For gardens, it's usually recommended that pipes have at least 450mm of cover. As for size of sump, that will depend on just how effectively it can be pumped clear. The trouble is that, as you drain your garden and store it in the sump, the groundwater in the surrounding land will most likely drain into your garden along the hydrostatic gradient created by the sump, and so, theoretically, you're draining not just your patch of one-third acre, but all the adjacent land, which could be 2, 3 maybe even 5 acres.

You really need to bring in a local drainage consultant to survey the site and advise you accordingly. I can't suggest any guaranteed solution without being familiar with the site, and Somerset is a bit off my patch, unless you can wait for the summer, when we usually have a week-long break with friends in North Devon.

Also, you should follow the manufacturers recommendations for filling with top-soil and the grass mixture. Ordinary turf could cause problems, especially if laid directly over the system units. All the grass paving systems rely on carefully designed components, which includes the sub-base, the rootzone and even the seed mix. You can't afford to cut corners, otherwise you compromise the system integrity.

The "all manuals everywhere" to which you refer must be the sales brochures put out by the manufacturers of the 50mm blocks to serve the residential and diy market - if you look at the actual standards and codes of practice published by and for the construction industry, you will find that 60mm blocks or thicker are stipulated for the vast majority of works. I would hazard a guess that you are not overly familiar with highway construction using concrete block paving, preferring to concentrate on contracting to the 'driveways' market, where these thinner units are a popular cost-saving item.

As for bed depth, 35-50mm is a typical specification. If a contractor can create a satisfactory pavement using a 35mm bed of sand, then why go to the extra trouble and expense of using 50mm depth? 35mm has been shown to provide an adequate 'cushion' between sub-base and paver, although, in practice, most contractors will aim for a bed averaging 42-48mm in compacted depth.

we are puzzled by a drain cover at the higher end of the garden (away from the house). Does anyone have a clue what this might be?

If you are part of an estate, it could be an access chamber to the main drainage system. On such a modern property, your local authority will have drainage plans on record at their offices.

How do we find out whether the water from the roof is draining into this?

Easy! Have you got any childrens' poster paint? Fill ahousehold or mop bucket with water and add a generous dollop of the paint to the water, sufficient to distictively colour it. Then, while a friend or partner keeps their eye on the channel in the mystery inspection chamber (IC), you can empty the coloured water into one of the gullies or pick-up points that takes water from the roof. If the coloured water appears in the IC, then you know the two are connected.

You can also buy special drain tracing dye from builders' merchants that do the same thing.

Who do I approach to advise me locally regarding necessary drainage for the garden without leaving it dry and hard in the summer? Is this something I am likely to be able to figure out myself.

A local builder or drainage contractor is your best bet, Kate. There's some basic guidance to installing land drainage on this site, and there's a faq I wrote for uk.rec.gardening entitled Improving Clay Soil HERE which you may find useful.

They are lovely old things, those tiles, and well worth keeping hold of. Good luck! :~)

Given you're using a van, I'd be tempted to go for a 150mm thick sub-base, rather than 100mm. You only lay a sub-base once, and it is the load-bearing layer for the entire pavement - might as well get it right first time. :~)

If the existing ground is suspect in anyway, then it might be worth putting in a decent sub-base to bear the weight of the concrete and the shed, plus all its inevitable paraphernalia, but in 99 cases out of 100, the above will be more than adequate.

The perforated pipe is probably the best solution, but you need to have somewhere to where these pipes can outfall, such as a sewer system, preferably a surface water system, or a ditch, stream etc. I doubt that a soakaway is going to be feasible given the conditions you report.

Terram is a brand name for a range of geo-membranes and drianage composites. The primary use for the Terram geo-membrane in the land-drainage business is to line land-drain trenches in order to prevent infiltration of small particles of siilt, clay, etc. that can clog the system. The drainage composites are used for fin-drains and are being used successfully on commercial drainage schemes, but I've never used them on a residential scheme; I suspect the price would be prohibitive.

In your situation, I would look at using an 80mm dia perforated flexible plastic pipe, as described in the land drainage section of this site. It's cheap, simple to install, and highly effective.

