goodbyegti Posted October 8, 2023 Share Posted October 8, 2023 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!): Link to comment Share on other sites More sharing options...
goodbyegti Posted October 8, 2023 Author Share Posted October 8, 2023 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. Link to comment Share on other sites More sharing options...
nod Posted October 8, 2023 Share Posted October 8, 2023 I bedded ours on mortar 5 years ago and they are fine They are extremely heavy and unlikely to move 1 Link to comment Share on other sites More sharing options...
bmj1 Posted October 8, 2023 Share Posted October 8, 2023 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. 1 Link to comment Share on other sites More sharing options...
Conor Posted October 9, 2023 Share Posted October 9, 2023 Mortar under the dpc, mortar above the dpc. A 20kg coping stone isn't going anywhere. 1 Link to comment Share on other sites More sharing options...
Canski Posted October 9, 2023 Share Posted October 9, 2023 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. 1 Link to comment Share on other sites More sharing options...
Canski Posted October 9, 2023 Share Posted October 9, 2023 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. Link to comment Share on other sites More sharing options...
goodbyegti Posted October 9, 2023 Author Share Posted October 9, 2023 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. Link to comment Share on other sites More sharing options...
goodbyegti Posted October 9, 2023 Author Share Posted October 9, 2023 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! Link to comment Share on other sites More sharing options...
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