Clay lump

[Bogart]

I need to support a beam on a thick internal clay lump wall. All calcs have been done by structural engineer so good on that point. What I would like is opinions on the following. The beam will rest on a concrete lintel hidden within the clay
lump. The concrete lintel will sit on a bed of mortar now here is where I would like advice. As the wall is internal it is dry and I can see if mortar is just put on it any moisture in the mortar will disappear straight into it.
So I think I have two choices, one is dampen the clay lump wall first the other is put a piece of DPC between the clay lump and the lintel. Any thoughts?

 

[george2019]

Should have just bumped your other thread!

Depends how lumpy the clay lump is... a DPM might leave voids whereas a good bed of NHL5 mortar (if you went that way) would mean better fill between the smooth padstone and the cut out in the clay lump.

Long term a DPM will do nothing and so I think careful treatment during construction (as described before - prewetting and covering with plastic/hessian) is better thing to do.

 

[Bogart]

Was only going to use a DPC strip to stop the mortar moisture being sucked into the clay lump. The clay lump is in excellent condition and the area for the lintel has been cut out very smoothly. Using M4 mortar, specified by structural engineer, as no need to use a lime mortar as intenal and being totally hidden behind plaster wall.

 

[88v8]

Don't think cement mortar is so sensitive to moisture loss. Not like lime, in that respect.
After all, a soft red brick wall is pretty sucky, one wouldn't damp that.

Just damp the lump a bit.

Ivor

 

[Bogart]

My sentiments entirely.