There are two main approaches to fitting glass to green oak frames:
♦ Direct - where the glazing is mounted either within, or onto the outer
face of, the green oak frame.
♦ External - where the glazing is carried by a separate frame fixed to
the exterior of the green oak frame.
Whilst we specialise in the fabrication and installation of structural oak
frames, we do not currently supply or fit glazing ourselves. However, here are
some examples of each which are in common use.
Direct Glazing
It is possible to glaze directly over, or within, a green oak frame. In many
cases, direct glazing can be the cheapest and most practical option, particularly
where there may be corner posts. We have built many frames where this method
has been used to good effect.
Its main disadvantage, other than the shrinkage and movement of the green oak as it
matures, is that it can be difficult to incorporate opening windows. Whilst roof
glazing can sometimes be carried by Capex-type channels, there may be the need for
a stabilised frame to mount a glazed roof on a conservatory.
Here are four common direct glazing methods...
♦ Glazed units may be mounted within the oak frame, secured and sealed
with seasoned oak glazing bars inside and out [fig 1]. Whilst this method
can perform well, it is not recommended for exposed locations. Additional sealing
against the elements can be achieved by fitting outer bars that enclose the edges
of the posts.
♦ The glass can be mounted within a rebate cut in the outer face of the oak frame
with seasoned oak glazing bars, similar to the method above [fig 2]. It provides a
more minimalist join between glass and oak frame, giving the appearance of a window built
into the structural frame when viewed from the inside, but can add complexity and cost to
the green oak frame and is not recommended for more than moderately exposed locations.
♦ Similar to the method above, the glass can be mounted within a shallower rebate
cut in the outer face of the oak frame and capped with an oak board fitted to the outer
face of the post [fig 3]. It can give the appearance of a window built into the
structural frame when viewed from both inside and outside, though adds slightly less
complexity and cost to the green oak frame. We recommend this approach where a frame may
be exposed to driving rain. However, external corner posts can appear slightly bulkier
where capping boards are mitred to meet.
♦ The glazed units can be mounted on the outer face of the green oak frame and capped
with an oak board [fig 4] to match the width of the post, similar to the method above.
Of the various methods of direct glazing, this best protects the green oak frame from the
elements as the green oak dries and matures. As with the method above, it can give the
appearance of a window built into the structural frame when viewed from both inside and
out without the need for rebating into the structural oak frame. However, more so than above,
external corner posts may appear bulkier where capping boards are mitred to meet.
External Glazing Frame
In exposed locations, you may be best off with a green oak structural frame supporting
a lighter external frame to carry the roofs, windows and doors.
An external frame made of seasoned oak (or coated aluminium or other material) can be attached
to the green oak frame at specific points to provide a stable, sealed envelope around the whole
structure [fig 5]. This means there may be fewer green oak intermediate posts, allowing more
light to enter and giving more scope for creativity and minimalism in the oak frame design.
The design, materials and performance of externally mounted glazing systems will vary
according to manufacturers specifications. An external frame can comprise opening windows,
doors, vents, roof lights, etc. On the roof, it would carry the glass on its own common
rafters. This offers the advantages of a light and stable exterior with an internal
structure to suit the character of your house.
The method of glazing will affect the cost of a frame. Rebated timbers [fig 2 & 3]
require a greater amount of carpentry, whilst those without rebates [fig 1, 4 & 5]
are simpler and less time consuming.
Direct glazing fitted within the oak frame and secured with seasoned oak
internal and external glazing bars (see fig 1).
Direct glazing mounted upon the outer face of an oak frame and secured with
external boards (see fig 4).
External glazing and roof frame supported by an internal oak frame (see fig 5).
Screws and Nails into Green Oak
Seasoned oak glazing bars, capping boards and external glazing frames need to
be attached to the green oak frame. They are normally fixed with screws or lost-head nails into the
green oak. Screws and nails should be stainless steel, brass or high-quality galvanized.
This is because bright iron will rust and tannic acid in the green oak
will react with the iron to cause black staining and corrosion.
However, stainless steel and brass screws tend to be softer than bright iron
or galvanized screws so they need to be fixed with greater care to prevent
snapping. This requires drilling thread holes prior to fixing. Occasionally,
there may be insufficient room for drilling, in which case a bright iron screw
of the same size can be screwed in and unscrewed to create a thread hole for
the stainless or brass screw.
In addition, care should be taken not to over-tighten screws to prevent snapping.
If you are using a cordless screw driver it is sometimes best to select as low a
torque setting as practicable with a view to tightening manually.
More Information
Links to sites offering details of fitting and finishing, as well as useful
calculators and tables, can be found in our Planning & Building Information
Resource.
This is a brief overview of some green oak frame glazing
methods, rather than a comprehensive guide. Methods of fixing and sealing will
vary according to the needs of the project and any manufacture's specifications.
Whilst glazing may be undertaken as part of a self-build or DIY project by those
with sufficient competence, this should be accompanied by appropriate
professional guidance.
