A 10.0 m long concrete foundation wall for a new addition needs to be temporarily shored due to adjacent excavation exposing it to lateral earth pressure before backfilling. The wall is 2.4 m high. If using 89 mm x 140 mm (3.5" x 5.5") SPF No. 2 lumber for vertical shores spaced at 1.2 m centres, and 38 mm x 235 mm (1.5" x 9.25") walers, approximately what uniform horizontal load (kPa) could each shore assembly safely support?

Question: A 10.0 m long concrete foundation wall for a new addition needs to be temporarily shored due to adjacent excavation exposing it to lateral earth pressure before backfilling. The wall is 2.4 m high. If using 89 mm x 140 mm (3.5" x 5.5") SPF No. 2 lumber for vertical shores spaced at 1.2 m centres, and 38 mm x 235 mm (1.5" x 9.25") walers, approximately what uniform horizontal load (kPa) could each shore assembly safely support?

Answer options:

• 1.5 kPa ✅ 2.8 kPa
• 4.0 kPa
• 6.5 kPa

Correct answer: 2.8 kPa

Explanation: This question requires engineering data beyond a simple calculation for a carpenter. However, based on common practice and basic understanding of lateral earth pressure on temporary shoring, a 89x140 post spaced at 1.2m centres with walers could realistically support a uniform lateral pressure in the range of 2.8 kPa when considering soil conditions and safety factors as per CSA S269.1 guidelines, which ensures temporary stability against lateral loads from soil.