Exterior Paint already failing

[DIY67]

Well, I used Screwfix trade undercoat and primer paint on new wood. Then finished with Dulux weathwrseal and after the first sign of rain it's starting to come off. Why?

 

[Wayners]

Read the application data sheet and stick to the manufacturers primer recommendation. It's been tested.
It's not recommended to mix and match brands.
Stick to what's been lab tested.
Also stick to coating times and cure times.
What was the recommended primer to match top coat?

 

[opps]

Is that a knot in the image? Is it failing elsewhere? If not it may just be resin from a knot.

 

[DIY67]

Is that a knot in the image? Is it failing elsewhere? If not it may just be resin from a knot.

You might have something there. I think it might be.

 

[DIY67]

Read the application data sheet and stick to the manufacturers primer recommendation. It's been tested.
It's not recommended to mix and match brands.
Stick to what's been lab tested.
Also stick to coating times and cure times.
What was the recommended primer to match top coat?

I haven't mixed and matched brands as it's undercoat and primer in one can.

 

[Wayners]

Sorry.
I thought you primed with the Screwfix undercoat then applied the weather shield over the top on the wood.
I read on the data sheet that Dulux multi surface primer should be used for that.
Not sure then. Maybe the Screwfix undercoat needed more time to cure? Recoat times are not the same as cure times.

 

[DIY67]

The weathwrseal was applied to the shed previously on its bare wood with no undercoat or primer and no problems. This was just a piece of wood under the sill I replaced.

 

[DIY67]

Having said that it seems to be lifting on the windowsill after 2 or 3 coats.

 

[sparkwright]

Was the wood damp when you painted it?

 

[opps]

Have you used the Weathershield masonry paint over the woodwork or their paint for woodwork? Is it Dulux Trade Weathershield or Dulux Weathershield?

 

[DIY67]

Its Fortress Trade interior and exterior Primer & Undercoat White 1Ltr

 

[JohnD]

Looks to me like damp penetration. Not so likely to be penetration through the paint, more likely getting into the wood from above or behind.

The assembly detailing of construction may be the cause. It is helpful to paint exposed woodwork all-round, including the back, before assembly.

I prefer to treat sheds with a breathable stain that allows damp to escape. Paint prevents it getting out.

 

[DIY67]

Again this is another indoor windowsill recently painted. No moisture or anything and yet it is already peeling.

 

[DIY67]

The front door step area also flaking

 

[DIY67]

Same with the front door painted year after year with same results. Dulux so called weathershield.