Paving slabs which way up

FAQ - Flags laid upside-down? Table of Contents. Introduction In theory, there should be no enormous performance issue if the stone is laid upside-down but a little bit of care an attention is needed. Slab being trimmed in India Further, because the arrisses the edges are not trimmed to set size, any jointing between inversely-laid flagstones will vary significantly in width.

Jointing issues. Related Pages. Welcome to the new-look pavingexpert website! When you finally come to laying your paving, you can use two taut string lines to guide the line and level of the paving. It needs to be high enough so that it can squash down slightly once you tap the paving slab firmly into place - so about 30mm or 40mm in thickness should be plenty.

Right, now comes the moment of truth. Lift the paving slab and lower it into place on top of the mortar, making sure not to catch the corners. Mix it gradually with a bit of water, until you reach the same smooth, damp consistency as you achieved earlier. Whatever you choose, the next steps are the same.

You can use a trowel or a pointing gun to compress the mortar mix into the joints between your paving slabs, and use a pointing bar to press it down or smooth it over anywhere you need to. If you accidentally spill any, make sure to scoop it up as soon as you can!

Now, for best results, once every slab has been laid, they need to be left to set for at least 24 hours, or longer in wet weather. The problem is, this can leave a lot of empty space between the mortar.

Water can quickly start collecting in these gaps, which can end up causing a lot of problems. Some smaller paving stones x mm can be awkward to stabilise due to their size.

Using a slightly wetter bedding mix will usually overcome this problem by causing the paving stone to adhere to the bed. When checking levels and surface profile regularity, use a long spirit level or a straight-edged length of timber to ensure adjacent paving stones are relatively level, with no high spots or hollows.

If there is any doubt, correct the problem at this stage — it is much easier to put it right now, before the joints are filled. Sets are usually laid one-at-a-time to accommodate the slight variation in thickness that is found with many natural stone paving products. For pathways and light-use patios, the sets can be laid onto a mm thick bed. Driveways or areas subject to heavier use will need to be constructed using a mm thick bed of concrete, and it may be necessary to include a sub-base strengthening layer of selected crushed stone or hardcore.

The bedding mortar described above for use with paving stones, can be used to lay sets into patios and along pathways, but for driveways, a concrete comprising four measures of mm chippings with two measures of coarse sand and one measure of cement should be used. Sets are normally laid in one of three arrangements: stack bond like a chess board , coursed where the stones are laid in lines or courses of the same width or decorative.

Stack bond needs sets of all one plan size, while coursed layouts rely on the stones sharing a common width but various lengths. Decorative layouts include complex patterns such as fans, arches and bogens — these patterns can be difficult to lay and are usually best left to specialist contractors. Stacked or coursed layouts are laid using a taut string line as a guide to both level and alignment. The bedding material is roughly graded using a shovel, laying out sufficient material to support a linear course of metres of sets to be laid.

It is levelled out using a trowel, and each set is individually placed, aligned and compacted using a rubber mallet, before placing the next. Ideally, when placed, each set should be mm proud of the desired level, so that it can be tapped down using the mallet, embedding the set into the mortar or concrete in the process. Using a short piece of 10mm timber can help ensure regular joint widths are maintained between the somewhat rough hewn edges of the sets. This rough hewn texture can make set laying quite a challenge.

To improve the final appearance, a tip is to lay the forward edge of the sets to a taut string line, allowing any variation in width to be taken up by the joint created between the newly laid sets and those of the preceding course.

Working to a taut string line ensures the sets are fairly accurately positioned for alignment and level. The riven texture can result in unexpected high spots or hollows within a course, so it is essential that the surface level is regularly checked using a long spirit level or a timber straightedge, and any problems corrected before proceeding.

It is a good idea to check in both directions, along the courses transverse and across several courses at a time longitudinal , as well as standing back and visually assessing the laid sets from several positions.

The calibrated thickness of the Global Stone Granite Cobbles allows the landscaper to lay them onto a screeded, bed prepared in the same way as for the calibrated flagstones. As with the small sets, these small pavers will need to be laid onto a mortar bed suited to the proposed use of the finished surface, ie: mm in light pedestrian areas, but increasing to mm with the possible addition of a compacted sub-base in tougher driveway conditions.

