Query regarding tile joint stagger on roof

[Mike10]

I was doing a job for someone today and they asked me to have a look at their roof which has been leaking during heavy rain recently.
The water has been appearing at the ceiling above the door. The ceiling is attached to the rafters so slopes towards the door. It would appear the water could be getting in anywhere and then running down to that point.

I checked the flashings around the roof and the velux windows and couldn't see any problems. None of the tiles are cracked or dislodged (apart from the odd cracked corner).

The only thing that seemed odd was that the tiles aren't staggered and the joints are aligned between rows. As these are interlocking tiles does that matter? does the interlocking take care of water going through the gaps?

 

[datarebal]

the flashing to the side wall looks poor. remake
the odd corner cracked...does matter, change damaged tiles
the tiles straight bond isn't an issue
*The tile channels blocked with moss is an issue, clear all channels*
double check tiles to velux to make sure moss and muck has not built up under the tiles on top of the side flashings.

 

[Mike10]

Thanks for that, I think I will start by clearing the moss off and double checking around the window flashings.

 

[chappers]

yep that could well be your problem, moss impedes the flow of water and can even draw water under the interlock.
Whilst the straight bond on interlocking tiles shouldn't be an issue, it's not normal practice and does make you wonder what else might be wrong.
If the ceiling is wetting up quickly after heavy rain, my bet would be on the veluxes

 

[datarebal]

every laid redland deltas half bonded?

 

[Doggit]

The doors quite wide, so where exactly does the water appear; that might give a better indication of where the problem lies. The interlock stops the water going down, but if there's a crack in one, then that might be an issue, but the overlap doesn't appear to great, so it might be driving rain coming up under the tiles. If it's getting wet near the doors, then whilst the flashing may need attention, it's unlikely to be causing the problem.

 

[Mike10]

The water drips through the ceiling dead centre of the doors on the inside.
There's a stain that extends about 2 feet either side of the centre point where it must have been pooling before it started coming through.
I'll get a pic of the inside when I'm next there, but that may not be for a little while.

 

[Doggit]

That suggests it's coming in by the velux windows, and travelling down the breather membrane, of theres damage to one of the interlocks just above the leak. Try putting a hose on the lower section, and see if it leaks, then put it between the veluxes, and then finally at the top of them.