Structural Integrity: Walls, Foundations, and Floors

When you build upwards by adding extra levels, you're placing a substantial new burden on your home's current structure. You absolutely must evaluate and potentially strengthen existing parts, ensuring that any new components are sufficiently supported.

How Your Current Walls and Foundations Handle the Load

• Load-Bearing Walls: When you extend upwards, you need to think carefully about how the extra weight will be held up. If you plan for new floor joists (the horizontal timbers that support the floor) to sit on a wall you already have, that wall needs to run all the way down through the property to the foundation. Alternatively, it must have strong intermediate support somewhere in between.

• Existing Openings: Imagine your ground floor has 'through lounges' (open-plan spaces) where a wall that used to bear weight has been taken out, or if there's already a beam supporting an opening. You need to inspect this existing beam. It must be robust enough to handle the extra weight from your new upper level.

• Foundations: You need to verify if your home's current foundations can withstand the additional weight from these new levels. It might be necessary to reinforce them by a process called underpinning (adding extra support beneath the existing foundations). For expert guidance, consult a structural engineer or your local building control body.

Building Your New Floors and Walls

• Floors and Beams: Your new floor must be capable of holding up everything inside the room – furniture, people, and the floor's own construction. It's improbable that your current ceiling joists will be strong enough for this increased burden. Because of this, you will need to install new, typically larger, floor joists. You can usually fit these new joists in between your existing ceiling joists. If your current walls possess sufficient strength, they might be able to support these new floor joists. Otherwise, you'll have to incorporate extra support, like steel or timber beams. These beams must also be properly supported themselves and designed to resist fire.

• New Walls: Any new walls you construct to divide rooms from other parts of your home might need to both carry weight (be load-bearing) and offer fire resistance.

Keeping Noise Down: Sound Insulation Requirements

You must include sound insulation between any habitable rooms (those designed for living in). If you live in a terraced or semi-detached property, your local building control body might also insist on better sound insulation between your new upper level and your neighbour's loft space. They could ask for a sound test, which depends on whether your neighbour grants access. You will also need to upgrade the shared party wall to ensure proper sound insulation between your home and your neighbour's.