Advice on cement for limestone block fence

[jc888]

Hi

Much appreciated if anyone could advice me on the cement mixture for a limestone wall fence.

I am using limestone blocks 500 X 245 X 190 to build a low fence (not retaining) and that and using brickie lite cement and on the bag the mixture is indicated as 1 part cement to 3 parts sand. I have followed the bag instructions and applying the cement to the blocks, however, once dried I get hairline crack along the edge of the blocks.

I am not sure if the crack would one day loosen the blocks or not but if anyone could advice on what I can do to avoid the dry crack in my glue.

I have just started on the wall and there are lots more blocks to complete so I would like to correct my mistake now to ensure the strength in the wall once cemented in.

Thankyou

JC

[tameriska]

Hi, working with limestone blocks, are you wirebrushing/ scraping the edges that the mortar will be applied to to remove the dust. Are you wetting down the limestone blocks before building them. Used to work with a builder, and thats the way we laid limestone, ( it holds twice its own weight in water)

[jc888]

Hi, working with limestone blocks, are you wirebrushing/ scraping the edges that the mortar will be applied to to remove the dust. Are you wetting down the limestone blocks before building them. Used to work with a builder, and thats the way we laid limestone, ( it holds twice its own weight in water)

Hi

Thankyou, for the reply.

And no I did not do any of that. This is my first project and I thought I can just plonk the blocks on top of each other with mortar in between.

Can I ask if I have to really soak wet the block or just a quick wet over.

Thanks again

Jake

[tameriska]

Hi, don't need to really soak them, just wet the block where the mortar is going to be, to stop the limestone sucking the moisture out of the limestone. Same goes for wetting it down if you are plannning on plastering it.

I cant remember the mix, but if you are going to point it, on flat faced stone, (put white stuff over the mortar joints to make the wall look uniform) Scrape out about 4, 5 mm of the mortar from the joints, keep the limestone dust, and use white cement (cant remember if you use lime as well) To point, use a trowel and work the mix into the joints, and to finish it off, cut a 6" x 6"x 2" block of limestone and use the large flat face to rub the excess off after it has set a little. If you find that the stone you are using to rub back is puttin g scratches in your wall, check the face, (our limestone can have small flints in it), and chip the flint out, and continue.

Here is a pic of my back wall, showing our limestone and the pointing. (the black lines are done while the pointing is almost set, done with a straightedge and builders pencil)

[tameriska]

Hi, hope the pic goes in this one

[jc888]

Hi, don't need to really soak them, just wet the block where the mortar is going to be, to stop the limestone sucking the moisture out of the limestone. Same goes for wetting it down if you are plannning on plastering it.

I cant remember the mix, but if you are going to point it, on flat faced stone, (put white stuff over the mortar joints to make the wall look uniform) Scrape out about 4, 5 mm of the mortar from the joints, keep the limestone dust, and use white cement (cant remember if you use lime as well) To point, use a trowel and work the mix into the joints, and to finish it off, cut a 6" x 6"x 2" block of limestone and use the large flat face to rub the excess off after it has set a little. If you find that the stone you are using to rub back is puttin g scratches in your wall, check the face, (our limestone can have small flints in it), and chip the flint out, and continue.

Here is a pic of my back wall, showing our limestone and the pointing. (the black lines are done while the pointing is almost set, done with a straightedge and builders pencil)

Got the picture, looks realy good.

Thankyou for the advice and I will try this tomorrow as there are still lots to do.
Now with the existing cracked mortar, do you think if I just use a sponge and work the new wet mortar in would this cover the crack lines or do I have to scrape some out?

[tameriska]

If you just want to cover the crack lines, I assume wetting the stone and mortar, and applying new mortar might cover the crack lines, worth a try.
As long as you reckon that the stones are solidly set, not sure if the mortar hasnt bound because of the moisture being sucked out.
The hairline crack would suggest that the mortar isnt binding to the face of the stone. Personally, I might re lay them, if its three plus courses high, but if its low, and they feel solidly set, you might get away with it. If they loosen up, its not too hard to cut the mortar and re lay them later.
If you are goung to paint it, be aware that is is going to suck the paint up badly unless it is sealed. There are sealers on the market fro that, cant rember if you can also use bondcrete and a water mix to seal it, should say on the tin.
Hope it goes well.

[Joister]

no experience with the limestone but have doing a bit of rendering of late on a mix of old concrete render and bricks - it's a mix as i took a chisel to the drumming bits of old render before applying new coats

mix i've been using has been 1 cement to 1 lime to 5 sand (put down a first coat of around a few mm's on the first day and then a second coat the day after which levelled the surface) - seems to have been working fine to date - been on for over 3wks and getting ready to seal and paint

thing i found useful was making sure the wall was moist - not dripping wet but moist - pretty much what tameriska said

i use one of those hand held sprayers that people use to water their paints - found that if i didn't have this handy the wall sucked the moisture up pretty quick before i could get to the moist bits before applying the render

i also gave the render a light sprays a couple of times after i'd finished

if it peels off or the walls makes for a new drum set i'll let you know

good luck - sorry can't be specific about the limestone