Sand/cement plinth at base of house - what paint to use?

Lulu58

We have a 1930s house with a sand/cement plinth running round the bottom of it.  Directly above the plinth is a single brick width 'ridge' which juts about about 1 inch or less.

The plinth has just been patched up and we would like to paint it (black or dark grey) when it has dried off.  The builder has suggested bitumen paint but I thought the plinth needs to be able to breath.  

I've looked online but everything I've found talks about bitumen paint as a damp course suggesting it's not breathable.

Can anyone help me with this?

Thank you.

stuart45

Sand/Cement plinths do tend to trap damp behind them. They often move away from the wall at the top slightly allowing moisture behind them. 
Is the brick above a plinth brick? I wouldn't use a paint likely to trap the moisture. 

Lulu58

stuart45 said:

Is the brick above a plinth brick? I wouldn't use a paint likely to trap the moisture. 

Thanks for your post, stuart45.

I'm not sure I understand your question - the ridge above the plinth is brick, and I can just about see a piece of slate as well.  Not sure if that answers your question or not?

Do you know if bitumen paint is breathable or not?

stuart45

These are plinth bricks, sometimes used to help form a plinth at the DPC. The slate is probably your DPC.
Bitumen is not breathable.
7644450280_c12307d48d_b.jpg (1024×768) (staticflickr.com)

Lulu58

stuart45 said:

These are plinth bricks, sometimes used to help form a plinth at the DPC. The slate is probably your DPC.
Bitumen is not breathable.
7644450280_c12307d48d_b.jpg (1024×768) (staticflickr.com)

Thanks, Stuart45.  

Our plinth brick isn't like the one shown in the photo.  See photo attached (I hope!) of ours.

As bitumen isn't breathable, would I be better just using a normal external paint?

stuart45

Looks like it's got a sand/cement fillet on top of the brick to give it some weather protection. The brick course is known as an oversailing course, often used near the top of a chimney stack for a bit of weather protection. 
The brickwork looks like it needs a repoint, unless they are recessed joints. 
Probably best to use a normal exterior paint.

Lulu58

stuart45 said:

Looks like it's got a sand/cement fillet on top of the brick to give it some weather protection. The brick course is known as an oversailing course, often used near the top of a chimney stack for a bit of weather protection. 
The brickwork looks like it needs a repoint, unless they are recessed joints. 
Probably best to use a normal exterior paint.

Thank you for that information.  It is very helpful.  Our chimneys do indeed have the oversailing course near the top.

I know this is hard to believe, but the brickwork you see has already been repointed ... bit of a sore point!!

I'll look  into exterior paint.

Thanks again.

stuart45

I can see some of it's been done, but they have used a recessed type joint. Probably to match the other joints that have worn away. Recessed joints are not the best for weather protection as they have a ledge for the moisture to sit on and soak into the wall. However your wall  looks like a cavity wall with is not so much of a problem as a solid one.

Chickereeeee

May I suggest you look at silicate paints (also known as mineral paints)?
These are supposed to be very breathable, much more than masonary paints. They also chemically bond with masonary. I have not used them myself for this purpose, so cannot recommend, but it is what I will use come painting time.

Lulu58

stuart45 said:

I can see some of it's been done, but they have used a recessed type joint. Probably to match the other joints that have worn away. Recessed joints are not the best for weather protection as they have a ledge for the moisture to sit on and soak into the wall. However your wall  looks like a cavity wall with is not so much of a problem as a solid one.

Thanks again, stuart45.

Some of our joints are recessed, but possibly because the pointing is lime and it's wearing away?  Some of the re-pointing is recessed, other bits are not.  The builder also used different colours of cement depending on who was mixing it I would guess!

I've been looking at masonry paint and I'm not 100% certain what to buy for use on a concrete plinth.  I'm thinking it needs to be breathable but also waterproof from the outside, ie rainwater etc?

Do you have any suggestions of the type of paint to use?  We would like a matt finish.

stuart45

Chickereeeee said:

May I suggest you look at silicate paints (also known as mineral paints)?
These are supposed to be very breathable, much more than masonary paints. They also chemically bond with masonary. I have not used them myself for this purpose, so cannot recommend, but it is what I will use come painting time.

These are an option to the standard masonry paints.