The Tandoor Site

Building: Base

First decide where your tandoor is going to be. Consider at least the following factors:

• Easy access from the kitchen
• Prevailing wind direction takes the smoke away from you and your neighbours
• Fire risks
• Ease of construction (soil makeup, access to the site from all sides)

Mark out the area of the concrete base. The books suggest that you use string and pegs for this. I found this difficult to do accurately and later in the project abandoned the marker strings which I had laboriously positioned. At this stage a rough mark-out using a straight edge and a spade is all that is required.

Excavate a hole for the ballast and concrete slab, 150mm deep so that the top of the slab will end up at ground level. Allow an additional clearance of 100mm all round the slab to allow space for the formwork. Make sure that the bottom of the hole is roughly level.

Cut four pieces of wood for the formwork. The pieces should all be 75mm wide. Two should be exactly the length that the slab will be wide, two should be 100mm longer. The short pieces will form two opposite sides of the formwork, as will the long pieces. Cut pegs and screw two pegs to each piece of formwork such that the top of the peg is level with the top of the form.

Take the first form and hammer the pegs into the ground so that the form is exactly where you want one side of the concrete block to be. Repeat with the other three forms so that an accurate square is formed: top exactly flat and level with the surrounding ground, bottom approx 75 mm above the bottom the the hole, each side 1040mm long. Pack waste soil around the outside to hold the formwork very firmly in place. It must be secure in order to withstand the weight of the wet concrete later.

Tip ballast into the formwork until it reaches the bottom of the forms. Compact it by jumping up and down on it then check that it's level and adjust accordingly. Line the hole with a layer of polythene (the bags that the sand and concrete came in are fine) to slow down the loss of moisture from the curing concrete into the soil. You're now ready to pour the concrete.

The amount of concrete is small enough to mix by hand but it must all be poured within two hours so don't start just before lunch! Mix the concrete according to the instructions on the bags then pour it into the formwork and spread it out with a rake or shovel. Keep pouring until it is just above the top of the formwork. Use a heavy length of timber, just longer than the formwork is square, to tamp down the concrete to fill any voids. Add more concrete as necessary. Then use the same piece of timber in a sawing motion across the top of the formwork to remove the excess concrete down to the level of the top of the forms.

Cover the concrete with a sheet of polythene and leave to cure for at least 24 hours before staring to build on it.