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Unit: Installation requirements

Section: Construction features

MSFKB3002: Determine requirements for installation

Competencies covered

MSFKB3002: Determine requirements for installation

Other structural features


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Now that we've looked at floor systems and external walls, we can talk about the difference between load bearing walls and non load bearing walls.

Then we can discuss the positioning of openings and the effect they have on the structural integrity of the walls.

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Load bearing walls

Load bearing walls support the weight of the structure above them. In the case of external load bearing walls in a single storey house, the weight comes from the ceiling and roof. In a two storey house, it would also include the first floor.

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In some single storey houses, the roof is supported by some of the internal walls in addition to the external walls.

The wall frame in this photo is load bearing because the roof truss above it is resting directly on the top plate, over the doubled-up studs.

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It's worth remembering that the size and grade of studs used in load bearing timber framed walls are designed specifically for the loads they need to withstand.

So any damage to a stud will have an effect on its ability to do its job.

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This includes notching or drilling holes to run electrical cables or plumbing pipes.

Building codes specify the amount of notching and drilling permitted, so licensed plumbers and electricians will know what is acceptable.

But as an installer, you should always remember that when you're working around load bearing walls, you need to minimise any damage to the studs.

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Non-load bearing walls

Non-load bearing walls do not support a load from above. In other words, if the internal wall is not bearing the weight of the roof or floor above it, then it is non load bearing.

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Some modern homes use roof trusses that span the full width of the building.

This means that only the external walls bear the load of the roof and ceiling, so all internal walls are non load bearing.

These internal walls are often called partition walls, because their only function is to partition off the rooms in the large internal space.

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Older houses with roofs that were built stick by stick by the carpenters on-site are far more likely to have some internal load bearing walls and some partition walls.

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Positioning of openings

You can probably see that before you create an opening in any wall, it's essential to know first how much load the wall is supporting. Windows in load bearing walls typically have a lintel above the opening, with secondary studs to help support the lintel.

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Renovation jobs that require a new opening in a wall, or a widening of an existing opening, or the removal of the entire wall, generally have plans drawn up by an architect or engineer.

The plans specify any additional structural work, such as beams and columns, that might be needed to support the load above the opening.

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Learning activity

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There's no better way to understand the principles of load bearing and non load bearing walls than to have a look at them in action. Try to find a timber or steel framed building under construction, with the wall and roof framing up, but before the bricklayers have got too far on the walls.

It's likely that the building will have a trussed roof, because that's the most economical way to build these days. Have a close look at the bottom chord of the truss as it passes over the non load bearing internal wall frames. You'll see that the bottom chord doesn't rest on these walls at all - it's only bearing point is at each end.

Now look for internal load bearing points in the building, that is, points where a wall is supporting part of the roof or the second storey floor above. What is holding up the load? Is it a wall frame or a beam? Is there a column involved?

Take digital photos and share them with your trainer and other learners in your group.

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