did you use silver sand for your black mortar? Using silver sand means that you need less of the messy dye to get a dark mortar than you would with a traditional red or yellowy building sand.

I'm afraid mortar work is, by nature, a messy job. Don't make your mix too wet; remember that many dyes incorporate a plasticiser, so you don't need much added water, and try working with two trowels - a larger brick trowel to hold the mortar and a smaller pointing trowel to feed it into the joints.

You might find it useful to 'mask' the edges of the flags as you work. You could use a bit of tin plate (a flattened baked bean tin, f'rinstance) or a piece of plywood, or even just a polythene bag (such as sand comes in) that you can move along as work progresses.

Although the mortar might stain at first, it soon weathers away to nothing. Don't expect to achieve a perfect, stain-free finish - it's just not possible. However, keep the staining to a minimum, and, if you do get a bit messy, wipe off as much as you can as soon as you can, then rub over the stained area with dry sand and, if necessary, wipe down with a damp cloth.

And most importantly, take your time!

Just another reason to use a washed silver sand rather than the red building sand.

because the riven flags vary in thickness, you really don't have much of an option - mortar is the only cost-effective laying material for this sort of application.

A friend in Shetland did something similar and they used a 6:1 mortar for the bedding, carefully selecting flags that would allow them to keep the bedding to a minimum. There was a lot of wastage, but, as you say, there's no real shortage of stone therabouts, so it was worth 'picking and choosing'.

The floor, which I keep promising to visit, was finished with a 3:1 pointing mortar, and then sealed with a matt-finish sealant.

Does that help?

there's no prog that can take a randomly-shaped area and generate a pattern using a set of pre-determined size flags- I've been trying to develop one since the days of the ZX81, and failed miserably!

A friend in the maths and computing business in Cambridge tells me this is known as the "Knapsack Problem" and is used to define how many ways a given number of 'pieces' can fit into a given shape. Apparently, it's been taxing better brains than mine for many years!

However, Bradstone have a gizmo that can generate a sort-of random pattern for their products for a rectangular area, but there's a few problems with it, not least of which is piecing-in around the edges and 'wastage'.

I have some layouts for 9-size patio flags and I can create a custom layout, in colour, in exchange for a few beers. Have a look at those I've put on the Random Layout page - if that's the sort of thing you want, then email me.

there's 3 grades of riven copy flags/slab - cheap but awful, mid-price and not too bad, and top price but damned good. It depends on how much you want to spend.

Quite frankly, I wouldn't entertain the cheapies. these are the sort of things you see in the DIY shed for 99p per 450x450x30mm flag, usually in a garish non-authentic colour. There's no size variation, so you can't create interesting or random layouts.

The mid-price lot are better, but they are definitely copies. They come in a reasonable size range, usually 5 or 6, colours aren't too bad, but the moulds are not very convincing and the finsh can be a bit iffy.

At the top of the range come the real beauties, such as Millstone by Stonemarket and Chancery by Marshalls. Top quality concrete, best dyes, best size rang (9 or 10 diff sizes), and you have a job telling them apart from genuine stone paving. Of course, you pay for that look!

Best advice I can give you is to work out your budget, and then I can tell you 2 or 3 'candidates' that would fall within your price range. The final choice has to be yours, because it's you that has to live with them.

If it's just for the flags, that gives you a budget of just under 13 quid per m², which is very tight for quality riven flags. You could have a look at the offerings from Bowland, Minster or Atlas - see the Concrete Paving Manufacturers Links page for contact details.

I'd be interested to hear how you get on, and what you think of the products these manufacturers offer.

What's the company name and address?

There's a page in the Block Paving section of the main site that deals with laying over existing. Have a read of that as it helps explain the problem with levels and thresholds.

PS - knock off Caps Lock when you type. Using all capitals is the 'net equivalent of SHOUTING!

Not been up to Rochdale for a while - has it thawed out yet?

the calculation, assuming 12mm joints is.....

nr of flags per m² × ½ flag perimeter × joint depth × joint width

....which gives.....

1200mm × 50mm × 12mm = 0.002m³ per m²

....so for 33m² you need 0.067m³ of mix.

Using a density of approx 1.9 t/m³, that comes to 125Kg, which, at 5:1 is 21 kg of cement and 104kg of sand.

If you buy a 25Kg of cement and 3 × 40kg or 3 × 50Kg bags of sand, that'll allow for wastage. You can safely use a 6:1 ratio for patios, so 3 bags of sand plus a 25kg bag of cement (what we call a 'half-bag')

If that doesn't work out, let me know!

the 150mm below dpc rule is used to protect your property from damp. No-one can stop you laying level with the dpc if you wish, but if you do, you face problems if you ever decide to sell up, as it's one of the things Surveyors pick up on.

