How to Lay a Concrete Lintel
Lintels are used to bridge openings such as windows and doors and will come in a variety of lengths and depths. Some lintels such as span lights which have a small depth are not designed to take a lot of weight, it is the role of the block/brickwork above them to do this. When choosing the correct lintel for the job it is best to consult a structural engineer or architect. This ‘how to’ shows you how to fit one.
1) Before the lintel can be laid the bearings must first be in place, this is what the two ends of the lintel will sit on. The structural opening of the window will be indicated on your drawings, or if this is part of a renovation project the best approach is to measure the size of the window frame and allow for 10-15mm tolerance. Therefore the height of the underside of the lintel should be measured from the top of the window sill as this is the opening into which the frame will sit.
2) When forming your bearings measure up from the top of sill height but allow for a 5-10mm bed underneath the lintel. It is wise to not have big mortar beds underneath any lintels.
3) If the lintel has only one reinforcing bar this must on the underside of the lintel. A lintel has reinforcing steel which runs through its length, this is in place to combat the forces of tension which attempt to stretch the bottom of the lintel. For this reason it is essential that if the lintel has only one reinforcing bar this must on the underside of the lintel.
4) Measure down to top of sill height and up to the underside of the lintel and tap with a lump hammer to achieve the desired height. It is common practice on a building to create a staff with various window and door heights on it as this is much easier than using the tape measure. A staff can be made from a length of 2”x1” timber. Some lintels will have a slight camber to them but this is often in an upwards direction so will pose no problems. However, if the lintel being used appears to bow downwards this must be taken into consideration and the measurement from the top of the sill should be to this point to ensure the frame will fit.
5) The front of the lintel must then be plumbed in with the wall below, and the top or underside levelled across the horizontal.
Always allow enough tolerance to fit the frame
The mortar bed underneath the lintel should not exceed 10mm
Always have the reinforcing steel at the bottom of the lintel
If possible build the bearings one day before the lintel is laid