Attic Firewall - old house

[Panmure]

Hi,
I need to build a solid block firewall between two halves of my old house. I've got the blocks but after carrying them from the truck to the garden I've got scared that they'll be too heavy for my old walls!

The walls are natural stone with lime and mortar, about 80 to 60 cm thick (nothing is straight!) and two stories high. I need to put about 5msq of wall up (following the slant of the roof).

Can these old walls take the weight?
What's the best way to prep the old walls ie: a mortar layer put onto of them, smoothed off and left to dry as a base?
How do I ensure that the block walls are fixed to the house walls and not just balanced on top (as a neighbour found his was - you could gently rock the whole wall as one solid lump!)

Thanks for your ideas/experiences

 

[Static]

The foundations should be checked that they can support the additional load if not then use a lightweight fire blanket.

 

[JohnD]

If it's simply a firewall, you could put it up with metal lathing and plasterboard. Much lighter and could be braced to the roof timbers to stop it falling over.

 

[Panmure]

Erm, as far as I'm aware the house doesn't have any proper foundations - it's a old conversion - it just sort of sits on the first level of stone. Really.

 

[Static]

Then go lightweight as JohnD suggests

 

[Panmure]

Actually, after looking around, I see that there's a recently breeze blocked wall at another end of the attic - I guess the walls are strong enough.

What's the best way of preping the wall tops to take the block fire wall?