Roof leak or condensation?

[GraPC]

I’m trying to find out if we have a roof leak or if the issue is condensation. We have had issues with condensation in the loft space previously and had tile vents fitted and it seems to have cleared this up.

The issue we’re still having is that a few sections of the roof beams are still getting wet but it seems to be at random times. Some mornings it will be dry and then wet later that day. Some times it will be wet during rain but then dry the next morning, some times it will be dry when raining and then wet the next day. When I say wet, it’s not soaking but more cold and damp to the touch. We’ve had the company that fitted the roof back numerous times and they can’t find a leak, we’ve had a second opinion and they can’t find a leak either.

I was wondering if rainy weather is causing high moisture levels which is being drawn in by the vents and then this is making the beams feel damp? Is that possible? Water is not dripping anywhere that I can see but the beams feel damp to the touch.

Is it possible that having vents fitted is making the loft colder and causing these sections to feel damp at times?

Yesterday was torrential rain all day and they felt damp when I got home from work but by the evening they’d nearly dried. If it was a leak would the wood dry that quickly?

Sorry for all the questions.

Thanks

 

[Ivor Windybottom]

Is your loft hatch sealed, along with all other openings, e.g. pipe/cable holes?

Also, what's the typical humidity in your home? If it's high then it will probably find its way into the loft, openings or not - it can pass straight through plasterboard if there isn't a vapour barrier.

A decent hygrometer or two may be a good place to start - if your home is damp then start at the source and work forwards instead of backwards from the symptoms.

 

[GraPC]

Is your loft hatch sealed, along with all other openings, e.g. pipe/cable holes?

Also, what's the typical humidity in your home? If it's high then it will probably find its way into the loft, openings or not - it can pass straight through plasterboard if there isn't a vapour barrier.

A decent hygrometer or two may be a good place to start - if your home is damp then start at the source and work forwards instead of backwards from the symptoms.

We had the loft hatch sealed when we had the vents fitted and there aren’t any pipes or down light holes in the loft. When we initially had the condensation issues it was all over the loft whereas now it’s just the 3 sections that seem to be damp at times. They’re all in different parts of the loft as well. When I feel the felt it’s dry but the beams are damp. Do you think this is more likely to be condensation than a leak?

I’m not sure what the humidity level is in the loft. According to our boiler thermostat the house humidity is 61%, but I don’t know how accurate that is?

 

[Ivor Windybottom]

61% sounds pretty normal (for the damp UK anyway). But if that's at 20-odd degC then that will condense if it gets into the loft where it's much colder.

It could be condensation but the damp spots are the bits that happen to be cold, e.g. where there's less material between the inside and out. So it will condense there, just as it does on a window. I'm not saying it is condensation, but that the fact it's patchy doesn't mean that it isn't.

Perhaps have a good look from underneath yourself with a torch the next time you get prolonged heavy rain.

Are there any unusual roof features in these spots - e.g. valleys, hips or flat parts?