Stone Wall Re-pointing Questions

[LarryN]

Hi all,

I need to get my front wall repointed as it's getting quite bad after this winter.

I'm a complete building novice though, and previously would have paid someone else to do this, but can't afford to, so have a few questions.

1. What type of mortar/cement would you recommend? I'd ideally want something that's pretty easy to mix. Would I need something lime-based given the type of wall (see pics below).

2. How much of the existing mortar would you recommend taking out? I'm loathed to take too much out in case the whole thing falls down!

3. Any other general tips/help before starting something like this? Anyone know any guides/videos to help me.

Thanks very much,
Larry.

 

[pred]

Firstly don't rush it, its not like you're getting paid to do a job, just keep Mrs LarryN sweet is your main problem.

Just do a few square feet at a time, depending on the muck they used before will effect how the old stuff comes out, I would start off with a pointing chisel and a few other small chisels and a small lump hammer, another tool I've found useful is an electric drill and preferably old drill bits, I would try for at least an inch or more deep, the wider the beds op perps the deeper to go, I would use pit sand or Holm sand 4:1 mix not to wet with a bit of plasticiser in the water, and a larger in the other hand.

 

[LarryN]

Hi Pred,

Thanks for the reply. When I said building novice, I should have clarified that with "assume you're dealing with an idiot".

I'm not sure I get you with your "the wider the beds op perps the deeper to go".

Is pit sand/holm sand available at somewhere like Wickes? A quick scan of their website and it's not obvious.

On the 4:1, that's 4 part sand, 1 cement and then just add water until it's a good consitency?

Thanks again.

 

[pred]

Hi Pred,

Thanks for the reply. When I said building novice, I should have clarified that with "assume you're dealing with an idiot".

I'm not sure I get you with your "the wider the beds op perps the deeper to go".

Is pit sand/holm sand available at somewhere like Wickes? A quick scan of their website and it's not obvious.

On the 4:1, that's 4 part sand, 1 cement and then just add water until it's a good consitency?

Thanks again.

The muck between the bricks, horizontal are the beds, vertical are perps.

Wickes, B&Q no problem.

Yes 4 sand 1 cement but add a splash of plasticiser in the water to make the mix managable.

 

[LarryN]

Thanks again Pred. No need to worry about lime then?

 

[pred]

No. I've only ever used that as an additive when using sand and cement on the walls internally, messy stuff.

 

[jeds]

Go to a local lime supplier and ask them to sort you out a lime based mix. The joints must be permeable enough to allow water and vapour to evaporate off. Portland Cement will make an impervious joint which will trap water and damage the wall and stones.

 

[LarryN]

I thought I'd read that for old stone walls like this you'd need a lime mortar. Is this hard to get hold of (quick scan of Jewson turns up no obvious Lime-based mix)?

Is it hard to work with given my cementing experience is limited?

Thanks.

 

[LarryN]

Just spoke to the local building supplier and they've got the lime mix, so any suggestion for a ratio for doing this?

 

[jeds]

1:2 or 2.5 should be sufficient. The sand gives the joint the correct texture and colour. Local sharp sand will be best but do a small area to test one out first. Dampen the joint with clean water (from a spray) before applying the mortar. Finish the joint slightly above flush. Don't try to build it out like you see some people (misguidedly) doing. When the mortar is firm give it a light rub with hessian. Cover with hessian to protect from drying out and if it's really warm you could wet the hessian with a watering can. But don't go mad.

 

[stuart45]

I'd probably use NHL 3.5 for that wall. You do need to mix it up for much longer than cement. We normally leave it in the mixer for about 20 minutes.
Next day have a look at it and hit it with a churn brush or similar if it's ready.

 

[tony1851]

I would use pit sand or Holm sand 4:1 mix

Might that be a bit on the strong side? The original wall would have been built using a softer lime mix. Although the masonry looks in reasonable condition, a hard mortar could initiate decay.


(I posted this just after pred's second post, over three hours ago. Is anyone else experiencing delays to posts?)

 

[LarryN]

I'd probably use NHL 3.5 for that wall. You do need to mix it up for much longer than cement. We normally leave it in the mixer for about 20 minutes.
Next day have a look at it and hit it with a churn brush or similar if it's ready.

Mmmmm. I was planning to do the mixing by hand. Is that a ridicoulous idea then?

 

[stuart45]

Have a read through this.
http://nshistoricplaces.ca/conservation_resources/documents/limeinhistoricbuildings.pdf

Add 50% building sand is you find it hard to use the mix with sharp sand.

 

[LarryN]

Thanks for the link. Scary on first look, but the actual bits about repointing are useful.

Anyone any experience with a ready mix lime mortar such as this (just trying to make the job easier for me)?

http://lincolnshirelime.co.uk/traditional-ready-mixed-lime-mortar-30kg-232-p.asp