Paving stones are best cut using a power saw or angle grinder, fitted with a diamond blade specifically rated for cutting stone or concrete. These can be hired locally and the hire depot will provide you with full instruction on how to use them safely.

Bear in mind that saw cutting of stone generates lots of harmful dust. Ask the hire depot about a water suppression kit to dampen down the dust and make sure you wear a suitable dust mask and safety eyewear. Smaller paving units, such as sets, can also be cut using a bolster or pitching chisel. Make sure eye protection is worn as small scalpings or shards are likely to fly up when the stone is struck. Align the bolster on the face of the set where the cut is required and strike firmly with a lump hammer.

It may take several blows to break the stone and it may be necessary to trim the cut edge in order to make it fit the gap. The joints between paving units can be filled with various materials.

While this is still a popular option, it can be slow and messy, especially if you are not familiar with pointing techniques. Happily, there are alternative strategies that might be suitable for your project. This traditional method uses a strong mortar four parts sand to one part cement to fill the joint. The mortar should be mixed in small quantities, say one 25kg bag of sand at a time, because pointing is a slow process and the mortar has a fairly short working life minutes depending on time of year.

Adding a plasticiser to the mix water makes the mortar far more workable. It is worth noting that some bags of cement contain a built-in plasticiser, so there is no need to add one to the mix water — check the packaging on your cement. This group of products is a modern development, and despite being somewhat costly when compared to traditional mortar, they are much, much faster.

The polymeric mortars are made from selected sand mixed with a special resin that starts to harden when exposed to the air or to moisture. The products are simply brushed into the joints, any excess is swept off the surface of the paving, and in hours, the material will have hardened to form a perfect joint. This technique can only be used when the surface of the paving is dry. The sand is supplied in plastic bags to ensure it remains dry and free-flowing.

There are several good reasons for this:. Many homeowners choose to seal their new paving to protect it from accidental staining and to reduce the risk of allowing algae and lichens to establish themselves on the surface and joints, discolouring the paving and masking the natural beauty of the completed work. There are many different sealants on the market, providing different finishes and often changing the appearance of the paving. Polyurethane sealants are best suited to concrete block paving rather than natural stone, but if the semi-glossy, slightly waxy finish is admired, there is no reason why they should not be used.

There are also specific sealants for specific stones. Sandstone is often more porous than, say, granite, and so some manufacturers offer sealants designed to suit the characteristics of individual stone types.

This is a top quality sealant suitable for use both indoors and out, and will protect your paving for years depending on how heavily used it might be. For those that prefer the richer colours that appear when paving is damp, Lithofin MN Colour Impregnator will give a permanent damp look and can be applied before using the StainStop sealant. Obviously, all paving should be in pristine condition prior to sealing. There is little sense in sealing in stains and empty joints, and so preserving them for several seasons more.

Prior to sealing, the paving should be thoroughly cleaned, and checked for any defects. Ensure joints are full and that there are no loose pavers or flagstones. Because faults and minor defects rarely show up straight away with new paving, as well as the possibility of efflorescence developing on a small number of installations, it is strongly recommended that all paving is left untreated for at least six weeks. Sealing immediately upon completion tends to seal-in problems and make them much more difficult to rectify.

Try to choose a time when there have been at least two days without rain or precipitation, and remember that users will not be able to access the paving for several hours following sealing. Also, avoid breezy days when there is a risk of dust and detritus being blown onto the freshly sealed surface. It is not possible to enhance the colour of a newly-sealed driveway. On those occasions when sealant treatments go wrong, the manufacturers will not entertain any claim where they suspect the application procedure was not followed rigorously.

Many sealants will require two coats to achieve full cover. This is especially true with new stone and paving that has not received any other treatment. The first coat tends to soak in and coverage can be worryingly low, just a couple of square metres per litre in some cases. However, the second or subsequent coat usually goes much further, five-eight square metres per litre is not unusual, and the coverage rates reported by manufacturers often aggregate the rates for the two coats.

Many sealants will dry or cure in two-six hours. Protect the paving with flutter tape, temporary fencing or barriers during this time. A good quality sealant will usually provide three-seven years of protection before it will need re-doing.

Cheaper sealants are often a false economy as they may last only one season.