If you must lay level with dpc, have a look at products such as Ready Step from RMC, which is a threshold drain, and, if at all possible, limit the high area to dorrways only. You could use a linear drain, but you are creating a potential damp bridge.

There is sound reasoning behind the 150mm below dpc rule - primarily that it prevents 'splashback' damp. It's not just something dreamt up for aesthetic reasons. Why do you feel you need to lay the paving so high?

You could use a simple channel, such as Keychannel from Marshalls, or even a Linear drain, if you preferred. Depending on the type of paving being used, you could also use a plain 'soldier course' of brick pavers and slope them towards a central gully. There's more than one way to skin a cat, as they say!

Try asking at your local BM. Again, from memory, I think the name of the product we used was 'Keim', but I may be confusing it with something else. I'll have a poke about in my files after I've had me tea and see if I kept any notes at the time.

It could take anything from 12 months to 12 years for your re-grading to settle and compact. It all depends on soil type, particle sizes, weather (honest!), traffic, and probably the winner of the Grand National on Saturday!

What you could do is get yourself a wacker plate and run that over the planned pathway a dozen or so times. Allow at least 450mm spread each side, so, f'rinstance, if you want a 1200mm wide path, wacker it 1200+450+450=2100mm wide.

You will find that the wacker plate sticks to the clay, but by spreading grit sand or scattering a sprinkling of DTp1 over the semi-compacted earth, you should be able to manage.

There are a couple of tools that are specially designed to compact earth/soil/clay. The first is a Trench Compactor, which is similar to a wacker plate but has a much more powerful engine and a wider plate. Secondly, there is a Rammer - a sort of motorised leg that bounces up and down and literally hammers the ground solid. You should be able to hire these via somewhere like Hewden Hire. The Rammer (aka Rampactor or Jumping Jack) is a bit of an experience the first time you use one, but they're great fun once you've learned to control them.

And, of course, you could always use a roller. A single drum might be a bit like hard work, but a double drum, something like a Bomag 75 walk-behind, might do the job, but be wary of getting it bogged down.

Let us know how you get on!

You should be ok laying the sub-base over the topsoil, but strip off any vegetation first, along with the top 25-50mm or so, as this tends to be soft or improperly compacted. Further, if you have soft, made-up or iffy ground of any sort, it might be worth putting down a separation membrane forst - something like Patio Partner from Terram, or Terram 1000, if you have a lrrge enough area.

As for the airbricks, one way of resolving this common problem is to build a small retainer around the airbricks, using bricks or concrete edgings. If the retainer is kept 150mm or so clear of the airbrick, this will ensure adequate ventilation, and, by raising the retainer by 25mm or more above the paving level, you can prevent almost all water (other than a few drips of rain) from getting anywhere near the airbricks.

As I said, this is a common pronblem and I've been building a page dealing with the most common solutions, but, it's not ready for upload just yet. However, if you can't understand what I'm wittering on about in the paragraph above, I'll sketch it out and upload a drawing for you.

Your solution using a linear drain is another oft-quoted solution, but, you really do need to have an outfall at one or both ends, even if it's only to a mini-soakaway. Without an outfall, you're more or less inviting trouble and you can almost guarantee the damned thing will fill with water! The best solution, of course, is to connect the lin drain to the existing SW system, if at all possible.

However, if you're going to be working slower than that, it may be worth doing half at a time, spreading around 10m² of bedding and getting that area flagged before deciding if you want to do any more that day.

I'd still get all the flags out of the way, first, though. Lifting one at a time and adding bedding will be a nightmare - you'll be tripping up over the unlaid flag, losing your tools, struggling to bring in the bedding material. It's always better to work in a cleared area.

if I use the sand and cement screed will this still require the settling allowance

Yes, it will, but only trial and error will determine just how much is required. The Stonemarket flags, along with many other cast flags, vary in thickness, and so a screed, while being useful, will not be 100% reliable. The claimed 37mm nominal thickness means they will be anywhere between 32mm and 42mm, and could even be 32mm thick at one edge and 42mm thick on the opposite edge.

However, you could prepare a screed, and then adjust as required with extra sand/cement for those flags that prove to be a little thinner than ideal. Even with a screeded bed of sand/cement, you still need to consolidate the flags once they're in position.

If I don't use the 5 dabs of mortar, do I use any mortar at all?

Only for pointing.

They do have their uses, but I reckon 95% of all patios have absolutely no need for a membrane. If you are constructing with a sub-base (what you refer to as 'hardcore') and then a cement-bound laying course, and a 35-50mm thick flag/slab, then only something like Japanese Knot Weed will be able to find its way through that lot!