2 - Flamin' 'eck! That's all a bit precise. It'd be a miracle if you *did* end up with a 30mm gap, as you've not allowed for the theoretical 3mm joint between each of the blocks. ;~)

On most jobs of this nature (bounded by fixed objects such as walls), it's not uncommon to end up with a situation where cut blocks are required. There's a fairly detailed discussion on cutting-in in the block paving section of my site, but just remember the golden rule: no block less than 1/3 of a full block. Don't be making up any fillets of mortar; it looks unprofessional and they inevitably crack. Use the cutting-in procedures I describe and the job will be so much better for it.

And don't be tempted to use 50mm blocks; get the proper 60mm stuff, or, if you can get a ood price, the 80mm blocks. 90p per block is ridiculous - you can get quality 200x100x60mm concrete blocks for less than 9 quid per m2 (18p per block), but you may prefer something a little more 'traditional', such as the Tegula by Marshalls, or the Priory range from RMC, which will both cost you around 15-17 quid per m2.

At 1300+ m2, you might be able to buy direct from the manufacturer. Certainly, RMC are fairly amenable to direct selling of full loads for cash up front, but Marshalls prefer everyone to go via a BM. I'd get at least 3 BMs to quote you for the supply - try 2 larger national firms, eg Jewson and TP, and get a smaller local firm to quote as well; they will often do you a better rate than the big boys in order to get your business.

Lovely cottage, by the way - whereabouts are you? You should build those great photos into a proper web page. :~)

Firstly, if the paving runs against the house or the garage, you must make sure that the top of the block paving will be at least 150mm below any damp proof course (dpc). Bear in mind that the blockwork and the bedding sand are likely to add up to 100mm of depth, so you'll need the existing concrete to be at least 250mm below dpc, otherwise, you're running the risk of creating damp problems within the property itself.

Secondly, you need to make some provision for draining the bedding sand that is, effectively, sandwiched between the concrete and the paving blocks. If the bedding layer becomes saturated, it can become fluid which can lead to rutting, settlement or worse. Make sure there are regular 'breaks' in the concrete base, preferably channels cut out approx 100mm wide that will allow any water held within the beddoing layer to drain away to to the sub-grade.

On commercial applications, we often incorporate a length of perforated drain specifically to carry away the excess groundwater held by the bedding layer, but this may not be feasible on a residential project.

Apart from the above, you simply treat the existing concrete as the sub-base layer and follow the guidance given elsewhere on my site.

Hope that helps. Good luck!

Now, if you introduce a pipe that has a big empty space in the middle of it, the water will flow into that space, thereby reducing the hydrostatic pressure in the surrounding material. It doesn't escape out of the pipe through the perforations because the hydrostatic pressure on the outside is still greater than that within the pipe, and so any water acquired by the pipe will flow, under gravity, along the pipe to some point of outfall.

It's all simple physics, really. :~)

The most difficult cuts in clays are those requiring a cut of more than 30 degrees from square, and the only viable answer is a the masonry saw, even at 60-75 quid for a couple of days, they are much quicker and less wasteful than any other method.

2 - Do you mean the trammel bars for establishing levels? We use 4.5m lengths of 20mm dia stainless steel conduit or 15x25mm U-section bars. They need to be kept flat to prevent twisting or bending, so don't just carry them on a transit roof rack!

3 - Not unless the soil was a light loam and completely free of stones, bricks, roots or other impediments. A machine-mounted auger is fine, but the hand-held yokes, even the two-man jobbies, are a waste of time.

Also, not sure exactly, but are you cutting wet or dry? Using a wet table masonry saw may also help to increase the blade length, along with making those difficult angle cuts much easier.

As for screed rails, I do a quite a bit of work with interlocking concrete paving stones, and use electrical conduit for my rails. I use a 1 inch (250mm) diam. rail. I use the heaviest grade available, and have no problems with it flexing or bending.

As for the auger, anything hand-held is a pain, even the gas type 2 man models. Your best bet is a tractor mount/skidsteer mount, and augers of varying diameters are readily available.

This phenomenon is not always because of inadequate cement content; it can be caused by contamination of the concrete, or exposure to heavy rain and/or frosts, but whatever, I would get the contractor back and pressurise them to replace it at their own expense.

Other than with freshly poured concrete, there is no magic ingredient you can apply to the surface that will render it hard enough for your purposes. If you get nowhere with your supplier, you might be able to scabble off the loose surface material and replace it with a 25mm thick screed of a granolithic mortar, bonded to the underlying concrete. See the concretes page for more info on granolithic mortars.

