I have had on going problems for ages with brown stains appearing on the external masonry around the bay window of our house (it is painted white - good quality masonry paint)
Last year we were due to have the whole house painted so I decided to strip the stained paintwork down to the bare stone in an attempt to finally resolve the problem - did this, then engaged a painter to decorate the whole house exterior.
He used Sandtex masonry paint and it looked fine when first applied, but after a few days it began to visibly yellow just on the bay window area.
After recoating again with masonry paint and having the same thing happen he decied to use some Zinsser stain block when he applied this is looked ok but as soon as he applied another coat of masonry paint on top the stains re-appeared.
By this time we were running out of time weather wise (late October) so decided to leave it and see how bad it got - it got pretty bad (see picture)
Finally summoned up the enthusiasm to tackle this again a few weeks ago so spoke to the people at Zinsser and showed them the picture.
They recommended using Blackfriar anti mould treatment followed up with two coats of 'Perma white external paint' did this last weekend - looked good but now the yellowing is starting to reappear again, so it lasted 3 days.
Sorry for the long post but is there any proven method to overcome this please?
In the past I have tried oil based undercoat under the masonry paint but that didn't work either.
Now - could I try oil based gloss which I can then flat down and apply masonry paint over the top, or - thinking outside the box I even considered a flat white aerosol spray as used in car body repairs.
As you can see I am desperate here so any help would be much appreciated.
Thanks
Last year we were due to have the whole house painted so I decided to strip the stained paintwork down to the bare stone in an attempt to finally resolve the problem - did this, then engaged a painter to decorate the whole house exterior.
He used Sandtex masonry paint and it looked fine when first applied, but after a few days it began to visibly yellow just on the bay window area.
After recoating again with masonry paint and having the same thing happen he decied to use some Zinsser stain block when he applied this is looked ok but as soon as he applied another coat of masonry paint on top the stains re-appeared.
By this time we were running out of time weather wise (late October) so decided to leave it and see how bad it got - it got pretty bad (see picture)
Finally summoned up the enthusiasm to tackle this again a few weeks ago so spoke to the people at Zinsser and showed them the picture.
They recommended using Blackfriar anti mould treatment followed up with two coats of 'Perma white external paint' did this last weekend - looked good but now the yellowing is starting to reappear again, so it lasted 3 days.
Sorry for the long post but is there any proven method to overcome this please?
In the past I have tried oil based undercoat under the masonry paint but that didn't work either.
Now - could I try oil based gloss which I can then flat down and apply masonry paint over the top, or - thinking outside the box I even considered a flat white aerosol spray as used in car body repairs.
As you can see I am desperate here so any help would be much appreciated.
Thanks