What Is Blocking in Construction? Essential for Stability and Support

June 12, 2024

When constructing a home, ensuring the structural integrity and longevity of various installations is vital. This is where blocking and backing play a crucial role in wood-framed construction.


Definition of Blocking

Blocking, also known as dwang, nog, noggin, or nogging, refers to short pieces of dimensional lumber used between framing members. They brace longer framing members, provide attachment points for fixtures, and prevent buckling under vertical compression loads.

"High school classroom blocks under construction, Bamaga, April 1972" by Queensland State Archives is marked with Public Domain Mark 1.0. To view the terms, visit https://creativecommons.org/publicdomain/mark/1.0/.

Primary Purpose

The main role of blocking is to stabilize longer frame members to prevent buckling. These blocks are placed at intervals specified either by building codes or structural engineers.

Resisting Twisting

Blocking helps resist the rotational movement or twisting of floor joists under load deflection. Diagonal cross bracing (herringbone bracing) or solid blocks, known as bridging, block bridging, or solid strutting, can be used to achieve this.

Illustration of Blocking

An effective illustration shows solid blocking with alternately displaced blocks to allow nailing through their ends, ensuring stability.

"Construction now blocks off the entire bus stop area" by Steven Vance is licensed under CC BY-NC-SA 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/2.0/.

Additional Uses

Blocking also serves as spacers or attachment points between adjoining stud walls, vital where interior and exterior walls meet or at corners using techniques like the "three-stud corner with blocking."

Supporting Fixings

Properly placed blocking (or grounds/backing/back blocking) supports the cut ends of wall claddings and linings. This is crucial for attaching items like cabinets, shelving, handrails, and vanities, helping distribute the weight across structural members.

Engineering Specifications vs. Grounds

Locations required for use as attachment points often do not align with those needed for bracing per engineering specifications. As a result, blocking may serve dual purposes, but often the two forms act independently in the structure.

"Construction site area in front of Masshouse Block M - Construction vehicle" by ell brown is licensed under CC BY-NC-SA 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/2.0/.

Materials for Blocking

Blocking is usually made from short off-cuts or pieces of lumber that are defective or warped, making them unsuitable for longer lengths.

Clarifying the Dual Roles

Blocking in wood-framed construction helps both in structural bracing and providing attachment points. The dual roles highlight the importance of precise placement for ensuring structural integrity and ease of fixture addition.

Common Scenarios Where Blocking is Essential

Floor Joists and Wall Corners

Floor joists often require blocking to prevent twisting under load deflection. Wall corners use blocks as spacers to maintain alignment and provide attachment support for adjoining structures.

Benefits of Proper Blocking Placement

Proper blocking placement simplifies the addition of fixtures and ensures structural integrity. It makes future upgrades and installations easier and more secure.

Construction Techniques

Three-Stud Corner with Blocking

This technique involves using three studs with blocking to create a sturdy and secure corner, essential for structural stability and avoiding gaps between walls.

Conclusion

The nuanced roles of blocking and the necessity for meticulous installation make it vital. Successfully performing blocking enhances the durability, safety, and efficiency of the completed structure.

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