Opening the back of the house up to the garden is the most-requested improvement we get asked about, and it is also the one where budgets go wrong most often. The doors themselves are only part of the spend — widening an opening, a new lintel and making good the floor and plaster can add as much again.
Below are realistic fitted prices for the three main options at common widths, plus the associated work, so you can build a total figure rather than a door figure.
Door prices by width
| Opening width | uPVC bifold | Aluminium bifold | Sliding patio | French doors |
|---|---|---|---|---|
| 1.8m (2 panels) | £2,200 – £3,000 | £3,000 – £4,200 | £1,700 – £2,600 | £1,300 – £2,000 |
| 2.4m (3 panels) | £2,800 – £3,800 | £3,800 – £5,200 | £2,100 – £3,200 | £1,700 – £2,600 |
| 3.0m (3 – 4 panels) | £3,400 – £4,600 | £4,600 – £6,400 | £2,600 – £4,000 | n/a |
| 3.6m (4 panels) | £4,000 – £5,400 | £5,400 – £7,600 | £3,100 – £4,800 | n/a |
| 4.2m (5 panels) | £4,800 – £6,400 | £6,400 – £9,000 | £3,700 – £5,800 | n/a |
The costs that sit around the doors
As a rule of thumb, if you are replacing an existing patio door like for like, the door price is close to the total. If you are knocking a wall about, budget for the door plus roughly 40–70% again.
- Widening a masonry opening with a new steel lintel: £900 – £2,200 including propping and making good
- Structural engineer's calculations where required: £250 – £600
- Building warrant or building control notification: £200 – £600 depending on the local authority
- Internal plastering and reveals: £250 – £600
- Floor levelling and threshold finishing: £150 – £500
- External render or brickwork repair: £200 – £800
- Integral blinds within the glass instead of curtains: £250 – £600 per panel
Which system suits which opening
| Opening | Best fit | Why |
|---|---|---|
| Under 2m | French doors | Cheapest, no track, full opening when needed |
| 2 – 2.6m | Sliding patio | Bigger glass area, no panels stacking into the room |
| 2.4 – 4m, garden used daily | Bifold | Opens almost the full width for parties and summer |
| 3m+, view matters most | Sliding patio | Slimmer sightlines, less frame in the way when closed |
| Tight internal space | Sliding patio | Bifold panels need somewhere to stack |
uPVC or aluminium?
uPVC bifolds cost noticeably less and insulate well, but the frames are chunkier, which is very visible on a three or four panel run. Aluminium gives slim sightlines and stays rigid over wide spans, and it is the sensible choice above about 3.6 metres.
For sliding patio doors the same logic applies, though modern uPVC sliders have improved considerably and are often the better value where the opening is under three metres.
Getting the specification right
- Ask about the threshold: a low or flush threshold looks better and is easier to walk over, but needs proper drainage detailing outside.
- Check the number of locking points and whether the traffic door has its own cylinder.
- Confirm the glass is toughened — it is a legal requirement in doors — and consider solar control glass on a south-facing elevation.
- Ask how the doors will be adjusted and serviced, and who comes back if a panel drops in year two.
Lead times and disruption
Made-to-measure doors are typically four to eight weeks from survey to fitting, longer for bespoke aluminium colours. Build that into any plan involving a builder, plasterer or decorator, because the trades have to be sequenced around the delivery date rather than the other way round.
On the day itself, a like-for-like replacement usually means the back of the house is open for two to four hours. Clear the room, lift anything fragile, and think about pets and small children while the opening is unglazed. Where a wall is being altered, expect the opening to be boarded or sheeted overnight for two or three nights.
Ask before you order who is responsible for making good the plaster and the flooring, and whether waste removal is included. Those two items account for most of the arguments that happen on garden door projects.
Planning your budget
Get the door quote and the builder's quote at the same time and make sure they agree on who is forming the opening, who is making good and who is supplying the lintel. That single conversation prevents most of the overspend we see on these jobs.
We fit bifolds, sliding patio doors and French doors across Central Scotland and will happily walk the opening with you before anyone starts knocking holes in walls.
Common questions
Replacing an existing door usually does not, but enlarging a structural opening is building control work and may need a building warrant in Scotland.
Want a straight answer on your own windows or doors?
DM Installations fits and repairs windows and doors across Central Scotland — Cumbernauld, Glasgow, Falkirk, Stirling and the surrounding towns. Free survey, written quote, and an honest answer on whether you need a repair or a replacement.
Related guides
Bifold vs Sliding vs French Doors
The three ways to open the back of a house onto the garden, and which one suits your opening, budget and habits.
When to call a proPatio Door Not Sliding Properly
Sticking, grinding and jumping sliders — the usual causes, the DIY fixes, and the repairs that need a professional.
Cost guidesHow Much Does Double Glazing Cost?
Typical supplied-and-fitted prices per window, whole-house costs by property size, and the things that quietly push a quote up or down.