Ok, we may have made a mistake but we've had the concrete block wall below DPC rendered with a sand and cement render.  We did this because concrete block walls don't quite cut it aesthetically.  

I am confident there is no bridging of the DPC.

 

Above the DPC sits our timber frame finished externally with a ventilated cavity and either STS cement boards + thin coat render, or vertical timber cladding.  There is a 45mm horizontal gap with inset mesh between the rendered blockwork below DPC and the external wall finish above DPC.  The DPC itself overhangs the rendered blockwork by 20mm or so, so we're confident there is no bridging issue.  The blockwork below DPC supports a ventilated block and beam floor as well as the timber frame, and is thus itself ventilated on the inside.  

 

My question is:  How to finish the render?   Can we leave it unfinished?  Can we paint it with a breathable masonry paint like Sandtex? (We're thinking a darker colour might look better.)   Will that below DPC render inevitably 'blow'?  

 

Thanks as ever for any thoughts or suggestions.

 

Some pics.  

 

Before:

 

How it looks now:

Edited October 2, 20251 yr by Benpointer

Sounds like a similar situation to me: Timber frame on blocks. We've just had the blockwork rendered below DPC (well, after they finished I went around with a cold chisel and made damn sure ALL the render finished below DPC, not just "most" of it 🙄). Vertical timber cladding stood off the timber frame ~62mm will hang down ~50mm over the render. We're just leaving it natural colour. I'm concerned that as the render permanantly exposed to damp (wicking up from the ground) any paint may blister off with time...hopefully the render itself won't blister!

6 hours ago, Dunc said:

Sounds like a similar situation to me: Timber frame on blocks. We've just had the blockwork rendered below DPC (well, after they finished I went around with a cold chisel and made damn sure ALL the render finished below DPC, not just "most" of it 🙄). Vertical timber cladding stood off the timber frame ~62mm will hang down ~50mm over the render. We're just leaving it natural colour. I'm concerned that as the render permanently exposed to damp (wicking up from the ground) any paint may blister off with time...hopefully the render itself won't blister!

Yes, sounds very similar.

 

I also have a concern about the paint blistering, hence the question - in the hope that someone has done this a few years ago and report on their experience.

Apols for bumping this one - still pondering whether to paint the sand and cement render that is below DPC, and if so with what? 

 

If anyone has any experience or suggestions they would be gratefully received. Thanks!

Edited November 17, 2025Nov 17 by Benpointer