Sandstone Patio with lime - what mixes?

[AMc]

We need to get the garden sorted out - most of the rubbish clearance is done, now I need to do the hard landscaping before I get a mini digger in to flatten it and turf.

We've chosen natural "fossil buff" sandstone for the paving which I'll be laying myself for reasons of poverty
I've laid Bradstone carpet stones before so I've got some experience but that was before I knew cement was evil. :twisted:

The manufacturer's laying advice is...
- dig down 150mm below DPC and another 150mm for foundations and paving.
- lay a 75mm compacted base of semi dry all-in ballast with cement 6:1 .
- Then a full bed of mortar 3 or 4:1 building sand to cement.
- Pointed with a dry 3:1 mix of builders and cement.

I have brick and concrete hardcore which I was planning on breaking down into <50mm chunks. Hoping to mix that with sharp sand left over from the building works which is also mixed with a fair amount of my now ruined gravel drive to create my own free all in ballast.

I want to use lime instead of cement mostly as it's a lower environmental impact product rather than it's breathability (as we're outside ).

I plan on
- digging down 300mm below the damp proof course (yes, there is one on this wall!)
- laying a 75mm base of hardcore <50mm bits bound with "some" lime and compacting.
- mix a dryish full bed of lime mortar of builders sand and lime to lay the sandstone.
- point with a mix of lime/builders sand.

What I don't know is what type of lime - NHL3.5 or something else for the base and mortar?
What mix for the base?
What mix for the mortar?
What mix for the pointing?

Any knowledgeable help gratefully received.

 

[AMc]

30 views and no comments at all - come on lime fans show me your mixes!

 

[robgil]

i would just use cement ,
you could try asking a lime supplier for advice. Mike wye or someone along those lines.

 

[AMc]

Paving does seem to be a concrete and cement only trade! It has occurred to me - I spent most of the morning search the interweb without much joy.

 

[Flyfisher]

If you've already searched the web then you've probably found www.pavingexpert.com, which is a very informative site. But not for lime!

I recently relaid an old brick path that had been pushed up by conifers. I don't know exactly what was originally used to lay them but I'm sure it was lime-based as it was very soft and easy to remove from the bricks. Consequently, I didn't want to bed them into concrete, just in case they need to be relaid in another 100 years or so.

Pavingexpert.com describes how to lay paviours using just sand, providing there is a solid foundation and retaining edges. So I took my cue from this and used a concrete mix over crushed hardcore as a foundation and also for bedding in two retaining lines of granite cobbles.

When all that had gone off, I used a 9:3:1 mix of sharp sand, hydrate, cement (the one that got me into so much trouble in a previous thread :roll: ) to bed in the bricks, but not to grout them.

My original plan was to just use soft sand for grouting, as for paviours, but my bricks are not actually touching each other (enforced by their pattern) as paviours would be so I was thinking about some sort of weak lime mix, but I haven't decided on that just yet after comments in a previous thread about poor weathering performance if I use a hydrate mix. So (horrors of horrors!) I might use a very weak soft sand/white cement mix for the grouting - something like 9:1 perhaps?

I'm not sure if that's of any help.

 

[Moo]

I laid a raised terrace using brick paviours (sp?) bedded on compacted soil topped with builders' sand using a huge spirit-level, a mallet, and a technique known as pig-ignorance. Five years on and it was still firm and level.

 

[JoceAndChris]

Cor Moo, I am impressed!

 

[Moo]

It wasn't all that difficult, actually, because bricks are relatively small and lightweight. More a question of plodding on, really.
The real problem was cutting the darned things to fit along edges and into corners. If you're thinking of doing it yourself, order a generous number of bricks to allow for some prodigious wastage!

 

[robgil]

how did you cut them in the end? any tips? ive got some pamments that i will be laying in my scullery and i have no idea how i am going to cut them.
ive thought about running an angle grinder down the cutting line then whacking them with a hammer.

 

[Flyfisher]

I think paviours are designed to be laid touching each other so they can't move about unless the retaining edges move outwards. Also, the retaining edges don't have to be too strong for just foot traffic whereas a car driveway or similar would be more demanding.

That was my original intention with my brick path but it wasn't possible as I wanted to keep to the original pattern , so I have some quite large gaps between the bricks and I think I'll need a solid, albeit weak, grouting in order to stop the bricks from moving as they are walked upon. At least they'll only get foot traffic and the ocassional wheelbarrow so I'm hoping they'll stay put.

Perhaps a photo would help to illustrate what I'm prattling on about:

 

[JoceAndChris]

So lovely - I need some!

 

[Feltwell]

how did you cut them in the end? any tips? ive got some pamments that i will be laying in my scullery and i have no idea how i am going to cut them.
ive thought about running an angle grinder down the cutting line then whacking them with a hammer.

Personally, I go for an "angle grinder and brick bolster" technique.

First off, get yourself a diamond blade - not that expensive and a million times better than a "normal" abrasive blade for cutting brick with. A small 4 1/2" grinder is fine, the aim is to score a line, not to cut right through (get a 9" grinder if you want to do that - but I wouldn't bother unless the cut face will be seen).