Geo-membranes should never be used as a substitute for sound preparation. If I had the choice between increasing the thickness of a sub-base to, say, 150mm from 100m, or using a geo-membrane, I'd go for the thickness increase everytime.

Don't risk it - you only need to lay good paving once, so do it right! :~)

As for preparing a dry bedding mix, we would typically mix enough to get us through a 'session', ie, a morning or an afternoon, rather than bulk mix enough material to cover the entire job. We use a portable mixer that churns out approximately 0.2 m3 per batch, sufficient to cover 4m2 at a time. Depending on the paving type being laid, we would expect to use 3-10 mixes per session.

With regard to laying the flagstones, I'd suggest individual bedding, rather than screeding, using a taut string line to guide final level. Screeding in advance is fine for paving units of regular thickness but is wasted on units such as natural stone flags, unless they've been cut to a standard thickness, as osme of the modern pavings are.

And the circular driveway, yes, I think our cars tend to be a bit smaller than what you are used to. The absolute minimum we would use for an arc is a 3 metre radius, but it all depends on the space available. Ideally, we prefer 4.5m or 6m radius.

The Millstones are a lovely flag, but they are not strong enough for a driveay, unless laid on a full concrete bed at least 100mm thick. Make sure there are no voids in the bedding and point with a decent mortar, a 3:1 should be fine, but use a silver sand and try adding a black dye; it looks much better with Millstone.

We laid Millstone to a private driveway near Northwich about 5 years ago and have had a problem with wear. The drive is quite narrow, so there is little room for manoeuvre and consequently, two 'stripes' of wear have appeared, where the light-coloured agg has been exposed on the run-in to the garage. Might be best to advise your clients before they commit themselves.

Hand mixing that quantity is a lot of work. 5m3 is around 12 tonnes dry weight - assuming you use a C7.5 equivalent, that's around 1.25-1.5 tonnes of OPC, 3.5-4 Tonnes of grit sand and 7-8 tonnes of gravel, which would cost almost as much as bringoing in ready-mix, plus you have to pay for a donkey to keep the mixer loaded while the tradesman is laying.

________
|__|___|
|___|__|

........featured on the front of their latest catalogue. This uses equal numbers of the 200x134 blocks and the 134x134 blocks. Using basic maths.....

2 x (134x134) = 0.0359m2 (square blocks)
2 x (200x134) = 0.0536m2 (rectangular blocks
=================
.....................    0.0895m2 per 'set'

.....and so, the ratio of each type of block is......

Squares = 0.0359 ÷ 0.0895 = 40%
Rects = 0.0536 ÷ 0.0895 = 60%

.....therefore, 40% of your total area needs to be square blocks and 60% needs to be rectangles.

You state that you have 45m2 to pave, therefore you will need approx 18m2 of the square blocks and 27m2 of the rectangles, plus a bit extra for wastage. There are 9m2 per pack of the brindle squares, so 2 packs will give you the 18m2 you need and just over 9m2 per pck of brindle rectangles, so 3 packs will give you 27m2, just as the salesbod told you.

However, this leaves no leeway for wastage. :~(

As for laying in curves, do you mean curved soldier courses as shown on the front of their catalogue, or circles as on p10?

Pricewise, I can't really comment, as the rate we pay as contractors tends to be slightly more favourable, but it depends on just whereabouts the work is located, particularly the distance from the nearest distribution plant. That price sounds fair for the quantity of work you have proposed.

Good luck!

from what I've seen of PIC jobs, they tend to use the block paving kerb units to form the riser of steps, and then use the PIC to form the tread. You could use almost anything, from engineering brick, stone cobbles/setts, edging kerbs or walling stone, depending on which pattern and colour scheme you have chosen

use a cementitious bed for the slabs. 1:10 cement:grit sand is usually strong enough, as you're not looking to create an incredibly tough bed, just to bind the sand sufficiently to prevent it from being washed out. No need to make a wet mix; a semi-dry mix is ideal, as it is less likely to stain your paving, gives you longer working time and is much, much easier to work with than a sloppy wet mix. There is (usually) enough natural moisture within the sands to initiate setting, but, if you have an exceptionally dry sand, you may need to add a little water, just enough to make it damo, not wet.

