Pros and cons - the paving is well protected from stains, it's less likely to be affected by moss/lichen and other vegetation, and the colouring is enhanced, but the treatment may need to be repeated every so often and some people are none too keen on the glossy 'wet look'. Some sealants offer a semi-matt finish which is more acceptable to some, but this tends to offer less protection that the 2-coat 'wet look'.

It all boils down to what look you like. Personally, I wouldn't use a sealant on stone flags outdoors, as I like the way they weather and the way the mosses and other vegetation take over, but I know that's not to everyone's taste.

However, for the conservatory floor, I'd go for a 100mm sub-base and then 100-125mm of concrete over a damp proof membrane, as any movement beneath the conservatory floor is much more of a problem than movement/settlement beneath a patio.

Have you thought of asking your local Building Control Office what they normally recommend for a conservatory floor? That's what they're there for!

What you need to avoid is the tops of any flint nodules poking through, as these may develop into 'rocking points' once the rest of the paving is laid.

The existing concrete should be firm. Any rubble you add must be thoroughly compacted, hammered down so there is no chance of any settlement. Use a hammer if you've no wacker plate, or stir in sand and cement and turn it into a weak concrete.

So, assuming you get all the base prepared, you can set about laying those wafers you've bought. I'm sure there's a law about minimum thicknesses before you can call them 'flags' and 25mm is well below it. These will be painfully fragile, so you're going to have to be very, very gentle with them.

I'd opt for a full mortar bed, as there's little or no chance of you being able to tap down the flags sufficiently on a semi-dry mix without the damn things falling apart. Mix the mortar at about 6:1 but keep it reasonably stiff - not sloppy so that is drips off the trowel, but stiff enough to stand in peaks, and for no water to drip out when you squeeze a handful.

Spread out a layer of the mortar over the base and ripple the surface with the edge of the trowel. Press the flag down into the mortar bed and then tap it very, very gently with a rubber hammer (a clonker, as we call them) until the flag is settled to the correct level. If you haven't got a clonker, put a piece of 3x2 over the flag and tap that with a lump hammer.

If the flag won't settle to the correct level with a few taps, take it up, scrape out some of the bedding and start again - don't be tempted to pummel it into submission: at 25mm, there's no chance of them bloody things being able to take any rough treatment.

Check your levels as you proceed, making sure you're sloping away from the house. Use a taut string line and/or a straight-edged timber to guide you.

TAKE YOUR TIME - a rushed job is a botched job.

Don't walk on the wafers...err...flags for 48 hours, so try to point-up as you proceed.

I'm not sure what this 10mm gap idea is - a typical joint is 10-15mm - did you mean 100mm (10cm)? Even if you did, I can't understand what the 'shingle' is supposed to achieve? Can you enlighten me?

If you have any voids in the rubble/hardcore sections, though, these are best blinded with sand before placing the mortar bedding. Ideally, when you come to start laying the wafers, the whole base should be a graded flat plane, sloping away from the walls, with no holes, voids or gaps.

So, if you use a 6mm blinding of sand, and a 10mm bed of mortar, you can keep the paving to 109mm below dpc, which is just about tolerable. If you omit the sand blinding, and keep the bedding thin (10-12mm) you can save a few more millimetres, but it's not worth fretting over.

Quarry waste varies from quarry to quarry. The stuff classed as waste from some of the northern limestone and gritstone quarries is usually ok for bedding, but some of the hardstone wastes, or slate waste, can be nothing more than a nuisance.

Dry jointing isn't suitable for riven paving that will be pressure washed - it's just a way of filling the gaps rather than creating a sound joint.

GeoFix, as you say, isn't the cheapest jollop on the market, and I have reservations about its use in wider joints because it does not bond to the paving itself. Even on relatively tight joints (6mm or less) I've managed to blast out GeoFix with a small Kew power washer.

I know mortar can be messy and is slow work if you're not used to it, but it's still the best option on these small domestic patios.

As we always said to the apprentices - TAKE YOUR TIME! And hurry up!

So, spread the sand, if you must, and compact it with the plate, but you;ll need to disturb the top 25mm or so to mix in a trowelful of cement as you prepare the bed.

B - Mortar: I assume you mean mortar for pointing and not that stupid, silly, nasty, amateurish 5-spot method of laying flags that is the universal indicator of a true eejit?

You measure in 'units', whether the units are spadefuls, half-buckets, kilograms, pint pots or whatever. You mix, for example, 4 spadefuls of sand with 1 spadeful of cement.

C- Retainer: If your flags are going to be higher than the immediately adjacent area, then you will need some form of retainer, and it should be a brick or concrete retainer, rather than wood, which can (and will) swell and shrink over the season. A flag -on-edge is a simple and cheap retainer, if one is needed.

I think the best way of tackling this job would be to cut out all the existing mortar to a depth of at least 25mm (1 inch for you non-metric N.Americans!) and then re-point with a new mortar that has been coloured and strengthened to meet your needs. It would be even better if you could cut out all of the 'grey' mortar and get down to the 'pink' pre-existing mortar, so that you're laying the fresh stuff onto a reasonably sound substrate, rather than overlaying the known-to-be-iffy grey patch pointing.

