Painting concrete window sills, surrounds, and roughcast walls in wet windy area

Hello,
I need to paint the concrete window sills and the window surrounds on my roughcast kit bungalow near the Atlantic coast of the Isle of Lewis in Scotland. They're painted at the moment but haven't been maintained for some years. The sills I think have been done with some kind of matt external paint and are crumbling but only very slightly and on the surface and not sufficiently to require skimming. The surrounds have been done with something more glossy.
The guy in the paintshop recommended a 3:1 water:PVA coat after scraping, and then some Dulux Weathershield. He didn't seem to know much about SBR or alternatives to that brand and type of paint.
Should I use PVA or SBR or something else? I thought for a while that maybe he's right at least on the PVA score because a decent paint will soak into the concrete which SBR being waterproof would hinder. I'd be grateful for advice from some of the knowledgeable people here.
And what should I do about the surrounds?
Third question... The walls are roughcast and look mostly okay for the time being although in places they are weather-stained and I plan to paint them. I was thinking one coat of SBR followed by two coats of masonry paint. Does that sound okay? Or would it amount to putting a vapour barrier on the cold side of insulation and thereby muck up the ventilation something rotten? I'd like to use paint that doesn't need to be recoated in the next 20-30 years.
Thanks in advance,
Harry
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Well for that length of time I suspect the only thing that would work is one of these professionally applied coatings. I'm not in an exposed area, but this wallcoat stuff if done right seems to be very good. Not cheap but at least to me only having two walls, cost effective. Brian
--
----- -
This newsgroup posting comes to you directly from...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Possibly masonry paint?

Sounds like a bad idea. PVA isn't waterproof - it's water soluable. Even EVA (external PVA) isn't waterproof, except inside mortar mixes. SBR is, but I don't know about longevity in highly exposed situations. Dulux Weathershield doesn't last long on masonry (from personal experience).
I don't have an answer, but I would have thought a masonry paint would be most appropriate and hence longer lasting.

I think that's a bit of a challenge. For that sort of life, I believe coloured renders are normally used.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I use a Stabilising Solution which is not PVA or SBR on masonry https://www.toolstation.com/shop/Painting+%26+Decorating/d150/Masonry+Paint/sd3174/Sandtex+Stabilising+Solution/p75668
-
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wednesday, September 27, 2017 at 5:12:11 PM UTC+1, Mark wrote:

my

r

oes

ike

nt/sd3174/Sandtex+Stabilising+Solution/p75668

I'd soak the sills with a 2 part product which cures whatever the condition s. Fibreglass resin, Rustins Plastic Coating etc. Then skim with a 2 part f iller (e.g. Profil from Toolstation). Then paint with anything you fancy, w hich should last forever because it will be on a non porous surface. IME no surface coating can cope with crumbly sills.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

With a masonry paint. you'd normally just thin it with water for a primer coat, if the surface is absorbent.
I've just used Bedec which you can order from ToolStation. On advice from here. Of course only time will tell if it lasts better than the previous stuff - but it is certainly difficult to get the lid off a used tin. ;-) But quite a bit more expensive than the common brands. It is said to remain flexible and to 'breath' .
--
*Broken pencils are pointless.*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.