The best sized gap between the slabs is really a matter of taste, but you will find that 100-150mm is usually the most pleasing to the eye.

1.5" = 35mm or so, which should be a deep enough channel for a 10mm or smaller gravel, but if you're using, say, an 18mm or bigger size, you may need to create a deeper channel, say 50mm. The size of the gravel does affect what size gap between slabs looks best, but it is still likely to be in the 100-150mm range; a bigger gravel suits a wider gap and vice-versa.

Good luck!

you should brush the dried jointing sand into your paving and leave a 'dusting' on the surface before compacting. The plate will vibrate the sand into the joints and you may need to top up as you proceed.

As for your lines, they should be absolutely straight, but some deviation is allowable, seeing as it's your own driveway. If you're happy with it, then that's all that really matters, but it is worth spending half an hour or so trying to persuade the blocks into straightish lines if you can.

from what you've told me, I would suggest using an interceptor/collector drain at the boundary of the property, and have it outfall to a ditch safely away from the garden. Depending on the exact site conditions, a fin drain might also be suitable. Have a look at the drainage section of the site for more info on both these types of drain, and let me know if you need more info.

it's not necessarily a silver sand that's used for the jointing in block paving; it's the grain sizes and range of sizes that are important, not the colour. In some parts of the country, the locally-available jointing sand is definitely reddish in colour.

As long as you buy a sand marked as a block paving jointing sand, you should be ok. To keep the sand more securely in place, you could use a weak solution of PVA watered-in once the joints have been filled, or use the Marshall's product 'Keybond', which is basically the same thing. These will have no effect on the appearance of the blocks themselves.

Alternatively, a quality sealant such as Resiblock 22 will prevent loss of sand in the future *and* seal your paving at the same time, although you do get a gloss or semi-gloss finish to the blockwork. This is the best solution to keeping weed colonisation of the joints to a minimum.

Good luck!

Pre-packed mortars have a finite shelf life. What you describe sounds like a perished (ie, knackered, useless, gone off) mortar.

Some slate can be slippery when wet, but cleaved slate (as opposed to sawn slate) is usually less so. Also, you may find that unsealed slate becomes colonised by mosses and algaes in shady, untrafficked spots.

There's been a surge of interest in slate laid on-edge over the past few years, but this is a challenge to do and to get to look right, not something I'd recommend for those with limited patience, but it is ver, very attractive as an edge detail or in smaller areas.

Aquaseal is not something I would use on slate; I'd use a high quality sealant, something like Resiblock 22, which I would expect to last at least 4 years, whereas the Aqualseal, being acrylic and not primarily developed for paved surfaces, could well turn out to be an annual task.

Good luck!

use a 75mm thick bed of Class E concrete (that's approximately a 1:3:6 mix of cement/sand/gravels). That should be fine for foot traffic. Keep the added water to an absolute minimum; the mix needs only be damp, not sopping wet. This will make laying the tiles that much easier and also reduce the amount of staining.

Jointing should be 6-10mm, I'd guess, and pointed with a 1:4 mortar.

Also, if the old concrete is cracked, these cracks can propagate through the new paving/concrete and make an unwelcome appearance in the new surface in as little as 6 months in severe cases.This is because the concrete beneath the new paving will continue to shift/settle over time. In some cases the added load/weight of the new paving actually accelerates the movement.

My usual recommendation in these cases is to rtip out the old concrete and start afresh. It's one of those things that might take you a day or so extra labour and a couple of hundred quid to sort out, but if you take the easy option and hope for the best, you won't half be pizdov if it does move! ;~)

PS - using all capital letters is the 'net equivalent of SHOUTING! - Do us a favour and make sure caps lock is off before typing. Good man! :~)

Rather than leave a gap, you should form a movement joint by using a piece of Flexcell or similar compressible board between the footting and the existing wall.

(2) you suggested that I align the movement joints with the piers. I am going to have to ask a stupid question. What did you mean by this? Do you mean having the movement joint at one of the edges of each pier?

It's a long time since we discussed this last, but, IIRC, I think I meant that the movement joints could be incorporated midway between piers.

If I did follow my suggestion of having the pier halfway along each length of brickwork, then I wouldn't have piers at either end of the entire wall. Would this be ok? Or do I really need a pier at each end to ensure long-term stability of the wall?

