Marks on plastered wall (water wont darken) & strange paint coverage?

[Mr. Clueless]

A few things i want to find out....

1) I mist coated the ceiling of the living room today. I went 1:1 paint:water. Dulux Supermatt. I know the tub says 1:3 wateraint but i went 1:1. It still seemed to cover the celing quite well though. Is this normal for a mist coat? I was expecting it to be very watery. It was to apply but i wasn't expecting much colour there once applied. It just seemed to cover it quite well. I didn't focus too much in one area either.

But on to more worrying things...

2) I splatted the walls, quite a bit in some sections, so i rubbed off this paint with a damp cloth as i wasn't yet ready to paint the walls. All was fine until i wiped one section & either side of where i've put a red X darkened up with the damp cloth but not this sweeping bit...

After it was damp i touched it & it was very sticky. I'm guessing probably the famous PVA?

I painted it with a brush & it seemed to cover ok (which i then wiped off). Whether it actually sticks to the plaster ok is another matter, but i wiped it off with the intention of coming here & seeing if i should prep it some way beforehand?

But then even where i have put filler had the same result & this didn't have PVA on top...

Then time was getting on so i did a small section & i was really surprised to see how the paint coverage turned out.

I've tried to find a before photo but i don't have any. There was nothing on this wall that indicated to me that any section of it would look different to any other section once painted, so that's why i was surprised to see this.......

What is that & why is it doing it?

Wall has been totally tanked using the K11 system. No salts or anything were forming on top. The plaster wasn't different in that section to the rest of the wall. It didn't feel colder than any of the rest of the wall.

This is only the first mist coat & who knows, subsequent coats may cover it. Though like everything else with this house, i doubt it. I just wondered why it looked like that, or a possible reason as to why?

 

[Mr. Clueless]

I think the ceiling is largely fine & will cover with more coats.

Not so sure about these splat marks though. I don't even know what they are...

Same marks, just with & without flash.

They weren't there after the original plastering job back in 2013/2014 whenever it was so it must've been from the most recent job (December 2015) when the wall next to it was done.

 

[Mr. Clueless]

Well i've been sanding & wiping down with a damp cloth & the strange marking is still showing through.

I don't know whether wiping down with a damp cloth is a fair indication as to the condition of the wall but i'm hesitant to get a load of paint all over the room only to find out 80% of it was a waste of time. At least with water it can dry out & disappear in no time.

Take this wall (the one with the socket - not the one to the right) for example...

I wiped that down, pretty much the full length with a damp cloth. Look how patchy it is. Sections of it don't even look like water has touched it.

Is that normal? Like i say, i'm hesitant to just throw paint on there only to find out i wasted my time. If it looks like water hasn't touched it, my thought process is it'll do the same for paint, surely.

The wall to the right of that was the same...


This was all done by the second plasterer we had in.

But i keep showing you photos of wet walls

So i took a dry one that they (Second plasterer) did. I saw the areas that i thought would react the same (look like water hadn't touched it) & sure enough it turned out the same.....




Compare this to a wall that the third plasterer we had in did....

Never mind the streaks in the lower section - that's only because it had started drying out.

When i wiped that wall down with a damp cloth the entire thing looked even with the exception of that small circle part near the top left section of where it's been dampened which wouldn't go dark which is only because it needed filling a bit there.




If this is any indication as to how paint will perform then that's a hell of a lot of sanding (& i've already sanded).


Is there a product out there (i know Zinsser do a lot of marvellous save-the-day products) that i can put on on top of all of this & then paint on top of that?

 

[misterhelpful]

Zinsser Gardz would be the one to turn to in this case. It will seal the plaster, and should adhere well, to give a sound surface for your paint.

http://www.zinsseruk.com/product/gardz/

I'm guessing that PVA is the culprit here as the patches you show resemble what happens when the finish skim is contaminated with it. I suppose it could be something in the tanking system reacting with the plaster but imagine that is less likely.
You will probably find, if it is PVA, that further coats of paint will begin to cover the patches, but you could encounter the worst case scenario and have the paint lift as you paint over it. Trying it is the only way to find out, but I think that Gardz may be the safest option.

 

[Mr. Clueless]

This is the problem to be honest - i don't really want to spend time/money painting a 7mtr-x-4mtr living room & then a hall only to find i'm wasting that time & money.

Regarding the gardz .... do you need to do anything with it?

1) Do you apply it direct to bare plaster (as in would the paint already applied need removing) or can you apply to both bare plaster & painted plaster - it doesn't matter, either/or?
2) If applying to bare plaster, do you have to thin it like you do with this Dulux Supermatt?
3) Same question as #2 but for when painting over an already painted/sealed surface?


I've also painted over a section that i've put a flexible filler on & this is also showing through the paint work (2 coats). Is this normal?

I wonder if the top coat has different properties (& would do a better job at turning the two-tone paint into a one-tone coverage)?

Thanks for your reply.

 

[Mr. Clueless]

Just did some research in to the gardz. Apparently it dries rock hard & is 'like a glue'.

With us having damp problems (even though everything has been tanked & should be fine) i wonder if applying such a thing would be a good idea? Does the wall need to 'breathe'? I know i'm risking sounding stupid there, but i'll ask anyway.

Everything i read about it was basically for plasterboard. Most of my plasterboarded walls are fine. It's the other walls that aren't. I'm assuming this isn't a problem?!

One video i saw said water wont penetrate it. As such i'm guessing it's best to mist coat the walls first, even if it is going to turn out patchy?


So many questions. Sorry, but i don't want to balls it up by making a big mistake somewhere along the line.