A lot of paving i see being laid now has a concrete base poured. Please enable Javascript to use MyBuilder. jobs, How to lay your paving slabs: First, you need to mix a fresh bed of mortar for each individual paver. This is a ‘catch-all term for a material that is popular in the south of England, and, because of the spread of nationwide Builder’s Providers/Merchants and DIY Chains, it is now found on sale in places where it normally wouldn’t be given the time of day. Although picture framing can, and does, occur with flags laid on other bedding materials, most cases are seen on flags that are porous or permeable, that have mortared joints, and that have been laid on a full bed of high slump mortar or concrete. However, there are many examples of smaller flags being laid on bound bedding and larger flags being laid on sand. no water should drip through the fingers when the mortar is squeezed. A 10:1 mix of sand/cement is around appropriate as this will stiffen the mix suitably. The parent rock is very important in determining the suitability of the fines for use as a laying course material. However you can use a dry mix if you wish. (adsbygoogle = window.adsbygoogle || []).push({}); There are two classes of bedding material: hydraulically bound and unbound. Can You Lay Paver Stones Across an Old Patio?. The current mix of sharp sand which is currently laid on should be a mix of 8/1 sharp sand to cement for a decent slab bedding. That's why sand-and-cement bedding is probably the best laying course material to recommend to low-skill contractors and all DIYers. You are strongly advised to seek professional, onsite advice for your project. You can use the sand you have for this mixed as advised, you don't want it stiff, loose enough to bed without the slabs sinking. How To Lay Paving Slabs On Sand - Simple: You Don't! Those wanting to attempt floating their flagstones on a mortar broth, as required by the BS-recommendations, are welcome to try but they pretty soon come to realise the impracticality of such a high slump. For paving projects that don't need to meet the exacting requirements of BS7533:4 2006, here are three mortar mixes plus one concrete mix that we've been using for in excess of 40 years. The sand also needs to be free-draining to prevent liquefaction of the laying course. Instead, what matters most is the fact that the mortars will set and provide a firm and stable support for the paving above. Mike Silvey Paving and Before you can start laying patio slabs, you need to dampen them so they don’t dry out your concrete too quickly. jobs, Consequently many contractors prefer to lay on a mixture of sand (or other fine aggregate) and cement, rather than on clean sand. However, a granular material that’s too chunky would not be satisfactory. Plasticisers help break down surface tension and keep the water trapped in the mortar while it is being used. feedback. What is really needed from the mortar is workability, consistency of mix, and strength: the addition of building sand makes for a weaker mortar. I think it will take you longer and it's important you sort your slabs for the reasons explained, using the wet or dry method. Terms and conditions At that time the building trade hadn’t become obsessed with portland cement, and every town of any significance had a limekiln, where limestone that may have been shipped in from a hundred miles away, would be burnt and crushed and slaked to form a lime suitable for mortar production. As a very, very general guide, flags specifically manufactured as small element paving, that is, pressed concrete or stone flags with a plan size of 450x450mm or less and a calibrated thickness, and having chamfered or rounded arisses, can be laid on unbound bedding: everything else is better laid on bound bedding. However, as stated above, a building sand makes a weaker mortar, and so using a plasticiser is preferred to adding an inferior sand. There are a number of instances in which you may wish to use sand -- as opposed to a sand and cement mix -- as a bedding material for paving slabs. This is the type of sand used to make ready-mix concrete, which is why it is sometimes known as Concreting Sand. Accordingly, a separate page examining the reasons why they are used, along with an examination of how they are prepared and how they are used on site has been created. Finally, the selected sand should have a low clay/silt content, as this will affect its ability to drain freely. It might also be known as sharp sand, grit sand, or coarse sand. With only 30-50mm depth, a mortar with a high compressive strenth hasn't the thickness to withstand exceptionally heavy loads. For commercial flag paving (paving in public areas) and for paving that will be subject to vehicular overrun (including driveways), the strength of