STEP 1 Determine where centre of timber studs are behind the plaster in the wall. Transfer to edge of shelf and use 16mm spade bit to drill 120mm deep holes in the shelf.
STEP 2 Squirt PVA glue into holes then tap lengths of dowel into each hole.
STEP 3 Round sharp edges at front of shelf with sandpaper, then apply a coat of stain and varnish with a cloth. Leave to dry.
STEP 4 Take an offcut of the hardwood and drill a 16mm hole through the centre of it. Use this as a jig to drill the holes in the studs for the dowels. Sit jig on top of tiles, align centre of hole with stud on wall and drill a 16mm hole through it into the stud. Drill hole 80mm deep to suit 9omm deep studs. STEP 5 Check that depth of holes in wall is more than the dowel protruding from the shelf and adjust if required. Squirt construction adhesive into wall holes, then insert dowels. Push shelf hard against the wall and hold until the glue grabs.