Patio flag laying

[Sapient Fridge]

I'm looking for some advice from people who have laid paving for patios. I've tried searching on the web but I keep getting contradictory advice.

I'm building a reasonably sized patio which will be around 6m X 3m when it's finished. The sandstone flags are 610mm X 455mm made from (natural rock, nice quarried look to them).

Most of the time there will only be very light usage i.e. we won't be parking a car on it or anything. The ground is pretty solid where the patio will be, earth and small rocks mostly. Incredibly dry at the moment because of the weather.

I'm trying to work out how to lay the flags as I've never done this before, the problem is that I keep finding different suggestions as to how to do it. For example both my DIY books and this site suggests laying the slabs on five blobs of cement (spot bedding):

this site says that doing so is a *very* bad idea:

far as I can tell my options are:

1) Compacted hardcore base, 5 spots of cement

2) Sand base, 5 spots of cement

3) Sand base, lay flags directly on it

4) 10:1 sand/cement base, lay flags directly on that

Currently I've hovering between options 3 and 4 (unsure of base thickness though, maybe around 3cm?)

Option 3 would be the easiest (no cement mixing needed) but will the flags move on top of it? There are around 60 flags so if it starts to shift then taking them all back up again and re-doing it will be a serious pain.

Also I was planning to fill the joints with mortar, is that a good idea?

The flags are fairly light coloured sandstone, do I need to seal them with something to stop them staining?

Any advice very gratefully received!

[The Natural Philosopher]

I didn't do mine the recommended way.

I made up some hardcore and gravel to about the right level, and then used a *wet* mix of about 6 or 7:1 sand: (white) cement.

Why?

Because the dry stuff wouldn't move...fine if these were all the same thickness..one could rake out level sand and plonk them on. But they are emphatically NOT, so I wet laid, and tamped em down with a rubber mallet.

This led to wet squidgy mortar oozing up between then, so that solved the 'grouting'...

However it has a disadvantage. You have to remove the surplus mortar. Scrape off the worst and then use a sponge in a bucket of water..you wipe rinse and squeeze, endlesssly..

However what results is a pretty good finish.

I used white cement and sharp sand, for a pale sand and gritty appearance.

[The Wanderer]

advice without hesitation.

[Phil L]

Or not.

He says 'professionals' don't use the 'blob' method but it's wrong - many of them do...the only drawback is that there is a possibility of voids underneath each flag - this makes no difference whatsoever for foot traffic and it's what I use for paths and patios, being the easiest and quickest method, drives and other areas which are subject to heavy use are built by

150mm of compacted hardcore with a 50mm bed of *trammelled* sand/cement and each flag p-l-a-c-e-d onto the surface, then lightly tapped in the centre.

To the OP, for ease of laying and to get good results, use 'blobs', and by blobs I mean even blobs, don't just throw a few bits of sand/cement into the area and try to lay on them of you'll never get them right, the best way is to use a measured blob for each corner, plus one for the middle, you can either use a large pointing trowel or well-worn brickies trowel but I've found the best and cleanest way is to use 4 inch plantpots (about a quid for

6) and make the sand/cement fairly stiff (use gritsand and no plasticiser) so that it stands up like a kids sandpie! The mix doesn't need to be any stronger than 6:1

[Aidan]

He says; "There is a third method, spot-bedding, but this is not considered suitable for a professional paving project."

He also says that; "On public and commercial works, it is rarely, if ever, allowed. (i.e., where there is a specification for materials and workmanship, written by someone knowledgeable). If your contractor is using this method, ask would they like a bucket of oats for their horses."

Yeeeeharrrrr!

There's a list of drawbacks about 1/4 way down the page, I count 7.

I'd stick to his advice. He does know his stuff.

[Douglas de Lacey]

And if you have any questions go to his Brew Cabin and ask himself. You'll get a lot of extra good sense specific to your own project.

Best of luck, Sapient! Douglas de Lacey

[Phil L]

I agree he does, but it's not holy scripture and most people laying patios (or a living) etc with flags use this method...doing it the other way is fine if there is an infinite amount of money, dumper trucks, free labour and grabwagons at hand, for someone's back garden it's not feasible. Also, apart from the voids, the other 6 are crap.

1) the solidified beds cannot be eaten by ants - they are solid. 2) underneath the beds is nothing but compacted hardcore, I seriously doubt any invertibrates are going to shift this. 3) When was last time you seen water collect on 1.5 inch diameter hardcore? 4) The removal of the solidified bed is immaterial because it's a rarity. 5) It is cheaper than solid bedding, and easier and quicker, not to mention better - HTH. 6) Comply with BS7533:Part4 my arse, if you lay a 600 X 600mm flag on 5 X 100mm blobs, by the time they have been tapped down, it's practicaly a solid bed anyway...there /may/ be a void of about 30mm wide and 10 deep between them, but show me the ant that's going to undermine that.

