The following guidelines are recommended by Revelstone as the manufacturers, as the correct way to install their cast stone products. However it must be understood that as Revelstone does not provide an installation service, the company cannot be held responsible for any defects which may arise from incorrect installation by contractors or clients. It is important that only experienced installers and contractors are used; do not use installers who are unfamiliar or inexperienced with cast stone products.
All installations are done at the users own risk.
STORAGE & HANDLING
All Cobbles must be handled with care to avoid damaging edges and surface of the product. All Cobbles are delivered to site on pallets and shrink wrapped to prevent damage. On delivery it is important that pallets are placed on level and stable ground. Once goods have been offloaded on site it is very important that cobbles are taken randomly from various pallets to ensure good color distribution between the various batches. Cobbles must always be handled with care to avoid breakages and chipping of the product prior to laying. Cobbles are heavy and bulky and suitable lifting and handling equipment should be used. The correct safety gear and protective clothing must be worn at all times i.e. gloves, dust masks, safety boots, etc.
Before starting the existing ground must be evaluated and the relevant subase or subgrade chosen (SABS 1200D degree of accuracy I). Every job will have different requirements and therefore the contractor must decide what is required in each situation. The following must be considered – existing ground conditions, finished paved surface levels, drainage of paved area and correct cobble choice for expected usage – 75 mm for high traffic/commercial and 50 mm-60 mm for residential/foot traffic.
COBBLE PAVING – GROUTED
- Before bringing in the topping remove approx. 100 mm lower than the required finished level of the paving – commercial use.
- Make sure that the bedding sand is free of roots and clay, etc. prior to compaction.
- A 20 mm-50 mm topping of clean white builders sand (sharp sand) is then compacted and prepared for the screed. (thickness to be decided by installer/contractor)
- For high traffic, steep or inclined driveways or roadways we recommend that the topping and screed be a mix of 10:1 sand and cement to give added stability to the base.
- The screed – a layer of slightly damp sharp sand 20 mm-40 mm thick (total of topping and screed not to exceed 50 mm-60 mm unless cement stabilized) – string lines and a straight edge are needed to level and get the correct falls and finished heights.
- The area is now ready to be paved.
- Starting at the bottom if sloped or from a right angle or straight edge, place the cobble making sure that the top finished level is about 5 mm above to allow for compaction.
- Continue laying in the chosen pattern ensuring that cobbles are taken off pallets randomly to ensure even colour distribution throughout paved area.
- Use an angle grinder with all the necessary safety equipment in order to cut the cobbles wherever gaps are – a diamond blade is essential.
- Edging – make sure that all edging cobbles are bedded on a concrete footing (4: sand/2: stone (6 mm)/1: cement) to ensure that edge restraints remain in tact and hold paving securely in place.
- Now that all cobbles are laid and cuttings completed sweep cobble surface clean of all debris.
- Before you grout the cobbles it is important to humor the cobbles – doing all the necessary adjustments for height and size, this may require lifting and swapping of cobbles to achieve a regular gap and straight lines.
- The paved area can then be compacted using a mechanical roller or flat plate vibrator (with rubber mat) into the surface bed.
- The area will require at least 5 passes over it to ensure it is thoroughly compacted and relatively level.
- As the product is simulated to replicate real stone cobbles these variations are essential in order to create the natural stone appearance – no perfect straight lines, etc!!
- Paved area may now be grouted.
- Standard grout mixture for cobble paving – is a 6:1 – clean sand to PPC Cement (Surebuild).
- In builders terms – 1 bag of cement to 3 standard wheel barrows.
- This mix (a wet slurry mix) is then pre mixed and dumped onto paving and hosed in with water, sweeping into joints to just below surface of the cobble. Avoid over filling the joints as this leads to excessive short term cracking of the top of grout and unsightly paving.
- It is vital to clean the cobbles off whilst grouting. This will determine the outcome of your paved area whether it is dull and has a grey film of cement left behind on the surface or not.
- Once paving is completed wet area consistently for 4 days afterwards especially during hot weather as this will allow area to cure at a normal rate and reduce joints drying too quickly (cement process needs water to cure). Allow no traffic over it for four days to settle and cure prior to use.
CLEANING OF COBBLES
- It is vital to keep the cobbles clean using water whilst laying and especially when grouting.
- Should the product be badly soiled or stained use acidic cleaners sparingly to remove grout and cement stains. This is however done at your risk and must be supervised by the contractor or installer responsible.
- A mix of water and pool acid – 10:1 doing small areas of less than 1 m2 at a time with a medium to soft plastic bristle brush, rinsing off heavily with water/ soap solution to dilute so as not to damage the cobble surface.
- A synthetic acid alternative – Nanoprufe Tile and Surface Cleaner – is recommended and is available from us.
- This will clean off most adhering cement, grouting and efflorescence marks appearing on the newly laid product.
- As it is a cement product it requires time after being laid to dry out to its original colour, etc. Often the cobble has a wet patch in the middle after being laid; this is because it dries from the outside in. This will disappear depending on how much moisture, etc. has been trapped under the cobble and how long this takes to move out through natural osmosis.
Please Note: The specification above is not suitable for heavy commercial conditions: extra consideration must be given in terms of the sub base, strength of the topping screed and grouting, correct thickness of product, condition of existing ground, long term usage, expansion joints, drainage and expected loads which the cobbles will be expected to carry.