New Roof - Cause For Concern ?

Hi All,

New roof, with breathable felt and eaves vents installed two weeks ago.

Reason for the new roof was condensation with last roof (Bitumen Felt and Rosemary Tiles).

I have been monitoring the conditions in the loft. Temp & humidity.

There are a few wet spots on the loft boards, which I am hoping is just drying out.

The hygrometer I used is calibrated and the values its reporting are very close to external conditions. What this means is that due to current weather over the last two weeks its 80+ humidity in there.

The landing and house are approx 60% humidity (via 2 dehumidifiers). The loft hatch is sealed. The landing temp is higher than the loft, but given loft is similar to outside, I don't think much warm air is getting into the loft.

How can I tell if the new roof is working as expected? How can the few wet spots be explained?

I did a question in google Gemini, its says its bad; I did the same in Chat GPT, it says no problem.

Might be the wrong place to ask, apologies if it is.

There should be no wet spots from water penetration below a new roof.

The breather membrane should be fitted with a sag between the rafters to aid air flow and any condensation run-off.

Not all breather membranes breathe to the same extent.

Most of the condensation in a roof void is caused by warm air from the rooms below. Check you insulation depth and coverage to reduce heat escaping.

I would avoid humidity readings unless you know what you are reading and interpreting.

^woody^ said:

There should be no wet spots from water penetration below a new roof.

The breather membrane should be fitted with a sag between the rafters to aid air flow and any condensation run-off.

Not all breather membranes breathe to the same extent.

Most of the condensation in a roof void is caused by warm air from the rooms below. Check you insulation depth and coverage to reduce heat escaping.

I would avoid humidity readings unless you know what you are reading and interpreting.

Click to expand...

Thanks. really appreciate the help.

There is definitely a sag in the membrane. The roofer made a point of highlighting that. He comes on the back of strong recommendations. I don't want to unnecessarily call someone back to a job, basis my lack of understanding, hence this post.

In terms of heat escape from downstairs. The insulation was checked for depth etc before he left the job. He was happy that it wasn't blocking vents, and didn't raise any concerns re depth etc. Due to the roof design, there are a few bits towards the eaves where you couldn't put the rolled insulation without blocking vents, so I am planning on putting some insulation board there, its shallower than the joists, so wont block anything. I haven't used that before, but I am sure I can find some guidance. The landing is completely different temp to the loft. Of course there is always a potential for heat escape.

In terms of humidity readings etc, I completely get your point, I started doing it to see if humidity was getting to a point, that with dew points etc it might condensate. Its more of an "educated" guess as to whether we have fixed our problem before winter starts to kick in.

Here is a photo of the "drips", condensation or drying out, I don't know?

What's above those drips? Where are they coming from? You need to determine if this is condensation or not.

For info, the breather membranes the industry sold us are not as breathable as they claimed, and condensation issues are rife even when everything about a roof is done "right". Over the past decade or so, a new range of more breathable membranes have been introduced which are supposed to perform better, but many contractors don't use them unless they are specified. Even so there are so many factors at play within a roof void, that a very slight imbalance can mean that condensation occurs and the only practical thing to do is manage it as best as possible.

BTW, has a breathable ridge been fitted too?

I don't have a photo of what is directly above the spots, so cant remember its a piece of timber or not. I will have a look and report back.

What I do know is that under the old system we have staining etc on the beams. This is a different area of the loft. As you can see I have some work to clean up a few bits.


Thanks for the information re membranes etc.

In terms of the ridge, its a dry ridge system, and I know that he cut the felt directly under the main ridge. Again he reasoned out why that was needed. Made sense. These spots are not under the main ridge.

Hi,

I have had a look, directly above the wet spots is just felt. I also spotted another wet spot in a different area. Surrounding Beams don’t feel wet or anything. The felt feels dry. Puzzled.

Are the spots anywhere near the above ridge ? Centre line

Yes, but the ridge would cross the spots diagonally if you like.

Difficult to explain, but it’s not the main ridge, it’s the one of the side of the roof. To explain the pattern it would almost be like the drip was being blown and landing where it does. That’s a shocking explanation. Will take a photo and see if that helps