Accurately measuring an existing door frame or opening is the crucial first step in fitting a new internal door. Proper measurements ensure you purchase a door that fits correctly, saving time and effort during installation.
Fitting an internal door involves preparing the opening, measuring the necessary dimensions, selecting the correct door type and swing, and then physically hanging and finishing the door. The foundational part of this process relies heavily on precise measurement.
Essential Steps for Measuring Internal Doors
Before you even think about cutting or hanging, you need to get the measurements right. This involves taking several key dimensions from the existing frame or the door you are replacing.
1. Measure the Door Width
The width of the door is the first critical measurement. You need to measure the width of the door opening horizontally at several points: the top, the middle, and the bottom. This is important because door frames can sometimes be out of square.
- Use a tape measure to find the distance from the inside edge of the frame on one side to the inside edge on the other side.
- Note the smallest measurement you get from the three points (top, middle, bottom). This is your maximum usable width.
- For a new door slab (not pre-hung in a frame), you typically subtract a small tolerance (e.g., 1/8 inch or 3mm) from the smallest measurement to allow for ease of opening and closing, and potential adjustments.
2. Measure the Door Height
Next, we focus on the height, which is just as important as the width for a seamless fit. Measure the height of the opening vertically from the floor covering (or where it will be) to the top of the frame.
- Measure the height on both the left and right sides of the frame, and also in the middle.
- If the floor is not level or the frame is not plumb, you will get slightly different measurements. Again, note the smallest measurement.
- Subtract a small tolerance (e.g., 1/4 inch or 6mm) from the smallest height measurement. This gap at the bottom is necessary for the door to swing freely over the floor covering. The gap at the top (after cutting to size) will be part of the overall tolerance.
3. Measure the Door Thickness
The thickness is also vital for ensuring the door fits properly within the door frame rebates (the cutout where the door sits when closed) and works with standard hardware like hinges and latches.
- Measure the thickness of the existing door or the rebate in the door frame.
- Standard internal door thicknesses are typically 35mm or 44mm (for fire doors). Ensure the new door matches this dimension.
4. Note the Door Swing
Understanding and noting the door swing is essential for fitting, specifically when selecting hinges, handles, and deciding which side the door should open. The door swing is determined by which side the hinges are on and whether the door opens into or out of the room.
- Determine Handing: Stand on the side of the door where the hinges are visible when the door is closed.
- If the hinges are on the left, it's a left-hand door.
- If the hinges are on the right, it's a right-hand door.
- Determine Opening Direction: Most internal doors open into the room they provide access to. However, note the intended or existing swing direction (inward or outward).
| Measurement | How to Measure | Why it Matters |
|---|---|---|
| Width | Top, Middle, Bottom of frame opening | Ensures door fits side-to-side; account for square |
| Height | Left, Middle, Right of frame opening (to floor) | Ensures door fits vertically; allows floor clearance |
| Thickness | Existing door or frame rebate | Compatibility with frame and hardware |
| Door Swing | Hinge side & opening direction | Determines hinge placement, handle orientation, and door type selection |
Moving Towards Fitting
Once you have these measurements, you can purchase the correct size door slab. The physical process of fitting involves:
- Preparing the Door Slab: If the door is slightly oversized (common for slab doors), it will need to be trimmed down precisely to the measured dimensions (minus tolerances).
- Mortising Hinges: Cutting recesses into the door edge and the frame to fit the hinges flush.
- Hanging the Door: Screwing the hinges into the door and the frame, aligning correctly.
- Routing for Latch/Lock: Cutting out the necessary parts for the door latch or lock mechanism and handle spindle.
- Fitting the Handle/Hardware: Installing the handle, latch plate, and strike plate on the frame.
- Final Adjustments: Ensuring the door opens and closes smoothly without binding, and the latch engages correctly.
While the provided reference focuses on the critical measurement steps, mastering these ensures you select or prepare a door that is the correct size and type, making the subsequent physical fitting process much more manageable.
