Martin Pentreath wrote:
Interestingly the Dulux Weathershield instructions expressly say:

"If the surface is still powdery after thorough preparation, seal it
with a coat of Weathershield Stabilising Primer, but do not seal
sound, new or bare surfaces."

I did get frost damage where I get driving rain..bouncing off flat
lintels over the windows etc. ..use a penetrating sealer on north and
west exposed areas.