Propping

Propping is temporary vertical support, acrow props, strongbacks, needle beams, installed to carry load while a wall is removed, an opening is cut, or a floor or roof is worked on. Where it carries structural load it is temporary works and must be designed by the engineer, not eyeballed on the day.

When you take out a loadbearing wall or cut a large opening, the load above it, the floor, roof, or wall over, has to be carried somewhere while the permanent beam or lintel goes in. Propping does that. Adjustable steel (acrow) props under needles or strongbacks pick up the load, hold it, and stay until the new structure is in and has taken the load.

The detail that matters is the load path all the way to the ground. A prop is only as good as what it bears on:

• The load has to land on something that can carry it, a slab, a sound bearing wall, or doubled-up bearers, not an unsupported suspended floor.
• Sole plates or spreaders distribute the point load so a prop foot does not punch through.
• Props stay in until the permanent beam is installed and loaded.

Propping is not the same as shoring. Propping is vertical load support; shoring is usually lateral support to an excavation or a wall at risk of moving sideways.

For a builder the rule is firm: do not improvise propping on loadbearing work. Get the engineer’s temporary-works design (prop type, size, spacing, needle size, and what it bears on), confirm the load actually reaches something that can take it, and do not strike the props early. Striking too soon, or propping onto a floor that cannot carry the load, is a common cause of mid-renovation collapse.

Also known as: Temporary propping, acrow propping.

Category: Structure / Temporary works.

Related

• Shoring
• Frame inspection checklist

See also

• Conventional roof framing
• Demolition licence class
• Timber framing basics

References

• Frame inspection checklist (Chalkline) (verified 2026-06-01)

---

Last updated: 2026-06-01. Verified: 2026-06-01. Quarterly review for currency.