Laying Natural Indian Sandstone Paving

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1. Setting Out

The first step in constructing a successful patio is accurate setting out, to make this task easier you will need the following items:

Fencing pins (Steel marker pins or thin wooden stakes)
Brick Line (Thin nylon string)
Spray-line (Marking paint)
Tape measure
Large right angle
Scale ruler, paper, etc

You must first have the shape of you patio drawn on paper with all dimensions marked. Accurate measurements will help you order the correct amount of materials, which will save wasted time and money. The drawing should be to scale so that measurements can be taken directly from the drawing and marked out on the ground. You must mark as many measurements as possible on your drawing including the boundaries of the site e.g. Fences, Walls, etc.

Now you’ve drawn your project out on paper it's time to start setting out. Start your setting out with a right angle away from a fixed point, for example a house wall. A simple way to do this is using the 3,4,5 method shown and described below. First put a fencing pin at the end of a wall or door. Put a second pin 3 meters away from the first pin along the same wall. Attached a piece of string to the first pin with a mark 4 metres along its length. Take this piece of string away from the house wall at approximately ninety degrees. Then measure between the second pin and the 4 metre mark on the string adjust the position of the 4m string until you have 5m between both points.

This will establish your first right angle, which will provide a starting point for your project. This line can be continued to establish the first edge of the patio area. You can then use this method to establish any of the straight lines need to mark out you patio area, as shown below. It can also be used to establish the centre point of any circles and curves.

We can now start to set out any feature with set radii, simply by establishing the centre of the circle or curve and placing a fencing pin at that point. Then attach a piece of string to the pin with a mark set at the desired radius, then mark the curve with spray-line as shown below.

When setting out uneven curves a different method is necessary. Firstly set out a right angle line running across, but a short distance away from the area where the curve is to be marked out, as shown below. When this line has been established using fencing pins and brick line you can then mark points along the length of the string at 300mm centres. Then at right angles away from the line you can start to plot the curve by measuring away from the line. For this method to be successful your drawing must be to scale i.e 1:50 or 1:100 are normal scales for small gardens. This will allow you to take measurements from the drawing and directly plot them on the ground


2. Sub Base Construction

The first thing to consider when preparing to lay paving is the provision of a suitable sub-base. This will work as the foundation for your paving. The depth of the sub-base will vary depending on soil type and site conditions, but generally 100mm of consolidated scalping (type 1) or hardcore (broken bricks and concrete) will provide sufficient strength for most paving jobs. On clay or unstable soil a greater depth of base will be required. Some landscape architects or very conscientious landscapers will specify a concrete foundation / base that the paving will then be laid on. This is a very successful method of construction for a sub-base but is generally better left to the professional contractor as mistakes are very hard to correct.

An important consideration when excavating for your sub-base is the finished level of the paving. It must be 150mm below the damp proof course or two bricks down, a slight variation in this height is acceptable but never go below 100mm unless drainage channels are to be provided. At this stage you should also bare in mind, rain water run off. In most cases your patio should gently run away from the house or any building except where drainage is to be provided. A slope of 1:100 or 1:50 will be sufficient, but depending on the lye of the surround land the fall could change. The sub-base should slope at the same rate as the finished level of the patio.


3. Laying Your Paving

The main method of laying Natural stone paving products is to individually bed each slab into a full mortar bed. This is mainly because of the variation of thickness of natural stone products. The five spot method is not really advisable as it allows water to sit under paving which can expand in cold conditions lifting the slabs. Thish also makes it harder to point the paving successfully, due to the large voids under the slabs.
The mortar bed is usually made up of six parts soft sand and one part cement but an alternative method would be to use six parts Washed Grit (Sharp Sand) to one part cement. This mix will provide a stronger foundation, but is slightly harder to work for your paving but either method will do a good job.

