Bi-fold & sliding door openings · Derry City and Strabane
Bi-fold & sliding door openings in Derry City and Strabane
Calculations, approvals, propping, steel and making good for bi-fold & sliding door openings across Derry City and Strabane.
- Itemised written quote
- Beam sized by a structural engineer
- Covering Derry City and Strabane and nearby
- Free survey visit
- Engineer's calculations arranged
- Building control handled
- Fixed written price once scope is agreed
- England, Wales, mainland Scotland & NI
Bi-fold & sliding door openings in Derry City and Strabane: how it works
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.
Across Derry City and Strabane, bi-fold & sliding door openings usually come up when people want more light, a better layout or a way through to a new extension. We work in Derry/Londonderry and Strabane and the surrounding villages. Whatever the reason, the beam is sized from calculations and the work is inspected before anything is covered.
Key points for your project
- In cavity walls a cavity tray above the new head directs any water in the cavity out through weep vents. Without it, damp can show inside above the doors, so the tray is lapped and sealed correctly as the brickwork is rebuilt.
- Both leaves of a cavity wall need support over the opening. Depending on the design, the outer brickwork may sit on a plate fixed to the beam or on a separate external lintel, and the engineer specifies which suits the loads and the look.
- 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.
- A wide glazed opening changes the security of the back of the house. During the works the opening is boarded at night if the doors are not yet fitted, and it is worth checking the locking and glass specification of the doors you choose.
- Very wide openings, or ones that run close to the corner of the house, may leave too little wall for the beam to bear on. In that case the engineer may specify steel columns or a goalpost frame standing on its own foundations.
What happens, step by step
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
A full plans application or building notice goes to Derry City and Strabane District Council under the Building Regulations (Northern Ireland) 2012 before work begins.
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 Derry City and Strabane
As a guide, budget £2,150–£6,000 including VAT for rear wall opening for bi-fold or sliding doors in Derry City and Strabane, based on published UK cost guides adjusted for prices in Northern Ireland (-14%).
| Job | Typical guide range | What it usually covers |
|---|---|---|
| Rear wall opening for bi-fold or sliding doors | £2,150–£6,000 | External wall opened up to about 5 m with steel, propping, cavity tray and making good (doors supplied separately) |
| Structural calculations for a beam | £220–£640 | Site measure or photos, beam and padstone design and calculations for building control |
| Widening an internal doorway | £860–£2,150 | Opening widened with a new lintel or short beam, approval where structural, and making good |
| Lintel replacement | £340–£1,030 per lintel | Propping, removing the old lintel, new lintel set on beds and brickwork made good |
Figures include our approximate regional adjustment for prices in Northern Ireland (-14%) and are rounded. How these figures are worked out.
Building control and neighbours in Derry City and Strabane
In Northern Ireland, structural work comes under the Building Regulations (Northern Ireland) 2012 and is approved by the local council's building control. For Derry City and Strabane that is Derry City and Strabane District Council. We submit a full plans application or building notice before work starts and book the inspections.
Northern Ireland has no Party Wall Act, so there is no statutory notice to serve. Where the steel bears into a shared wall, the title deeds and the general law apply, and agreeing the work with your neighbour in writing first is good practice.
Bi-fold & sliding door openings by town
Bi-fold & sliding door openings in Derry City and Strabane: your questions
Which towns in Derry City and Strabane do you cover?
We cover towns including Derry/Londonderry and Strabane, plus the villages and smaller towns around them.
Can you work on older or listed homes in Derry City and Strabane?
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.
What does a bi-fold opening quote include?
Our itemised written quote covers the survey, calculations, building control, propping, removing the wall, steel and padstones, outer leaf support, cavity trays and closers, temporary weather protection and making good. Doors, threshold drainage and patio work are shown separately unless agreed. The price is fixed in writing once the opening size and specification are agreed.
Do I need a steel beam for bi-fold doors?
Usually, yes. Bi-fold and sliding doors need wide openings, and in a load-bearing external wall that span is normally carried on steel. The engineer designs it for strength and stiffness, because glazed doors can stick or be damaged if the beam deflects. A small opening under light loads might only need a lintel, but that is the engineer's call.
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 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.
How soon can bi-fold & sliding door openings start in Derry City and Strabane?
Start dates depend on the engineer's calculations, the building control approval and any agreement needed with neighbours. We give you a realistic timetable after the survey and keep you updated as each approval comes through.