masonry paint All manner of questions and solutions to problems and issues surrounding the subject of brickwork, blockwork and stonework

[Daniel3103]

Hello,

I have some blockwork that is apparent underneath a couple of rendered walls. The photo below shows one of these places. I would like to paint the blockwork, and I am looking to use a light-coloured paint to make it look similar to the rendering above.

I have two questions:

1. White streak marks sometimes appear on the blockwork. These marks are vertical. Any idea what they are, and do I need to do something about them?

2. If I use masonry paint, will it make the surface look homogeneous over the blocks, hiding the individual blocks and the mortar between them? Or do I need to spread a layer of cement over the blocks first?

[stoneyboy]

Hi daniel3103
The white streaks will be limescale leaching out of the block work.
If you paint the blocks with masonry paint the block pattern will still be apparent. If you render first the limescale will still come through and in curtain weather conditions the block work pattern will shown as darker shapes.
Regards SB

[Daniel3103]

Hi daniel3103
The white streaks will be limescale leaching out of the block work.
If you paint the blocks with masonry paint the block pattern will still be apparent. If you render first the limescale will still come through and in curtain weather conditions the block work pattern will shown as darker shapes.
Regards SB

Thanks for clarifying.

Regarding the white streaks, is there a type of treatment I can use to sort the problem, so that the limescale doesn’t come through once the wall has been painted? That is, if these streaks are indeed limescale. I’ve had a closer look and I think some of them may be, especially those that appear more prominently after rainy weather, but some streaks are there all the time and they look like render that has leaked when the top of the wall was being rendered.
Also, is there an undercoat or a cement I can use to put on the blockwork first before painting it, so that the blockwork is not apparent once it’s been painted?

[stoneyboy]

Hi daniel3103
It would appear that the wall is a retaining wall with higher ground levels behind it. If this is the case you will never stop salts appearing and any render you apply will eventually be blown off, probably in patches.
If it is not a retaining wall it is difficult to imagine the reason for the half rendering. You could try rendering the lower half and painting it but it’s very likely that the salts will come through the render and paint layer within a few years.
Regards, SB

[Daniel3103]

Hi daniel3103
It would appear that the wall is a retaining wall with higher ground levels behind it. If this is the case you will never stop salts appearing and any render you apply will eventually be blown off, probably in patches.
If it is not a retaining wall it is difficult to imagine the reason for the half rendering. You could try rendering the lower half and painting it but it’s very likely that the salts will come through the render and paint layer within a few years.
Regards, SB

Yes, the wall is a retaining wall. The render is not applied straight to the wall, there is a gap with some cladding and beads in between. This was done so that the render wouldn’t peel off.
I’ll see what I’m going to do about the lower half of this wall. I’m thinking of painting it, while trying to find a barrier layer between the blocks and the paint.

[stoneyboy]

Hi daniel3103,
I would suggest you thin down your masonry paint so it can ba sprayed, this will have two advantages: the paint will get into all the rough block surface and it will be a thin coat which should be porous, allowing the wall to breath. Just accept that every year or so it will need repainting to cover salt marks.
Regards SB