Advice on pebbledashing

My son lives in a Victorian red brick house, the top half of the exterior pebble-dashed. This was grey and worn. He has had it renewed and painted white which made a big improvement to the house. But red/brown stains keep appearing through the paintwork. These stains didn't appear to be there before the work. The builder has been back twice now to repaint but the problem persists and he (the builder) is losing patience! Anyone out there suggest what the problem is and how it can be fixed permanently? Any sound advice much appreciated.

Has the builder left any nails or screws in the brickwork before he pebble dashed it?

Thankyou melv. worth investigating.

I think you may have a post -V house with some wall ties which are erupting.They were not galvanised and when wet would corrode,expand and push the two leaves(of wall) apart.The outer leaf is displaced and the wall collapses.There again it could be buried metalwork eg old fixings.Your builder really should have addressed these issues prior to rendering.

---------- Post added 21-10-2013 at 15:57 ----------

My son lives in a Victorian red brick house, the top half of the exterior pebble-dashed. This was grey and worn. He has had it renewed and painted white which made a big improvement to the house. But red/brown stains keep appearing through the paintwork. These stains didn't appear to be there before the work. The builder has been back twice now to repaint but the problem persists and he (the builder) is losing patience! Anyone out there suggest what the problem is and how it can be fixed permanently? Any sound advice much appreciated.

The builder needs to use an oil based paint to blind any metal objects- a good builder would have drilled out the offending items before the base coat was applied.

If it's a Victorian house it wont have a cavity. You could apply a stain block to the stained areas, however, if it's metal it will eventually expand & 'blow' the render off the wall. You could use a metal detector to find the metal.

What pebbles did he use some have iron deposits in and they produce what looks like rust

Thanks for all replies. All make sense and worth investigating. The builder is in the Fed of Master Builders and my son had used him for another job with which he was very pleased. A big problem is that he is wanting to put the house on the market early next year and if he persists in getting the builder back, it won't look good to show that there's an on-going argument with the builder.