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Posted: Fri Aug 03, 2007 10:53 am
by scaryjones
Hi,
I’m about to build my first patio using Indian sandstone, on top of an old concrete patio that’s already in place. Now, I’ve had conflicting advice, people telling me to use a dry mix with sharp sand and others telling me to use a wet mix with builders sand. I’ve come to the conclusion that a wet mix will be the easiest for me, as I can lay it slab by slab and there’s no need for tamping.
Now, given that info can someone confirm that I’m doing the right thing by ordering the following for an area od 14 sq meters:
1 Tonne of builders sand
8 bags of cement (to create a wet mix in the ratio of about 6 : 1)
14 Sq meteres of Indian Sandstone
My plan is to mix the sand and cement on a per-slab basis and then lay them individually, making sure to keep them level. The patio has an existing fall on it that heads towards a drain, so I’m going to keep using that.
Does this sound like the right way to do this?
Thanks!
Posted: Fri Aug 03, 2007 11:48 am
by Ted
scaryjones wrote:Does this sound like the right way to do this?
No!
Read the site!
Posted: Fri Aug 03, 2007 12:15 pm
by scaryjones
Ted wrote:scaryjones wrote:Does this sound like the right way to do this?
No!
Read the site!
Cheers for that helpful reply. I have read the site, and it says to do it on dry mix of sharp sand and cement, after tamping it down.
Which is what I was going to do. Until I talked to some builders who lay patios and they said I was wasting my time doing it that way and that a wet mix using builders sand was the proper way to do it, a slightly higher ratio and individually lay the slabs onto this wet mix.
Hence my confusion. I went to a patio center to source the slabs and noticed that thay had their display patios layed onto a concrete base, which made me more confused, they seemed to concur with the wet base mix.
But then this site seems so helpful and so much work has gone into it that I'm inclined to think that its correct and not the other people.
So, I'm waiting to place this order for the materials and I've no idea what to order. I'd prefer not to have to tamp it as I've no access to a machine and tamping by hand would be a nightmare. So the wet mix seemed ideal.
So, rather than simply dismissing my query could someone who has experience doing this maybe point me in the right direction? If dry mix / sharp sand is the way to go, then what are the downsides to the wet mix option and why would anyone (let alone those with ample experience) recommend it over the dry mix?
I'm at a loss, so any help is really appreciated. Thanks!
Posted: Fri Aug 03, 2007 12:53 pm
by nelly05
scaryjones wrote:Hi,
I’m about to build my first patio using Indian sandstone, on top of an old concrete patio that’s already in place. Now, I’ve had conflicting advice, people telling me to use a dry mix with sharp sand and others telling me to use a wet mix with builders sand. I’ve come to the conclusion that a wet mix will be the easiest for me, as I can lay it slab by slab and there’s no need for tamping.
Now, given that info can someone confirm that I’m doing the right thing by ordering the following for an area od 14 sq meters:
1 Tonne of builders sand
8 bags of cement (to create a wet mix in the ratio of about 6 : 1)
14 Sq meteres of Indian Sandstone
My plan is to mix the sand and cement on a per-slab basis and then lay them individually, making sure to keep them level. The patio has an existing fall on it that heads towards a drain, so I’m going to keep using that.
Does this sound like the right way to do this?
Thanks!
builders sand = no no. You need grit/sharp sand.
If you want to do it on a wet mix then thats fine, thats how im doing mine, but you must use grit sand as opposed to builders sand.
Is the existing area a patio or a slab.
Is the existing patio of sound condition with no movement.
Others will come along with more detailed info but they are the basics you need to check.
REgards
Posted: Fri Aug 03, 2007 1:01 pm
by scaryjones
Thanks for the reply.
Firstly; the base is a poured concrete base, solid but slightly flaky and ugly as hell.
Ok, so sharp sand it is. I've been told that sharp sand in a wet mix is a nightmare to work with, is this the case? This is all so confusing.
The main thing I'm concerned with is whether I need to tamp or not, as I really don't think I'll be able to get my hands on a machine to do so. Thus wet mix seems ideal.
So, as of now I'm buying sharp sand.
Now, the ratio, does 8 bags of cement to a tonne of sand seem about right to you?
Thanks again for the reply.
Posted: Fri Aug 03, 2007 5:41 pm
by PHDA
I'm no expert but i've just done my own patio using Indian sandstone.
These are the things you need to consider:
If you are laying on top of an existing patio next to a house you need to be 150mm below existing damp course. You are likely to be above this so will have possible problems with damp.
If its not next to a house then you can lay the slabs on a wet mix of 10:1 sharp sand to cement. There is a calculator on the site to tell you how much sand/cement you need for a given area. I'm sure the experts will tell you not to lay on existing concrete but if the concrete is solid I can't see you having too many problems if it s just for light foot traffic. Just consider the height of the DPC. No tamping is required for a wet mix, just lightly tap the slab to bed it down.
Posted: Fri Aug 03, 2007 6:27 pm
by Rich H
By tamping I assume you mean screeding. This is neither necessary nor desirable with IS as the slabs vary in thickness, sometimes considerably.
I know you've said you've read the site but use of unusual terminology might well have led Ted and others to believe otherwise.
Trying to use a wet buildING sand + cement (mortar) mix would be a nightmare to do and result in salty circles appearing in the surface.
Lay a full bed of sharp sand and cement PER slab using a spade or trowel to first feather the mix. Lay the slab and consolidate it with a rubber mallet.
See under 'individual bedding' for more:
http://www.pavingexpert.com/layflag1.htm
Posted: Fri Aug 03, 2007 9:07 pm
by Tony McC
All this is covered in great detail here.
