Bi-fold & sliding door openings · Dorset
Bi-fold & sliding door openings in Dorset
Bi-fold & sliding door openings across Dorset, designed by a structural engineer and signed off by building control.
- Survey, design and installation in one
- Covering BH1, BH10, BH11, BH12
- 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 bi-fold & sliding door openings in Dorset
Bi-fold and sliding door openings are wide gaps formed in an external wall, usually at the back of the house, to take a run of folding or sliding glazed doors. A steel beam carries the wall, floor and roof loads above, and it is designed stiff enough that its movement does not press on the glass or stop the doors running.
Looking for bi-fold & sliding door openings in Dorset? We work in Christchurch, Poole and Bournemouth and the surrounding villages. Our teams handle the calculations, the building control approval, the propping and the steel itself, and leave the opening ready for plastering and decoration.
What to expect
- External walls can have gas meters, boiler flues, soil pipes, outside taps or cables near the new opening. These are found at survey and moved by the right trade, with any gas pipework done by a Gas Safe registered engineer as the law requires.
- The structural work for a typical bi-fold opening usually takes three to five working days. Doors are often made to order, so the steel goes in once opening sizes are confirmed and the doors are fitted soon after.
- The house is open to the weather between taking out the wall and fitting the doors. Temporary sheeting or a boarded frame keeps rain out and the house secure, so the gap between the structural work and door fitting should be kept short.
- Replacing a rear window with doors in a house is usually permitted development, but front elevations, listed buildings, flats and homes where permitted development rights have been removed may need planning permission or another consent.
- Door suppliers quote a structural opening size, which allows for the frame and fixing tolerances. Agreeing that size before the steel is designed avoids reveals that are too tight or gaps that have to be packed out later.
How the job runs in Dorset
Look and measure
We check the wall, the span you want and what the wall is carrying, and photograph anything the engineer needs to see.
Design and price
Calculations come back from the engineer and we confirm your fixed written price, line by line.
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.
Fit, inspect, finish
The work is propped and the steel installed and packed tight. After inspection the opening is boxed, plastered and left clean.
Guide prices for bi-fold & sliding door openings in Dorset
As a guide, budget £2,600–£7,200 including VAT for rear wall opening for bi-fold or sliding doors in Dorset, based on published UK cost guides adjusted for prices in the South West (+3%).
| Job | Typical guide range | What it usually covers |
|---|---|---|
| Rear wall opening for bi-fold or sliding doors | £2,600–£7,200 | External wall opened up to about 5 m with steel, propping, cavity tray and making good (doors supplied separately) |
| RSJ supply and fit (single beam) | £820–£2,580 per beam | Beam supplied, delivered, lifted and packed on padstones, with propping (calculations and approval priced separately) |
| Structural calculations for a beam | £260–£770 | Site measure or photos, beam and padstone design and calculations for building control |
| Opening into a rear extension | £2,600–£7,200 | Original rear wall removed with a beam or goalpost, approvals and propping, coordinated with the extension build |
Figures include our approximate regional adjustment for prices in the South West (+3%) and are rounded. How these figures are worked out.
Building rules for Dorset
Structural openings in English homes need building regulations approval before work starts. The local council's building control team can deal with it, or you can use a registered building control approver. Either way the steel is inspected before it is covered, and a completion certificate is issued at the end. Keep it safe for when you sell.
Terraced and semi-detached homes often need party wall notices, because cutting into a shared wall to take a beam end is notifiable under the Party Wall etc. Act 1996. Allow at least two months for the notice period unless your neighbour agrees sooner.
Bi-fold & sliding door openings by town
Local questions answered
Can you work on older or listed homes in Dorset?
Yes. Older homes often have lime mortar, timber lintels or shallow footings, which the engineer allows for. Listed buildings need listed building consent for internal structural changes as well as building regulations approval, and that must be in place first.
How much do bi-fold & sliding door openings cost in Dorset?
As a guide, budget £2,600–£7,200 including VAT for rear wall opening for bi-fold or sliding doors in Dorset, based on published UK cost guides adjusted for prices in the South West (+3%). The exact figure depends on the span, what the wall carries, access and the finish, and is fixed in writing once the scope is agreed.
Should I order my doors before the opening is made?
It helps to choose them first. The supplier's structural opening size and threshold detail feed into the steel design, so the opening is formed to suit the doors exactly. Many people order once the engineer has confirmed the opening, then time the structural work so the gap is weathered for as short a time as possible.
Do I need planning permission for bi-fold doors?
Usually not for a rear opening in a house, as this generally falls within permitted development. Planning or another consent may be needed for front elevations, flats, listed buildings, conservation areas with extra controls, or homes where permitted development rights have been removed. We flag this at survey so you can check before work is booked.
Can I have a level threshold with bi-fold doors?
Often yes, but it has to be designed. The inside floor, outside paving and drainage all need to work together so water cannot run in, usually with a drainage channel outside and the right damp-proof detail under the door frame. We look at levels at the survey and plan the threshold with the door supplier.
How wide can a bi-fold door opening be?
There is no fixed limit, as it depends on the loads above and what the beam can bear on. The engineer designs the steel and, for very wide openings or ones near a corner, may specify columns or a goalpost frame. The door system's own maximum panel sizes and configurations also need checking.
Do I need a party wall agreement for bi-fold & sliding door openings in Dorset?
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.