I'm not familiar with what's available in N.America, but a good mix would be 4 parts building sand, 1 part cement, plus your chosen colour dye, and then a strengthener, such as SBR (Styrene Butadiene Resin ) which makes a normal mortar much harder and creates a stronger bond between the paving and the mortar itself.

There's a product I know is sold in the US that might be suitable - Dynabond (or is it Dynobond? ) Anyway, it's an epoxy-based mortar, so it will be incredibly hard-wearing and strong.

Once you've got the mortar, follow the guide given on the Pointing page to fill in the empty joints. Feed it into the joints and then smooth it off so it's 1-3mm (one-eighth inch ) lower than the surface of the flagstone.

H ope that helps

Score the old, stubborn mortar pointing with the angle grinder to a reasonable depth (25-40mm ) then use a hammer and bolster/chisel to break out anything lect behind. You'll need mask and goggle, of course, but it's not that hard a job.

The bit about crusher run inmproving drainage is rubbish. It's no different to using sand bedding.

With dog runs, you really need a gully present so that you can swill down the area with a hosepipe from time to time. If you leave open joints in the paving, the urine finds its way into the bedding, and the sub-base or sub-grade, and begins to stink after a few weeks.

As for your bedding sand -

24 2x2s = 24 × 0.6m × 0.6m = 8.6m²
 
@ 50mm bedding = 0.43m³ @ 1.8 T/m³ = 0.8T

And the reason I have so much time to create and maintain the site is that I've been forced into very premature retirement due to an accident and I'd do anything to avoid having to watch daytime TV all day, every day!

Let us know how you get on.

taking your Q's one at a time...

The size/shape is fine for using that particular flag, but I'd suggest adding a brick edging or something to give a contrast. One type of paving all on it's Jack Jones looks a bit bland. Even something like a rope top edging around the diamond bed in the centre would help 'enliven' it.

Pattern and Design - well, that's a BIG question, as I can come up with hundreds of designs, but it's finding one that suits you without being OTT or overly fussy, which would look daft in such a relatively small area. If you do go for the random stone, then a random pattern would seem to be the order of the day. Pinks Hill do a Layout service, or you can email me.

Finally, I would not let bloody interior decorators anywhere near a paving job!! Interior decorators are scared of the rain and the mud, and those nasty rough paving materials might scratch their baby-soft little hands - leave them inside sewing hems on curtains or ballsing-up the colour scheme, and insist on a professional paving contractor.

I'm really surprised that the Loss Adjusters have suggested you use IntDecs - if you had a gas leak, would they recommend a glazier? Each man to his trade: insist on a paving specialist. There's dozens of 'em around that part of the world.

If your beloved is really keen on planter pockets within the paving, replace the 600x600 unit with a 600x300 and a 300x300 in a 'L' shaped arrangement, leaving a 300x300 space for the plants.

However, if a circular hole is what is required, then the simplest DIY method is to stitch drill all around - do you know what is meant by stitch drilling or should I explain? The 'professional' way would be to use a core drill, but then, the professional wouldn't want a 200mm hole in the centre of a wet-cast flag!

If these were hydraulically pressed flags, it's possible to cut a hole of almost any shape in the centre using just hand tools, as we had to do as part of our training back in the 1970s, before power saws were common. A dying art, I'm afraid.

good to see you back - your patio endeavours have entered the annals of paving history!

Option 3 is the best solution. Buy a bag or three of cement (not Slabfix or Postmix or any of those other over-priced products) and sprinkle it onto the area to be paved in the following hour or two. Stir it in with a rake or the back of the spade, and that will do.

If your existing sand bed is around 50mm thick, then a 5mm covering of cement will be plenty - or approximately a spadeful per square metre.

I'd work on a couple of metres at a time, and see how you get on. If you spread and stir an area larger than you can actually complete, don't fret. As long as you don't compact it solid, it should break up pretty easily the next day and can be mixed in with some fresh sand and cement.

Let us know how you get on.

Also, the mortar pointing mix is very brittle, at 1:1:2; isn't it dazzlingly bright?

If flags are rocking, then, as they've been laid on a mortar bed, they will have to be taken up, the mortar broken out and fresh mortar placed in the bed before re-laying the flag.

If some of the flags sound 'hollow', it may indicate the dreaded 'spot bedding' rather than a full mortar bed or the preferred full dry-mix bed. Spot bedding is a discredited bedding method, but is still being promoted by some manufacturers who want to make it seem easy to lay flags, and by eejit tv presenters who really ought to stick to grinning inanely in front of the camera and leave paving and groundworks to those who actually know what they're doing.

Your contractor should tell you whether they have used a full bed or spot bedding. If they've used spot bedding, ask for their reasoning and why they have not used a full bed.

The loose and/or rocking flags will have to be relaid. One of the problems with mortar or spot bedding is that any movement or rocking only gets worse with time - it never corrects itself. You should keep your wallet closed until the loose flags are fixed.

