Structural alterations, new openings and steel support in Marylebone. Trusted, professional, 30+ years' hands-on experience.
From new openings to replacement joists and supported structures, GS Renovation carries out structural alterations across Marylebone's mansion blocks and period flats in W1. Three decades of Westminster experience mean we design the right fix, prop and pour it safely, and see it through building control while your neighbours in the block carry on undisturbed.

Marylebone's purpose-built flats were laid out for a different era of living, so alterations here range from forming a new opening between rooms to replacing tired timber joists and creating supported openings where a section of wall must go. In the older mansion blocks, floor structures can sag or bounce after a century of use, and replacement joists or strengthening are common alongside any layout change our clients ask for.
Every one of these jobs starts with a structural engineer sizing the beam or joists for the actual loads involved. Steel bears onto padstones, temporary props take the weight while we work, and demolition is staged so nothing is ever left unsupported. Underpinning is rarely needed in an upper-floor W1 flat, but where a ground-floor or lower-ground home shows movement, we can design and carry that out too, all under building control.
Internal structural alterations are governed by the Building Regulations, not planning permission, and Westminster City Council's building control inspects and certifies the work. Planning only enters the picture if your flat is in a conservation area or listed building and you alter the exterior, which is common in parts of Marylebone. Inside your own flat, the real gatekeeper is usually the freeholder, whose licence to alter must be granted before a beam is installed.
We manage that whole chain for you. The engineer's calculations go to the managing agent for the licence to alter, the same drawings satisfy building control, and we plan the works around the block's rules on working hours and access. Because so many Marylebone flats sit above or beside occupied homes near Oxford Street and the West End, we prop carefully and keep the site tidy so the building keeps running normally.
For structural alterations in Marylebone, GS Renovation gives you a single accountable team from survey to sign-off. Our engineer sizes every beam and joist, we secure the freeholder's licence to alter and building-control certification, and we work cleanly around your block's rules. Thirty years-plus in W1 mean the props go in right and nothing is left to chance.
Punctual, worked hard, and did exactly what he was asked and what he said he would do. Overall, a very high quality job. Will use again.
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
Really happy with the quality of remedial works carried out by George in putting other previous tradesman work right. He was very helpful, honest and…
FAQ
The method is deliberately dull: measure, scope, itemise. Nothing about structural alterations are quoted over the phone for a Marylebone home, because a blind figure is a figure that changes later. We look at the W1 property, allow for its red-brick mansion-block construction, and issue a written quotation. GS Renovation works that way throughout Westminster and it is why the figures hold. Email info@gsrenovationltd.co.uk with the W1 address and we will arrange a free survey. As a rough guide, structural alterations in London ranges from roughly £1,500 for a simple opening to £15,000 or more where underpinning or major works are involved (indicative London ranges, MyBuilder and Checkatrade, 2026). Your figure depends on the size, specification and condition of the property, which is why we survey before quoting.
Yes, modestly, and the time is worth spending. Working around original features in a Marylebone home means structural alterations proceeds carefully rather than quickly, particularly near cornice, sash windows and original floors at a W1 property. GS Renovation agrees with you beforehand what is being kept. The Westminster City Council inspections are booked around that sequence so nothing waits. Ring 07472 424 226 and GS Renovation will describe how a W1 property in Marylebone is protected during the work.
Because it is inspected and certified, not simply declared finished. Westminster City Council inspects the structural stages of structural alterations at your W1 property before anything is concealed, and the completion certificate is handed to you at the end. GS Renovation also appoints the structural engineer where the design requires one. That paperwork is what a buyer's solicitor asks for when a Marylebone home is sold anywhere in Westminster. The Westminster certificate arrives with the W1 handover pack.
The structural engineer. GS Renovation is a contractor: we appoint and coordinate the engineer, arrange the temporary works, and build to their design at your Marylebone address. We do not produce calculations ourselves, and any builder claiming to is worth questioning.
Usually earlier alterations that were never done properly. Structural alterations at a W1 property of that age regularly uncovers removed structure, notched joists or wiring that predates any certificate, and each is costed and agreed before we continue. GS Renovation names the likely candidates at the Marylebone survey. Westminster City Council is notified where a change affects approved work. Ask on 07472 424 226 what structural alterations commonly uncovers at a W1 address of that sort of age.
Usually no. Internal structural work is controlled by the Building Regulations, so Westminster building control certifies it rather than the planning department. Planning only applies if you change the exterior of a listed building or a home in a conservation area, which covers much of Marylebone. Inside the flat, your freeholder's licence to alter is normally the approval that matters most, and we arrange both.
Never for a Marylebone address. Charging for travel would make the structural alterations figure depend on where our van started rather than on your W1 property, which is not how GS Renovation prices anything. Distance only matters well beyond Mayfair, and we would say so upfront. Call 07472 424 226 for a no-obligation quotation. The survey across Westminster is free in every case. Two similar homes across Westminster would receive comparable figures either way.
Every Service, One Team
The same trusted team, 30+ years' hands-on experience and free, no-obligation quotes apply to every GS Renovation service in Marylebone. Explore what else we do locally:
Same Service, Nearby Areas
We carry out structural alterations across Marylebone and the surrounding areas. Explore a nearby location:
Free, no-obligation quote for structural alterations in Marylebone. Rated 4.9 from 31 reviews on MyBuilder, fully insured, and building control handled for you.