Further, the vast] majority of weeds on patios and driveways don't come from beneath the paving; they grow into the paving from above, by colonising the joints and sending roots into any little fissures they can find. No membrane can stop that happening!

Have a read of the geo-membranes page, and the Landscape fabrics page, and that should help explain further.

Unless you are on boggy or made-up land, or if you're using a particularly open sub-base (ie, one with a lot of voids) there is probably no reason whatsoever to use a membrane, unless you like wasting money.

I've built over 1,000 patios since 1988. I've used membranes on two of them, that's less than 0.2%. With driveways, the incidence rises to around 1.5%, but that's still the exception, rarther than the norm.

It's a basic product within the construction industry and is sold by every Builder's Merchant I've ever known. If you ask for plasticiser, they'll sort you out.

There's dozens of brands, such as FebMix, PlaMix; it comes in powder form and in liquid form, but the liquid is best for diy use. You can buy 5 litres, which is enough to last the average diy'er about 5 years, for around 3 quid. Follow the dosing instructions on the container, but it's roughly two capfuls of Plasticiser to a 10 litre bucket of water.

If you're using a cement dye, some of those contain a powder-form plasticiser, so check before spending more money. Also, if you only have a little mortar work to do, a small squirt of wash-up liquid works almost as well - just add enough to give a light froth on the water - don't be tempted to overdo it!

These circular marks, are they perfect circles, more or less central to the flags? If so, they are marks left by the vacuum lifts used to move the partially-cured flags around the factory. You normally only see these marks on pressed flags, rather than cast flags. If that is the cause, they're marked for life, I'm afraid.

Have you any photos?

Basically, the concrete nearer the edges of the flags has dried out partially during the curing process, while that in the centre has remained 'damp'. The result is a difference in final colouration.

(It's not quite correct to think of concrete as drying. The curing process is a little more complex than that, and is a change in chemistry, rather than an evaporation of water content. However, the water content of a concrete does have an effect on the actual curing process, and so, if the moisture level is not uniform throughout the concrete, you can end up with a colour or shade variation in the cured final product.)

Now, sometimes, this disappears over time, usually a couple of months, but I have known it to last for 12 months or so, but eventually, it usually does disappear, although not always completely. In some cases, there is a faint but permanent difference in shade between the centre of the flag and the edges.

If you were to go back to the manufacturer, I'm fairly certain they would not be interested in an exchange or refund, and will probably give you the old line about them being a 'budget' or 'utilitarian' flag, rather than a top-of-the-range product, and, in the words of the prophet, you gets what you pays for.

In your case, I'd go back to the manufacturer/supplier. There's no harm in asking if they will offer a (partial) refund, as you're "terribly disappointed" with the finished effect. It's got to be worth a try.

I don't think youd get very far claiming it to be a manufacturing fault, although a good lawyer could argue that it probably does constitute poor manufacturing procedures. Your best line of attack is that the flags don't look the same as those in their brochure or on display in their yard. You need to go for the aesthetics rather than the composition.

Is that any help?

Thats fantastic. many thanks for your your expertise.I can address the situation in a much more informed and therefore effective manner now.

Try to avoid tracking cementitious bedding onto the flags while you're working, if they're wet, and leave the pointing for a dry day. If you have a roll of polythene or visqueen, you could use that to sheet over the work and protect it from the worst of the weather.

If you do get cement on the surface of the flags, swill them down with clean water before you pack up for the night. It's a damned sight easier to get rid of cement while it's fresh, rather than waiting for it to set and bond, especially with them Chancery, which aren't exactly cheap!

Let me know how you get on, and, if you take any piccies, let me see them, as there's another avid reader of this Forum who is considering using Chancery for their patio area, and just needs to be convinced that they will look ok.

My missus has an uncle that shares your name. Amazing fact number 12254!

Personally, I think tight joints will always look like tight joints and it's one of those things that will catch your eye every time you look at the finished paving. If it really does look 'tight', then it's got to be worth slicing an edge of the flags to get an even joint, but the determining factor is, "Can YOU live with it?"

If you do need to take off a thin slice, an angle grinder or cut-off saw is the only safe way to do it with these cast flags. Make sure you wear goggles!

You don't need to butter the joints, but the finish will be far superior if you do. The mositure from the butter will help initiate setting in the dry mortar jointing mix.

How you lay the circle and square depends on the site. I find the easiest way is to lay one edge and then work across, making sure the centre is higher than the edges so that it drains adequately.

Setting screed rails about 150mm outside the line of the paving, and then using a wooden stake tapped in on the centre point with 25-40mm of fall to the outside edges allows you to screed off with one end of the screeder 'anchored' to the central stake and the other travelling over the screed rails.

