Build with Mark - Install Prehung Door Trim.

Ask Mark a Question Are You Building a Home, Adding On, Repairing or Renovating? Click the ask Mark a question link above and submit your question. It'll be featured here on the site in the subject category.

	© Mark Saville 2006	Install Prehung Door Trim
			Trim for prehung doors of the knock-down type is really no different than any other door trim and can be installed very easily with a cheap mitre saw or a manual mitre box if that is what you have. The pieces of trim will come in sets consisting of a 3 ft piece for each top jamb and 4-7 ft pieces for the side jambs. The type of wood will match the material that the door is made of and will only include the most basic profile that the door company can get away with. Basically a 2-1/4" 3000 profile or colonial will be provided. Some even pass off 1-1/2" as standard.
	The photo below shows a 3-1/2" trim. Installation is carried out by first installing the top trim and then the sides. This way you only have one mitre to fit instead of two. If you elect to install the two side jamb trim pieces first then fit the top trim to the sides, you'll have both mitres on the top trim to fit. Start by measuring the top trim from inside of jamb to inside of jamb and then adding 1/4" to leave a 1/8" reveal between the door jamb edge and the trim or casing. Tack the top trim on and then measure and cut the side jamb pieces. Try the mitres to make sure you have a good tight fit, re-trim if necessary and then once the fit is perfect, glue the joints and nail the trim to the jamb and the rough framing behind the wall finish. Trim is not just for looks it also helps structurally to keep the door frame solid. You can also straighten the jamb between your shims using the trim. For situations where the door jamb is a little too wide and the trim is flat against the wall, your mitres may be hard to fit and it will be necessary to 'back-cut' your mitres and cut them off the 45 degree mark a little.