Cutting of Mitres
Measure wall. Mitre-cut scotia to length. When a scotia or cornice has the same projection down the wall and across the ceiling, a mitre box is a handy aid. When cutting mitres, always keep the wall edge of the cornice uppermost on the outer side of the mitre box.
To suit position A on the ceiling illustration.
To suit position B on the ceiling illustration.
To suit position C on the ceiling illustration.
To suit position D on the ceiling illustration.
With decorative cornices however, the ceiling projection is generally greater than the projection down the wall. Proceed using the same principle as when using a mitre box. Position the cornice ready for cutting. Measure the ceiling projection and mark on the top member of the cornice. Draw a line from this mark to the edge of the cornice. Your now have the correct angle for your cut. Use the same principle for all internal and external mitres.
Working from the centre line of one wall, ensure that a matching module or part of a module occurs at each end of the first wall (designs are in repeating modules).
Use the same principle for the other walls. It is likely that the last mitred cornice may not match, this is not considered abnormal.
Fixing into Position
Mix cornice cement according to instructions on the bag. Spread a bead of cornice cement along the full length of the back edges of the cornice or scotia. Press the buttered cornice firmly into the wall and ceiling angle, extruding surplus cornice cement. Pin in position by temporary nailing at the top and bottom edges of cornice. Clean off excess compound with a small broad knife or the heel of a small tool.
Using a small paint brush and clean water, clean top and bottom members of cornices. Now fill all mitres and externals with cornice cement (using a small tool). Before cornice cement sets hard using a paint brush and clean water brush off all mitres and externals of any excess cornice cement. When the cornice cement has set hard you may remove temporary nails and fill any small holes with cornice cement.
Using a paint brush and clean water on decorative cornices and a sponge on plain cornices., wipe cornices all over for that professional finish.