Which is the right mortar

[Andy and Sarah]

We are renovating the typical 19th century french house and need to fix and repoint a few internal stones prior to plasterboarding. we have been advised not to use sand and cement but rather a sand and lime mix.

However, when we go to Castorama / Leroy / Pont P there are just loads of different bags of mortar mix and our 'building' French is not up to determining which is the most appropriate - can anyone advise

[Northender]

Just a thought but why would you want to point the walls if you are going to cover them with plasterboard?

I thought the idea of using lime mortar was to let the walls breathe?

Seems pointless when you're covering them up with plasterboard.

[Anton Redman]

The problem with pointing in concrete mortar :  The pointing is stronger than the stone so every time you repoint you are taking chunks of your wall.  The concrete has no give so small movements always mean cracks which lime mortar may absorb.

[Ron Avery]

Anton I presume you meant cement mortar, concrete mortar can be a little bit lumpy[blink]

For just tightening up a few stones on an inside wall to be covered later just use a mortar mix of ciment+chaux (sold as LM plus) and sand. 1 to 5.  The lime content  allows a bit of movement.

[La Guerriere]

Buy sand sand, buy some lime. Chaux bagged up (hydraulic lime) St Astier NH3.5 or similar. Try 1:3 chaux / sand but you can fiddle with the mix to taste.

[Ron Avery]

[quote user="La Guerriere"]Buy sand sand, buy some lime. Chaux bagged up (hydraulic lime) St Astier NH3.5 or similar. Try 1:3 chaux / sand but you can fiddle with the mix to taste.[/quote]

...................before hiding it behind plasterboard[:-))]

 

[BIG MAC]

[quote user="Northender"]

Just a thought but why would you want to point the walls if you are going to cover them with plasterboard?

I thought the idea of using lime mortar was to let the walls breathe?

Seems pointless when you're covering them up with plasterboard.

[/quote]

1. Because if you don't sort it now then you could end up having to remove the plasterboard later to do what could be done now

2.Peace of mind

3. Old mortar droppings behind Plasterboard could create a damp bridge

4. Friable mortar behind Plasterboard could allow movement in the wall itself thus compromising the new finishes in front

 

 

[Jo]

[quote user="BIG MAC"]

3. Old mortar droppings behind Plasterboard could create a damp bridge

 [/quote]

I have two plasterboarded rebates by the kitchen window which are damp with the paint peeling, have been trying to work out where the damp is coming from,  and there is obviously something crumbly behind the board as you can hear it rattle when you bash the wall[blink] I bet that's my problem! Thanks!

[BIG MAC]

So a 4,3,1, localised repair then 2? Bon chance and happy to help

[Andy and Sarah]

Thank you all - just want to secure the stones behind the plasterboard - don't want then falling behind the board and hitting pipes, cables etc.

Will try and find the sand and Chaux ready mix at L Merlin.

Thanks again

[Dave&Olive]

hi ok

                  just make sure you vent the cavity as well

                  Dave