Drilling into concrete or steel lintels has presented problems for years to DIY enthusiasts and professional alike. For concrete lintels the answer is to start your fixing holes with the smallest masonry drill bit you can get, normally 3mm, and work up to the size you require. The smaller the drill bit the easier it will go through concrete. If you hit steel reinforcing in the concrete lintel however, there is no choice but to move the fixing hole or follow the instructions and diagrams below.
Steel lintels are even more difficult to fix to as, once you have drilled through the plaster and reached the steel lintel, you must then swap drill bits for a high speed steel bit and then use self tapping screws to fix the item you wish to hang. This is a very difficult process not least because once you have drilled the hole for the self tapping screw, you then have to locate it again to put the screw into it. Considering there is always at least 20mm between the surface of the plaster or plasterboard to the lintel, this is no mean feat.
A much easier option which will always give you a good fix is to glue a section of timber to the head (soffit) of the window opening and fix to that. The construction adhesives available these days are wonderful and as strong as any mechanical fixing. Always read the manufacturers instructions as some construction adhesives recommend the surfaces to be glued together should be damped down slightly first.
In the example we have given here the client chose to have a timber glued the full width and depth of the soffit. At which point it could have been filled with wood filler and decorators caulk and painted. You could just fix a narrower timber up to the soffit and fill and paint it.
A piece of planed square edged (PSE) timber was cut to length and a heavy weight construction adhesive applied to the back. Plenty of adhesive is used. The 
timber is pushed up into place "wiggled" about to make sure the adhesive spreads between the soffit and the back of the timber and then the timber is pulled down again. This is to make sure no air is trapped in the adhesive to spoil the adhesion. Then the timber is pushed back up and pinned into position with props made from 2 x 2 inch sawn timber with an off cut of the 8 x 1 inch timber cut down and fixed across the top.
Once the adhesive had set (24hours) the props were removed and at this point we would ordinarily have filled any gaps or nicks in the timber and primed, undercoated and glossed the wood to match the room. On this job however the client wanted the soffit to match the window frame itself rather than the plaster opening so we fixed a length of PVCu facia board "Cappit" in position over the timber. Cappit is one name for the section of plastic used to cover facia boards when the property is being made "maintenance free" The gutters are then re fixed to the facia covering.
The cappit is glued up to the timber and the same procedure is used to hold the cappit in place for 24 hours. When completely set the soffit is ready to fix to. Using pilot holes (see our related projects, left) normal screws can be driven up through the plastic and into the timber for a solid reliable fix for any kind of window blind, curtain poles or curtains.
