Plinth Bridging DPC

[chrisjones77]

Our Victorian terrace has an external rendered plinth bridging the DPC. Based on damp specialist survey I've taken it down to what I thought is below the slate DPC - see attached images. However on taking the render down further looks like there are further slate courses - what are these ??

My question is what to do know:
A) take all render off down to ground and repoint with lime mortar (although much brick work is damaged) ?
B) as above then re render to just below DPC ?

Also is lime mortar better than cement as it allows moisture through ?
I've never done pointing or rendering (DIY novice) so is this a specialist thing or achievable for a beginner ?!?!

Any help or advise appreciated.
Thanks
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Untitled

• chrisjones77
• 30 Nov 2014
• 1

Untitled

• chrisjones77
• 30 Nov 2014
• 1

 

[theprinceofdarkness]

Normally the mortar course that includes the slate DPC is thicker then then normal mortar courses. So I think the lower level is the proper original DPC. Unfortunately its is now too low compared with the concrete path.
I would lift a floorboard inside to figure out where the damp is coming from and what that air brick is meant to be doing.
Taking that rendering of the plinth is a double edged sword, it might encourage more evaporation from the lower bit of the wall, but it will suffer from more splashback due to the rain.
Frank

 

[ree]

I doubt that your original slate DPC has failed - its correctly located below the joist tails if the air brick position is any indicator. It was probably 150mm above ground level.

The Damp company that drilled the useless too high line of holes, and probably installed the new'ish air brick, did not take into account that the plinth was bridging the slate DPC and creating any damp conditions.

As above, examine the sub-floor joisting, and interior wall decorations and skirting for damp or rot.

Remove the plinth and probably rake out to 20mm and re-point in 4:1:1 S&L&C or 3::1 S&L. Consider re-pointing the whole elevation. Replace any perished brick. The green hue on the concrete surface is splash from above - gutters etc. so maybe use Thompsons Water Seal or similar on the lower courses?

Practice pointing in an obscure area and see how you get on - if you start smearing brickwork then stop.

 

[chrisjones77]

Thanks to you both for replying, so nice to have some reassurance!
I think the lower slate course is the proper DPC, why it was rendered over is crazy and anyones guess. Cowboys.

The specialist damp survey I've had (a non commercial independent survey) recommended its removal, unfortunately our kitchen/oven etc is the other side of the wall, so investigation into the sub floor under the suspended timber floor (which is also covered in rubbish laminate.) will mean major disruption which we are planning in spring.

I don't believe that injecting a new DPC is the answer (more a money grabbing solution). The Victorians built these places correctly we have just messed them up over the years. I also can't believe there is anything wrong with the slate as we have no subsidence.

Think the plan is to remove right down to ground, repoint with lime mortar and (eventually) take out the in situ concrete patio, lower the external level and deck over so its permeable outside with less splash back.