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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Painting, Decorating & Tiling Questions >> Can anyone help? https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1153151566 Message started by madsanj on Jul 17^th, 2006, 4:52pm

Title: Can anyone help?
Post by madsanj on Jul 17^th, 2006, 4:52pm

Hi,

The exterior rear wall of my 1930's house is pebble dashed and pained with some cheap masonry paint from Wickes I believe. There are copper/brown "leaks", which I assume is rust, probably from unsealed nails/fixings behind the render/pebble dash?

Is there any way to treat these areas prior to re-painting, maybe use a PVA Building glue? Any ideas? I haven't a clue obviously :-[

Am I able to post a picture of the problem?

Cheers for any advice/comments.

Title: Re: Can anyone help?
Post by CWatters on Jul 17^th, 2006, 6:35pm

If they are rust stains I would treat the metal with a zinc based primer - better still pull them out and replace with suitably pretreated nails.

Is it possible these are cavity wall ties? In which case the problem maybe more serious.

To post a picture see the start of this thread..
http://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?board=j;action=display;num=1143304221

Title: Re: Can anyone help?
Post by madsanj on Jul 18^th, 2006, 3:53am

Thanks for commenting. Here are the photos:

http://img3.freeimagehosting.net/image.php?4a06497205.jpg

http://img3.freeimagehosting.net/image.php?178655f647.jpg

I guess it is possible that the rust is from cavity wall ties. I'm not sure how to be sure? Out of curiosity (and fear!!) why might the problem be more serious?

I dont think it is practical to pull out the offending rusty fixings in favour of some treated ones as they're not easily accessible. But I agree it would be the best remedy. Do you know of a suitable zinc based primer product that I can purchase from a DIY store? I assume the PVA Building adhesive advice I have previously been given is poor?

How about one of these products?

1) Toolstation Industrial Primer 500ml White, described as "Rust inhibitive primer which is ideal for building up repaired surfaces to a smooth consistent finish."
2) Toolstation Cold Galvanising Spray 500ml, described as "Ideal for use in coating pipework and steel fabrications to reduce corrision."

Both can be found here: http://www.toolstation.com/index.html?code=60070

Thanks for your help. It is much appreciated ::)

Title: Re: Can anyone help?
Post by CWatters on Jul 18^th, 2006, 10:27pm

wrote on Jul 18^th, 2006, 3:53am:

Wall ties hold the two walls of a cavity wall together. If they are rusted through you can get bowing of the walls. It's not allways a problem in practice but a buyers surveyor will pick up on it if you come to sell. A surveyor would probably ask for a endoscope inspection of the wall ties and if they are failing he might advise the buyer to reduce his offer to cover the cost of having them fixed.

Rusting metal expands and can crack the render letting more water in and causing more rust. Anything you do might only be a temporary fix until the metal is removed.

Zinc based primers work well on bare metal but if you can't get at the metal and just want to cover up the staining then I'm not sure what to suggest. Probably need to find a primer designed for use on render.

Title: Re: Can anyone help?
Post by WOLF on Jul 18^th, 2006, 10:50pm

gloss paint or a stain blocker!!

don't use PVA , as it is water based , enhancing the rust!!!

now where is Hammy when ya need him!!!

Title: Re: Can anyone help?
Post by madsanj on Jul 20^th, 2006, 2:01am

Thanx for your comments and advice guys. I will be returning the PVA and have ordered some rust converter, which although is water based (eeek :o) claims to neutralise rust and prevents it re-occuring and forms a tough black coating which can be overcoated with a solvent based primer to top coat; and industrial rust inhibitive primer. Both from Toolstation. Also in hand is some gloss paint (cheers WOLF) :-D

Again, thanx.

Madsanj

Title: Re: Can anyone help?
Post by hamilton on Jul 20^th, 2006, 10:40pm

I suggest giving the affected areas a good scrub to remove as much rust as possible. Then apply a coat of zinc phosphate primer which has excellent adhesion and is a good rust inhibitor.

When this is dry, touch up with some white undercoat, slightly thinned out with some white spirit. when dry, paint with a couple of coats of masonry paint.

Crown Trade is as good as any.