Flat roof flashing / cavity tray - 1970s house

[mmaatt]

1970s semi detached house, pebbledash render on cavity wall. Garage, with flat felt roof was build in 80s, I believe, at the side of the house.

There isn't any lead flashing where the flat roof meets the house wall. It was just mortar. I've painted it liberally with bitumen paint and that has reduced water ingress down that wall to the odd occasion.

I intend to get it done properly this year, and I understand that means getting lead, or similar, chased into the wall?

No problem with that, but researching flashing led me to learn about cavity trays, which I assume I don't have anywhere in the house, since there are no weep holes in the render. Is that common for a 70s build?

I assume it's not uncommon to skip the tray when a garage extension is done, as the internal wall of the garage can cope with a bit of moisture, unlike a proper extension of the house?

Anyway...my main question is whether getting the flashing done properly will make things worse, or if it's still worth doing.

Thanks in advance for any guidance!

 

[Deluks]

'Getting it done properly' do you mean the garage itself as an extension or just the flashing?

If you're sure that any ingress you currently experience is just down to the poor flashing, and the pdash is in good nick, then you might get away with no cavity tray. It would certainly save you some money by omitting it. Do you have any openings in the wall beneath the flat roof?

 

[mmaatt]

I mean only the flashing and roof covering. It'll remain a garage.

I'm fairly confident it's the flashing that's the problem but not sure how I could be certain.

The render appears in good nick, although there's always stones coming off it.

Hence I'm not inclined to open up the wall for a cavity tray. I'm mainly just checking that getting the flashing done properly, but without the cavity tray, won't create a new problem and push water back into the wall and affect the house when it would otherwise come into the garage. Does that make sense?

Below the flat roof it's just render wall on the side, with some holes drilled for pipes and electrics.

 

[Deluks]

If it were me, and I had no signs of damp internally at this part of the wall, I would proceed in the same manner.

 

[cdbe]

As your house is rendered the risk is pretty low, and if it's a traditional garage (drafty door, where you keep your lawnmower etc) then a bit of moisture will just evaporate. If it's a "habitable" style garage - gym, utility etc there could be an issue - but I've never heard of anyone needing to do anything when doing an official habitable conversation - which actually surprises me a bit! as I can't understand how moisture will escape from the bottom of the cavity, especially if the floors are solid on both sides.

 

[mmaatt]

Thanks both. I think that makes me confident enough that getting the lead flashing chased into the wall and doing nothing else is the way to go.