Door frames are an important concern when it comes to security and are often overlooked. No matter how sturdy the door or secure the locks, if the door hinges have been drilled into a flimsy frame it can be kicked down in seconds by someone determined to do it. Because most locks and dead bolts protrude into the door jamb and rely on it for support, choosing the right frame is a vital part of ensuring that your doors are securely attached.
What materials are available?
Door frames are most commonly made of wood; this is usually the fastest and cheapest material for framing doors, but wood can be vulnerable to splintering and cracking under pressure, and weakens over time. Some door frames have a reinforcing steel overlay which prevents this from happening, but other materials such as uPVC, fibreglass and aluminium or even a composite blend of wood and resin will all achieve similar effects and make the door frame more reliable.
Some doors are sold pre-hung - that is, already attached to the frame via hinges, for easy installation and a close fit.
What different shapes & types exist?
A basic door frame consists of two jambs running vertically parallel on either side of the door, with the lintel forming the crosspiece at the top and the sill forming part of the threshold on the floor below. No matter what the shape of the door, even if it is non-standard, the frame will need to provide a seal for the door when it is closed, so the frame will be designed with that primarily in mind. This can compromise stability somewhat, especially if the door is an uneven or irregular shape.
What difference do various shapes and materials make?
Different shapes and materials can alter the strength of the door frame, for better or worse. Selecting a material which will not only look good over time but will hold up under sustained pressure is worth spending the additional time and money on. Rectangular door frames offer a strong support structure, and changing or adding additional angles to a frame may add weak points which can be exploited.
One big difference that different materials can make is their ability to transfer heat into and out of a house. Metal, for example, is an excellent conductor of heat and can easily act as a very effective thermal bridge (a weak point through which you'll gain or lose heat). Metal door frames can be made with thermal breaks though, which will help to prevent this while still giving you the look you want. Timber, by contrast, is a fairly poor conductor of heat and does a pretty good job of keeping heat in or out of your home - as do uPVC, fibreglass and similar materials.