Wet underside of roof

[Mahtem]

Last winter I had damp patches on my bedroom ceiling.
When I went in the loft I could see that the timbers were wet with water dripping off them. The weather was cold and dry so I think that I have had excessive condensation on the slates which had dripped onto the roof timbers.
There is no felt beneath the slates and only a couple of inches of insulation above the ceiling.
The house had not been lived in for a few months and I can only assume that when the heating was put on it started to dry the house out sending the moisture upwards.
How do I prevent this happening this year?
Should I leave the heating on while I am away?

 

[joe-90]

You need better ventilation. Warm moist air shouldn't reach your loft.

 

[datarebal]

and better insulation

 

[^woody^]

You need better ventilation. Warm moist air shouldn't reach your loft.

What if warm moist air gets in through the ventilation?

 

[SASroofer]

A couple of roof vents are probably your best option.

 

[Mahtem]

Thanks guys for your advice. I assume that you mean better ventilation in the house and in the roof.
The roof has a valley and it is here that the problem occurs. On the non-valley side I think the water drips outside or on the external wall, on the valley it drips on to the ceiling. There is ventilation on three sides at the eaves. But as you say, perhaps it needs ventilation higher up the roof.
Downstairs has open fireplaces still but the upstairs ones are blocled. Perhaps vents in these would help.

.

 

[Vegeta]

Hot air should not reach the loft space, so more insulation and at least for roof vents. 2 high an 2 low.
If its the valley thats leaking then it will be water marks. If its dampness the it will be mouldy.
Unused chimneys should be vented any way.
But it sounds like a vally leak to me.
Look and see if its cracked little futher up than the leak is. If so replace the lead with code 5 lead. dont bother with any patching.