Fitting a new door

A general look at how to trim doors, fit doors, fit door frames and fit architrave.

The following pages cover some basic information on fitting new doors - please always refer to manufacturer's instructions for individual doors.

Many doors are built so they can be trimmed a little for a perfect fit. Although there is a limit to how much can be removed from specific doors because trimming a door too much can compromise its integrity. Remove equal amounts from opposite sides to ensure the door maintains a uniform look, particularly if it is a panel or panel effect door. Also, whenever you trim a door you will be exposing untreated edges which will need to be sealed.

The door frame, usually called a  door lining  for internal doors, will hold the door in place. Find some information here for installing an internal door frame. It's important the frame is assembled correctly and is installed straight, level, and plumb. The door itself can then be installed easily and will work correctly. Doors and frames can wear over time, or become damaged, and need replacing. New frames for internal doors are usually sold separately from the door slab, and come as a frame kit, with jambs, head, and stops, to be assembled on site.

External door frames  are often sold ready-assembled by the manufacturer, and they can be fitted using the same basic method you'd use to install a pre-hung door set. If the frame needs assembling on site it's often called a knockdown frame, or frame kit, and usually has the joints pre-cut for ease. It should be constructed by a competent joiner so it will comply with Building Regulations for external doors. You can use a registered installer who can issue a proof of compliance certificate on completion, or you'll have to pay a fee to the relevant Building Control Body so they can inspect the finished work.

A pre-hung doorset  is a door which comes ready-assembled in a frame, and often has its hardware already fitted. This can also be called a door set or door assembly. They will often be more expensive than buying the separate parts, but will be significantly easier to install. Make sure you follow the manufacturer's instructions for specific door sets.

Doors need to be replaced sometimes, for aesthetic reasons, or because a door has been damaged or worn. The following information describes how to fit a new door into an existing frame. Before you fit any new door you need to make sure it has been properly finished with the correct type of treatment with the right number of coats. Doors come from the manufacturer as either fully finished, pre-finished with a primer ready to paint, or unfinished so you can apply your own finish. Anywhere you have cut the door, to trim it to size or for fitting hardware, also needs to be finished. Finishes are typically paint, stain or lacquer, and you should always follow the manufacturer’s guidelines for individual doors. You should use a high-performance treatment to ensure your doors last as long as possible and you do not invalidate your warranty.

Some doors intended for glazing are supplied without the glass panels in place, known as unglazed doors. This allows you to select the glass you want and install it yourself. Internal   and  external doors   can be supplied as unglazed and ready to have glass fitted. You must select glass that is suitable for use in house doors, and for the area the door will be used in, particularly taking into account if it's an external or internal door. The way you will fit glass in an internal door is slightly different to how you will fit it in an external one. Always check the manufacturer's instructions for details on a specific door for what glass should be used and how installation should be performed. 

The   Architrave  of a door is the trim which you see around the door frame of internal doors that hides the gap where the frame meets the wall. It can also be referred to as moulding, Architrave will usually be supplied separately to the rest of the frame, as one long piece to be cut up, or shorter, ready-cut pieces. Most architrave parts are joined at the corners with 45-degree mitred ends to form 90-degree corners. If necessary, you'll need to measure and trim the pieces to the right size and shape. It's best to fit the door leaf before you fit the architrave.