the bond formed between bed and flag, and between the bed and the substrate, is often the most important factor. UK VAT Registered: 850 4121 63. Forest Pennant Stone for Bristol Eco-Home, Forest Pennant to provide stone for Worcester Library, Marshalls to close Transformation Centres, Marshalls make a splash with permeable paving, New look and new catalogue for Bradstone Ireland, New block mix offers environmental benefits, say Marshalls, Acheson-Glover get weaving at Linen Green, Tatton 2006:Paving, plants & perspiration, Acheson & Glover score national awards hat trick, New lightweight block splitter from Probst, Kitemark Award for Irish Paving Manufacturer, New Bradstone Display Area for Creagh Concrete, Formpave launch new range of British Stone, New Guide and New Products from Tobermore, New Concrete Specs from December 1st 2003, Concrete Block Permeable Paving and the Clogging Myth, Permeable Bedding Mortars from SteinTec TuffBau, - health & safety implications: dermatitis, cement burns. There are two acceptable methods of laying flags - individual bedded and screed bedded. They also overlook that 10:1 is not all that much ‘weaker’ than an ST1 concrete , the old 1:3:6 mix, roughly a 7.5N/mm². One question that comes up quite often in regard to this semi-dry mix, is the cement content. Always wear protective gloves and wash off all tools when finished. Sometimes, by changing to a moist mix bedding, these problems can be reduced or eliminated. For whatever reason, they can’t seem to get the bed right, and the flags are either too high and end up being cracked when hammered hard to force them down, or they are too low and need to be lifted and re-bedded. A patio gives you a lovely area to plant shrubs for privacy, to have barbecues with family and friends, or enjoy a quiet respite from work. Lay a 1-inch layer of coarse builder's sand over the gravel and compact it firmly with a plate compacter. How to Lay Slabs. Similarly with gabbros and diorites and most of the igneous and/or metamorphic rocks of Scotland and Northern Ireland. The three key factors in determining the suitability of a grit sand are: So, the ideal sand is a free-draining, gritty sand that does not retain water. If you’re laying a small patio, do this in a wheelbarrow, for larger areas it’s worth hiring an electric cement mixer. It’s actually a basalt or a dolerite, intruded when the region around Ardnamurchan was volcanically active many millions of years ago, If you were to take those hexagonal blocks up at Giant’s Causeway, and crush them down to a 1-3mm particle size, you’d have a pretty good whinstone! It's also provides a clean method of working. As mentioned above, you can lay on a hard base such as concrete if it was already there and leaves room for the paving plus 5cm of cement. It also means that, when the next flag is laid, some of that flag’s excess mortar can be pushed back under the preceding flag, upsetting its previously accurate level. In order to be able to carry out these functions, a material that is granular in nature is required, because such a material can be spread and levelled as required to suit the site. At the same time, evaporation is driving off moisture from the edges and the surface of the flags. There are three slumps that can be used for bedding paving: semi-dry; moist; and wet. Some of this cement-contaminated water is absorbed by the flags and carried through capillaries within the flag. This phenomenon is particularly noticeable around the edges of the flag, and so that’s how it acquired its name - the resulting stain often looks like a picture frame around the flag. What was once a freshly laid asphalt or concrete patio eventually begins to lose its luster through time and weathering. Consequently, the degree of skill required to make a bed that will be ‘perfect’ is much reduced compared to that needed to make such a bed from sand alone. The semi-dry mix tends not to be picked up and carried by tools and boots, so there less risk of accidentally staining the flags during the laying process. Although there’s no real need, most moist mixes are prepared with a slightly higher cement content than a semi-dry mix: something like a 6:1 mix. By adding a small quantity of water to the mix, the mortar is able to ‘flow’ albeit to a limited extent and so find an accurate level beneath the flag. Laying Indian sand stone patio slabs on uneven concrete base, Laying Indian sandstone slabs but not sure what gaps should be, Find This method can be used for both patios and driveways. feedback. Whether it's an unbound sand or grit, a cement mortar, or anything else, this page looks at what is used, what benefits it brings, and how it should be laid. I Agree with Patio & Drives slabs should always be laid on a full bed mix especially natural sandstone as