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Further paving options

Interesting ways with paving

Common paving stones and techniques dictate a pretty regular approach to paving, using regular sized stones or paving blocks or bricks and laying them out to regulation square or brick bond pattern. Figure I shows some effects which can be created with regulation size pavers. You may choose to lay the major part of your paving area in one pattern and break it up by introducing a different pattern as a centrepiece or at regular intervals throughout the paved area. And with this maybe introduce different colours of pavers.

Your materials checklist 

  • Slate tiles
  • Brick sand
  • Cement
  • Limil
  • Mortar colouring (for the jointing)
  • Slate sealer
  • Timber for straight edge
  • Timber for screed strips

Tools for the job 

  • Rubber Headed Mallet
  • Straight Edge
  • Tape Measure
  • Spirit Level
  • Spade
  • Wheel Barrow
  • Bricklayers Trowel
  • Stringline
  • Bucket
  • Large Sponge

Handy hints to make the job easier 

  • Make sure your paver and sand suppliers deliver to a spot as close to your work areas as possible. Handling heavy materials can result in many weary, backbreaking hours of unnecessary effort.
  • To make the laying process easier, place small stacks of pavers (about 10 a stack) along the laying side before you begin.
  • A hammer may be used to tamp pavers into the sand bed if you haven’t a rubber mallet – but place a piece of wood over the paver first to avoid splitting.
  • When it becomes necessary to walk on newly-laid pavers, first place planks or a sheet of plywood over them to spread your weight. 
  • Set a spirit level on top of a piece of wood long enough to span a number of bricks to constantly check that your surfaces are level in all directions.
  • For convenience, sand should be stacked on the side you propose to start working.
  • Never tamp or vibrate while the edges are wet. 
  • A better job will result if the pavement surface finishes slightly above the surrounding ground to prevent surface water running across the paving.
  • On sloping ground, a dish drain can be laid along the high side to intercept any surface water.
  • Never use beach sand – it contains salt and could stain your pavers. Make sure your paver and sand suppliers deliver to a spot as close to your work areas as possible. Handling heavy materials can result in many weary, backbreaking hours of unnecessary effort.
  • To make the laying process easier, place small stacks of pavers (about 10 a stack) along the laying side before you begin. 
  • A hammer may be used to tamp pavers into the sand bed if you haven’t a rubber mallet – but place a piece of wood over the paver first to avoid splitting. 
  • When it becomes necessary to walk on newly-laid pavers, first place planks or a sheet of plywood over them to spread your weight. 
  • Set a spirit level on top of a piece of wood long enough to span a number of bricks to constantly check that your surfaces are level in all directions. 
  • For convenience, sand should be stacked on the side you propose to start working.
  • Never tamp or vibrate while the edges are wet. 
  • A better job will result if the pavement surface finishes slightly above the surrounding ground to prevent surface water running across the paving.
  • On sloping ground, a dish drain can be laid along the high side to intercept any surface water.
  • Never use beach sand – it contains salt and could stain your pavers.

Slate paving 

Slate is a rather soft material and needs to be laid on a solid base of concrete as any movement will cause spalling of the edges and in most instances cracking. Also, slate thicknesses and the smoothness of the underside means that the tiles need to be laid on a mortar bed and for best results the joins filled with a mortar seam. Aside from different slate materials, there are two types of slate thickness available. One is a uniform machined thickness and the other is a split paver where the thickness of each paver and indeed even thickness on one paver varies. For ease you will find it easiest to work with the regular paver machined to uniform thickness and this is what we look at in steps 1 to 3. For the split paver refer to Step 4.

Step 1: The concrete base 

For pedestrian traffic areas a concrete slab of 60mm thickness reinforced with light reinforcing mesh will be needed, for vehicular access areas such as driveways a 75mm thick reinforced concrete slab. If laying tiles over an existing concrete slab inspect that the surface provides adequate runoff for rainwater. If water holds in any areas then allowance will need to be made in the mortar bed thickness and level to rectify this problem.

Step 2:  Preparing the slab for tiles

Mix up a mortar mix for the top of the slab at the ratio of 4 parts sand, 1 part cement and 1/2 part limil. It is easiest to mix the mortar in a wheelbarrow, and a batche mix to the ratio of 8 sand, 2 cement, 1 limil is a good amount to work with. Dry mix all the ingredients thoroughly before adding water, add water gradually while mixing until the mortar mix is a consistent creamy consistency. It should not be runny but to the point where it can be shaped into a ball and hold itself. Dampen the surface of concrete with water and sweep off any excess. The thickness of the mortar bed should be 10mm thick. To make economical and easy spreading of the mortar use some 8mm thick screeding strips (Fig. 3), space the strips one metre apart, shovel some mortar in between and spread and screed off with the straight edge. Next scrape the mortar surface with the pointy end of a trowel to give furrows about 50mm apart (Fig. 4). 

