Getting work done on damaged roughcast - advice please

gubar

Hi,

we had some issues with penetrating damp which has been traced to some cracked render (roughcast or pebbledash - from the 1930s, with semi-smooth stones I think, painted over) on the rear wall of the house and the chimney stack. We are in the process of getting quotes to have this repaired.

Both quotes so far have suggested removing and repairing broken sections, using a base coat, a mesh, then the top coat. One said he would use krend, the other didn't specify (I've asked for more information).

One has suggested just patching, the other patching, plus going over all the roughcast on that one wall. So the broken stuff is removed, then the whole wall is gone over for a complete new coat of rough cast.

This would all need to be painted, since the whole house is already painted.

Anything I should be aware of, or look out for when getting these quotes? I've already asked them for a more detailed breakdown of materials and processes, so I can post that back here.

I have read conflicting things online about putting roughcast over roughcast - some suggest it's fine, others that it's not.

I am also unsure of whether the original roughcast was cement or lime based. Is there an easy way to tell, and will this affect what can be put on top?

Thanks for any information,

g

brightontraveller

Explains roughcast and pebbledash differences different mixes, repair, solutions to water ingress etc

http://www.buildingconservation.com/articles/pebbledash/pebbledash.htm

nobulljusttruth

I have never seen a repair that matched . The chance of replication old dash is almost impossible.,

If damp is behind concrete / cement based renders it cant get out. silicone based renders like K-rend, Webber etc, breath and need no paint. They do however only come in smooth or brick effect. Not dashed.

Plasterer

nobulljusttruth wrote: »

I have never seen a repair that matched . The chance of replication old dash is almost impossible.,

If damp is behind concrete / cement based renders it cant get out. silicone based renders like K-rend, Webber etc, breath and need no paint. They do however only come in smooth or brick effect. Not dashed.

You can match pebble dash if you know what your doing, correct stone size and amount thrown etc. you can also get k rend rough cast. To answer your question your 1930's house will be done with sand and cement not lime ( Portland cement was being used forty years prior) don't have a patch done with k rend though waste if money as the rest of your house is in sand and cement.
You can render over render however it's not something I would do personally as you are going over years if paint and therefore cannot guarantee longevity.