these are calibrated to a certain thickness not like some which i have seen on a spot bed mix which i had to repair from other tradesman. Sand and Gravel Calculator | Calculate how much sand or gravel you need for your project | Buildbase Our 450mm Buff Peak Riven paving slabs are now just £3.74 ex. 4 One aspect of the British Standard (BS 7533:4 2006) mocked above that does make sense is the use of permeable mortars for the bedding of some commercial and public pavements. It has the same consistency as a bricklaying mortar, and following on from above regarding water/cement ratio, an even higher cement content is normally used. Avoid contact with wet cement, mortars and concretes. Do not use building sand - it's too soft. For some reason, people expect a much higher cement content; they think the bedding material needs to be incredibly strong and hard, when the truth is that, for a patio or other pedestrian area, as long as the bedding doesn’t sink and it stays put, that’s all that is really needed. And there are three key reasons why they are not suitable: Using clean sand (that is, sand with no cement) as a laying course is all well and good, and is a method still used on many larger commercial projects, but it does require a significant degree of skill to ensure that the sand itself is fully compacted when the flags are laid. Once you have your first corner marked out you can then build the rest of the frame. This is the sand used to make a bricklaying mortar, and it may be known by a range of other names: soft sand, masonry sand, plastering sand, pointing sand: any of these are NOT suitable. You can make the hole a little shallower than this if you would prefer the base of your building to stand slightly raised from the ground to help with drainage. they have a relatively high clay and silt content, which again makes them less free-draining than is required. Lime mortars are softer and more flexible than cement mortars, and this makes them eminently suitable as a bedding mortar, especially for specialist applications, such as the laying of reclaimed materials, cobbles and, as we are beginning to re-discover, stone paving. Lay the sheet on the bed of gravel or sand, maintaining a minimum gap of 1 cm or wider (Japanese spacing) Use a rubber hammer to eliminate any unevenness Fill in the joints between the sheets with gravel or sand to provide greater stability to the surface If you just lay the slabs on a sand bed and dry sweep the joints it will not last at all.Just look at all the websites on path and patio laying and the will say the same. There are problems in certain parts of Britain and Ireland obtaining suitable sands and several projects have failed because an unsuitable local sand was used in preference to importing a certificated sand. You can make the mix by using the cement mixer or, if you don’t have one, a simple wheelbarrow and shovel: Start off by making a mix of 4 or 5 parts building sand, 1 part cement and water to create an even consistency. The bedding is the layer within a pavement structures that allows the paving to be placed over whatever lies beneath, whether that’s a sub-base , a sub-grade or even something like a pre-existing concrete base . The Scottish Highlands are probably the best example of such an area. Our Privacy Policy / Use of this website and its content implies acceptance and agreement to abide by the Terms & Conditions All information, specification and drawings used on this site are intended for guidance only. If you use soft However, there are some aggregates that may be used when a grit sand is not available for whatever reason. 100% positive The current mix of sharp sand which is currently laid on should be a mix of 8/1 sharp sand to cement for a decent slab bedding. How realistic is that in a market where the typical cost of the remarkably popular Indian sandstone flags averages only 20 quid (25 Euro) per square metre? An exceptionally hard mortar is not required, so there is no overriding need to use a Class II equivalent (which would be 4:1): 6:1 will be ample. Lay slabs on a bed of mortar 5cm – 8cm deep Privacy notice It "cushions" the paving units, and accommodates any variation in thickness there might be in the paving units themselves, to ensure that the finished surface is smooth and even. If it’s good enough for road kerbs, it’s more than good enough for a garden path or a patio! A word of caution: this 'slump' can be problematic in hot, dry conditions. Changes in the way paving is specified, and the materials that are used for jointing, are driving the increased use of these permeable bedding mortars, particularly on commercial projects, streetworks and some industrial sites.

can you lay paving slabs on building sand and cement

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