Bell cast

[Moggaman]

Hi. In my new build, my missus wants no bell cast plinth at the bottom just the plaster running all the way down. 
Is there any reason I cannot do this?

thanks

 

[ProDave]

I assume you are talking about render on the outside not plaster?

 

This is surprisingly common around here to see this done but I wonder how it works properly.  The bottom of it is below the DPC and so will be prone to getting tamp from the ground and bridging the DPC.

 

I had exactly this on a previous 1930;s house.  The walls had "rising damp" in several places, completely cured by removing the lower render and terminating it with a bell cast just above the DPC and leaving the lower brick exposed.

 

So I do wonder what troubles are being stored up for the future if you do take the render all the way to the ground.

[Annker]

Yes you can take the render all the way to the ground but as Prodave says the issue would be that the render material bridges the horizontal DPC.

Therefore you need to introduce a horizontal movement joist at DPC level that will separate below DPC render form the above DPC render.

Something similar to below would work.

 

Edited January 20, 2022 by Annker

[Temp]

Not all manufacturers approve their render for use below the DPC. Check before buying.

[Annker]

On a recent project part of the building had a dropped DPC level.

 

The client wanted the bellcast at a common level all around the building and render below DPC as typical.

So we installed the bellcast detail at the higher DPC and then introduced a movement joint over the portion of the DPC that was at the lower and therefore exposed level.

Weber approved of this arrangement.

 

The movement joint achieves separation of above/below renders however what is absent is the protection that a projecting bellcast provides above the DPC. 

The bellcast is essentially a drip detail and I'm not sure how that can be acheived where the render above/below DPC is set at a common thickness.

 

    

 

Edited January 20, 2022 by Annker