Blocking (
dwang
In construction, a dwang (Scotland and New Zealand), nogging piece, nogging, noggin or nog (England and Australia; all derived from brick nog),Fleming, Eric. ''Construction technology: an illustrated introduction''. Oxford: Blackwell, 2005. 123, ...
, nog, noggin, and nogging) is the use of short pieces of
dimensional lumber
Lumber is wood that has been processed into uniform and useful sizes (dimensional lumber), including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). ...
in
wood framed construction to brace longer members or to provide grounds for fixings.
Uses
The primary purpose of blocking is to brace longer frame members to help resist
buckling
In structural engineering, buckling is the sudden change in shape (Deformation (engineering), deformation) of a structural component under Structural load, load, such as the bowing of a column under Compression (physics), compression or the wrin ...
under vertical compression. The intervals for the blocks are specified in the building code or as calculated by a structural engineer.
Blocking also resists the rotational movement, or twisting, of floor
joist
A joist is a horizontal structural member used in Framing (construction), framing to span an open space, often between Beam (structure), beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joi ...
s as they deflect under load. This may take the form of diagonal
cross bracing
In construction, cross bracing is a system utilized to reinforce building structures in which diagonal supports intersect. Cross bracing is usually seen with two diagonal supports placed in an X-shaped manner. Under lateral force (such as wind ...
, or ''herringbone'', bracing between floor joists. When solid blocks are used instead of diagonals it is called ''bridging'', ''block bridging'', ''solid bridging'' or ''solid strutting''. The illustration, right, shows solid blocking. Note how they are displaced alternately to allow nailing through their ends.
Blocking may also provide spacers or attachment points between adjoining stud walls, for example, where an interior and exterior wall meets, or at a corner where techniques such as the "three-stud corner with blocking" are used.
When correctly placed, blocking also provides ''grounds'' (also ''backing'' or ''back blocking'') for supporting the cut ends of wall claddings and linings or for attaching items such as
cabinets
A cabinet in governing is a group of people with the constitutional or legal task to rule a country or state, or advise a head of state, usually from the executive branch. Their members are known as ministers and secretaries and they are ...
, shelving,
handrail
A handrail is a rail that is designed to be grasped by the hand so as to provide safety or support. In Great Britain, Britain, handrails are referred to as banisters. Handrails are commonly used while ascending or descending stairways and escala ...
s, vanity tops and backsplashes, towel bars,
decorative mouldings, etc. Properly placed grounds make the second fixings easier once the walls are lined and they distribute the weight of heavy items across structural members. However, the locations required for use as grounds are dictated by the needs of the fittings and these often do not coincide with the locations required by the engineering specifications for use as bracing, consequently, the two forms may be present in the wall acting independently. When used only as grounds rather than as bracing, they are typically shallower.
[Simmons, H. Leslie. ''Olin's Construction: Principles, Materials, and Methods''. 9th ed. Hoboken: J. Wiley & Sons, 2011. Print.]
Blocking is typically made from short off-cuts or to make use of defective,
warped, pieces unsuited for use in longer lengths.
References
{{DEFAULTSORT:Blocking (Construction)
Building engineering
Carpentry