Coping stones no DPC

[andyp187]

I’ve recently moved into a house with a recent (5yrs) flat roof extension out the back. The extension has parapet walls topped with coping stones. Not long after we moved in we noticed damp at the right angle with the ceiling and after an inspection of the roof it seems there is either no DPC or only a partial DPC under the stones and it is leaking into the walls through the joints. Additionally the drips on the coping stones were bridged with mortar at the joints leading to water running down the walls and further ingress. At the moment I’ve stemmed the damp by filling the joints with CT1 and covering in a tarp secured with bricks. I’ve also ground out the mortar with a grinder.

I’ve had a couple roofers offer different solutions, one would like to lose the stones and recap in lead, another would lift and re-bed with a DPC. My question is what would you do?

 

[Deluks]

What's on the other side of the wall? Is it exposed?

 

[datarebal]

If the copings are lose, then the answers in the thread title .

 

[andyp187]

What's on the other side of the wall? Is it exposed?

Yeah, it’s an outer wall

 

[Deluks]

I would retrofit the dpc, but make sure the cavity tray is in place and installed correctly, assuming you have one.

 

[andyp187]

I would retrofit the dpc, but make sure the cavity tray is in place and installed correctly, assuming you have one.

Thanks . There are weep holes in the wall so I assume there are cavity trays. That being said they didn’t do a DPC which seems amateur AF so worth checking

 

[andyp187]

Such fine work by somebody…

 

[Deluks]

What's the tray doing? Why didn't it direct the water back out?

 

[andyp187]

What's the tray doing? Why didn't it direct the water back out?

If there is a tray it’s so far down you can’t see it

 

[Deluks]

Any insulation?
You could be getting internal condensation from a cold bridge. (Even with insulation fitted)
The insulation should be high enough to meet the roof insulation.

Methinks you might have a bigger job on your hands.

 

[Deluks]

Also those coping should have a mechanical fixing to stop them from coming loose and falling on your neighbours head.

 

[andyp187]

Also those coping should have a mechanical fixing to stop them from coming loose and falling on your neighbours head.

Or mine! There is insulation, certainly wouldn’t surprise me if condensation were or became an issue however, damp only appears when it rains and did stop when i sealed up the joints with CT1 as a temporary measure. I’ll be getting a builder in to have a look

 

[acesumper]

Hi Andy, Coping stones- there's so much contradictory advice out there. But there is a great vid on utube entitled 'Sweating and wet parapet wall' by Steve Roofer. His advice, and that of IKO seems to make a lot of sense. Having said that, I've just spent the last hour trying to track down the recommended IKO Hyload Permabit DPC without much luck. And by default, I've no experience yet of it in use.

 

[acesumper]

After another hour spent trying to buy IKO permabit, I've given up. Now going to use Visqueen Zedex High Bond dpc