What Do Structural Engineers Do and When Would I Need One?
Not sure how this specialist profession fits into your renovation project? Read on...
Kate Burt
24 April 2020
Houzz UK. I'm a journalist and editor, previously for the Independent, Guardian and various magazines. I'm now excited to part of the editorial team at Houzz UK & Ireland, bringing the best of British and Irish design, interiors and architecture to Houzz.com.
Houzz UK. I'm a journalist and editor, previously for the Independent, Guardian and... More
As a homeowner, you may be clear that you want an architect, an interior designer, a builder – or perhaps a carpenter or plumber – to help turn your dream project into a reality. But what about a structural engineer?
To many homeowners, this profession may be a bit of a mystery. Who is responsible for hiring this specialist – you or your architect? How much will it add to the cost, and do you need to consult one if you’re just knocking down a non-supporting wall? All these questions and more are answered by our panel of experts.
Professional advice from: Mark Goddard of Entuitive UK; Cat Hoad of Absolute Project Management; Ovi Constantinescu of MODEL Projects
To many homeowners, this profession may be a bit of a mystery. Who is responsible for hiring this specialist – you or your architect? How much will it add to the cost, and do you need to consult one if you’re just knocking down a non-supporting wall? All these questions and more are answered by our panel of experts.
Professional advice from: Mark Goddard of Entuitive UK; Cat Hoad of Absolute Project Management; Ovi Constantinescu of MODEL Projects
What does a structural engineer actually do?
Structural engineer Mark Goddard puts it in its simplest terms: “They’re the person responsible for making sure the building stands up. They design the load-bearing elements of the property, such as walls, columns, floors and foundations, to ensure all the building loads – people, furniture, floors, roof, wind and so on – are safely transmitted to the building foundations.
“They’ll also provide drawings, calculations and specifications on all projects where structural works are taking place,” he adds.
Structural engineer Mark Goddard puts it in its simplest terms: “They’re the person responsible for making sure the building stands up. They design the load-bearing elements of the property, such as walls, columns, floors and foundations, to ensure all the building loads – people, furniture, floors, roof, wind and so on – are safely transmitted to the building foundations.
“They’ll also provide drawings, calculations and specifications on all projects where structural works are taking place,” he adds.
How soon should a structural engineer be getting involved in your project?
“Right after the clients agree the final design,” technical designer Ovi Constantinescu says. “The drawings and calculations are required at the final stage before they’re submitted to Building Control and builders for tender.”
The engineer should make a site visit and conduct an analysis before starting work on the drawings and structural calculations. “He or she must check the soil conditions, existing foundations and, if possible, structural walls, and draw up sketches showing this,” Ovi says. “Based on the structural analysis, we – the architects – will keep as many of the existing elements of the house as possible. We try to avoid demolishing unnecessarily!”
“Right after the clients agree the final design,” technical designer Ovi Constantinescu says. “The drawings and calculations are required at the final stage before they’re submitted to Building Control and builders for tender.”
The engineer should make a site visit and conduct an analysis before starting work on the drawings and structural calculations. “He or she must check the soil conditions, existing foundations and, if possible, structural walls, and draw up sketches showing this,” Ovi says. “Based on the structural analysis, we – the architects – will keep as many of the existing elements of the house as possible. We try to avoid demolishing unnecessarily!”
Under what circumstances do homeowners typically contact a structural engineer?
“People who are looking to extend a property or want a structural survey to obtain a mortgage will often search online and approach us directly for our services,” Mark says.
Typically, though, it will be an architect or other design professional who will contact Mark’s firm. “Generally, we’re asked by an architect to develop a fee proposal on behalf of a client, but our contract will be with the client,” he says.
“The client can employ the engineer,” Ovi says. “However, communication is more efficient if the architect deals directly with the structural engineer, especially to resolve any issues and finalise the drawings.”
“People who are looking to extend a property or want a structural survey to obtain a mortgage will often search online and approach us directly for our services,” Mark says.
Typically, though, it will be an architect or other design professional who will contact Mark’s firm. “Generally, we’re asked by an architect to develop a fee proposal on behalf of a client, but our contract will be with the client,” he says.
“The client can employ the engineer,” Ovi says. “However, communication is more efficient if the architect deals directly with the structural engineer, especially to resolve any issues and finalise the drawings.”
What are some of the most common types of residential projects that require this expertise?
“[You need a structural engineer] any time the layout is being changed in such a way that the load-bearing arrangement of the building might change,” project manager Cat Hoad says.