[The Natural Philosopher]

The bigggest problem with dot and dab is that the 'grouting' tends to fail and then dirt and seeds get in and you end up with grass in the cracks.

[Sapient Fridge]

In message , Douglas de Lacey writes >The Wanderer wrote: >> On Wed, 19 Jul 2006 06:37:33 GMT, Sapient Fridge wrote: >>

Chuckle, I think I need it. I'm not sure I'm much wiser than when I first asked for advice though. It looks like there is a bit of a religious divide on the subject of laying flags.

Ah well, at least nobody has said that laying onto sand directly is a good idea, so that probably rules that one out.

I've just read the blurb which came with the flags and that says that they should not be laid on top on concrete spots as well so at the moment I've veering towards the 10:1 sand/cement sold bed (even though it's going to be a fair amount of work mixing and laying that amount of cement).

Many thanks to everyone who has commented.

[Aidan]

Mine was laid with spot bedding, by a previous owner (honest!). My experience; Voids all over, I think that is mainly to do with sand being washed out. Cracked flags. Rocking flags. No water. Flags settled all over the place.

The worst bit about it is that it's slug heaven; they live in the voids, millions of the buggers, and come out at night and devour anything green.

I'll be relaying it. I won't be using spot bedding.

[Mathew Newton]

I'm watching this thread with interest as I'll be undertaking a similar project shortly.

For what it's worth, my Bowland Stone catalogue has a DIY guide at the back and it says to use the '5-blobs' method... (although it doesn't specifically state not to use any other particular method either)

Mathew

[somebody]

[snip]

Having recently laid 8.5m x 5.5m (on a hill) so the farthest edge is almost 600mm high (anyone remember the "hire a crusher" thread) I'm afraid your "reason 5 above" is every bad comment I ever heard about my patio whilst I was preparing it. People's comments usually included phrases like "getting away with it" etc.

In the end I came to the conclusion that most of the time, when people said "I didn't do it like that" or "I wouldn't do it like that" it was usually because they were either too tight or too lazy to do it properly.

As your reason 5 says .... "Cheaper, easier and quicker" .... I don't see "proper" in there anywhere and I'm not sure I'd agree with "better".

Would you believe, the old patio (which I was replacing because it was so sunken in places it was actually getting dangerous) was laid on 50mm sand on earth. It was a hazard. Even with that, people were saying "why not just lay the new one on sand". I was too shocked to give any sensible answer.

Like the retaining walls that had no footings and had already fell over, when I replaced them and dug/poured strip foundations, people were actually saying "you don't need footings for that"... "I didn't do it like that" etc etc. Absolutely unf***ing believable.

Apologies if that doesn't actually apply to you Phil, I speak only from personal experience of my one and only patio (and general other building works being done in and around the place) - I am by no means an expert, actually I'm probably not even upto amateur :-)

[Phil L]

I'm simply saying that the pavingexpert's advice that anyone using spots is a cowboy is completely way off the mark...using spots on top of sand is always a mistake because as you found out, the sand washes from underneath each spot, making the patio like a ride on 'The Waltzer'

The thing is with solid bedding, is that it's rarely done correctly by DIY'ers, hence my advice to the Op to use blobs

The pavingexpert also lays directly onto a solid sand bed...he does mention adding a small amount of cement but only as a choice, personally when I lay solid beds, the mix is about 8:1

No apologies are needed, it's common sense (which you seem to have in abundance) which tells you that you *do* need footings and that you should

*not* lay just on sand, although I have laid flags for several local authorities who still lay flags on plain sand.

I have no argument against pavingexpert, but it's just opinions, I could put up my own website saying that laying on spots is the preferred method and everything else is cowboy country - it's not, it's *my* opinion and it's not gospel neither.

[Phil L]

Sand and spots/blobs are always a bad idea, spots are perfect on compacted hardcore and this is the only time I use them, a bed of sand is not required....to be perfectly honest, the best and ultimate sub-base for flags is a solid concrete base - litterally just pour and level a huge mass of concrete, allow it to set, then lay flags on top of it like you would lay bricks - they can never rock, sink or anything else, but this is just not feasable nor desired by most customers...the next best thing is to excavate

150mm all over and lay MOT (crush&run) and go all over it with a 1 tonne vibrating roller (not a whacker plate) and the surface is as solid as it will ever be...the exact levels and runs can be got with the roller, all that is left to do then is to lay the flags on 5 big blobs of sand/cement which is the easy bit, it's all the digging and levelling which takes the time and effort. Sand is probably the worst thing you can lay flags on, as you and several other posters have already stated, but I'm no expert :-p

Slugs live everywhere, I've taken huge slabs of concrete up and found them underneath so I'm afraid it doesn't matter what you put the flags on, they'll come back...what you need is some large hedgehogs

[Guy King]

The message from "Phil L" contains these words:

With TCT claws.