Cold roof nightmares

[tikroh]

Hi there,

I have tried so many places and people and now I happen to have stumbled across this forum which has my hopes up...

I am an absolute novice DIYer trying to insulate an already existing outer building for my small lizard collection.

I thought insulation would be easy, however the theory that seems to go in to cold roofs to ensure they are warm, and do not rot seem to be much more complex than I imagined...

The problem I have is that I have no ventilation or overhanging from the flat roof to add some.

Is there any other way I can sort this and make it work?

I have built a stud wall away from the already existing brick wall and this has a 50mm gap the whole way around the room, including up in to roof.

Hopefully the photos explain better than I can..

I did try and put board up, but after 3-4 days I started to see water marks coming from under the roof beams, I took it down and the roof was soaked.

Finally, in regards to wall insulating, I do not need ventilation other than what I have correct? I still have a 50mm gap from wall.

I guess what I am asking is, am I OK to fit the rest of the PIR boards to the walls without worrying? I do not need to seal walls or anything stupid?

Any help massively appreciated. Losing sleep over this as Winter and Storms draw in quickly.

Thanks

Photo 1 ) Looking upwards from wall into roof.
Photo 2) Wall Insulation.
Phot 3) Roof side 1.
Photo 4) Roof side 2.

 

[DiyNutJob]

Water is coming from where? Best to get that fixed or it will ruin everything else.

 

[tikroh]

No water as such.

When I looked up I saw water marks coming through the beams either side of the 1 where I had laid insulation.

I had basically done 1 strip, between 1 beam.

If you look at the final photo, imagine that gap between the 2 beams had a strip of PIR board between them.

What I saw is water marks in the 2 canals either side, just starting to seep across.

Complete novice and really struggling to explain myself. Was hoping someone would =D

Thanks

 

[Mr Chibs]

When you say water, presume you are talking about condensation.

Lots of flat roofs are now warm roofs insulation on outside, which will help stop condensation.
Insulation on inside can promote it, hence the need for ventilation. Can you add any ventilation?

If not, I've seen it mentioned on here, that you can push the insulation boards up, tight to the underside of the roof and leave no gap, the idea being condensation can't form. Not something I've done, so wait to see what other comments you get from others who have.
I'm presuming you will be using insulation boards for the roof?

 

[Deluks]

You say that you have 'no overhanging' on the roof.
Does it have a gutter, where does the rainwater go?

If you removed one of those bricks that sit between the rafters, would it lead to the outside?

 

[tikroh]

Yes Mr Chibs, condensation. It was really quite damp though. Also yes, exact same boards, only 75mm instead of the 50mm I have for walls.
I'm not sure I like the idea of pushing the insulation up tight, surely you can't get it tight enough without perfectly faced wood on roof and PIR boards?

Yes Deluks it would. Is that what I need to do? Remove a brick each end in every rafter and replace with a vent (I saw some that look like bricks?)

I was hoping I could remove a brick high in the wall and that would cause ventilation behind the studwork and up in to rafters. Is this something that anyone has heard of working?

Like this..

 

[DiyNutJob]

Are you sure it's condensation? I can see a gap above the curtain, opening to the out side. Condensation can only occur when warm air meets cold surface. Having a gap like that, I don't imagine there is much warm air.

 

[Deluks]

Yes exactly that. You could fit an air brick between each pair of rafters to add airflow.

You will then need to leave a minimum of 50mm airgap between the underside of the roof and the insulation, and preferably insulate underneath the joists as well.

Looks like you have 100mm deep joists, so wedging 50mm of insulation between, flush with the joists, and then a minimum of 25mm underneath (or as much as you can bear to lose ceiling height)

Don't forget your vapour barrier, a thick plastic sheet over the whole lot, or aluminium tape over all the joists and edges of the insulation boards.

For airflow, it's really advisable to have cross ventilation, ie: the air can pass from one side of the roof to the other.

Do check that the roof definitely isn't leaking after a heavy rain shower before proceeding.

 

[tikroh]

Thanks all.

I can confirm it is definitely not leaking. The "Gap" you can see is the gap between the top of the door and the closing panel. That sheet is over the door.

It was only soaked under the one board I had put up as tester, and I had watched it for 2 weeks prior in bad weather with no leaks, and since - no leaks.

I had put up a length of PIR board, and only left 1 end open with air flow (Not parallel air flow, as I mentioned with not taking the PIR all the way to the walls and thinking the air flow would go up and under. 2-3 days later it was soaked. The room would have been a steady 22 degrees.

The joists are actually measuring about 125mm at the highest point, and 100 at lowest. I have 60mm PIR board.

Adding 20 air bricks is not ideal, but if that is my game plan, then that is what I must do.

 

[Deluks]

On the other side of those top bricks is there a fascia on the outside?
You could just knock out a brick and have your vents on the fascia/soffit.

 

[tikroh]

I have no real idea, so here are images

The roof isn't great, I need to get it done come the warmer weather, but i just need to get through winter.
Thanks

 

[DiyNutJob]

If the roof isn't great then the water is coming from the outside. Trying to insulate a failing roof seems a waste.

 

[tikroh]

The water is categorically not coming from outside, as I have stated.

When it appeared and I found it, it had not rained for a over a week, since removing it is has done nothing but raid 20 hours a day, and there are no new water marks, wet marks, dampness or wetness anywhere in the room.

The underside of the roof was very cold, and very wet upon removing the single piece of PIR board I had put up.

I am absolutely going to replace the roof, there is no question of that, however it's November and I have just moved house with a lot of costs involved.

I simply cannot afford to do the roof this side of Christmas, and due to having live animals in the building, I need to keep it warm over winter.

For this reason, my plan is to insulate it best I can, and replace the roof early 2024.

Given the roof is NOT leaking, I feel insulating now will not result in making me any worse off.

I think the best solution given is to add air bricks in to each end of the areas between each beam. Although this is 18 air bricks, it seems my simplest option given I cannot do the roof right now.

 

[Mr Chibs]

If you are replacing it early 2024, then why not just lash-up some cavity batts/rockwool for the the time being (for the animals)
Then, when time to replace, build a proper warm roof.

 

[DiyNutJob]

If it's that categorical, then I better not tell you I spend a lot of time playing with exterior facing timber. I know a problem with a single look. Failed paint and rotting wood are classic signs. I wouldn't have much faith on them felts either. If moisture is a problem, then a dehumidifier is probably the easiest solution that will carry you over for a year or two. Breaths do produce moisture, but unlikely to a degree where it becomes a major problem unless you are keeping jungle animals that live in humid environments.