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Foundations


Foundations come next; you need to make sure that the digger above has done the foundation trenches that we will require for the purpose of this exercise. As a general rule the width of trenches should be a minimum of 3 ft for outer walls and 2 ft for inner walls. We need to pour ready mix concrete into these trenches and the cost of them are based on 1 cubic meter. So how are we going to work out how many cubic meters of concrete we will need for our foundation.


We start by adding the length of the external walls around the house, for example if a house is rectangular shape and measures as 16 meters by 8 meters our measurement would be 16+16+8+8=48. The concrete is usually poured at a level of at least 300 mm, so which approximately would be a third of the cubic meter, so divide the figure of 48 by 3 which would give you 16.


This means that you will require approximately 16 cubic meters of ready mix for your external walls. In order to work out the the required amount for the inner walls do the same as above by measuring the length of all internal walls but this time divide the figure by 5 instead of 3, so lets say that the total length of your inner walls are 35 meters. Divide 35 by 5 and you will get a figure of 7 cubic meter for your ready mix.


Adding the figure of 16 for external and 7 for internal, you will require approximately 23 cubic meter of ready mix. The approximate cost of ready mix is €78.50 for 25 N, €82 for 30 N and €86.50 for 35 N (inclusive of VAT). On top of this cost you have to add the labour cost and the cost of reinforced steel bars which are placed inside the poured ready mix. The average cost of the reinforced steel bars are €3.50 per 20 ft and and these should be placed in a form of a mesh in the concrete.


After the ready mix has set, you need to start building up the walls up to floor level of the building. On average, a block is approximately 43 cm long x 20 cm high and 10 cm wide so work out the length of the walls in the house by meter and divide by 0.43 to give you the number of blocks needed for every row. Do remember, you have to sets of walls for exterior and one for the interior. If for example we have a house as above which is 16 meters by 8 meters what you will have is 16+16+8+8= 48 x 2 =96 as it is external walls and then add up the inner walls which for this example we measure as 35. Therefore, we have 96+35=131 meters of wall per row of the house. We then divide 131 / 0.43= 304.6 lets say 305.


Depending on how many rows of blocks you need from the top of ready mix to ground floor you can work out how many blocks you will need. For example if you are 1 meter above the ready mix you probably need about 6 rows of blocks as each block is 20 cm high and you need to have to laid flat for the base at the thickness of 10 cm each. When working out the amount of blocks needed add 20% for corners, cuts and breakage’s and deduct the amount for big gaps like French doors, garage doors and big windows. And do remember that the block layer might need different size blocks depending on the project but the cost is almost the same per bell of blocks. The average cost of blocks is €600 per 1000 blocks.


Now that you have the structure of the foundation done, you need to fill it with proper material. It is recommenced that you use a fill like lime stones and do not go for anything cheap as you will regret it later when the floor moves, cracks and deeps. The cost for this depends on how deep the space is in the foundation structure. You should have a mix of 4” and 2” for the base level to make sure that you have a solid and compounded floor. The cost of limestone is calculated on the weight basis and it is approximately around €12 per Ton. The amount needed will depend on the space you need to fill inside the foundation structure.


After the hardcore has been compacted by a vibrating plate which should cost around €30 per day to hire a layer of sand goes on top to stop any sharpness from the stones puncturing the barrier. A lorry load of sand would approximately cost between €200-€300 depending on the size.


Radon barrier should come next at a cost of approximately €220 per roll of 20 x 3 meters. Work out the area it needs to cover and the amount you need.


Floor insulation is next and this should be at least 2 inches thick at a cost of €80 per bell of 15. These are usually 4 ft x 2 ft.


The floor concrete would then have to be poured with floor mesh inside. The cost of floor mesh would approximately be €25 for an area of 2.4 x 4.8 meters. The cost of ready mix would be €80.50 per cubic meter for 25 N strength. The amount needed would be based on the floor area divided by 10 for a 10 cm thick floor or divided by 6.67 for a 15 mm thick floor. For example, an area of 16 x 8 meters would be 128 square meter divided by 10 is equal to 12.8. Therefore, you will need approximately 13 cubic meter of ready mix.



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