It is essential to measure the doorframe in a number of places across its width and height. Make a note of any discrepancies in the measurements as they may help when fitting the door. Internal doors are normally divided into four categories panel, moulded, flush or fireproof doors. They are normally thinner than exterior doors as they are built for interior use.
There are different panel designs available ranging from 6 wooden panel doors to 15 glazed panel doors. Finishes are usually in pine, interior hardwood or primed white. They consist of two vertical stiles and horizontal rails enclosing the panels. The panels are made of plywood, solid timber or glass. Two kinds of glass panel doors can be purchased. The cheaper type consists of one sheet of glass covered by the horizontal and vertical rails. This means the paneled door must be fitted when it contains the glass. The second type is fitted to the frame and then the glass panels are added to the door individually. This makes the door lighter to handle when hanging.
Depending on the location and usage of the door, putty and beading may be used, but if the door has a wood finish, beading alone will suffice. Silicone sealants are also available in a variety of finishes.
Moulded doors are shaped from a sheet of wood, plastic or fibreboard and then bonded to a timber frame. They are often classic in design with moulded panels. Some are available ready finished in a variety of colours.
Flush doors are lighter and cheaper than other types, consisting of a narrow timber framework completely covered with either hardboard or plywood on both sides. Inside the frame it can be solid chipboard, semi-solid filled with strips of timber or a cellular core of paper honeycomb. They often have narrow lippings, although some are reinforced in positions where hinges or locks can be fitted.
If the doorway is a particularly awkward size and there is a large section to cut off, a flush door may prove unsuitable, as there is only a limited amount that can be cut off the timber framework without leaving the door structure weak. This could lead to the door warping or twisting. You should not remove more than 4mm from each side of a flush door and 9mm from the top and bottom.
Fire resistant doors
A fire resistant door is thicker than other types. They contain heavy grade chipboard or a heavy core of fire resisting compressed straw. They are there for a purpose, giving between 30 - 60 minutes of fire resistance. They are usually flush robust doors that should always be fitted into a hardwood one-piece rebated frame and fitted with an automatic door closer. If a glass panel is preferred, Georgian wired glass must be used. Building regulations require fire resistant doors when a door leads into an adjoining garage and when a door opens into the loft room.