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I am painting our entire wooden house (about 40 years old). Some is painted and some is stained. I have already started some sections and have some questions/concerns. Where I have painted the stained section, the undercoat has started to yellow/discolour. What am I meant to put on there before the undercoat?
The painted section is also not adhering, I think it is oil based and I asked the bunnings paint section man and he said the undercoat I bought would be fine to go straight on and I didn't need to sand the wood. I have spent a lot of effort painting this section and the paint just scratches straight off, it's not sticking to the wall at all. Is this normal? was I meant to stain?
Please help! Pictures attached.
Hi @indiaww,
It sounds like the stain is bleeding through your undercoat, which can happen if the original stain isn’t properly sealed. If you're seeing discolouration, you'll need a stain-blocking primer like Zinsser CoverStain Primer Sealer to prevent bleed-through before applying your topcoat.
For the painted section, when you say it's not adhering, are you referring to the undercoat or the final topcoat? Provided it was just a stain on the area and not a stain and varnish, then you should be able to apply an undercoat directly over it. It's varnishes that require sanding.
Could you let us know what undercoat you used? That will help determine if it’s the right product for the job.
Please let me know if you have any questions.
Mitchell
Thanks Mitchell. For the undercoat I am using British Paints White water based 4 in 1 prep primer sealer undercoat. When I use the sealer how many coats do I need to do? do I do the undercoat on top of that?
With the painted section, I have done 2 coats of the undercoat but if I scratch the wall it comes straight off. As I was painting the second layer of undercoat where the roller bumped the wall the paint came straight off.
Thank you 
Hi @indiaww,
Was it raw timber that you've painted the undercoat over, or did it have a shiny surface? Would you be able to take higher-quality photos of the same timber elsewhere so I can try to ascertain whether it is coated? If the undercoat hasn't adhered correctly, it's likely that the surface wasn't compatible with being coated with a standard paint. We really need to work out why it isn't bonding before we apply any other layers.
The sealer would likely require two coats to block the stain out fully. However, first, we need to identify why the undercoat didn't bond, and secondarily, we need to decide whether this coat needs to be sanded off and the underlying timber prepared to accept a coating. It sounds like the timber needed to be sanded first to remove a coating on it that prevented the undercoat from soaking in.
Mitchell
