Architrave is the trim around a door which over time can become damaged with items being banged against it, especially children’s toys or when moving furniture. The architrave may be a decorative feature (such as used in period decor), or you simply wish to replace a plain architrave with a more decorative design.
You could always pay a contractor to do this work for you. Even in that case it is always better to know what they should be doing, after all they are spending your money.
Remove the old Architrave - Use a crowbar to prise away the old architrave, start on any side and work from the bottom upwards continually moving the crowbar to a new position. Place a block of wood beneath the crowbar to prevent damage to the wall surface.
Prepare the Door frame - With the old architrave removed, prepare the door frame for the new architrave. Use a claw hammer or pincers to remove any old nails that may have been left behind and remove any old paint from the surface using a sanding block.
Measure up - Measure the internal width of the door frame and add 12mm to the overall length, this will allow the architrave to be set back from the inside of the frame.
Mark up - Mark out the required length on the bottom edge of the architrave, use a mitre box to cut the ends at 45° making sure that the top edge of the architrave is longer than the bottom.
Replace the Architrave from the top - Nail the architrave in place starting with the top length. Set it back from the door frame by 6mm (1/4") and make sure that an equal amount projects at each side. Remember to check that you are using the right nails with your local hardware store.
Finish up - Fit the side lengths by butting them up to the top length and making sure that they too are set back from the edge of the door frame by 6mm. Punch all the nail heads below the surface and fill the holes and any gaps between the mitred ends with wood filler, sand down and either paint or varnish.