Structural Engineering for Renovations vs New Builds : What You Need to Know

Key Differences Between Renovations and New Builds

• you're not always 100% sure what you're dealing with in an old building versus having clear design targets from day one in a new build

• working out how to put temporary supports in place and how the construction process is going to go down

• how you interact with the existing materials and the history of the building - not always easy to figure out

• the fact that you can't always get in and out of an old building without causing a mess and disrupting things

• different approval and documentation requirements, depending on whether you're working on an old or new building

• a much higher risk that there might be hidden problems lurking in an old building

• you often have to rely on surveys to get a sense of what's going on

Structural Engineering for Renovations

Renovation projects are all about working with an existing structure, so what you usually have to do is take a look at the building and figure out what's going on. Typically this involves looking at things like the type of construction used, the way loads are passed through the building and any signs that the building might be moving. And when you're dealing with an old building, structural engineering is more about adapting what you've got rather than creating something brand new. That's why you've got to clearly state your assumptions and have a good system in place for reviewing them as you go along - because if you don't, it's a recipe for disaster.

Structural Engineering for New Builds

New build projects are a completely different ball game - you've got a clear idea of what you want to achieve and you can start designing the structural scheme from scratch. Engineers will work out what loads the building is going to be exposed to, what the layout is going to be and what kind of performance you need to get out of the building. It's true that there's still some uncertainty involved, but it usually comes down to things like the state of the ground conditions. That makes it a lot easier to design because you can usually get a pretty good handle on things as long as you do your investigations in a timely and proportionate way.

Information and Surveys

The quality of information you have available really changes the way you approach things in both renovation and new build projects. When you're working on an old building, you often have to rely on drawings that turn out to be out of date. Building surveys and measured surveys can really help fill in the gaps and give you a better idea of what's going on. When you're working on a new build, things like site investigations can make all the difference in terms of designing a good foundation and understanding the state of the ground.

Structural Calculations and Deliverables

Renovation projects often mean doing targeted structural calculations to justify specific changes to the building. New builds, on the other hand, require comprehensive calculations that cover the whole structural system. Just how detailed things get really depends on the complexity and risk of the project rather than how big or small it is.

Common Risks and How to Reduce Them

1. get those surveys done early on so you can get a better handle on things

2. stage your design process to match the info you have available

3. be open and clear about your assumptions and review them regularly

4. plan how you're going to put temporary supports in place and how you're going to sequence the construction process

5. make sure your structural engineers are working hand in hand with other disciplines

6. always allow for the possibility that there might be unknowns that you don't know about yet

Budget and Programme Impacts

Renovation projects are often the ones that are going to be hit with cost variations because of all the unknowns, while new builds are a bit more predictable but can still be hit with delays and cost overruns if you hit problems with the ground or get hit with late design changes.