Soft Mortar

[DodgySailor]

Hi,

I just bought a new house build circa 1930. I am removing the wallpaper and in some areas the plaster has come off exposing the brickwork. I noticed that the mortar holding the bricks toghether is quite weak and can be scrub off very easily with just a screwdriver. A couple of bricks seem a bit loose .I have to say that the external wall is a double wall with an insulation cavity apparently typical form the 20s. Other internal walls seem to have the same type of mortar. Is that normal in these type of constructions or is the cement just gone off?I read somewhere that the cement used in internal walls is porous to allow the wall to "breath". Is this correct?

 

[jeds]

It's hard to know what you mean by soft? Your house is most likely built with lime mortar - which generally is soft. The beauty of lime mortar is that over time it will re-knit after movement. Unless it really is falling down my guess is that it's fine. Could you inject a squirt of adhesive into the loose joints. Some thinned PVA will bind it quite well.

 

[DodgySailor]

Well by "soft" I meant it crumbles easily with just a screwdriver. I was just concern about the strength of the wall and the plasterer told me that the mortar just went off as it is very old. Then I read that this may be normal in this old buildings. I am not sure the plasterer new much about it. So can I assume this is normal then?

 

[jeds]

Is it black/dark grey?

 

[DodgySailor]

Is more grey... I have attached a pic:
//www.diynot.com/network/DodgySailor/albums/9276/35478

 

[^woody^]

Internal mortar is supposed to be soft to allow for the regular movement- which would otherwise crack harder mortar

In fact its only purpose is to keep the bricks apart

 

[flameport]

Then I read that this may be normal in this old buildings.

It is. Probably millions of houses and other buildings just like it. Old plaster falling off is common as well - only the wallpaper holding it together.

 

[DodgySailor]

Thanks for your input. That is what I thought.
DS