How damp should the bricks be for repointing?

[GillesF]

Hello

While waiting for lime plaster to dry I want to start repointing with lime mortar in my cellar. These are regular clay bricks and I have scraped out the old crumbled mortar to a depth of 1 to 2cm, the height of the joints is variable from 0,5cm to 2cm.

I have experience with NHL but not with lime putty mortar for repointing. How "wet" should the wall be before repointing? I assume I need to spray the wall for several days before starting the work?
And when should I start "slapping" the joints with a brush after application? With NHL during summer this was usually already the day after but lime mortar dries much slower, especially in a cellar ...

Thanks all!

 

[jamest]

I can only speak from my own experience and I have only ever pointed brickwork with lime putty based mortar and never in a cellar, but I have pointed both internally and externally. For internal pointing, I have found the following procedure works well:

(1) the bricks need to be damp, but definitely not wet. If there is any wetness at all (visible liquid), the lime smears over the brickwork and produces a horrible looking job. They don't need to be damp all the way through, moderately damp around and in the joints to be pointed is enough. I found that spraying in the joints with a mister fairly liberally about an hour or two in advance, then topping that up just a little, about 10 minutes before starting, worked perfectly well. With larger areas, I tended to top up the damping down as I went along.

(2) you should mist spray your pointing every couple of hours after the mortar's in the joints to stop it drying out too quick. I found that if I completed an area of pointing by mid morning, I could sometimes use the churn brush on it in the evening (about 12 hours later), but I liked to leave it about a day. In the cellar, you'd probably need longer, maybe two days. The lime should be firm, but soft enough to press your finger nail into it, but not to make a finger print.

(3) Hit the joints hard with the brush. Once you're done, keep misting every few hours for a couple more days (I misted for about 4 or 5 days when pointing externally or in the summer, to be on the safe side). Might not need it as frequently or for as long if your cellar is humid.

I've always had good results with that process and I've always used a relatively dry mix for the mortar.

 

[stuart45]

The ideal amount of dampness in the older, more absorbent bricks for bricklaying and pointing is for them to be damp throughout the brick apart from the surface. That way there's enough suction in the brick to form a bond with the mortar and not smear the facework, but it's damp enough just below the surface so not too much moisture is taken out of the mortar.
There used to be a test in the USA where they used an eye dropper to time how long a dime sized drop took to soak into a brick.