Expander mortar

[Vandrak]

I am going to cast in a small slit where there are water pipes, PVC pipes, etc. What I am wondering is how much pressure the expanding mortar exerts. Is it strong enough to crack the pipes?

 

[bruschen]

In most cases, expansion mortar is only "shrink-free," meaning it does not exert any pressure on your pipes. Read the packaging.

Do you really need to pour in concrete then? Can't you use foam sealant or something similar to seal it? How big is the hole and where is it located?