Connecting new DPC to existing...

[24sevenv24]

Hi all

Couple of questions regarding DPC. I am building an extension which will consist of a timber internal leaf and blockwork external leaf, I have laid the first course of blocks and im at the DPC of the existing brick built house.

1) When connecting the new DPC to the existing, should I rake out the mortor of the existing wall in order to overlap or just butt the new dpc up to the existing?

2) I will tie the new blocks into the existing wall using a starter kit but do I need to install a vertical dpc also? I see lots of videos online where this step is skipped?

Thanks!

 

[DAZB]

The overlap on a dpc should be a minimum of 100mm and yes it is usually a vertical dpc too but as you say it does not always get installed. Has your architect given you a spec as it should all be on there ?

 

[24sevenv24]

Thanks DAZB so I need to rake out 100mm into the existing wall and overlap new with existing. I haven't got an architect, submitted my own plans to building control where I mentioned that new DPC will meet old which was approved, but I see plenty of videos where the builders do not rake out the existing wall to form an overlap, they simply match the DPC level and butt it up to the old. I will rake out the old and poke 100mm in to the existing wall.

Question regarding the vertical dpc, is it simply a case of grinding a slot and poking and securing a strip of DPC in, in line with the outer block leaf? The other half of the DPC which is left flapping the open air, does this need to be secured in any way to the block work?

Thanks again

 

[DAZB]

Yes just rake out room for the dpc to overlap and then point it back in and that way it keeps the continuity of the dpc. The vertical fits into a slot you grind as you mentioned and you can secure it with sealant and then it will stop any damp transferring across to the inner course.

Detail of vertical damp proof course inserted during construction of an extension Stock Photo - Alamy

Download this stock image: Detail of vertical damp proof course inserted during construction of an extension. - RDP6HD from Alamy's library of millions of high resolution stock photos, illustrations and vectors.

www.alamy.com

 

[24sevenv24]

Yes just rake out room for the dpc to overlap and then point it back in and that way it keeps the continuity of the dpc. The vertical fits into a slot you grind as you mentioned and you can secure it with sealant and then it will stop any damp transferring across to the inner course.

Detail of vertical damp proof course inserted during construction of an extension Stock Photo - Alamy

Download this stock image: Detail of vertical damp proof course inserted during construction of an extension. - RDP6HD from Alamy's library of millions of high resolution stock photos, illustrations and vectors.

www.alamy.com

Thanks very much!