wrong undercoat: not an issue or unmitigated disaster????

17 Jun 2014
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United Kingdom
For some reason, my brain seems to have had a lie in early this morning when my novice attempt at DIY continued. Having cleaned and sanded two exterior 1/2 brick /1/2 render garden walls and stabilised them with appropriate stuff yesterday , I was up and at it buying and applying undercoat early this morning. I didn't stop until both were finished and stood back feeling faintly proud of my attempt as I bent to down to read the back of the tin for drying times. Only then did I read the small print at the top of the tin and realised I'd applied exterior timber undercoat (Dulux Exterior flexible undercoat) instead of an exterior masonry undercoat. It was a flipping expensive one promising all sorts of protection against raging snow blizzards and hurricans and golfball size hail storms for at least two centuries (OK I"m exaggerating just a wee bit here but you get the picture!) Doh! Does anyone know whether this is :

a) an unmitigated disaster requiring stripping it all off and starting again (noooooooo! )
b) not a big deal and I can keep this particular diy drama quiet and I carry on with the masonry topcoats I'd planned for tomorrow
c) requires new masonry paint instead of the handy 5 litre tin I had spare from years ago which is still in good nick.

I've tried to see whether the paint I've used is oil based or latex based , so as to try and match the top coat with the same base at least, but can't find anything on the tin! Any suggestions anyone? I'm a bit new to the whole DIY thing, not to mention recently needing reading glasses which I didn't have on me in the Dulux shop hence perhaps explaining why I maaged to pay a fortune for the wrong product and then stick it on the wall! aghhh!

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As to water oil based just look at the cleaning instructions for brushes on the tin. If is says clean up with water / soap it's water based if white sprit it is oil.
Can be a bit confusing if it just says brush cleaner though ;)

Just mix a bit with water if it does not react in any way separating or floating on top and just thins it, it is water based.

As to the faux-pas well I would just carry on and hope for the best you will never get it off masonry anyway :cry:

As you suggest try to stay with the same type of paint chances are you will get away with it I have seen concrete posts painted with wood preserver that held up well.

I would give it a day or so the see if anybody else has a suggestion then "keep calm and carry on" :D
Thank you so much for replying. Much much appreciated.

Yes confusingly the tin just advised 'brush cleaner' which I took to mean white spirit and washed brushes in that. Will dip something in it today and try your test. I also tried to ring Dulux but apparently all their technical staff are unavailable due to 'training'.

I did wonder why the brush that I'd brought for masonry painting seemed to loose so many hairs in the thick gloopy undercoat. It was driving me round the bend! I was quietly blaming myself (and Dulux) for being lured into buying an all in one kit (brush, rollers etc) but perhaps it was in fact a case of wrong brush with wrong paint!

I'll do as you say and leave it for a day incase someone else has any more light to shed on my DIY dilema or til Dulux finally finish their training and advise.

Despite the disaster it looks great!!!

Thanks so much for advice. I've a feeling I'll be visiting this site a lot more during my forthcoming exploits and adventures with DIY!

Well just incase anyone else ever gets into this situation.... I've just spoken to Dulux who advised that the undercoat is oil based and the masonry water based. Their advise was to sand back the wall and then leave it 2 or 3 weeks to get rid of any remaining solvents. They thought that as the undercoat has a sheen to it, it would be hard for the masonry to adhere to as is.

Ohhh... and that all I had needed to do was used a 5 paint to 1 water solution of paint as an undercoat in future.

Note to self: Take reading glasses with me when shopping in future!!
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Click on product data sheet


That one looks like it is white sprit based.

This one scroll down water based


Hope it helps.

Either way there is a fair chance you will get away with water based top coat if that is what you have left over just try a small section and let it dry for a day or so.

With old paints just be careful not to use any that have been stored where they may have been damaged by frost.

Please post how you get on :)
Oh dear! I just saw your post, see how you get on with sanding off if it is a complete nightmare one answer although quite expensive would be to use another primer for difficult surfaces over the shiny paint.

Zinsser Bullseye 123 will take even on plastic surfaces can be used inside or out, it is water based and can be overpainted with water or oil paints.

Dulux will play safe but still best to follow their advise not to paint directly over it with the topcoat.

Just one last thing if the garden walls do not have a damp proof course the paint may well flake in time, that will not be a fault with the paint or application of it it just happens in time.
My guess is that if the brush came with the paint, it's probably a cheap-ass brush, hence why it readily gives up it's bristles.

I'm not really an expert on painting so not really sure what to suggest but I think you'll find getting the existing stuff off will be the biggest pita going. As suggested, I'd maybe experiment with a small patch and see what works. I'd probably start by putting the top coat on as planned and see if that works. If it doesn't, maybe try putting the masonry undercoat over the timber undercoat and see if that works. If you're having adhesion problems, I wonder if it may work to rough the undercoat up with a wire brush?

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