Load-bearing wall removal is the point in most renovation projects where the character of the house genuinely changes, and it is also the point where things can go wrong in ways that are much harder to fix than a poorly-installed kitchen. Opening up a downstairs, removing a chimney breast, cutting a doorway through a supporting wall – each of these involves calculations and craftsmanship that homeowners cannot easily verify by eye. Understanding what proper Structural work and knock-throughs work looks like helps enormously with knowing whether the work being done to your house is being done properly.
Every structural change needs the sign-off of a structural engineer before it happens. That is not optional and it is not a formality. The engineer calculates the loads travelling through the wall or beam – dead loads from the structure above, live loads from occupancy, wind and snow – and specifies the beam, padstones and connections needed to take over what the wall was doing. A quote for structural work that does not include an engineer’s calculation is not a proper quote. The cost of a structural engineer’s visit and calculation is a few hundred pounds and it is money well spent.
The specification the engineer produces tells the builder exactly what steel to fit, what size, what grade, what padstones to sit it on, and what connections to make at each end. A typical downstairs opening involves a rolled steel joist – a common size for domestic use is around 152 by 152 by 30 UC, or something in that family – sitting on padstones at each end. The padstones spread the load from the concentrated end of the beam over a larger area of masonry, and without them, the wall below can crush.
Temporary support while the wall comes out is the phase where an inexperienced builder is at their most dangerous. The load carried by the wall has to go somewhere while the beam is being fitted, and that somewhere is a series of acrow props sitting on load-spreading needles or plates. If the propping is wrong – too few props, propping too close to the wall being removed, no load-spreading beneath the props – the ceiling above can crack, the floor above can sag, or in the worst case the structure above can begin to fail. A competent builder plans the propping before touching the wall and often takes photos of the propping arrangement for their own records.
The Building Control inspector needs to see the work at specific stages. The engineer’s calculations go in with the Building Regulations application before work starts. The inspector visits when the beam is in position but not yet enclosed, to verify it is the correct beam, sitting on the correct padstones, with the correct bearings. Once approved, the beam can be encased in plasterboard or otherwise concealed. Any builder who wants to enclose the beam before the inspector has seen it is asking you to accept a work that has not been signed off, and that is a problem that surfaces later when the house is sold and no completion certificate exists.
Once the structural work is complete, the finish work makes the difference between a room that looks intentional and one that looks like a wall was knocked out. Beam encasement, alignment of the ceiling either side, choice of down-stand or flush finish, treatment of the ends where the beam meets the outside walls – all of these are small decisions that shape the look of the final room. A good builder will discuss the options before boarding over the steel, not present you with a fait accompli.
Structural work is not something to try to save money on. The engineer’s fee, the correct steel, proper padstones and competent propping are all essential, and the difference between doing them right and doing them cheaply is much smaller than most homeowners assume. Any building company in Bournemouth worth using will do the job to the engineer’s specification without shortcuts. Those are the only ones worth hiring for work of this kind.