Rear extension steels · Welwyn Garden City
Rear extension steels in Welwyn Garden City
Rear extension steels for homes in AL6, AL7, AL8, designed by a structural engineer.
- Survey, design and installation in one
- Covering AL6, AL7, AL8
- Inspected before it is covered
- Free survey visit
- Engineer's calculations arranged
- Building control handled
- Fixed written price once scope is agreed
- England, Wales, mainland Scotland & NI
Planning rear extension steels in Welwyn Garden City
If you live in Welwyn Garden City, rear extension steels can usually be planned and priced after a single survey visit. It sits about 10.5 miles from Luton, which we also cover. We cover AL6, AL7, AL8 and AL10, and we fix the price in writing once the layout and scope are agreed.
We work alongside your builder or as the steel package within the wider build. We arrange the engineer's design, coordinate building control, prop and open the rear wall at the right stage of the programme, and fit and pack the steels so the extension can be finished around them.
What to expect
- When bi-fold or sliding doors sit directly beneath the new steel, the beam has to stay stiff enough not to bind the door panels. The engineer sets a tighter deflection limit, which can mean a deeper or heavier section than strength alone would need.
- The opening is usually formed once the extension walls and roof are up, so the house stays secure and dry. Leaving it too late can hold up plastering and floor screeding, so the steel date is agreed with the builder early on.
- Columns carry concentrated loads, so each normally sits on a pad foundation designed by the engineer. Digging these inside an existing kitchen or through a solid concrete floor takes planning, especially where drains run close to the back wall.
- In older houses the rear wall may be solid brick in lime mortar, with timber lintels and shallow footings beneath. The engineer may ask for trial holes to see what the wall stands on before deciding where the steel will bear.
- Two-storey rear extensions add a second level of loads to think about. Steels at first-floor level may carry the existing rear wall of the bedrooms or tie the new roof into the old one, so the engineer looks at both floors together.
Four stages, one team
Free visit
A short visit to Welwyn Garden City to see the job, agree what you want and check the bearings, floors and services that affect the design.
Calculations
The engineer's calculations and a simple drawing are prepared for your opening and shared with you before anything is ordered.
Building control
We submit a building notice or full plans application to the local council's building control team, so approval is in place before the wall is touched.
Steel in, made good
On site we prop, open up, fit and pack the steel, then fire protect, box in and plaster once the inspection is done.
What do rear extension steels cost in Welwyn Garden City?
As a guide, budget £2,650–£7,400 including VAT for opening into a rear extension in Welwyn Garden City, based on published UK cost guides adjusted for prices in the East of England (+6%).
| Job | Typical guide range | What it usually covers |
|---|---|---|
| Opening into a rear extension | £2,650–£7,400 | Original rear wall removed with a beam or goalpost, approvals and propping, coordinated with the extension build |
| Steel column or post | £530–£1,590 per column | Column supplied and fitted with base and cap plates on a pad foundation |
| Side return extension steelwork | £3,700–£9,000 | Beams and posts along the old side wall line, propping and approvals (extension build extra) |
| Structural calculations for a beam | £260–£800 | Site measure or photos, beam and padstone design and calculations for building control |
Figures include our approximate regional adjustment for prices in the East of England (+6%) and are rounded. How these figures are worked out.
Building rules for Welwyn Garden City
In England, taking out a load-bearing wall or putting in a beam is building work under the Building Regulations 2010. It needs approval from building control, either the local council's building control team or a registered building control approver, through a full plans application or a building notice. Part A covers the structure and Part B covers fire safety, which is why steel in homes is usually fire protected.
If the beam bears into a wall you share with a neighbour, the Party Wall etc. Act 1996 applies, and a party structure notice must be served at least two months before that work starts. We arrange this through a party wall surveyor.
Rear extension steels in Welwyn Garden City: your questions
Can I stay at home while the work is done in Welwyn Garden City?
Usually, yes. The work area is screened and floors are protected. The rooms either side of the opening are out of action for a few days, and there is some noise and dust while the masonry comes out.
What happens at the survey visit in Welwyn Garden City?
We look at the wall, the floor and ceiling either side and what sits above, measure the opening you want, and note cables, pipes and access for the steel. It usually takes under an hour and there is no charge.
Who designs the steels for a rear extension?
A structural engineer. Your architect's drawings show the layout, but the engineer calculates the beams, columns, connections and foundations. We arrange those calculations, or work from an engineer's design you already have, and make sure the details suit the builder's programme.
Do I need a steel beam for my rear extension?
If the original back wall is being opened up into the extension, almost certainly yes. That wall normally carries the first floor and the wall above, so a beam, columns or a goalpost frame takes over the job. A structural engineer confirms exactly what is needed once the opening width and loads are known.
What is a goalpost frame in an extension?
A goalpost frame is two steel columns with a beam across the top, bolted together and standing on their own foundations. It is used where the opening is so wide that little masonry is left to bear on, or where the existing corners cannot take the load. The engineer decides whether one is needed.
Do I need a party wall agreement for rear extension steels in Welwyn Garden City?
Yes, if the beam bears into a shared wall: the Party Wall etc. Act 1996 applies in England and Wales, and a party structure notice must be served at least two months before that work starts. We arrange it through a party wall surveyor.