Cut a line using your grinder - do wear ear and eye protection plus a dust mask - it is noisy, smelly and any bits that fly off could damage your eyes. Then use a brick bolster and lump hammer to make the final cut. If your brick is hard then putting cuts on the side faces as well helps to "guide" the break from using the bolster.

I cut several thousand bricks when doing my garage, so I could make a modern cavity wall look like a solid 9" English bond wall - to match the house.

Alternatively, you can hire brick cutters - which are sort of a guillotine for bricks. These are intended more for people doing new block paving work - for a situation where you're cutting bricks for an internal floor I wouldn't have thought you'd get a clean enough cut with this - depends on if you're covering up round the edge with skirting board or not I guess. This method would be quicker and cleaner.

 

[Schoolmarm]

I want to use lime instead of cement mostly as it's a lower environmental impact product rather than it's breathability (as we're outside ).

And it sounds like it is next to the house so Lime is still best.

 

[robgil]

grinder and bolster sounds good , no skirting (i dont do skirting ) , plaster right down to the floor so i will cut as good a fit as i can then grout with lime , or probably cement as they are going down onto a cement floor in diy mans self build blue peter project extension from a 1970's diy magazine centrefold monthly 12 easy steps readers follow along for beginners.

 

[AMc]

I have read and learnt a lot from pavingexpert.com but their only references to using an all lime mortar is a link to a self building FAQ which is dead and using hydrate as a plasticiser.

The paving I'm laying is natural sandstone in blocks from 300mm x 300mm up to 600mm x 900mm with variable thickness so I need to use a proper bed to fully support them - if there's movement underneath I could easily crack them. Thankfully the heaviest load will be me and a beer

I'm planning on leaving a 6"/150mm gap between the house and the patio, dug down to the same level as the rest of the base but filled with hardcore and topped with gravel. Half the corner I'm paving has a DPM as we had to take it to foundation level and rebuild it. The other half has no DPM but is battened & dry lined inside so I'm not overly concerned about damp.

@robgill I would lay your pamments into a lime mortar so that if they need to come up again you can clean them down and lay them again (as we did 100 years after the last brickie). Once they're in cement they're pretty much ruined. Brickie #1 did a bad job of getting a smooth bed so lots of them rocked and have had to be relayed. Brickie #2 who "learnt lime" on my house from the poles doing other work did a much better job because he was more careful in making the bed even and continuous and none of his have moved. IIRC they both used a 6:1 mix of sharp/hydrated lime...which makes me think perhaps I'll do something similar under the patio.
The pamments and bricks were grouted with a mix of kiln dried sand and hydrate (probably the wrong lime) brushed into the gaps. This has (mostly) worked out but its a horrible job so wear a mask and gloves.

 

[Flyfisher]

The pamments and bricks were grouted with a mix of kiln dried sand and hydrate (probably the wrong lime) brushed into the gaps. This has (mostly) worked out but its a horrible job so wear a mask and gloves.

Interesting. That's the sort of thing I had in mind before being told off for using hydrate, although I wasn't going to use dried sand as I thought some moisture was needed to facilitate carbonation. Was this also a 6:1 sand/hydrate mix?

Can you elaborate on the "mostly" and what you did about it?

 

[AMc]

The pamments and bricks were grouted with a mix of kiln dried sand and hydrate (probably the wrong lime) brushed into the gaps. This has (mostly) worked out but its a horrible job so wear a mask and gloves.

Interesting. That's the sort of thing I had in mind before being told off for using hydrate, although I wasn't going to use dried sand as I thought some moisture was needed to facilitate carbonation. Was this also a 6:1 sand/hydrate mix?

Can you elaborate on the "mostly" and what you did about it?

Sure - the kiln dried sand was used to get the mixture as fine as possible. You want it fine so it can be brushed deep into the cracks and as dry you can to try and prevent staining on the surface. Once in place a soggy mopping/misting with water provides the moisture for carbonation though in retrospect I don't think I did enough of this over a long enough period which may have lead to some of the problems with loose bricks.
The mix was 'about' 6:1 as it was mixed by hand in a bucket with a tiny splash of water, otherwise the lime simply 'fell through' the sand into the bottom of the bucket. You only need a small amount of kiln dried to cover a large area. IIRC I used 3 bags to do about 30m2 so it's worth the expense.

The mask is very important because the sand is horribly fine, it dusts up and gets in your lungs as does the dry hydrate which hurts The first bit I did with a hand brush and a lot of care. Later when I had to do it over and over I discovered a stiff broom was just as good, faster and got your face away from the clouds of horrible dust.

The "mostly" being there are some bricks where the grout either didn't bond and subsequently hoovered out or mMy biggest problem - Brickie #1 had left great trowel gouges in the bed, even at the edges of the brick. So the grout would fall down a tiny gap and clog it, a bit of heat expansion or movement and the grout fell into a big void.

 

[Flyfisher]

Thanks for that comprehensive explanation. Very helpful. The 'misting' confirmed what I thought about the carbonation. Interesting point about 'ordinary' soft sand being too damp to prevent staining. I think I'll try a small experiment with some spare bricks as I'm going to need a fair bit of grout between my bricks.

 

[Penners]

a technique known as pig-ignorance.

At last! Someone with the same qualifications as me.

 

[Schoolmarm]

Ah, I aspire to pig inorance.