“This is obvious if you are, for example, removing the back wall of a house to build an extension,” she says, “but you should also bear this in mind if you’re ‘opening up’ any walls to connect spaces or put in a new door or window.”
Search structural engineers in your area in the Houzz Professionals Directory.
“[You need a structural engineer] any time the layout is being changed in such a way that the load-bearing arrangement of the building might change,” project manager Cat Hoad says.
“This is obvious if you are, for example, removing the back wall of a house to build an extension,” she says, “but you should also bear this in mind if you’re ‘opening up’ any walls to connect spaces or put in a new door or window.”
Search structural engineers in your area in the Houzz Professionals Directory.
“Even if the wall doesn’t look as if it’s load-bearing, it’s definitely worth checking, especially in older houses that have been renovated in the past, as the structural arrangement might have changed from its original layout,” Cat says. “In one house, we were removing a built-in wardrobe from a loft conversion and discovered – in time, fortunately – that one of the ‘walls’ of the wardrobe was supporting one of the roof timbers!”
Ovi adds that engineers will also often be called upon to investigate the soundness of a structure before it’s exposed.
Ovi adds that engineers will also often be called upon to investigate the soundness of a structure before it’s exposed.
Which other occasions would call for a structural engineer?
“An engineer could be used to examine defects to the structure caused by trees, drainage, cracks, or geotechnical-related problems,” Ovi says. “Site visits from an engineer are also important where demolition is to take place.”
“An engineer could be used to examine defects to the structure caused by trees, drainage, cracks, or geotechnical-related problems,” Ovi says. “Site visits from an engineer are also important where demolition is to take place.”
How much do structural engineers cost?
Mark says that his firm would normally expect to charge around 1.5% to 2% of the construction cost, depending on how complex the work is.
Cat says that for residential renovations, structural engineers’ fees will be in the mid-thousands. “Maybe £3,000 to £9,000, depending on the work needed. It’d be less for a simple opening up of a structural wall.
This all then varies depending on the existing structure of the house and the extent to which you want any structural elements hidden. For example, if you’re happy to have a boxed-in ‘downstand’ beam, that’s usually cheaper than having the beam recessed into the ceiling void to achieve a flat, seamless ceiling between the two areas.”
“It’s very different from engineer to engineer,” Ovi notes. “Some charge extra for small updates and site visits.”
Mark says that his firm would normally expect to charge around 1.5% to 2% of the construction cost, depending on how complex the work is.
Cat says that for residential renovations, structural engineers’ fees will be in the mid-thousands. “Maybe £3,000 to £9,000, depending on the work needed. It’d be less for a simple opening up of a structural wall.
This all then varies depending on the existing structure of the house and the extent to which you want any structural elements hidden. For example, if you’re happy to have a boxed-in ‘downstand’ beam, that’s usually cheaper than having the beam recessed into the ceiling void to achieve a flat, seamless ceiling between the two areas.”
“It’s very different from engineer to engineer,” Ovi notes. “Some charge extra for small updates and site visits.”
Do remember that the structural design will then need to be implemented by the contractor and this can involve reasonably expensive materials – steels, concrete, and so on – and often quite a lot of labour time. “For example,” Cat says, “you’d need lots of person labour to lift and position beams in tight spaces, to dig and pour foundations, to do underpins in sequence or to negotiate around drains.”
Another cost (and time) element to factor into the structural part of your project is that you may also need a ‘temporary support specialist’ as well as a structural engineer.
Cat explains: “They design – as the name suggests – the way in which the building is held up temporarily between you knocking down the wall holding up the floor above and sticking in the beam. It doesn’t stay up by itself… Structural engineers may not deal with that, especially for a minor job. It’s not usually a huge cost, but it’s one that’s often overlooked until later than is ideal.”
Finally, she adds, the extent of the structural work will affect whether you need to go through the Party Wall Act procedure, which creates additional steps, time and cost. If you aren’t able to spare the time or budget for this stage, you’ll need to let your structural engineer know, so she or he can – if possible – work out the design without it affecting any party walls or adjacent foundations.
Another cost (and time) element to factor into the structural part of your project is that you may also need a ‘temporary support specialist’ as well as a structural engineer.
Cat explains: “They design – as the name suggests – the way in which the building is held up temporarily between you knocking down the wall holding up the floor above and sticking in the beam. It doesn’t stay up by itself… Structural engineers may not deal with that, especially for a minor job. It’s not usually a huge cost, but it’s one that’s often overlooked until later than is ideal.”