Laying on a full bed, either of mortar or semi-dry, helps spread any load applied to the paving, whereas spot bedding means the flag is only properly supported in certain parts and is left to 'bridge' the gaps in those parts where there is no bedding. With a relatively thin flag such as these, a full bed does impart some extra strength, but spot bedding exacerbates their inherent weaknesses.

The brittleness of the mortar is not a major issue, but it will crack and come loose if there is any movement in the flags. It's overly strong for pavement pointing, but it's really not a big problem - I'm more concerned about the spot bedding than the pointing.

Have you got anuy pictures of this Desert Sand? I saw some at Shrewsbury Flower Show on Saturday and it looked very nice, but I'd like to see pictures of it laid in larger areas.

There's a hollow under the flags and there shouldn't be. If the flags are concave, then it is the responsibility of the flagger to adjust the bedding to ensure the concavity is catered for and does not result in a hollow, empty void beneath the flag.

Vacuum! I can't wait to tell my dad that one!!

Looking forward to seeing the piccies - if you want to post them to this thread, see the HELP file, or you can send them to me via

What colour is the slate? A dark mortar often looks really good with slate paving.

Using a grey or a dark brown/black mortar will help emphasise the slate and not the pointing. Grano tends to dry a very bright colour, like a greyey-bluey-white, so go with the darkened mortar.

If you have any piccies, we'd love to see them. I've just added a help file on Posting Images - see the HELP link at the top of the page.

these are best laid on a full bed or mortar on top of the membrane.

Allow the mortar bed to be slightly larger than the size of the flag/slab - so, if you're laying 450x450mm flags, let the bed be at least 500x500. Use a 4:1 mortar (Class II ) and make it just damp enough to cling together. Level it out with a trowel, place the flag and tap it down to level so that it beds into the mortar completely. Without standing on the flag, test it for rocking with your hands and pack extra mortar into any low corners. If there is any movement of the flag on the mortar, it will only get worse with time.

Keep off the flags for at least a day while the mortar cures, and then they should be fine.

The de-icing salts can react with the pigments used to create the colour in the flags and make them go all funny. Reds turn to browns, buffs go quite dark and some of the darker greys/charcoals can turn either very, very black or actually be 'bleached'. It seems to depend on the actual 'salt' used and the type of dye used in the manufacture of the flag.

As with any 'chemical' treatment of paving, it's always best to test a small, discreet corner of the paving before trying it out on the main body of paving. If at all possible, try not to use salt in clearing the ice. Quite often, a spadefull of grit sand sprinkled over a frosty or icy surface ius enough to provide adequate traction, and there's no chance of the run-ff contaminating the adjacent garden, as happen with table salt and the de-cing salts sold at BMs and the DIY sheds.

I had the bloody document in my hand yesterday, and I was thinking about adding a few words on PSVs to the site, but can I find it now!

BS7263 for concrete flags or BSEN 1341 for natural stone

The fall will need to be around 1:60, certainly no less than 1:80.

the usual spec for UFH with stone flags is to lay them on a bed of semi-dry mortar, around 10:1 with just enough water to make it damp. I'm not sure what the idea is of using PVA on the backs of the flags, unless some eejit thinks it would make the flags 'stick' to the mortar, which is not even necessary!
Movement joints are not normally required, unless this is a very large project.

As for the cable system, all I can advise is to follow the manufacturers instructions to the letter and it all usually works. Usually.

Point the flags with a stronger mortar, a Class II (say 4:1), and tool it smooth. Allow the flags to stand for at least a week before applying the HG Gunk, so that the moisture level in the bedding/jointing can stabilise, and then be prepared to rub, rub, rub to achieve the desired effect.

Good luck!

So, quantities - this depends on bed thickness, which in turn depends on the flags you're planning to lay all a being a regular thickness....but, assuming you'll be using a bed that's an average of 35mm thick, then the equation you need is simply one for volume, ie, area multiplied by thickness, and then use the info on the Concretes and Mortars page to calculate your requirement in kg or 40kg bags or 1kg agg bags etc.

As a rough guide, I reckon you'll need summat like 150 kg of cement and 1200kg of grit sand, plus maybe 80kg of building sand for the jointing.

Next, movement joints. If you've only 19m², it's unlikely you'll need one, but, for completeness, there's some detail on them on the Concrete page and on the Resin Bonded Aggs page.

And finally, the jointing. If you've no confidence in your ability to point the flags without staining then you might want to use GeoFix or another polymeric sand. You can read more about these expensive products on the Alternative Jointing page.

And finally, just before I go to bed, leave the 'impregnating' until the very last, at least a week after laying, so that the mortar bedding has a chance to stabilise.

I'd be most interested to hear your experiences while laying this floor, as, I'm sure, would many readers of this forum, as UFH is becoming more and more popular and it's something I've only installed a few times myself. Your insights could be invaluable, as would any piccies you manage to take.

Treat yourself to some nice clay pavers or even the small clay cobbles from Marshalls. They are also a 'natural' product and look grand with natural stone, whether it's from India or from Northern England, and they only cost about the same as reclaimed materials.