Hard surfacing FAQs

Having moved into a new house, I find that parts of the garden become waterlogged after heavy rain and take three or four weeks to dry out. Is there anything I can do about this?

Many new gardens on housing estates are poorly finished, with a layer of topsoil deposited over ground that has been compacted by building work and heavy machinery, and so has formed a hardpan some inches below the surface. As a result water is slow to drain down to the water table . Thorough cultivation to break through the pan can often solve the problem.

If ground water is still persistent, land drains may be necessary in order to lower the water table. Trenches should be dug in a herringbone pattern sloping at a gradient of 1 in 40 to terminate at a soakaway filled with builder’s rubble. Clay pipes 100 mm (4 in) in diameter are laid on gravel at a depth of about 1 m (3 ¼ ft), with broken tiles over the joints. Topsoil, which should be stacked separately, must be replaced last

I have several jobs to undertake, including laying a patio and building two brick walls. How do I estimate the quantity of materials needed?

Materials these days are expensive and you can make considerable savings if you estimate accurately. A simple scale drawing on graph paper will quickly tell you the number of square or rectangular slabs of given size needed for a patio. For 1 m2 (10.8 sq ft) of a wall that is 225 mm (9 in), or two brick-widths thick you will need 100 clay bricks. Where other shapes are involved, remember that the area of a triangle is half the base times the height, and the area of a circle is the square of the radius multiplied by 3.14.

I want to build a patio using precast concrete slabs, but I am bewildered by the vast range available. Can you offer any advice?

When choosing a slab think of the overall design of the area. Close to a building, ‘architectural’ shapes look best, so choose squares or rectangles. Away from a building more informal shapes such as crazy paving, pentagons, and hexagons may look better, blending well with grass and plantings. Avoid conflicting colours for what should essentially be a simple surface, and for strength and durability choose slabs 38 or 50 mm (1 ½ or 2 in) thick.

What is the best method of laying rectangular slabs of old York stone?

There are three methods of laying slabs, whether they be precast concrete or natural stone. The simplest is to level and compact the ground and rake out a 50 mm (2 in) layer of soft sand, the slabs being bedded onto this. Rain can, however, quickly undermine the surface, making it unsafe. A more durable finish involves laying 100 mm (4 in) of well-compacted hardcore or crushed stone. The slabs can be bedded on five blobs of mortar made up from 3 parts of sand and 1 part cement. This technique is suitable for virtually all garden situations. Where heavy wear is expected, as with a drive, 150 mm (6 in) of hardcore will be necessary, the slabs being bedded onto a continuous layer of mortar. But bear in mind that any services (water mains, etc) underlying the site will be difficult to reach.

When I park my car in front of the garage I get ugly oil stains on the tarmac drive. Is there any way I can disguise this?

Oil drips are unsightly and, on tarmac, destroy the surface. An interesting solution involves laying an area of cobbles in the affected part; this also adds interest to an otherwise dull expanse of hard surfacing. The cobbles should be bedded in mortar over hardcore and must be packed as closely together as possible. The surface will be durable and could form part of a larger composition of paving and planting, the irregular shapes of the cobbles masking any drips. Oil stains on surfaces other than tarmac can be removed with a proprietary paraffin-based solvent.

The steep ramp up to my garage needs relaying. Is there any way that I can provide a non-slip surface that will be safer in bad weather?

The cheapest way of doing this is by using concrete. Lay a firm base of consolidated hardcore to the required slope or ‘fall’. Boards should be used as forms (shuttering) down either side, and if the slope is steep a relatively dry mix should be laid to prevent the surface moving; a board tamped across the surface will give a ribbed, non-slip finish.

An attractive but more expensive ramp can be laid in hard bricks, stable pavers, or granite setts, which should be ‘haunched’ (set up at a slight angle) to provide a good grip for tyres and shoes alike.

Can you tell me the right concrete mix to use for laying a strong, durable garden path?

