Joists running into a wall are the strongest clue it is load-bearing — but only calculations settle it.
The wall is replaced by a steel beam on padstones, sized by a structural engineer, with the ceiling propped before anything is cut.
This is building work. Full plans gets a decision in 5 weeks; a building notice lets you start 2 days after submitting.
The document that matters afterwards is the completion certificate — usually within 8 weeks of finishing.
Beam bearing into a shared wall? That is two months' notice to your neighbour, and it is the longest lead time on the job.
Taking a wall out is the single most transformative thing you can do to a Cardiff terrace, and the
single easiest to get wrong. The work itself is a day or two. Everything that makes it safe and legal
happens before anyone picks up a hammer, and it is worth understanding because it is also where the
cost and the programme actually live.
First question: is it holding anything up?
Homeowners usually arrive certain the wall is “just a partition”. Sometimes it is. The
tell-tales that say otherwise are simple enough to check yourself before we come out, and they stack
up rather than stand alone.
The one that catches people out: a wall that looks like a partition downstairs but carries a wall or a bath above it. We check the floor above before we say anything about the wall below.
What replaces the wall
A steel beam, sized by a structural engineer for your actual spans and loads, sitting on
padstones — solid pads that spread the point load into the masonry either side.
The padstones are not an afterthought; they are the reason the beam does not punch through the wall it
lands on. Undersized bearings are one of the commonest defects found later.
Before any of it, the floor above is propped — Acrow props and strongboys taking
the load off the wall so it can be removed in a controlled way. The props stay until the beam is in,
the padstones have gained strength and the load has been transferred deliberately rather than by
gravity and hope.
Where the beam lands is a design decision, not a site decision. On a terrace the ends usually sit in the party walls, which brings the neighbour into it — see below.
The approvals, and what each one costs you in time
Internal alterations rarely need planning permission — the exceptions being listed
buildings, where listed building consent is required whatever the wall is made of, and flats. What
they always need is Building Regulations approval, because structure is exactly what
the regulations exist to control.
There are two ways in, and they behave very differently:
For a single structural opening a building notice is often perfectly reasonable. For anything with several openings, or where the calculations are finely balanced, full plans is the safer route because the argument happens on paper rather than on site.
The neighbour, and the two months
On a terrace or a semi the new beam usually bears into a party wall, and cutting into a party structure
is notifiable under section 2 of the Party Wall etc. Act 1996. You must serve written
notice on the affected neighbour at least two months before that part of the work
starts. It is separate from planning and separate from building regulations, and on a mid-terrace there
may be two neighbours to notify.
In practice this is the longest lead time on the whole job. Serve it while the drawings and
calculations are still being finished and it costs you nothing; leave it until the scaffold is booked
and it costs you two months. Our
planning and building regs page covers
the same notice from the loft conversion angle.
Open plan, and the staircase problem
Knocking a hallway into a through room is where a structural job turns into a fire safety job. Once the
staircase opens directly into a room rather than a protected hall, the escape route changes character,
and building control will want that dealt with — typically through alarm provision and, depending
on the layout, a protected route to a final exit.
It is entirely doable and thousands of Cardiff houses have done it. What it is not is free, and it is
not something to discover after the wall is down. If the hallway is part of your plan, say so at the
first visit so it is priced and designed rather than improvised.
What goes wrong
No calculations. A beam sized by eye is a beam sized by luck, and it is invisible once it is plastered.
Undersized padstones. The beam is fine; the masonry under its ends is not.
Props struck too early. Cracked ceilings above, and doors that stop closing upstairs.
No completion certificate. The work was fine. The paperwork was never closed out, and it surfaces during a sale years later.
The party wall notice nobody served. Cheap to do, expensive to have skipped.
Sources. Application routes, timescales and completion certificates from gov.uk,
“Building regulations approval: how to apply”, which covers England and Wales; party wall
notice periods from the Party Wall etc. Act 1996. Beam sizing, padstones and propping are described as
we build them, and every one of them is settled by a structural engineer's calculations for your
specific house rather than by anything on this page.
A short site visit tells us whether the wall is structural, where a beam could land and what the opening does to the room above — which is most of what decides the design and the price.
