5/05/2011

Imported Stone Paving for Patios and Gardens from Xiamen China

Introduction


Natural stone has been a popular choice for paving for thousands of years, but it's place as the most popular choice was usurped in the early 20th century by the advent of concrete flags. As a family's disposable income grew in the later decades of that century, the choice of concrete flags grew exponentially, but one of the most popular styles were concrete copies of those natural stone flags. Concrete copies offer a number of advantages - they are cheap, compared to the genuine article; they can be cast to modular sizes, making patterns or coursing much simpler; they can be produced at fairly regular thicknesses, whereas natural stone might be anywhere from 30-100mm thick; and they can be packaged for sale via retail outlets other than Builder's Merchants.

As technology progressed, so the realism of the imitation riven flags improved, and, by the late 1990's, the copies had become so good that they were all but indistinguishable from the real thing, and the consumer was offered a wide range of 'qualities' from the cheap, utilitarian 450x450mm pressed units selling for under a tenner per square metre, through medium priced multi-size ranges and on to the top-of-the-range items, featuring realistic looking textures and colours and selling for 20-30 quid per square metre or more.  yorkvale paving
 Leeca Paving Stone ;Email:sales@leecastone.com

Then came the imports. Stone flags could be quarried, hand-dressed, packed and shipped from developing countries for a fraction of the price of British or Irish sourced stone. In some cases, the packs of flags were literally being used as ballast aboard ships delivering other goods to the EU. And the market was ready for it!
The explosion of interest in 'lifestyle tv' had convinced homeowners to carry outdoors those spending habits previously restricted to decor for inside the home, and we started hearing trendy garden designers spouting nonsense about making "outdoor rooms", spending huge sums of money creating gardens and patios that might only be used for a couple of months of the year, but the market was primed and the people wanted to spend.
So, the two driving forces of supply and demand met head on and a new interest in patio paving took off. Suddenly, genuine stone paving was available, in modular sizes, in convenient thicknesses (or thin-nesses, depending on your viewpoint), in a stunning range of colours and styles, and not only was it readily available for half the price of good old British York Stone, it was cheaper than the better quality concrete copies! You could now buy genuine stone flags, brand new, hand-dressed, for 20 quid per square metre or less, and it was only the anoraks like me that could tell you that it wasn't 'real' york stone.


A World of Stone
And so, we are seeing more and more stone imported from more exotic parts of the world. Most noticeably, there has been a surge in the supply of an  Leeca Paving Stone which sells under a bewildering array of names, some attempting to sound vaguely "Northern", even though the stone has never been anywhere near the north of Britain, while others emphasise their sub-continental origins with names like "Raj Green" or "Modak Brown".
There are also granites from Brazil, marbles, porphyry, limestones, travertines and slates from southern Europe, all supplied as what we would term 'flagstones', as well as cubes, setts and cobbles in hardstones such as granite, gabbro and diorite.
The remainder of this page considers the more popular imported stones.
  
Quality and suitability
There's a tendency for some less reputable traders to supply the imported sandstone as 'York Stone', when the nearest it as ever been to that county is probably the dockside at Hull. While much of what is imported is of sound quality, there is some shi....err, rubbish that is barely capable of holding itself together. If buying imported stone, always check the competence, that is, how well cemented are the grains, how 'tough' is the stone. A simple check is to attempt to crumble a corner of a flagstone between the forefinger and thumb. The poor quality material will disintegrate under pressure.
There are different grades of quality. The best stone is sold as 'firsts', and this tends to be very good quality suitable for all sorts of projects. Then comes the 'seconds', which may not be as neatly finished, or is a less attractive type of stone, but is, generally speaking, more than adequate for the vast majority of patios. And then there's the "seconds rejects", which varies enormously in quality, from 'not too bad' to 'truly abysmal'. It should be noted that many dealers will not reveal the exact grade of their stock, and in many cases, price is not a reliable indicator. We have seen dreadful imported sandstone selling for £28 per m², and we have seen a gorgeous deep red sandstone that is as hard-wearing as any Yorkstone but sells for a mere £14 per m²  delaminating stone
Poor quality stone has started to de-laminate in the soggy British weather
Obviously, because the vast majority of this stone has been around for only a decade or so, it's difficult to say how it will perform in the longer term, or how good it is at coping with British/Irish winters and the near-perpetual damp we have to endure, but there are valid concerns regarding "algaefication", where the stone seems to go green almost overnight as its porous surface is readily colonised by algae and lichens.
See Cleaning Paving page for notes on cleaning algae and lichens
A notable point that was brought up in the Paving Forum on this site is that much of this imported material has undergone no form of approved testing, so data for Water Absorption, Slip Resistance, Compressive Strength etc., may not be readily available, especially with the cheaper sources. This lack of information may render them unacceptable as new paving on certain civic or commercial projects. However, the better quality importers will be able to provide data on request.

