Repairs: walls

The 2 most common causes of flat lintel failure are:

• failure of the reinforcing bar in an RC lintel;
• corroded or inadequate end bearings in a steel boot lintel (the usual minimum bearing being 150mm).

If the end bearings are corroded, temporary alleviation can sometimes be achieved by cleaning off rust and expanded oxidised steel from the bearing ends with a needle gun, before repainting the metal. Eventually, however, the corrosion will re-assert itself and the lintel will ultimately fail.

If the spot welds have started to fail, a helical relieving beam in the masonry above (if there is room) may be feasible for short term effect; likewise, if the end bearing is inadequate (frequently they are as little as 80mm). Internally the dry-lining always seems to take care of this on new construction work and nicely masks everything. But advise your client that the unit will need to be replaced in the foreseeable future if a reduced end-bearing is confirmed (usually the result of sloppy site work).

Solution 1 (temporary): defective RC lintels

If not too severely affected, the concrete can be rebuilt around the 'remet' bar.

The steel bar has to be cleaned down and stabilised with a treatment to make the surface inert, before rebuilding the face in an epoxy-modified mortar.

Sometimes an anode can be built in by a specialist remedial contractor, as a retrofit measure. This anode will reduce the future effects of galvanic corrosion of the steel (which may be a problem, for example, in an aggressive marine climate).

Note: if a lintel that has insufficient concrete cover over the bar is then repaired, this will extend its life, but nevertheless it will one day need replacement.

If you have to replace the lintel with a like-for-like new RC lintel, allow for reconstruction of at least 3 courses of new brickwork above, plus (probably) a complete new damp-proof tray and cloaking detail.

Solution 2: Steel boot lintel

The steel boot lintel is now ubiquitous and is often specified without a second thought.

Note: the quality of the surface coating can be critical to its application and lifespan.

If you read the manufacturers' small print and guidance, most advise that the ends of the beams should be painted. Extra paint protection is advised in marine climates. Without it the lifespan can be as little as 40 years or so before the bearing ends deteriorate. Most buildings have a 60-year lifespan when designed (and in practice may last 100 years or more), so precautionary works to extend the life of components are sensible – and cheap if done during the original construction, compared with the cost of a later repair.

Solution 3: Crack stitching

If the cause of the problem can be arrested, then the helicals can be set along the joints of the brick or stonework to re-secure the wall fabric across the cracks and spread some of the loads around the weak plane caused by the fracture.

Insert helical ties to reinforce a poor-quality masonry bond or to stitch across a crack/fissure