New dpc joint to old, hot poured asphalt dpc

[RedHerring2]

Anyone any suggestions. The old dpc appears to be a hot-poured asphalt type dpc which appears to have been laid on top of a layer of mortar, and spans accross the cavity(filled with ballast).
Each time I try lifting a brick carefully to try and preserve a bit of the old dpc, the lot just lifts with the brick. I've gone back along about three bricks so far with the same result.
So I have virtually nothing to overlap with the new dpc.

Anyone's experience/suggestions would be welcome.

I doubt that BCO will be able to see it afterwards, but I'd like to try and get some continuity, if possible.

 

[joe-90]

Have you considered leaving it and using a silicone cream DPC in the mortar course?

 

[RedHerring2]

Sorry, Joe. I'm not sure I fully understand your response.

The new dpc is for the extension, and the old dpc is in the existing solid 9" wall. (Although there is an exisitng cavity below dpc). I'm toothing in to that existing wall for the new extension, (on exisiting footings at that point)
Spec says dpc 2000g hyload or similar.

 

[joe-90]

Oh right. Sorry I misunderstood.

 

[theoldun]

Your DPC is not hot-poured asphalt, but old Astos bitumen felt DPC. Even when it was new, it was very brittle, and we used to have to cut of and throw away the last 300mm on the roll as it was nearly always cracked. Pity they have stopped making it as it was very handy for packing joists, door linings etc.
We have a big old Sandvik hand brick saw, no longer made now, and we saw the bed joint out 150mm long and slide the new poly damp in.
Your best bet, use a 5.5x160 SDS bit and stitch drill 100 to 150mm along the DPC bed joint either above or below the DPC, which ever is the thickest. Get old hand saw and saw rest of slot out. When end of saw worn out, cut worn bit of saw and use next 150mm of saw.
Slide new poly damp into slot and then bed and lay damp in normal fashion.
oldun

 

[stuart45]

We have a big old Sandvik hand brick saw, no longer made now,
oldun

I bought one about 30 years ago and it's still in use. It's great for toothing or cutting out a coulple of bricks from BOE course. I even used it to cut some of the bricks in our porch.

Untitled

• stuart45
• 30 Oct 2010
• 1

 

[RedHerring2]

Thanks, Oldun. Mortar is pretty soft so I'll try with an old hand saw.

Hmm, thinking that, what about a reciprocating saw or even a jigsaw with a blade for metal?

Although I guess there's more control with a handsaw.

I'll see how I go with the handsaw.

 

[theoldun]

If you have a reciprocating saw, stick a Dewalt demolition blade in and that will do the job. Did not know whether you had recip saw, thats why I said stitch dirll.


Stu. Ours is bit bigger than yours. Had it close on 50 years. Been re-toothed twice, needs doing again. Wish we could buy another one. Bet the price would be 200 quid now.
oldun