You MUST use grit/coarse sand, and NOT building sand. The slump you choose to use is up to you, but mosit or wet mix is easier for DIYers. Adding a plastiociser to the mix makes it much more workable.
Don't mix one bed's worth of mortar at a time - you'll soon get bored of that. Mix one bag of sand at a time, or two bags if you're feeling really adventurous.
Posted: Mon Aug 27, 2007 9:37 am
by scaryjones
Ok, have bought the stuff. 1 tonne of sharp sand and 14 sq meters of indian sandstone.
Now, to finally put this issue to bed, can someone confirm that, given that I'm laying this patio on top of an existing concrete base, that I do NOT need to compact the bedding layer?
I realise that under normal circumstances, and if I was using a proper sub layer that this indeed would need to be compacted. However, seeing as I'm simply laying on top of an existing concrete base I therefore have no need for compacting.
I'm presuming here that the slabs will eventually be self-compacting when they're layed on the sand bed I prepare.
So, before I make a mess of this, am I correct in not compacting at all, simply lay out the sand, level it and lay the slabs on top?
Thanks!
Posted: Mon Aug 27, 2007 9:49 am
by Suggers
3 people have now said, including the boss, that compacting the bedding layer is unnecessary. Where on the main site does it tell you to do this?
Posted: Mon Aug 27, 2007 10:38 am
by scaryjones
Suggers wrote:3 people have now said, including the boss, that compacting the bedding layer is unnecessary. Where on the main site does it tell you to do this?
I'm glad you asked that, I was starting to feel like people's reactions to the questions I posed here was somewhat exasperated, as if I was making up and repeating obvious questions to annoy people with!
So, to quote from the "laying flags" page, layflag1.htm:
The bedding material should be spread to the area and compacted either by trampling or with a couple of passes with a plate compactor ...
So, either that is badly phrased or I'm wrong in thinking that I don't need to compact the bedding layer. Hence my questions, hence my confusion and hence the frustration of people here when seemingly dealing with someone who can't follow simple instructions. If the instrcutions were clear and advice consistant then there'd be no problem.
When faced with potentially doing this wrongly and having to undo however many hours of work, not to mention the costs involved, I'm sure you can understand why I'm trying to get this all 100% clear before I lay my first slab.
Posted: Mon Aug 27, 2007 11:13 am
by Rich H
Rich H wrote:By tamping I assume you mean screeding. This is neither necessary nor desirable with IS as the slabs vary in thickness, sometimes considerably.
I know you've said you've read the site but use of unusual terminology might well have led Ted and others to believe otherwise.
Trying to use a wet buildING sand + cement (mortar) mix would be a nightmare to do and result in salty circles appearing in the surface.
Lay a full bed of sharp sand and cement PER slab using a spade or trowel to first feather the mix. Lay the slab and consolidate it with a rubber mallet.
See under 'individual bedding' for more:
http://www.pavingexpert.com/layflag1.htm
That's because you've been advised to do individual bedding, and you're still quoting/reading the screed bedding bits of the website.
To summarise: use grit/sharp sand as the site describes - make as much as you can in each batch, lay a few slabs and repeat.
Compaction is only required for screed bedding which is absolutely not suitable for your application.
Sorry to say that if you spent more time reading the advice and less time getting on your high horse this would all be obvious.
Posted: Mon Aug 27, 2007 11:35 am
by Suggers
Rich beat me to it - you're not gonna be screeding - look in the FAQ on the layover page under bedding.
Posted: Mon Aug 27, 2007 12:05 pm
by scaryjones
Rich H wrote:Rich H wrote:By tamping I assume you mean screeding. This is neither necessary nor desirable with IS as the slabs vary in thickness, sometimes considerably.
I know you've said you've read the site but use of unusual terminology might well have led Ted and others to believe otherwise.
Trying to use a wet buildING sand + cement (mortar) mix would be a nightmare to do and result in salty circles appearing in the surface.
Lay a full bed of sharp sand and cement PER slab using a spade or trowel to first feather the mix. Lay the slab and consolidate it with a rubber mallet.
See under 'individual bedding' for more:
http://www.pavingexpert.com/layflag1.htm
That's because you've been advised to do individual bedding, and you're still quoting/reading the screed bedding bits of the website.
To summarise: use grit/sharp sand as the site describes - make as much as you can in each batch, lay a few slabs and repeat.
Compaction is only required for screed bedding which is absolutely not suitable for your application.
Sorry to say that if you spent more time reading the advice and less time getting on your high horse this would all be obvious.
Thanks for the reply. The tolerance levels by some people for questions are quite low, however, I feel like I have to clear a couple of things up.
Firstly, it appears my earlier use of the word 'tamp / tamping' confused people. It's always been the word I've heard used for this type of work and it means compacting and is defined here: LINK
As a result of this (and in fact in the post you quoted) people somehow assumed I meant screeding when I said 'tamping', which obviously I didn't. Because of that assumption, people then assumed I'd somehow been thinking that screeding was the way to go, again I didn't. I simply didn't know which was the best option, I thought I'd ask here and while some people were very helpful, others just blasted out one liners or accused me or getting up on my high horse!
The quote in my previous post, the one saying compacting is necessary, wasn't from the screeding section of the website, it's from the laying flags page and it covers all the bedding methods. The quote comes from a paragraph that doesn't specifically mention any of the types of bedding, hence my confusion.
So, thanks again to the people that replied. I wasn't coming to this forum with any agenda or attitude, simply a desire to know how to do it right and I think my reaction to some of the replies was entirely justified.
Posted: Mon Aug 27, 2007 8:01 pm
by Suggers
Hey Scary - I think you've cleared the air - nobody here has an axe to grind - did ya start today? - lovely day here in Engerland - a nice moist mix? - don't rush it, & let us know how you get on - all the best.