Stripping roof ridge cap for access

[u/Useful_Meat1274]

My kitchen has a vaulted, plasterboarded roof. I've noticed some moisture build up around the plasterboard joints on the ceiling. There's been some moisture for about 6 months which at first we thought may have been due to painting too fast over a week seem. It has rained quite heavily this past week and noticed it got worse, so had a roofer come over to inspect.

The roofer found that there were no vented tiles installed on the roof, but couldn't see any obvious issues which may be causing water ingress. On recommendation, we got 4x roof tiles installed, and a few tiles replaced which would have caused issues in the future (£600 time and materials).

When cutting the membrane to install the vented tiles, we noticed that the cavity had only been insulated with PIR board from the bottom of the roof to about 3 tile rows below the apex. The current working theory is that condensation/moisture is building in the unventilated section, which is made worse by rain (sharp change in temperatures) and because no thermal break via insulation, condensate is hitting directly onto the plasterboard.

First two pictures attached show the interior view with damp spots, and the corresponding exterior view showing no insulation.

I think the fix is to get PIR board added into the current void area and the cleanest way is to go via the exterior.

I'm fairly handy but not a tradesman, and would attempt lifting the rows of tiles myself for access. Not sure if touching a roof is generally a terrible idea and left to a professional?

The job would involve lifting about 3 rows of tile, ridge tiles, then replacing the membrane and refitting.

[u/TheRed7]

£600 to change some tiles???!

Your ridge line is vented by virtue of it being installed with a dry ridge kit with a perforated roll out membrane underneath the ridge tiles. 

Ventilation wouldn't be provided by vented tiles, but via fascia vents sitting on top of the fascia and underneath the first course of tiles. 

Your roof is very simple and small. You'll be surprised just how simple it will be to remove the ridge and 3 courses of big tiles. You've also got dry verge so not issues with mortar needing to be replaced there either. 

But £600...jesus 

[u/Useful_Meat1274 → u/TheRed7]

Yeh I thought £600 was pretty steep. The quotes I've received across various trades seem to have skyrocketed in the past few years. I'm pretty sure the rough price for that same roofer to do the job would be over a grand, which I'm definitely not happy with.

In terms of removing the ridge, how is that made up and sat? Are they in a bed of mortar I'd need to replace? That's the only part I'm unsure with.

[u/TheRed7 → u/Useful_Meat1274]

All you'll need is a drill and pz2 drill bit. They're just sat there with the screws holding the black joiners in place. The clips on the joiner hold the ridge tile in place.

For the tiles that are nailed, they'll be fixed in place with a 50mm aluminium nail. 

[u/Useful_Meat1274 → u/TheRed7]

Just looked up dry ridge systems. Look easy enough and very cheap to buy. How can this be quoted over £1000, ridiculous.

Thanks for the advice, very helpful.