Walls are made of concrete blocks. These blocks usually measure at 43 cm by 20 cm by 10 cm thick. If you are going to work out the number of blocks needed in a project you have to measure the length of a wall in meters and then multiply by around 2.3. For example, if a wall is 5 meters long, you multiply 5 by 2.3 which gives you 11.5 blocks.
Now that you know how to work out the number of blocks, you work out the complete length of the house taking into consideration the double cavity walls for the exterior shell and do the calculation to find out how many blocks you need for each row.
You then multiply these rows by the required height of the walls, remembering that each block is approximately 20 cm high. For example if you have 11.5 blocks in a row and the room is 2.2 meters high, you have to multiply 11.5 by 11 (2200 /200 mm) which gives you 126.5 blocks.
Unless you have got a lot of external doors and windows, it is suggested that you do not take away the space saved by them as you will find out that there would be a lot of breakage’s for corners by the block layers. It is always better to over estimate that under. However, if you do have a lot of doors and windows you can do the same calculation and deduct the amount off the total.
Remember that you might need different size blocks depending on your project. The average cost of blocks is €600 per 1000.
The other costs involved in a wall are the insulation, wall ties, cills and lintels, and some DPC which cost around €5 to €20 per roll depending on the size.
The cost for cills and lintels is decided by how long they are and the type. Cills work out approximately at €5 per ft and lintels at €3 per ft (Light weight). Do remember that you need two lintels for every door and window. Insulation costs vary depending on the thickness required, they usually come in sizes of 1.2 m by 0.6 m approx. and they cost around €80 for a bell of 15 including the ties. The exact cost can be found from any good builders merchants.
Please note: If the lintel required is more than 3 meters long , you might need an RSJ ( Reinforced Steel Joint) to take the load.
You should never put a RSJ under a supporting wall as there is a chance that it might collapse in case of fire. Do consult a qualified architect or engineer.