Some folk like to start in the centre and work out to the edges, but this need you to determine the centre of the circle exactly, and, if you're working to a solid edge, such as a wall, it's all too easy to realise that you're 25mm out and the whole lot has to be 'nudged' one way or t'other to fit in the last few flags.

Once the whole square is laid, you may need to adjust joint widths to get a balanced look.

11m² would take a tradesman around 2-3 hours, complete. If you allow yourself a full day, you should have plenty of time. Don't worry too much about the pointing; concentrate on getting the ground covered and you can catch up with the pointing the following day if necessary.

Let me know how you get on.

Good luck!

As long as you're happy with the results, then that's all that matters.

For your jointing, use a 4:1 mix of building or silver sand with cement, and, if you do need to relay, the easiest method is to prise out the flag(s) in question, scrape out the top 20mm or so of the bedding and replace with a wet 6:1 mortar, then re-position the flags and tap them into place with a rubber hammer. Any excess mortar bedding should squeeze up between the joints.

This is a better method for replacing individual flags within a patio, but, if you're relaying 3 or more adjacent flags, a semi-dry bed can be used.

There should be enough residual moisture in the sand and the joint itself to initiate setting, but you could always encourage it with a light sprinkling of clean water via a fine rose fitted to the watering can.

I prefer mortar for pointing, but I know it can be a nightmare if you're not confident in handling it and avoiding too many stains. Still, it's worth trying it out in a discreet corner - you never know, you might have a natural talent!

Have you taken any pictures?

Once you've got the edge flags bedded in place on the mortar, individual bedding is the easiest way to lay the rest of the flags, but, if you prefer to use a screed, then cut a notched screeder board, as shown for laying block paving. Assuming the riven flags are 35mm thick, a 30mm notch should be sufficient, but one of the problems with screeding from riven flags is that the screeded level tends to reflect the ups and downs of the riven surface. You can elinmoiate the worst of this by using a float or short straight-edged timber to tittivate the bedding layer once the screeded board has levelled it out.

HTH

Depending on the size and layout of your paving, you will need to provide movement joints at regular intervals. 3 metre centres seems to be a popular choice for movement joints in flagged patios and driveways, but final choice depends on site conditions and bed thickness.

Give the flags a soaking 12-24 hours before you plan to point them. You don't need to drown them, just enough to cover them with water until it begind to run off rather than be absorbed. Make sure you allow plenty of time for them to dry before doing the actual pointing.

Make up your mortar as stated - 200:1 with the plasticiser is fine; you won't do any harm by adding it at, say 150:1, but you won't do any good, either. It doesn't make a better mortar the more you add - it really does work best at low concentrations and it's always best to follow the instructions on the container.

Point the joints as described, then cover them with sacking, polythene bags, strips of timber or anything you have that will keep the moisture in place for the first 24 hours or so while initial setting takes place.

You may still get micro-cracks within the mortar, but it's not critical unless the cracks are at the interface of the flags and the mortar, which indicates the flags are moving and aren't settled down fully.

After the first 24 hours, you can remove the covers and sweep clean the joints with a soft brush.

As for RLC Pavings, I've never heard of them, but then, there's dozens, possibly hundreds of small, local manufacturers that I've not come across in my time, especially if they aren't based in the NW of England. If you get me a full address or a website url, I'll get in touch with them and add them to my list.

Let me know how you get on with the pointing.

The spot bedding method that Marshalls insist on illustrating, both on their site and in their latest arty-farty-can't-see-the-bloody-flags catalogue is aimed at the amateurs and is their marketing depts' attempt to make flagging seem easy.

Spot Bedding is a bad thing for any and all the reasons listed on the Flagging page. The use of a 10:1 semi-dry bedding is the equivalent of a full mortar bed.

Quite why Marshalls suggest Heritage can't be successfully laid on unbound grit sand has not been explained to me, but I have a simple arrangement with Marshalls - I won't tell them how to manufacture flags, kerbs and block pavers as long as they don't tell me how to lay them.  

Hope the weather holds out for you, Dave. I saw the sun shine in Rochdale once - 1973 it was, when my dad did the 'road and sewers' for a housing estate in Syke.

If you don't fancy the paver edge course, you can create the same effect by laying a 300mm wide cours e of the Heritage against the wall, giving each 300mm wide flag 20-30mm of fall AWAY from the wall, and then carrying on as outlined above.

Finally, a chalkline is by far the best way to mark your levels. Fixing timber battens is time-consuming and a waste of good timber. Use the chalkline or even a string line, and check your work with a spirit level as you progress.

Are you going to take any photos of this job, Dave? I'd like to see the end product and/or some 'under construction' piccies.