Step 3:  Laying the tiles 

So the tiles can be laid with straight joins a string line is tied to a stake at the two extreme ends of the area to be tiled, on the inner face edge of the tiles (Fig. 5). Lay the first row of tiles onto the mortar bed, gently easing them into the mortar so the surface area of each tile is even to the one next to it. Lay progressive tiles into position next to the adjacent tile as shown in Fig. 6, with a 10mm space between each tile. This space is for the mortar joint, and also allows space for some manipulation to get tiles aligned with each other should you need to. Lay several tiles, and then settle them into the mortar bed with a slight tap from the rubber headed mallet. This is to be done to give the tile complete bedding and at the same time align the surface of each tile to a consistent height. Do not push the tile into the mortar to the point where the bedding is oozing up through the joint. It will be necessary to measure progressive rows of tiles from the edge of the job to maintain a parallel line on each row, and to ensure that all rows are straight you will need to set up a string line for each third row of tiles (Fig. 7) or alternatively lay out a 70 x 35mm straight piece of timber to butt tiles to. To hold the straight edge in place lay several bricks on it. Keep a bucket of clean water and a sponge handy at all times so you can clean the surfaces of tiles as work proceeds. Do not allow any excess mortar or mortar smears to dry on the tiles.

Step 4: Jointing the tiles 

First thing you need to do is decide whether or not you want to add colour to the mortar jointing. As a rule, grey or black colour goes well with slate, but in outdoor situations natural jointing is pleasing to the eye also. The mix ratio for the jointing is the same as the mortar. If using coloured mortar be careful to follow the manufacturers mixing instructions as too much colour can weaken the mortar making it dusty when dry. Allow the tiles to dry for two days before walking on them, and then carefully pick your way in the middle of the tiles. Once again mix up the mortar mix in the wheelbarrow for the jointing. Time spent being prepared and careful with the application here will save a lot of fiddly cleaning up at the end of the job. Remove all loose material such as stones or twigs from between the pavers prior to doing the jointing. A vacuum cleaner is ideal for this. Equipment needed here is a small brickies trowel and a scrap piece of three-ply measuring 300mm x 200mm. Place a ribbon of mortar on the ply near one edge, put the ply over the joint to be filled (Fig. 8) and gently push the mortar into the joint with the trowel. Continue in this manner until all joins are completed. As you proceed clean off all excess mortar from the slate with water and a sponge. Allow the joint mix to set for 24 hours before walking on it. Treat the surface with care, as in a weeks time the surface will be sealed with special slate sealant.

Step 5: Split slate pavers 

The problem with laying these tiles is the varying thickness of each tile and the different thickness on each tile from one end to the other. Due to this factor somehow we have to prepare a bed which will suit each individual tile, provide full contact surface support and still provide a uniform surface finish. This is not possible in the manner in which we laid the mortar bed in Step 2 above. Make a box up 2mm larger than the overall dimension of the tiles and I0mm thicker than the thickest part of the thickest tile (Fig. 9). Lay the box over the slate tile with the back surface of the tile facing upwards. Fill the box with mortar over the tile, and scrape surplus off so that the level of mortar is to the top of the box. Doing this to each individual tile of course creates a uniform overall thickness. Firstly wet the concrete area to be tiled and sweep off any excess water. Remove the box, carefully lift the tile and flip it over and place it in position. Do the same for subsequent tiles, working one by one until the job is completed. The obvious thought is ”This is so much trouble, I’ll just create a thick mortar bed and press the tile down into it to uniform level and clean up the excess mortar”. Please be advised that this does not work as one would imagine, and indeed creates a far inferior job and a frightening amount of cleaning up. Allow the mortar to dry for 48 hours, and then grout the joins as in Step 4. Unless you are after a special finish available only from the split slate we recommend that you proceed with the machined slate option.

Step 6: And finally 

After a week or so has passed since the last grouting of the joint purchase some slate sealant from your local Mitre 10 store and apply it over the new surface. This should be done on a clean and dry finish and is necessary to hold the colour of the slate and also protect the slate from stains such as rust or fatty liquids and such. This sealant will need to be reapplied on a routine basis, refer to the manufacturers' instructions and recommendations.