Homeowner planning guide
Structural Alterations in Older Residential Buildings
Why opening up a period house needs more care than a modern one, and how the work should be sequenced.
Structural alterations in older buildings, such as removing walls, forming large openings or adding storeys, depend on understanding how the existing building carries its loads. In older houses that's often less obvious than the drawings suggest.
Why older buildings are different
Pre-war houses commonly have solid masonry walls, lime mortars, timber lintels, shallow foundations and, in parts of Sussex, materials such as bungaroosh or flint. Internal walls that look like partitions may carry floors or roofs. Previous alterations may have changed the load paths without being recorded.
The engineer's role
A structural engineer designs the beams, columns, bearings and any foundation work, and specifies temporary support during construction. The design should reflect the actual wall construction. That sometimes means opening up selected areas before the design is finalised.
Opening-up and contingency
Until plaster and floors come off, some conditions can't be confirmed. Agree in advance how findings will be reported to the engineer and how any changes will be priced.
Temporary works
Removing support from a loaded wall requires temporary propping to a planned sequence. This is part of the engineered work, not an improvisation on the day.
Approvals
Structural alterations need Building Regulations approval. Work to party walls may need notice under the Party Wall etc. Act 1996. In listed buildings, structural alterations will usually need listed building consent.
Next step
If you're planning structural alterations as part of a larger project, discuss your project with us.
How older houses carry loads
Structural alterations to old houses need care because these buildings often work differently from modern ones. Floors may bear on internal walls that look like partitions. Chimney breasts carry stacks above. Lintels may be timber. Foundations may be shallow brick footings on clay or chalk. Walls may be solid brick, flint or bungaroosh rather than cavity construction.
Removing walls in a period property
Before removing walls in a period property, establish:
- What the wall supports: floors, other walls, chimneys or the roof.
- What the new beam will bear on, and whether that masonry is strong enough.
- Whether the wall contains historic features or, in a listed building, needs consent.
- How the floors either side will be levelled and joined.
The engineer will design the beam and padstones; the contractor should open up the bearing points before the steel is ordered, so the design reflects what is actually there.
Common structural changes in older buildings
- Opening up the rear of the house for a kitchen extension.
- Removing chimney breasts, which needs the stack above to be supported or removed.
- Forming new door openings in solid walls.
- Strengthening timber floors for new bathrooms or heavy finishes.
- Repairing or replacing failed timber lintels and decayed joist ends.
Moisture and structure are linked
In older buildings, structural problems are often caused by moisture: leaking gutters rotting joist ends, raised ground levels saturating wall bases, or cement render trapping water in soft masonry. Structural changes to older buildings should include fixing these causes, otherwise the repair will fail again.
Temporary works and sequence
Props, needles and staged removal protect the building while loads are transferred. Rushing this stage is the most common cause of cracking in rooms above. A careful contractor will monitor existing cracks before, during and after the work.
How can you tell whether a wall is load-bearing?
There is no reliable way to tell from the surface, and tapping a wall proves nothing. These are the clues an engineer looks for:
- Floor joists. Joists normally span the shorter distance across a room and rest on the walls at each end. Lifting a floorboard upstairs shows which way they run and which walls they sit on.
- What is above. A wall with another wall directly over it, or one under the point where roof timbers land, is probably carrying load.
- Position. In a typical terraced house the wall between the front and back rooms, known as the spine wall, supports the floors and often part of the roof.
- Construction. Solid brick is more likely to be structural than timber studwork, but in older houses timber partitions sometimes carry floors, and some are braced frames that stiffen the building.
In Brighton and Hove, internal walls may be bungaroosh or timber frame with brick infill, and neither behaves like modern masonry. Treat every wall as load-bearing until an engineer has confirmed otherwise.
Lintels, beams and padstones
A lintel spans a door or window opening. A beam spans a wider opening and carries more load, and in domestic work it is usually steel. A padstone is a block of dense concrete or engineering brick under each end of the beam, which spreads the load into the wall so the masonry beneath is not crushed.
The beam itself is rarely where things go wrong. Problems come from what it rests on: soft old brickwork, a pier that is too narrow, or a foundation that was never meant to take a concentrated load. This is why the engineer may ask for trial holes at the base of the wall before finishing the design. Sometimes the answer is a steel post on a new concrete pad instead of bearing onto the old wall at all.
Do structural alterations need approval?
Yes. Removing or altering a load-bearing wall, forming or widening an opening, removing a chimney breast and altering roof or floor structure are all controlled under the Building Regulations. Building Control will want the engineer's calculations and will inspect the beam and its bearings before they are covered.
If the work affects a wall shared with a neighbour, including cutting into it to seat a beam, the Party Wall etc. Act 1996 requires written notice, normally two months before work starts. In a listed building, structural alteration also needs listed building consent, inside as well as out.
Record the building before work starts
Older houses nearly always have some cracks. Before structural work begins, a schedule of condition should be prepared: dated photographs and notes of existing cracks, uneven floors and sticking doors in your house and, where a party wall is involved, next door.
It protects everyone. If a crack appears during the work it can be dealt with promptly, and if a neighbour reports one that was already there, the record shows it. On more sensitive buildings, simple gauges fixed across existing cracks show whether anything moves while loads are being transferred.
Fire protection for new steel
Steel loses strength quickly in a fire, so a beam supporting a floor in a house normally needs at least 30 minutes' fire resistance. This is usually achieved by encasing it in fire-rated plasterboard or coating it with intumescent paint. It is a small item that is easy to overlook, and Building Control will check it.
What to ask the engineer
- Have you seen the building, or are you working from drawings alone?
- What have you assumed about the walls and foundations, and how will that be checked?
- Is opening-up needed before the design is final?
- Will you design the temporary support, or is that left to the contractor?
- Will you inspect the work on site?
An engineer who has visited, asked for investigation and set out a sequence of work will produce a design that needs far fewer changes once the wall is open.