The best method for mixing mortar is to use an electric or petrol mixer, this will save a great deal of time and they are inexpensive to hire at about £25 per week. The best way to use a mixer is to firstly put half the mix into the mixer then add water, let it mix thoroughly and then add the second half. You would normally get 12 shovels full of grit / sharp sand and two of cement into the standard mixer. Be very careful that shovels of grit and the cement are the same size to keep the mix consistent and strong.

 

4. Cutting Natural Stone

Most natural stone paving projects will involve some amount of cutting. The best way to undertake this is to use a petrol or electric cut off saw or angle grinder. These machines used in conjunction with a diamond tipped cutting blade will make any necessary cuts through Indian sandstone, limestone, slate or travertine paving reasonably easily.

All cuts must be carried out on a firm flat surface. You should ensure your tools are serviced correctly, you are wearing all recommended personal protective equipment, you are fully trained on the equipment you are using and you have fully read and understood the manual. If you are in any doubt as to the safe operation of your tools seek professional advice before commencing your project.

If you are looking keep the hand dressed finish to your natural stone paving, the best way is to turn the paving upside down and cut into the back surface stopping approximately 5-8mm away from the finished surface of the paving. Then place the cut over a solid straight edge material such as a wooden block and break the slab along the cut. This can be tidied with a hammer along the cut edge.


5. Pointing and Sealing

Pointing is one of the last and most important stages of getting your patio looking right, and finished properly.

There are a few options with pointing and all have their advantages in certain applications, here we will look at the traditional method of sand and cement, as well as air-cured pointing products, and kiln dried sand.

As the hardest wearing method, a sand and cement joint is generally considered the best way of pointing in on patios, particularly on Sandstone Paving, and quite often Slate. Pointing is undertaken when the Slabs have been laid and given time to dry (normally 24-48 hours) and must be done in dry, frost free conditions, to allow the pointing mortar adequate time to dry and harden.

The first stage is to make sure all gaps to be pointed are dry and clean, and then the mortar can be mixed. An average ratio of sand to cement would be 5 parts sand to 1 part cement, you can go stronger than this however weaker is not advisable. Only mix around one wheelbarrow/bucket full at a time though as it will harden if left for too long. Mix the sand and cement together adding water as you go to get to a nearly liquid consistency, now you can start pointing your patio.

You will need two trowels ideally, one for getting an amount of mortar out of the bucket/barrow, the other for pushing into the joint and firming down. Work your way along each joint feeding mortar in off of one trowel with the other and pushing it down to fill the joint thoroughly, you will be aiming to evenly fill each joint without overloading it, as getting any wet mortar on to the surface of the slab will prove difficult to get off later on. Gradually fill all of the joints with the pointing mortar, mixing more as necessary, until all are filled, you are now ready to smooth down the joints for a nice tidy finish. The best way of smoothing down the joints is with a pointing iron (or the end of a trowel handle) or, for an alternative look, a pointing trowel can be used to groove the pointing to creating a rain channel in each joint.

Once you have tidied your pointing there will some debris remaining which should be swept off with a soft brush, and at all times go across your joints, as you can disturb the wet mortar if you sweep along the joints. Once clean you now only need to wait for the pointing to dry which can take up to 24 hours depending on conditions, but generally will take around 12 hours or so.

Another method is to use an air curing pointing compound. Which is very easy to install and can last just as long as traditional pointing. Again before starting the joints need to be clean and dry, and it is then a simple case of opening the bags and sweeping the compound in using a soft brush, and once swept in press into the joint with a trowel or pointing iron, and then leave to cure sweeping off any residue that has hardened after a few hours with a stiff brush. This is a very simple and effective way of pointing, but manufacturers’ guidelines should always be followed, and it is worth checking the suitability of the area to be pointed in this way, before starting work.

The final method is only suitable for Paving which is to be butt jointed (as you would with block paving for example) like most of our Travertine Paving Products. This is simply brushing in a fine Kiln-Dried Sand over the area to fill small gaps in between the paving slabs. This is only suitable for patios laid on a full mortar or concrete base as there is then little chance of weed growth in between slabs. The sand simply acts as a filler, preventing the gaps filling with dirt over time.

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