5

Making doors and doorframes

INTRODUCTION

The making of doors – as with windows – is nowa-
days mostly in the domain of large manufacturers
using CNC (computer numerical control) production
processes and CAD/CAM (computer- aided design
and manufacture). Also, engineered composite- and
architectural fibreglass- doors have a sizeable slice of the
market. However, small- and medium- sized joinery
shops do still get asked to make bespoke timber doors,
be it mainly for exterior types, including shaped- doors
(Tudor- headed, etc) and one- off, non- standard size
internal doors. Regarding purpose- made exterior
doors (and their frames), it must be mentioned that
these should comply with the amended Building
Regulations’ AD (Approved Document) Part L1A
and L1B: Conservation of fuel and power in new and
existing dwellings, regarding achieving the current
U- value of 1.8W/m^2 K to meet the DER (dwelling’s
energy rating).

COMPLIANCE WITH AD, PART

L1B

Although any upgrading to the insulation of dwell-
ings is mutually beneficial (to the Government via the
Building Regulations addressing the environmental
issues and to the occupiers of a property, reducing
their energy bills and their carbon footprint), such
regulations were not previously enforceable retrospec-
tively on existing dwellings. However, the amended
Part L refers to exterior doors and windows as
‘thermal elements’ that – if replaced – are regarded as
controlled fittings (controlled by having to comply with
the upgraded energy rating). But the obligation to do
so, only applies to a whole unit, i.e. including the door-
frame. The replacement of a door (or a window) into
an existing, retained frame, therefore, does not have to
meet the Part L standards – although, where possible,
it would be sensible to do so.

UPGRADING

There are at least five ways to upgrade new

exterior timber- doors and doorframes to achieve

lower U- values: 1) by pre- grooving the rebated

inner- edges of the frame to receive compression

weather- strip seals (illustrated further on in the

chapter); 2) by fitting and fixing a good- quality

patent weather- seal/draught excluder to the frame’s

sill; 3) by achieving a finished door- thickness of at

least 45mm; 4) by using rigid insulating- material

such as sheet cork or Celotex insulation board

snugly sandwiched between double panels; and

5) by glazing any fixed- light areas with 24mm

sealed units using low- E (low emissive) glass and

Warm- Edge spacer bars.

BASIC DOOR KNOWLEDGE

Basically, doors are usually referred to by standard

sizes and the number of panels or glazed areas that

they contain. And those without panels (which are

covered with plywood or hardboard) are usually

referred to as flush doors. Combined references

might also be applied, such as half- glazed flush door,

or four- panelled door with raised- and- fielded panels.

We must also know the difference between internal

and external doors. The latter – apart from usually

being slightly wider than internal doors – have to

be strong enough to provide security and withstand

extreme weather conditions on one side, yet not lose

their balance from the different conditions on the

other – so they are usually thicker, therefore heavier,

and of a more substantial construction than internal

doors.

More importantly from a structural viewpoint,

doors – some quite heavy, as mentioned above – hang

free from their hinged side and the framing arrange-

ments have to withstand this suspended load. In the

case of panelled doors, the framing strength is achieved

by the jointing of the horizontal rails to the vertical