The Brew Cabin

Posted: **Thu Aug 13, 2020 10:47 am**

Hi all,

I re-pointed a small section around a patio slab a few months ago, when dry it looks fine and almost matches the existing mortar

When it rains, I get the effect shown in the photos, the existing mortar will dry very quickly to a light grey colour, the mortar I added remains damp for hours after.

The new mortar was a slightly damp 3:1 mixture of soft sand and cement

It looks as though the old mortar has some sort of water resistance which my newer mix doesn't

I am going to dig out my last effort and replace, can you recommend a product/mixture I can use to (almost) match the old mortar?

Many Thanks,
Chris

Posted: **Thu Aug 13, 2020 7:58 pm**

Your mix was too dry by the looks of it, so it's almost become porous.
It needs to be wet enough so it clumps together when you squeeze it in your hand

Posted: **Fri Aug 14, 2020 8:57 am**

dig dug dan wrote:Your mix was too dry by the looks of it, so it's almost become porous.
It needs to be wet enough so it clumps together when you squeeze it in your hand

Thanks I didn't know that, so the amount of water added when the mortar is mixed effects the porosity when it sets ?

Posted: **Fri Aug 21, 2020 7:34 pm**

Apologies for being late to this - had all sorts of health issues with angina during the heatwave and now an arthritic knee that is driving me mad with pain.

It's almost impossible to match an existing mortar unless you have a record of what proportions were used, what sand, what cement, what additives, quantities of additive and, probably, what you had for breakfast.

Any variation in any of the key comp[onent and you *will* get a different hue to your mortar.

Two options:

1 - live with it. There are far greater problems in the world right now.

2 - cut it all out and start again.

I know which I'd choose!

Both mortars will weather and in a few months' time, maybe a year or slightly more, they will look far more similar.

The Brew Cabin

New mortar doesn't match existing on patio