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What is your structure asking you to spend?
Structure and design · Episode 22
Alison Wallis with Tina Patel and Bart Kolosowski
An open corner, a hidden beam or a slightly lower floor can look like a small design choice. What does it ask the structure to do?
Structural engineer Alison Wallis joins Tina and Bart to explain the hidden work behind a home—and how early conversations can find more efficient solutions.
That column could become a feature—and save a lot of steel
Bart recalls a project where the homeowner wanted an open corner without a column. The architect and engineer instead made the column a deliberate feature of the design.
Alison explains the wider principle: shorter spans and direct routes for loads can make the structure more efficient. Removing supports can mean heavier steel, more demanding connections and changes to the foundations.
Compare structural options alongside the architecture and cost plan. A column is not right for every brief, but seeing the alternatives helps you decide what an uninterrupted opening is worth to you.
01
Keep useful supports
Test columns and retained walls.
02
Compare beam options
Balance depth and steel weight.
03
Investigate the ground
Replace assumptions with detail.
04
Review the knock-ons
Include foundations and water.
A hidden beam can be heavier than a deeper one
Alison explains why stiffness depends on where material sits within a beam, not just how much of it there is. A shallower beam can need substantially more steel to do the same job.
The conversation also distinguishes strength from movement. A floor may be safe yet feel bouncy, and brittle finishes or glazing can need much tighter control of deflection.
Tell the team which sightlines, ceiling heights and finishes matter most. Ask how those choices affect the structure, and compare any saving in the context of the whole project.
Before filling the trench, understand the ground
Drawing on London projects, Alison explains how clay, moisture and nearby trees can influence foundation design. The existing house and ground investigations give the engineer information that assumptions cannot.
She describes a study comparing foundation options and their embodied carbon—the emissions associated with materials and construction. Reducing concrete can help, but cost, buildability and contractor methods still need to be considered.
Ask which investigations will help your engineer choose a suitable foundation. Test alternative solutions with the team rather than assuming the deepest trench or the lowest-carbon option is automatically best.
Lowering a floor a little can change the whole job
The hosts explore the request to lower a basement floor by a few hundred millimetres. Once the new floor build-up is included, the excavation may extend below existing foundations.
Alison explains underpinning and the need for carefully sequenced work. Bart brings in labour and temporary works, while Tina adds the waterproofing implications of working below surrounding ground.
The discussion also considers a perimeter ledge that might be incorporated into seating or joinery where the design permits. Explore the engineering and architectural options before treating a lower floor as a simple alteration.
Three decisions to take into your project
01 Explore options before fixing the look.
Compare supports, spans and beam depths with the architect, engineer and cost adviser.
02 Use investigations to inform design.
Ask what is needed to understand the existing structure and ground conditions.
03 Price the whole intervention.
Include sequencing, temporary works and waterproofing when comparing structural changes.
The full conversation
Structural engineer Alison Wallis of Weave Engineers joins architect Tina Patel and quantity surveyor Bart Kolosowski to explain foundations, frames, floors and the choices that affect them.
The full conversation also explores deflection, cracks, clay soils, embodied carbon and underpinning. It shows how communication between architect, engineer, cost adviser and contractor can turn an ambitious brief into a buildable solution.
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Explore a related episode
Episode 19: Budget or design: which comes first?
Keep the structural design aligned with the wider project budget.
Episode 20: Which savings quietly cost you more?
Distinguish useful early spending from false savings.
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