Sizes

One very important point that should be noted, by both contractors looking to lay these flags and clients looking to buy them for their homes, is that the sizings can be a bit strange, to say the least. While most of these flags are generally 15-30mm in thickness, which does have an effect on laying methodology, it's the plan sizes that have a direct bearing on design, layout and patterns.
There are two distinct 'schools' of sizes. Some suppliers offer flags in modular metric sizes, so you find sizes that are found with BS Paving and cast Patio Flags, such as 600x600mm, 450x450mm and 600x300mm, all of which aids coursing, patterning and/or the creation of random layouts.
However, quite a lot of the flags seem to follow a non-logical set of dimensions. Instead of a 600x600mm unit, we find a 560x560mm unit, which is based on a 140mm module (all sizes are multiples of 140mm). But then there's 560x400mm units and 750x560mm, which don't seem to fit into any modular scheme. Indeed, some ranges are completely baffling and result in dramatically uneven joint widths when laid to random layouts rather than coursed layouts, as can be seen in the image opposite.  uneven joints
Uneven Joint widths
So, when sourcing these flags, check on available sizes, and whether they are modular. If you're laying coursework, then it's not as critical as it would be for a random or patterned layout.
The most popular sizes seems to be based on the following set, and the flags in the range are, roughly ± 5mm of the sizes shown in the table and chart below...
Modular
Imported
 Leeca Paving Stone ;Email:sales@leecastone.com1120x560mm

Add caption
 840x560mm
700x560mm
560x560mm

420x560mm
280x560mm
420x420mm
280x280mm
 
sizes
Popular Imported Sandstone Sizes
 ruler
Spoiled for choice...
What follows is a selection of photographs illustrating some of the more popular imported sandstones that are available through a selection of the better quality suppliers. All these images were taken by myself, or by friends of the website, with the intention of portraying the stone as realistically as is possible on a web page. There's no trick photography, no arty-farty designer styling, no fancy lighting - just photos of the stone flags as they appear in the display areas of the named suppliers.
It is strongly recommended that you visit a supplier and see the stone laid out as shown here before making a purchase. Buying from photos, catalogues or looking at one or two flags dragged from a rickety wooden crate is not a good idea. All of the suppliers listed here are delighted to welcome visitors to their premises and to show buyers a wide range of stone paving to make sure they get the stone best suited to their tastes and their pockets.
This page features mostly sandstone flags. Subsequent pages will feature other types of stone flags, including limestones, granites, whinstone, slate and more.

rock unique  Rock Unique, based just outside Sevenoaks in Kent, have scoured the world to find quality stone paving materials.  rock unique display
This is a small selection from their range of Indian Sandstone flags. Rock Unique carry one of the most comprehensive inventories of stone for paving and flooring in Britain and a visit to their sales office just at the end of the M25 spur to Sevenoaks is time well spent, as the ever affable Chris and Mike can show you a range of stone that it's just not possible to illustrate on this one page.
 Leeca Paving Stone ;Email:sales@leecastone.com

patio circle
Circle feature with squaring-off kit  mixed brown tumbled setts
Mixed brown riven paving with tumbled setts
raj green
Raj Green - in the dry  raj green
Raj Green - wet, with tumbled clay pavers
fossil mint
Fossil Mint  kotah Blue
Kotah Blue Limestone

porphyry setts
Porphyry setts  One of the more intriguing products from Rock Unique are there mesh-backed porphyry setts.
The setts are cut, dressed and mounted onto a strong polypropylene mesh backing, so that, when it comes to laying, all that needs be done is to prepare a level bed, drop the mesh setts into place, consolidate with a plate compactor and joint them! It really couldn't be easier!
More info from Leeca Paving Stone ;Email:sales@leecastone.com
 
