Finishing a parapet wall

[goodbyegti]

How do people fix down their coping stones when you're supposed to have a DPC underneath them?

 

Everything I can find seems to involve drilling holes near the mortar joint between coping stones.

 

Eg these things (where is the DPC!):

 

[goodbyegti]

For interest, here is my parapet. The silver flashing tape is temporary and will be replaced with lead. The wall is 100mm thermal block, 90mm phenolic board, 25mm surecav, 125mm stone. I have a GRP roof (2 x 450gsm) which comes up one side of the parapet. There is a cavity tray so far, formed from a DPC. The stone masons did something crazy with the weep vents, but seem to work well enough. They also ordered the wrong size coping stones, so I need some wider ones.

 

 

[nod]

I bedded ours on mortar  5 years ago and they are fine They are extremely heavy and unlikely to move 

[bmj1]

13 minutes ago, nod said:

I bedded ours on mortar  5 years ago and they are fine They are extremely heavy and unlikely to move 

 

We've done the same.

[Conor]

Mortar under the dpc, mortar above the dpc. A 20kg coping stone isn't going anywhere.

[Canski]

if it was mine i would use slurry primer on the copings. As for fixings we have done dozens of these as per spec drilled through the DPC and never had a problem. A small squirt of silicone may help.

[Canski]

I am also interested to know how the discs that show through your GRP can be avoided. I have 18 mm ply on firings then 200 mm PIR then 18 mm OSB3 on the top. I am toying with the idea of GRP over EPDM due to having a roof lantern. The finish on yours is what I'm after rather than pigs ears on the EPDM. 

[goodbyegti]

8 hours ago, Conor said:

Mortar under the dpc, mortar above the dpc. A 20kg coping stone isn't going anywhere.

I agree generally. I guess if water got under the stone then ice formation could lift it.

[goodbyegti]

4 hours ago, Canski said:

I am also interested to know how the discs that show through your GRP can be avoided. I have 18 mm ply on firings then 200 mm PIR then 18 mm OSB3 on the top. I am toying with the idea of GRP over EPDM due to having a roof lantern. The finish on yours is what I'm after rather than pigs ears on the EPDM. 

 

I guess you could glue the ply/pir/osb sandwhich together. Not sure I would want to try it!