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Best Wall Protection Against Rain

Posted: Mon Sep 30, 2019 1:53 pm
by Mark-J
Hey all,

Before I paint the exterior of my (rendered) shed, I need to prime it against the weather. I'm getting damp walls on one side and even some water coming in where the base of the wall meets the floor. It's not much, and it's more, a case of wetness than actual pooling water. I've dug a drainage trench along the base of that side of the wall, and it deals with 90% of the water build-up as it's channeled into a soakaway, but when it pours the floor is still getting moist/wet. The other three walls are fine - it's just that side of the shed because it gets hammered by the weather.

What's considered the best primer for stopping any moisture coming through the walls?

I once said I couldn't afford the price of an item I wanted to buy, and I was told: "You can't afford not to buy it." Anyway, I'm in that exact same situation again so I am prepared to pay premium prices if I have to. I don't want to scrimp now and pay double for it at some later date.

Any recommendations?

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 10:07 am
by OchAye
You are throwing the kitchen sink in this with the jargon.

The primer is there to prepare the surface for the top coat(s) of paint. For external masonry paints the primer tends to be a stabiliser for powdery surfaces. So the question perhaps is what paint not what primer. Perhaps a solvent based masonry paint is your best bet, here is one example or google "pliolite" as all the major companies make similar. I am not sure the above is a solution to the problem you describe, perhaps you need a waterproofing product.

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 10:46 am
by Mark-J
Thanks for the replay Ochaye

I thought the primer was also a waterproof, my mistake.

Perhaps I'll be better off with a waterproof solution then. Can anyone recommend a good product?

Thank you

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 10:47 am
by London mike 61
I have used Thompson’s water seal on some brick work that had water dripping on to it and it’s been pretty good at stopping any water penetrating through to the inside.
Might be worth a go

https://www.thompsonsweatherproofing.co ... rproofing/

Mike

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 11:08 am
by Mark-J
London mike 61 wrote:
Tue Oct 01, 2019 10:47 am
I have used Thompson’s water seal on some brick work that had water dripping on to it and it’s been pretty good at stopping any water penetrating through to the inside.
Might be worth a go

https://www.thompsonsweatherproofing.co ... rproofing/

Mike
Thanks Mike!

The rendered walls are a little gritty/powdery so do I still need to prime them and if so does that happen before the waterproofing or after I've put it on?

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 11:18 am
by OchAye
Brush the walls with a stiff bristle brush (scrubbing brush). No primer (again). You must not put the stuff over a painted surface, you cannot paint over it. Check the data sheet of the product. If you want a decorative finish check paints.

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 11:28 am
by Mark-J
OchAye wrote:
Tue Oct 01, 2019 11:18 am
Brush the walls with a stiff bristle brush (scrubbing brush). No primer (again). You must not put the stuff over a painted surface, you cannot paint over it. Check the data sheet of the product. If you want a decorative finish check paints.
Sorry, I'm not sure what you mean.

You say "you must not put the stuff over a painted surface" and then you said "you cannot paint over it". So if I can't put it over a painted surface and I can't paint over it, are you saying I just use the waterproofing and no other paints?

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 12:18 pm
by OchAye
Mark-J wrote:
Tue Oct 01, 2019 11:28 am
are you saying I just use the waterproofing and no other paints?
Yes :-( Basically, if it repels water, it will repel paint (I think).

From this https://www.thompsonsweatherproofing.co ... ater-seal/ click on the link that says "Download Technical Data Sheet", and that is the instructions you need.

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 12:34 pm
by Mark-J
OchAye wrote:
Tue Oct 01, 2019 12:18 pm
Mark-J wrote:
Tue Oct 01, 2019 11:28 am
are you saying I just use the waterproofing and no other paints?
Yes :-( Basically, if it repels water, it will repel paint (I think).

From this https://www.thompsonsweatherproofing.co ... ater-seal/ click on the link that says "Download Technical Data Sheet", and that is the instructions you need.
You're absolutely right.

It says:

• Do not use over masonry paint or on pre painted surfaces
• Do not use prior to painting with masonry paint

So the sidewall will be rendered only and the other three walls will be painted as I've already bought the paint. Small price to pay though if it means I'm waterproofed.

Thanks Ochaye!

Best Wall Protection Against Rain

Posted: Tue Oct 01, 2019 4:35 pm
by OchAye
Hold your horses .... I looked earlier as I had come across them before. Everbuild/Sika also make some stuff, but the specs do not say if they are paintable or not. I guess, they are not paintable as they seem to be based on waxes or silicones but...

Examples:
https://www.everbuild.co.uk/product/sika-water-seal/
https://www.everbuild.co.uk/product/402-waterseal/
https://www.everbuild.co.uk/product/408-super-seal/

Ask the company if any of them are paintable with water based masonry paint (I assume you got water based masonry paint).