Timber doors

Different types of timber can be used for doors: pine, spruce, oak, beech and birch, either as solid wood or as veneer. There are two main construction techniques for doors: framed and panelled doors and flush doors, both of which are built up with a solid timber frame. Both types usually have sealing strips as well as hinges, door handles, housing for the locks and other ironmongery.

16.3

Re-use of windows in a semi-climatized room in Krinkelkroken kindergarten, Trondheim (Norway). Architects: HS0 Arkitektkontor AS, 2000.

16.3

Re-use of windows in a semi-climatized room in Krinkelkroken kindergarten, Trondheim (Norway). Architects: HS0 Arkitektkontor AS, 2000.

Framed and panelled doors are built with a wide timber frame (Figure 16.5). This was traditionally fixed together with wooden plugs, but nowadays it is glued. In the spaces between the frame, solid timber panels are placed, or panels of chipboard, plywood, hard fibreboard

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The principle section of a sustainable window construction. Gaia Lista, 1995.

16.4

The principle section of a sustainable window construction. Gaia Lista, 1995.

16.5

A framed and panelled door.

16.5

A framed and panelled door.

or even glass. These are slotted into the groove on the inside of the frame. To stop the frame bending, it is usual to split it into two, turn half of it through 180° and glue it together again. This lamination is not necessary for internal doors between dry rooms.

This type of door has poor thermal insulation properties and is usually used internally. Two such doors with a porch in between, however, should give a good internal thermal climate in most conditions.

Flush doors also have a frame, but not as large as the frame of a panelled door (Figure 16.6). A flush door is stiffened by thin layers of board, fibreboard or plywood, fixed with adhesive or pins on both sides. External doors must use a water-insoluble adhesive. Thermal insulation can be placed in the space between the layers of fibreboard, such as expanded polystyrene, mineral wool and porous fibreboard, woodwool slabs, wood shavings, etc. For light doors it is usual to add a sound insulating layer of corrugated cardboard or layers of interlocking wood fibre bands, a waste product from the wood fibre industry. In fire doors, non-flammable sheets of plasterboard or other mineral materials are inserted. A flush door can also have glazing, but glazing will need its own frame.

Common adhesives used in door manufacturing are phenol-resorcin-ol-formaldehyde (PRF), phenol-formaldehyde (PF), polyvinyl-acetate (PVAC) and polyurethane (PU) (see Chapter 17). Casein glue, animal glue and soya glue can also be used. Doors are often delivered ready to mount, so they have either a polyurethane varnish or an alkyd or linseed oil painted finish.

The environmental aspects of timber doors are good, but it is quite clear that the choice of insulating material, glued boards, sealing strips, surface treatment and ironmongery all play their part in production consequences and have potential effects on the internal environment.

Doors can often be re-used, especially robust, solid framed and panelled doors. It is also an advantage if the door leaf can be dismantled with the doorframe intact. The manufacture of a new doorframe can be expensive, especially if its dimensions are not to the current standard. This assumes that the doorframe was originally fixed for simple dismantling, preferably with screws.

Defective doors of solid timber can usually be energy recycled or composted, but laminated products have to be deposited at special tips, or burned for energy recovery in incinerators that clean the fumes.

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