Preparing The Site
Any paving should always be laid out on a base that is firm, level and well drained to help make sure that long term stability and service is possible. Here, getting the ground work just right is crucial.
All vegetation and top soil should be taken away to about a depth of about 200mm to 250mm over the area that needs to be paved. You can mark out the area with retaining board or pegs, then adjust the height to meet up with the required finished surface levels. This will help you to make sure you have a fall of 1:80 out from buildings and walls for proper surface drainage. Additionally, you need to make sure that finished paving level comes in at at least 150mm, or two brick courses, just below the level of damp proof course. Once excavated, you should rake the material level to help guarantee a depth that is even. Then, you can compact the entire area using a plate compactor.
For the next stage, you need to set up edge restraints all along the area that has to be paved, which may include existing walls) by using concrete edging or block kerbs. Concrete edgings or kerbs need to be bedded into approximately 100mm of the concrete mixture, set to the required level, at about a 45 degree haunch upside about half of the kerb or block height. This step cannot be missed, as it helps to keep the blocks and sand that they are sitting on from moving.
Your drainage gratings, underground drainage or recessed manhole covers need to be installed at this stage if you need them. It is recommended that product guidance is looked for if you need technical information regarding drainage.
This area should be back filled using 150mm of a MoT/crusher run that is compacted to 100mm. On this, you can put down a layer of sharp sand that is slightly damp. The sharp sand is better for drainage than building sand, making it less prone to getting washed out. When the sharp sand goes down, it needs to be at a depth of 50mm and compacted using a plate compactor. A second layer gets applied to a depth of 20mm, then using string lines, a straight edge and screeding rails, a second layer gets leveled for correct falls.
When you lay the concrete block paving, you need to begin from the bottom of any slope, with the best position being from a straight edge or a right angle. If you work from several packs at a time, you will be able to ensure a good distribution of colors, and this is essential when you have a mixed sized product like Woburn Rumbled range.
Take care to place your blocks over the laying course, making sure they are about 4-5mm over the desired finished level. After the full blocks are laid out, use your mechanical block splitter for cutting any blocks needed to fill in pieces or at the retaining edges. The pieces of concrete block that are smaller than a third of a full block should be avoided. After you are done, sweep the area and use your plate compactor to compact it all down for about two or three passes.
The jointing of your block paving is best when completed in a dry period. You can apply kiln dried sand to your block paved portion, then brush the joints with a soft brush, making sure that they are all filled in fully. Then, use your plate compacter over the paved area again, pushing the sand into the joints. After this has been done, you can check for gaps in the joints and fill in wherever you need to, then compact once again. Sand in the joints might also have to be topped up for a few months after job completion.