It all depends on the size of the wall. You really ought to consult a structural engineer for any wall greater than 1200mm in height, as my speciality is paving rather than wall-building.

Think of how a bridge is built.....They build collums, then span the road surface between the two columns, usually putting expansion joint at that point.

A good example would be to take a 3 blocks of wood and place them 5 meters apart. Now, if you have 2 5 meter long boards, would you place them so that each board would span from one block to the next, or would you take one, teter-totter it on the middle one, and then cut the other one in half and place it on the two ends maybe screwing it together then at each joint.

The answer is simple, you would span the two boards from block to block and not cut one in half.

The wall is much like a bridge, spanning between the two pillars. Each pillar, over time, will eventually begin to heave/sink, moving independenty of each other. Thats why you need joints AT the pillars, not in the middle.

As for the ends, I would definitely say yes, have pillars. Again think of a bridge, and how the ends are set on a foundation (this time the side of a river/culvert/etc not a pillar) you need the support on each end, or the wall will sink there and crack at the next pillar or inbetween.

The wall is basically a 'bridge' from pillar to pillar. Thats the way I think about it.

Hopefully I helped some and didn't confuse the daylights out of you.

I said that you should use a semi-dry mix, not a wet mix, so yes, you will be able to walk upon it.

2-Do I lay out a bay and walk over raised planks setting the paving as I go

Not necessary with a semi-dry mix.

3-Do I place the slabs directly on the wet mix.

Do NOT use a wet mix - it will be a nightmare.

You'll hardly notice the break in pattern after a couple of weeks. For small paths and the like, it may be wise to consider a pattern that reduces the number of small pieces of cutting-in required, such as, say, a running bond.

How large are the gaps? If over a half inch, they could be a trip hazard in the near future. Sand will not fill gaps for very long if they are that large, as if will wash out quickly.

I would suggest cutting as the best solution. You may have to pull a few sections up and actually cut a row or two of the cobbles to maintain the pattern. (i mean you may need to trim a few down in a row so that you don't have to just stick one little sliver in)

Lot of good info on the saws here at the sight if you look in the tools section. Should be able to rent one, but the blade will be pricy as they charge you for wear.

the joints need to be sealed in some way. My preferred method is to use pitch, as described on the site, but you could use a high-strength mortar, preferably one enhanced with SBR, an additive you can buy from Builders' Merchants. Also, a dark coloured or black mortar looks much better with cobbles/setts.

I recently sealed a fan-pattern driveway for a reader of this site and will be putting up some pictures in the near future. I used pitch, for the traditional look and the finished job now looks wonderful, even if I say so myself. :~)

However, if it's slabs, then you can lay them on a 10:1 sand/cement semi-dry mix on top of the existing concrete. A 35-50mm thick bed plus the 40mm or so thick slab will give you an additional 75-90mm on top of the concrete which should keep you below the recommended 150mm clearance from paving to dpc.

Don't use a wet mortar for bedding - it *will* make a mess and is much harder to lay on than a semi-dry bedding mix.

The 150mm below dpc is a good recommendation but not always possible or feasible and so you have to use your discretion. I would, perhaps, elevate the patio to 125mm below dpc rather than expose the foundations of a wall, but, without being completely familiar with your site, it's not possible for me to say exactly what I would do.

Keep the bedding to a minimum, say 35mm, or even 30mm if you're only using decorative patio flags and there will be no vehicular traffic. The paving should slope away from the wall, so you should find that at, say, 500mm out from the wall where you're clear of the footing, you can revert to a fuller construction method.

However, you mention that the 'grade' of your drive is only 1% which makes me suspect you are not UK-based, as 'grade' is not a term we use in that context; it's far more common in N America.

If that is the case, there's not much I can do to advise you, as I have no knowldege of the the paving market on the left hand side of the pond. You could try some of the links featured on my site to grass paving companies and see if they have outlets in your neck of the woods, but beyond that, there's really very little I can say.

Meanwhile, if I've completely misread the situation and you are stuck in these soggy islands like me, I'd suggest you contact Cooper Clarke in Bolton (address on Links page) and ask them about their EcoGrid range - that has often proved to be the most cost-effective solution for smaller, residential grass paving projects (ie, less than 500m2)