porphyry squares

Porphyry stack bond setts  porphyry fan
Porphyry Fan

Flagstones from other importers
Goldleaf
Goldleaf Riven from Global Stone  KB Modak
Modak Riven from KB Global Stone
Greyfell
Greyfell Riven from Stoneflair  Sawn6
Sawn 6-sides from BBS
 A selection of other flags, including sawn stone, which has a completely different texture and character from that of riven stone.
Riven paving has a more natural look, but its irregular surface is not to everyone's taste and some designers believe that the sawn/honed finish, which is smooth but NOT slippery (as some people seem to think), is better suited to modern, contemporary patio design, and the riven is best left to the traditional 'cottagey' look that remains popular with British and Irish garden lovers.
 Banded Banded sawn paving from Stonescape
Brown-buff random pieces
Brown-buff random pieces  Brown-buff 450s
Brown-buff 450x450mm flags laid chequerboard pattern

Circles
Circles are a popular feature, either built into larger patios or as stand-alone features within the garden. Many of the larger suppliers offer a range of circles, featuring a centre stone with one, two, three or more outer rings of pre-cut flags, giving a selection of different diameters.
All the circles featured here come as 'kits', that is, as complete sets with the requisite number of pieces required to form a whole circle, and some of the bigger suppliers also offer "Squaring-off Kits" as an optional extra. These squaring off kits provide the odd-shaped bits required to fit a circle feature into a rectangular "orthogonal" patio.
 Modak Circle
Modak Circle from Butterfields
Mint Circle
Mint Circle from KB Global Stone  Compass Circle Compass Circle from Stonemarket

Fossils (allegedly)
Many suppliers offer flagstone featuring these intriguing 'Fossils', which, admittedly, do look like ferns or some other simple plant from pre-history, and are a fascinating talking point when the client is showing off their new patio. However, they are actually a trace stain, created by a reaction of metallic oxides within the stone that has lain buried for millions of years before being exposed to the atmosphere when the stone flag was cleaved in the quarry.
Still, it's a nice thought, and makes the flags even more attractive!
 Fossil
"Fossil" sandstone
 ruler
A warning about acid cleaners
Over the last few years, there have been a number of reports to this website regarding a frightening discolouration that can occur with some imported flagstones, setts, kerbs and associated items when washed with an acid or an acid-based cleaner.
These cleaners (also known as Patio Cleaners, Acid Washes, Brick Acid, Cement Remover and dozens more) generally contain 3-10% hydrochloric acid (HCl aka Muriatic Acid) and are commonly used to clean minor staining and, in particular, cement and mortar stains from newly laid pavements. This is a well-established practice with some other paving products, where it generally has no effect on the paving other than to get rid of the offending stains, so it generally comes as a surprise to the unwary contractor when what were a lovely light grey flag suddenly turn bright orange.
The problem is caused by a chemical reaction (you knew it would be!) between the hydrochloric acid and iron-based minerals that naturally occur within the stone. Without getting bogged down in all sorts of complicated stuff about ions and covalent bonds, the acid causes the iron that was previously locked-away within the stone to be released and exposed on the surface. Sort of. Ish.  acid stained flag
It doesn't affect all imported stone, and it seems that different batches of the same product react differently at different times. It's not been possible to collate comprehensive data as many of the suppliers haven't been too forthcoming about whether the stone they supply is affected, and if so how badly, and under what particular circumstances, but from the feedback to the website, it seems that...
    The lighter-hued sandstones are more susceptible than the darker ones
    The longer the acid is in contact with the stone, the worse the discolouration
    Stone that was pre-wetted before acid-washing is less severely affected
    The discolouration is stronger if the acid wash is undertaken in bright sunshine
    The stronger the acid (in %age), the worse the effect

....of course, this is very much a generalisation and individual experiences can, and do, vary.
At the moment, there is no known fix, despite what some of the less trustworthy suppliers and contractors are telling fretful homeowners. A sealant, even a bloody good sealant, will NOT make this effect disappear. The claim that Oxalic Acid will reverse the effect remains unproven, but it does seem to reduce the visual impact of the lightest stains. Grinding, shot blasting, and other abrasive treatments can reveal a 'clean' face but they dramatically and irreversibly alter the texture of the stone. Further, stone that has been well and truly soaked with acid in an attempt to get rid of heavy cement staining, the discolouration effect continues for several millimetres into the body of the stone, so abrasive treatment can be futile.  acid stained flag
The only sure and certain method of avoiding this problem is not to use acid in the first place! When stone paving requires cleaning, use household bleach diluted to 50% with clean water. To get rid of cement or mortar stains, rely on mechanical action wherever possible.

1 comment:

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