Finally, she adds, the extent of the structural work will affect whether you need to go through the Party Wall Act procedure, which creates additional steps, time and cost. If you aren’t able to spare the time or budget for this stage, you’ll need to let your structural engineer know, so she or he can – if possible – work out the design without it affecting any party walls or adjacent foundations.
The house down the road didn’t need all the support our engineer has specified – do we really need it?
“Occasionally, clients will talk to a ‘helpful’ neighbour who says, ‘When we did our extension, we didn’t need [a beam of that size/ a new foundation/ to underpin next door] – or whatever it is that the structural engineer has recommended,” Cat says.
“While it’s possible that some engineers over-specify,” she says, “it’s much more likely that the arrangement of this particular house is different from your helpful neighbour’s place, or that you are doing a slightly different bit of work, or that the Building Regulations have changed since the neighbour did their work.”
“Occasionally, clients will talk to a ‘helpful’ neighbour who says, ‘When we did our extension, we didn’t need [a beam of that size/ a new foundation/ to underpin next door] – or whatever it is that the structural engineer has recommended,” Cat says.
“While it’s possible that some engineers over-specify,” she says, “it’s much more likely that the arrangement of this particular house is different from your helpful neighbour’s place, or that you are doing a slightly different bit of work, or that the Building Regulations have changed since the neighbour did their work.”
What’s the link between what a structural engineer does and Building Regulations?
“Our calculations and drawings will be submitted to Building Control and checked to ensure they comply with Part A of the Building Regulations,” Mark says.
Cat adds: “Even if you’re sure the wall you’re moving isn’t load-bearing, if the work has to be certified as compliant with Building Regulations, the Building Control officer might need a structural engineer’s report and calculations proving that isn’t the case. You – or your interior designer/project manager – can check this with Building Control.”
“Our calculations and drawings will be submitted to Building Control and checked to ensure they comply with Part A of the Building Regulations,” Mark says.
Cat adds: “Even if you’re sure the wall you’re moving isn’t load-bearing, if the work has to be certified as compliant with Building Regulations, the Building Control officer might need a structural engineer’s report and calculations proving that isn’t the case. You – or your interior designer/project manager – can check this with Building Control.”
How is a structural engineer’s work relevant for Planning Permission?
Usually, in a domestic renovation setting, you won’t need structural drawings upfront to obtain conditional Planning Permission.
“However, it’s a good idea to run the plans past a structural engineer for at least a sense check that the structure is going to be straightforward – or within your budget,” Cat says.
A worst-case scenario is that you could get Planning Permission for your project, then consult a structural engineer later, only to have to apply to change the plans, eating into your budget and schedule.
Usually, in a domestic renovation setting, you won’t need structural drawings upfront to obtain conditional Planning Permission.
“However, it’s a good idea to run the plans past a structural engineer for at least a sense check that the structure is going to be straightforward – or within your budget,” Cat says.
A worst-case scenario is that you could get Planning Permission for your project, then consult a structural engineer later, only to have to apply to change the plans, eating into your budget and schedule.
What should a homeowner look for in a structural engineering company?
“The company should have a number of chartered structural engineers within the practice and have a minimum professional indemnity insurance of £1 million,” Mark says. “Good experience of working with older buildings and the challenges of extending and modifying existing buildings is critical.”
Tell us…
What projects are you planning that might require the expertise of a structural engineer? Or have you used one in the past? Share your stories in the Comments.
“The company should have a number of chartered structural engineers within the practice and have a minimum professional indemnity insurance of £1 million,” Mark says. “Good experience of working with older buildings and the challenges of extending and modifying existing buildings is critical.”
Tell us…
What projects are you planning that might require the expertise of a structural engineer? Or have you used one in the past? Share your stories in the Comments.
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Michael Lowe Garden Designs - indeed - excellent points! Personally, though, thanks to what I've learned about our crashing biodiversity, and how much biodiversity dwells in back gardens, I no longer approve of building in gardens - other than reconstruct a shed, or maybe install a little greenhouse!
Kate Burt - brilliant - yes, I found it! Thank you so much for taking the time to do that. Hugely appreciated. And it seals Houzz's place as my long-time favourite website ever. I'm not even joking. :) Not only is it a friendly, generous, helpful place, with inspirational ideas, but the web design is (usually) smooth and elegant,.
Is it common practice for structural engineers not to visit a property and just provide their calculations from a drawing? This happened to someone I know and he still charged a small fortune (he was arranged by the architect). Seems risky, the drawings were very basic