There are three basic mixes for concrete work in the garden. Mix A, consisting of 1 part cement, 2 ½ parts sand, and 4 parts coarse aggregate by volume, is suitable for ‘footings’ or floors of garden buildings, lightly used paths, and hard-standing areas. Mix B, 1 part cement, 2 parts sand, and 3 parts coarse aggregate by volume, is a stronger mix suitable for most drives, heavily used paths, concrete paths, retaining walls, and steps. Mix C, 1 part cement and 3 parts sand by volume, is the strongest mix, suitable for bricklaying and bedding slabs on a prepared surface.

I am bored with my present patio of grey precast slabs. Can I improve its appearance without lifting the entire surface?

A large single-colour surface can often seem heavy and overpowering, and the introduction of a second material—for instance, brick (a possible link with the house), granite setts, stable pavers, or even planting—can make all the difference. Lift a number of slabs, adjust the foundation levels by excavating to the required depth, and insert panels of the new material, making sure that the surface is level with the surrounding paving.

I like the idea of brick paving but have been told that this may break up in frosty weather. Is that true? I have also seen a number of traditional paths in different patterns. Is there any particular merit in using one or another?

Bricks come in a wide range of types and finishes and the main criterion for their use as paving is their strength. To prevent the surface shattering in freezing temperatures the brick must be hard and well fired. Engineering bricks are hardest of all, having a glazed surface, but they can look a little clinical in a garden setting. Many ‘facing’ bricks are suitable; they come in a wide range of finishes and standards of durability. If in doubt, check the characteristics of your preferred bricks with the supplier.

There is a number of traditional patterns of laying. Stretcher bond and soldier courses lead the eye on if laid along the line of a path; basket weave and herringbone are more decorative, but the latter involves a certain amount of cutting of the bricks at the edges of a path.

I want to make a gravel drive. Is there any way of laying one that will avoid that annoying problem of treading the stones into the house?

Gravel is a cheap, practical surface that blends well into most situations, and thorough preparation is the key to a sound surface. For a drive, a well-compacted hardcore base at least 150 mm (6 in) thick is essential. A 50 mm (2 in) layer of coarse gravel comes next, followed by a similar thickness of hoggin (a clay binder). The latter should be slightly damp and thoroughly rolled to fill and bind the underlying surface. Finally top it off with a 25 mm (1 in) thick layer of 10 mm (% in) size gravel, rolling again to consolidate the surface.

I have a tarmac drive and I wish to extend this surface in the form of a path around to the back door. Is this a difficult job?

No. Asphalt and bitumen are the two tarmac surfaces available, the latter requiring rather more work and being suitable for drives or a path expecting heavy wear. For your purpose asphalt should be fine. Lay a well-compacted 100 mm (4 in) layer of hardcore and spread ash over this to fill in the cracks. Asphalt can be bought in bags and is laid cold by raking out and then rolling. Finally a dressing of gravel or chippings should be rolled into the surface. Remember to lay the path to a slight camber or fall so that water will run off it.

I want to lay a large patio area but find that slabs would be too expensive. Is there a hard-wearing but cheaper alternative?

Why not use a concrete, which can be laid to a number of finishes? Use a good base of hardcore ‘blinded’ with a weak mix of concrete to level the surface. Above this the concrete patio should be laid in panels no larger than 3 m (10 ft) square to avoid it cracking. The ‘expansion joints’ inserted between the panels can be decorative as well as practical; they should consist of wood planks 10 mm (3/s in) thick and as wide as the depth of the concrete. Why not build up a grid of paving stones, woodstrips, or courses of brick, and infill these with concrete?

The concrete surface finish can be varied, a wooden float giving a rough finish and a steel float a smooth one; perhaps most attractive of all is ‘exposed aggregate’, which involves sprinkling the surface with water and carefully brushing it with a stiff broom just before it sets, to expose the small stones.

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