Sikkens query

[ando]

Hi,I've been using sikkens rubbol primer plus and rubbol Xd gloss on exteriors a few times,when using it on windows,fascias,doors etc that have been previously painted in a different product I.e. Dulux weathershield gloss ,after prep work I've been applying 1 coat of the primer plus primer/uc then 2 Xds ,I was recently told by sikkens that if the existing coat was sound I don't need to uc I was just wondering if this was right I've always uc in the past and is the primer plus ok to coat over excisting sound paintwork ,many thanks

 

[dcdec]

Undercoating promotes adhesion as well as covering minor surface defects and creating film build, surprised sikkens don't recommend it even over sound surfaces. On the occasions i've called any paint company my impressions have varied from clearly talking to the tea lady to knowledgeable , sound advice.
I u/c as standard because i regard it as best practice, carry on as you are Ando.

 

[ando]

Cheers mate I will carry on undercoating

 

[joe-90]

I think if the surface was nice and smooth I'd skip the undercoat. I'd sand it with an electric sander though.