Rusty mark on wall. How to cover once and for all?

[Muchtoomuchtodo]

At the edge of our bay window there is a corner bit of wall that must have some metal underneath the plaster.

When we paint it, after a year or so a rusty mark seeps through again.

Are there any products that I can put on to stop this from happening?

I think your major issue is to find out why the metal is rusting. Is there a crack in the rendering/brickwork?

show us some pictures please.

As well as the rusty mark, stand back and show the rest of the wall round the window.

A photo of the outside, including the roof of the bay, the gutter, rainwater pipe and windowframe may also be informative.

Thanks.

I’ll do pictures tomorrow when it’s light outside.

You can buy a sealant. You paint it on before painting the paint over the top. It traps stains. They will continually come through paint otherwise. Its ofter used on discoloured drugs watermark which always show through. Fantastic stuff. You might need a specialist paint shop.

Ok. Got some photos.

And one more including the upstairs bay

Think I might need someone to look at those cracks.....

Looks like water getting in the cracks and rusting the beading on the inside of the wall. I’d have it looked at sooner rather than later.

You need to have the pebble dash render repaired or redone where it has been damaged as a result of your new window installation.
You need to have a surveyor check there has been no structural damage causing movement because of the new windows. (It is possible the old window frames were Weight bearing, wheras, unless litels were added, UPVC ones arent). Assuming its just a case of a repair of the outside render to stop water ingress, do that and paint the inside with sealant before painting over it again.

Oh bugger! I really hope it’s not structural. Funds won’t stretch to that. Lack of funds is one of the reasons that I’m needing to get the paintbrushes out myself!

the cracking pattern on the pebbledash is rather odd. I was wondering if it was an amateur job done off a ladder, the size the person could do with a bucket of muck.

Rain can penetrate cracks in render, and can collect in spaces or bubbles where it has come away from the wall. I think there is water penetration, somewhat higher than the rust marks you can see, because it will be tracking downwards. The wet patch is probably bigger, because the steel reinforcing corner bead under the plaster only runs down the arris. The bead is galvanised and takes a while to start rusting (stainless and plastic beads are also used now).

You may detect loose, hollow sounding render if you knuckle it. Or you may be able to see bubbles where water has collected behind and expanded when it froze. Often the size of a pancake.

It might fall off.

Render is not structural.