When measuring either your internal or external door ignore the current door size and follow this advice and any relevant advice offered throughout our DIY pages, the whole point of measuring each and every door opening is to avoid mistakes............ or complacency.
Width: Measure each door between the frame at the top, the middle and the bottom.
Tell us or choose a door(s) to suit the widest size, always remember that you are responsible for making sure that the widest size can be adjusted by you to suit the narrow area of any part of the opening without compromising the stability or affecting the look of the door.
Height: Measure from the carpet/floor covering to the underside of the timber lintol.
Thickness: Now and only now do you measure the door to find out how thick it is at present, with Interior doors you may have to compromise and fit a slightly thinner door, this does not normally present any problems.
REMEMBER WHEN MEASURING FRAMES; The above advice may be different if ordering a door and frame, always check the overall outside sizes of the frame against the overall inside sizes of the frame and choose the correct combination of those sizes to suit the opening and to ensure the frame will go into the opening, this may involve you ordering a frame that is slightly smaller than the current frame, now measure the frame breadth, ie; from the inside face to the outside face, you can always add a sub frame or concealed plates to make a frame fit the width or height but it can be very difficult and sometimes impossible to adjust the frame if you have ordered it too big.
Beware: Do not assume all internal doors in your house are the same size or thickness, check them all.
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