Lime Mortar & SP +

M

Megan birnie

New Member
Hi,

I have just signed up to this forum and I am in need of help and advise if possible please.

I live in a granite cottage which has major damp issues, an independent damp specialist came out and advised that the render on two of the external walls (third isn't rendered) is sand and cement when it should be lime so the building can't breath.

Now the time has come to re do the rendering, we were hoping to remove the render, repoint with lime mortar and then just paint it. Our local lime company have advised using a product called Beeck SP plus which appears to be used to waterproof/harden the granite.

I was wondering if anybody has used this product before or anything similar And had good results with it?
We don't want to scaffold the house do it all and then find in the winter it's not been successful and have to re render the whole house instead!

Thanks

Megan
 
Granite stone that needs hardening ??? I was under the impression that granite was one of the hardest grades of stone ? It does sound like the sand and cement render is trapping water against the stone blocks but have you identified the cause of the damp ?? It may be as simple as blocked gutters or rain water pipes ? Is the out side ground level higher than the internal floor levels ? Is the damp in your bathroom only, because if it is , it could just be lack of ventilation. Before you spend your money you should find the reason for the damp
 
Hi you need to apply a traditional horse haired plaster which can be done in 2 or 3 coats depending on the finish you are looking for. This is not a hydraulic lime as nhl lime has not been cured. I do this every day and stick to a company called mike wye for materials as it has been slacked of for 3 months and left in a barn to mature. Waterproofing the house can cause problems if you don't have a cavity. I would use a lime specialist as its much more involved then normal renders and shouldn't ne messed with by some one who hasn't done it before! Hope this helps
 
Definitely a job for a specialist. There are different grades of nhl. For rendering onto granite you need to use nhl5. Get it wrong and it'll be a costly mistake.
 
I agree with pug, a natural hydraulic lime ( a NHL ) hydraulic lime will set quicker. Hydraulic lime will set under water so no problem with the British weather. A none hydraulic needs carbon monoxide to set, so depending on the thickness you may have to wait along time between coats,
So as I first said a hydraulic lime render, with pozzolanic additives a breathable render which can be applied with out to much time between coats.
Basically the French rating system for lime is - 12% active clay 12 to 18% active clay and 25% active clay i.e. NHL 2. 3.5 or 5
 
Nhl lime has not been slacked of and the stronger it is the less breathable so a nhl 5 is more as less the same as using a normal sand and cement render! Yes a lime putty will take much longer to set but will cure your damp as it will alow the walls to breathe. Nhl 5 is only added to the mix on lath work to increase setting time and add strength. What do you think people used 100s of years ago?! The traditional way is the best if you ask me!
 
WOW stoke plasterer dont no what you lot do in stoke! but where i live thats what myself, the grade listed conservation officer and english heritage say to do on the barn im working at may be you could teach us all a thing or too and could give mike wye the leading lime producer in the uk a lesson on what to do with his own materials!!!!!!!!!!!!!!!!!! Jump back on the multi-finsh son you dont know what your talking about!
 
Tell you what Mr expert have a look at his video for Venetian plaster lol lol he can't use his own product.
Read your batsford or your milliar, you really don't want a really hard lime on a ceiling or stud, it's good advice ( you can take it or you can leave it) we have recently done 500m2 of lath and plaster using 13,000 meters of lath and had no problem at all. Thats probably two or three days work for you boy.
 
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