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The product covered in this section is 'Internal Doors'.  Find out about the different types that you are most likely to use, their sizes and construction.

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Internal Doors


Doors are made in several standard sizes to meet most domestic needs.  Modern homes tend to have standard-size joinery and most internal doors are the same size. The standard is usually 1981 mm x 762 mm (6ft 6in x 2ft 6in), though there are a variety of other sizes available, which are intended for wider and narrower openings such as under the stairs or 'walk-in' cupboards and the WC.  The chart below lists these sizes, but I should point out that not all styles of doors are made in this full range of sizes.  Internal doors come in two thickness 35 and 40 millimeters, 35 millimeters being the most widely used. Internal Fire Doors are 44 millimeters.  
Internal doors are usually much lighter than external doors, this is because of their thickness and the material and method used in their construction.

Standard Internal Door Sizes
864 x 1981 mm 2'- 10" x 6'- 6"
838 x 1981 mm 2' - 9" x 6'- 6"
813 x 2032 mm 2' - 8" x 6'- 8"
762 x 1981 mm 2' - 6" x 6'- 6"
686 x 1981 mm 2' - 3" x 6'- 6"
610 x 1981 mm 2' - 0" x 6'- 6"
533 x 1981 mm 1' - 9" x 6'- 6"
457 x 1981 mm 1' - 6" x 6'- 6"
926 x 2040 mm Standard Metric
826 x 2040 mm Standard Metric
726 x 2040 mm Standard Metric
626 x 2040 mm Standard Metric
525 x 2040 mm Standard Metric



Internal doors come in three forms: Panel, Flush and Pressed Hardboard

Panel doors are made in the traditional way using hardwood or softwood timber with either mortice and tenon or doweled joints. The timber members that make up the door are grooved, or rebated and beaded to take a variety of panels.


There is a drawback with 'Flush' or 'Pressed Hardboard' doors which is that they are 'Hollow Core', filled with a lightweight paper honeycomb. The surrounding framework of the door is only about 25 mm thick and limits the amount that can be taken off the edges if it happens that the opening size is smaller than the standard size.


Flush Doors are made up of a simple softwood frame (usually stapled together) and covered in either plywood or hardboard.  The two edges are usually finished with a hardwood edging strips known as 'Lipping'.  The most basic and cheaper doors are not edged in this way.

Pressed Hardboard Doors are made like flush doors and differ only by the embossed surface, which gives them, the 'panel door' look.  The embossed surface can be grained or smooth


Another important point regarding hollow doors is that; if they did not have what is known as a 'lock block', it would not be possible to fit a lock, latch or handle, as they require a least 80 mm of timber to fit into. The manufacturer fits the block into the door during construction and as the name suggests, is simply a block of wood, about 300 mm long (or less) fitted to one edge of the door.
After the door has been produced, it is stamped with 'Lock' or 'Lb', indicating which side the door that the block has been positioned.  Without this stamp, you could end up fitting the hinges on the wrong side of the door and have nothing to fit the lock or handles to.

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