Lime torching

[Ciaransmith]

Morning all,

We have a section of our old roof without any membrane underneath and when its blows a certain way when raining it pushes (i think) up the slate and into the roof. I am thinking of lime torching as a way to fix this. My question is, everywhere ive looked it says to use non hydraulic lime, but ive got a ton of nhl2 left over.

Any reason why i cant use this stuff mixed with sharp sand?

Thanks C

 

[stuart45]

It needs to be as breathable as possible, so you could replace some of the NHL with hydrated, as well as some horse hair.

 

[Ciaransmith]

Ive read somewhere that the magnitude difference between NHL and hydrated is small enough to not cause an issue, please correct if this is wrong.

Also can i use the plastic equivalent or horse hair. I believe its just little strands of plastic

 

[Jblakes]

we had pretty much the same problem but a small sloping old roof. We planned to remove the tiles and fit a breathable membrane, but due to a number of issues that needed solving at the time, we didn't have the funds available.

We used a mix of what we had left, NHL, lime putty, sharp sand and plastic strips (the new horse hair apparently). Its been 3 years later and we have had no sign of any rain/rotting/insects etc, from what was a leaking roof from driving rain. So i guess like stated above, mix some NHL with a more breathable lime, although i'm still not sure there is that much difference between any of the lime mortars. Pretty sure @a twig posted a youtube video of this a while ago and they all performed similar (within reason) of each other