Make your floor, roof or wall strong enough for what you plan to add
For owners planning heavier finishes, a bathroom upstairs, storage, a loft room or a change of use. Describe what you want to add and compare quotes from structural engineers who check and strengthen what is there.
Existing floors, roofs and walls were designed for the loads of their time. You may now want to add something heavier: a stone floor, a bath, a home gym, shelves of books or a heavier roof covering such as stone slates or clay tiles. You may be adding a room or changing how the building is used. In each case the structure may need strengthening. The engineer first works out what the structure can carry and what you want it to carry. They then design the smallest practical upgrade: doubling or deepening joists, adding steel plates or beams, stiffening a roof frame or supporting a wall. The aim is a result that works and that building control can approve.
How a professional can help
- Working out what is there: They identify joist sizes, spans, wall types and roof framing, with some opening up where needed, then calculate what the existing structure can carry safely before any design starts.
- Floors for heavier loads: For a new bath, stone flooring, storage, a gym or a piano, they check the floor for strength and sag. They design extra joists, steel plates or new beams where it falls short.
- Roofs for heavier coverings: If you want stone slates or clay tiles in place of a lighter covering, they check the rafters, the main roof beams and the points where they rest on the walls. They design strengthening where the roof needs it.
- Walls taking new loads: Where a wall must carry a new beam, floor or roof load, they check the brickwork or blockwork and the foundations beneath. They design padstones (solid blocks that spread a beam’s load), piers or local thickening.
- Changing a building’s use: When a barn, store or office becomes a home, floor loads and requirements change. They assess what the new use needs from the structure and identify which floors and walls need upgrading.
- Detailing the work so it can be built: They show builders how to fit the strengthening with the least disruption to ceilings and finishes, including temporary support and the order of work.
Is this right for you?
- You want a heavy finish, such as stone flooring, or a bath or hot tub on a floor that wasn’t designed for it.
- You are changing a roof covering to something heavier and want to know whether the roof timbers can take it.
- Your building is changing use, for example from storage or office to a home, and the floors need checking.
- A survey or building control has queried the capacity of a floor or roof and you need a design to put it right.
How the project usually runs
- Brief and survey: The engineer asks what you want to add and where, then inspects the building and records spans, sizes, supports and the condition of the floor, roof or wall.
- Assess existing capacity: They calculate what the existing structure can carry and compare it with the new loads, showing where it works as it is and where it falls short.
- Strengthening options: Alternatives are set out, such as extra joists, steel plates, new beams, posts or lighter finishes, with what each means for headroom, disruption and programme.
- Design and approvals: Calculations and drawings go to building control where approval is needed, along with details of temporary support and the sequence of work.
- Work on site: Strengthening is installed by your builder, and the engineer can check it before it is covered, particularly steelwork and its supports.
What affects the cost
- How far the new loads exceed what the existing structure can carry.
- The type of strengthening: adding timber alongside joists is usually less work than inserting steel beams and supports.
- How much finishes, ceilings and flooring must be removed and replaced to reach the structure.
- Temporary support needed while the strengthening goes in.
- How well the existing structure is known, and how much opening up is needed to confirm it.
- Whether the change needs other upgrades, such as fire, sound or insulation, for a new use.
Building control and consents
- Strengthening a floor, roof or wall is often controlled structural work, so Building Regulations approval, or a building warrant in Scotland, may be needed. Building control expects calculations and drawings.
- Changing a building’s use can need planning permission as well as Building Regulations approval, and the rules vary across England, Scotland, Wales and Northern Ireland.
- Listed buildings and conservation areas may need consent for strengthening that changes historic fabric. Structural engineers cover the whole UK.
- In England and Wales, strengthening that involves cutting into a shared wall may bring in the Party Wall etc. Act 1996.
Questions people ask
Will my floor take a freestanding bath or a stone floor?
It depends on the joist size, spacing, span and condition, and on how the load is spread. Some floors can take it as they are, and others need strengthening first. An engineer can check from a visit and calculations, and design extra joists or beams if needed. Weights vary, so tell them the actual product you have in mind.
Can strengthening be done without taking down ceilings?
Sometimes. Where the floor above can be lifted, new timbers or plates can often be fitted from above. Otherwise the ceilings below may need to come down. The engineer can design the strengthening with access in mind and talk through the options with your builder to keep the disruption down.
What if the existing structure turns out to be different from what was assumed?
It happens, especially in older buildings. A good engineer builds in checks, such as a few exploratory openings, and visits once the builder has exposed the structure. If something is different, they review it and issue an updated design. Having the design in writing and the engineer on call reduces delay.
Does a heavier roof covering mean strengthening the roof?
Not always, but stone slates or clay tiles can add substantial weight compared with a lighter covering, and in older roofs the timbers or walls may not cope. An engineer checks the rafters, main roof beams and supports, and says whether strengthening is needed. Tell them the actual covering you plan to use, because weights vary between products.
Is strengthening worth it, or should I rebuild?
It depends on the condition of the structure and what you want it to do. Strengthening is usually less disruptive and keeps more of the building, but if the structure is badly decayed or the new demands are large, replacing it may be simpler. An engineer can compare the options before you commit.
Available across the UK
Professionals cover the whole of the UK: England, Scotland, Wales and Northern Ireland. Planning and Building Regulations differ between the four nations, and your professional will work to the rules that apply where your property is.
- Get free quotes
- Floor Joist Design and Strengthening
- Floor Loading Assessments (Hot Tubs, Gyms, Heavy Equipment)
- Timber Floor and Roof Repair Design
- Building Regulations Drawings
- Concrete Repair and Reinforcement Corrosion
- Period Property and Conservation Structural Repairs
- Subsidence Repair Design
- Wall Stitching and Crack Repair Design
- Wall Tie Failure and Bulging Wall Repair Design
- All services
- Find your area