How to add a DPM under an existing stud wall

[Omnibuswoman]

 

In our semi built workshop we have two rows of breeze blocks, on top of which is a strip of DPM, followed by the wooden frame for the walls. On the front wall we forgot to put the DPM on top of the blocks before putting on the frame, and now we are thinking about whether or how to add a DPM there before we add the cladding and finish the structure.

 

I've tried digging out the mortar that sits on top of the bricks with a multitool, but without much success. I also tried to get a saw in there to cut out some mortar, but again without any real success.

 

My questions are: how important is it that we have this DPM strip in place? Is there an alternative to removing the mortar that is easier? Should I consider just paying someone who knows what they are doing to do this? 

 

I've added a picture that has the wall in it - it isn't a picture of the wall as such but it was the best one I could find.

 

[MikeSharp01]

Hmmmmm - you definitely need to find a solution for this otherwise any damp will rise into the walls. You may be able to inject a DPM chemical into the blocks this is done on older houses where no DPM is present. Have a look at what is out there that might be DIYable.

[tonyshouse]

Jack the frame up, lever it up and slide dpc in - last resort is to bang slates in as they will act as a dpc 

[markc]

26 minutes ago, tonyshouse said:

Jack the frame up, lever it up and slide dpc in - last resort is to bang slates in as they will act as a dpc 

+1 to this, won’t be too difficult to jack up using wedges or acros.

[Omnibuswoman]

Thank you! Can I use a car jack for this? I’m guessing I only need a few mm to work with to get a dpm slid in..

Edited November 19, 2021 by Omnibuswoman

[markc]

Just now, Omnibuswoman said:

Thank you! Can I use a car jack for this? I’m guessing I only need a few mm to work with to get a dpm slid in..

Yes, car jack with a timber on top etc, or a piece of timber, add packers to make it just over length and tap knock it in until vertical to give you a few mill of lift.

or crowbar, chisel etc, lever up and put a temp wedge in.

[Mr Punter]

I like to use a spade or my Big Mutt for this sort of thing.  Wide strong blade and a long handle.

[Pocster]

5 hours ago, Mr Punter said:

Big Mutt

SWMBO ??

[Omnibuswoman]

On 19/11/2021 at 08:33, markc said:

Yes, car jack with a timber on top etc, or a piece of timber, add packers to make it just over length and tap knock it in until vertical to give you a few mill of lift.

or crowbar, chisel etc, lever up and put a temp wedge in.

Thanks for this Mark. Are you able to point me to a YouTube video or draw a quick sketch of what you’re describing please? I have never used a jack before and can’t quite picture what a timber on top of a jack looks like!! (Total novice here)

[markc]

2 hours ago, Omnibuswoman said:

Thanks for this Mark. Are you able to point me to a YouTube video or draw a quick sketch of what you’re describing please? I have never used a jack before and can’t quite picture what a timber on top of a jack looks like!! (Total novice here)

Hi, depends on what car jack you have and where you can lift/support your structure.

think of putting a fence post on top of the jack to make it much taller (assuming you will lift under a rafter or door header etc. Be careful to make sure it is vertical and jack is secure or the timber will want to push out …. With force.

an acro prop is the safer and easiest way of supporting/lifting joists or a doorway etc.

[joe90]

Is the ceiling In yet?, if not get some 4x2 a little longer than floor to ceiling joist height, against the wall at the bottom at an angle and slide (wollop) against the ceiling joists, this will lift it the small amount you need.

[Omnibuswoman]

brilliant! Thanks so much. We have plenty of timber, and no ceiling on as yet, so will have no problem doing this.

[Onoff]

Haven't you already got a DPM under the slab / DPM at the base of the blocks where they sit on the slab?

 

If so, and the blocks are being clad externally, I can't see the issue of how they will get damp hence maybe leave as is. 

[Omnibuswoman]

1 hour ago, Onoff said:

Haven't you already got a DPM under the slab / DPM at the base of the blocks where they sit on the slab?

 

If so, and the blocks are being clad externally, I can't see the issue of how they will get damp hence maybe leave as is. 

 

We have a DPM and radon barrier underneath the concrete slab which laps up and under the blocks around the edges, although where it ends and at the corners is a bit messy and I'm not wholly sure what we should do with that. But for the most part i think it's ok. 

[Omnibuswoman]

@tonyshouse @markc @joe90

thank you all so much for your advice on this. Just wanted to update that this was successful and not too difficult. I’ve uploaded a couple of pics which are not that fascinating but a testament to the excellent advice you all gave me. Thank you! m

[tonyshouse]

Well done and UW