spot on with the comment about incomplete quotes.I have seen this plenty of times and the cheap quote often ends up the dearest.I wouldnt go a lot further until this fool has confirmed that NOTHING else has been missed otherwise you may well come up short if you have a tight budget.

Hi there, Its very typical of that age property to not have felt and those that do have been done in recent years. Felt is a back up for reasons such as tiles slipping or breaking over time, also in severe weather I have known water to rise up roof in strong winds and into the roof area especially with slate as there is no lap/ridge like there is on concrete tiles. Once the loft is converted it will be difficult to know that you have a problem until you start seeing damp patches on the new ceiling or walls. Many un-felted roofs stand the test of time and do not leak, however my advise is as you are having a new conversion I personally would get the roof felted. It will give the peace of mind an ensure there will be no problems in the future. Hope that helps Mike