If you are planning to buy a new Bespoke front door and think your old frame is still in good condition you can check this in 3 easy steps:
a. Check the frame for rot. Use a house key (not a screw driver or chisel, these are too sharp) to poke the cill and the bottom of the frame verticals. You are looking for soft timber. If you find soft timber then the frame is rotten and needs to be replaced.
b. Use a spirit level and tape measure to find out if the frame is square. Most frames are not square. If the verticals are more than 20mm off the vertical line then a new frame is required. If the head or the cill are more than 25mm off the horizontal line then a new frame is required. If the head or the cill are not level then you must tell the customer that the door will not look straight at the top or the bottom, but there is nothing you can do to change this unless you change the frame.
c. Check the frame for cracks/ splits. These can be caused by a break-in in the past. If there are splits around the hinges then the new hinges won’t carry the door and the door might drop. This means the frame must be replaced. If there are splits around the locks then the door may not be as secure and the frame might need to be replaced. If the splits around a lock keep are small, then a London bar might help to re-inforce the frame and the old frame could be kept.