5 min read
This is the question we get asked most on extensions. Both open the back of the house up; they just do it in very different ways.
How much actually opens
Bi-folds fold back almost completely — you can open up to around 90% of the aperture and genuinely merge the room with the garden.
Sliders open to roughly half (two panes) or two-thirds (three panes), because a panel always has to slide behind another. If throwing the whole wall open matters, bi-folds win.
How it looks when closed
Sliders win here. Fewer, larger panes mean far less frame in your view — a two-panel slider has one vertical join, where a four-panel bi-fold has three. If you're looking out at the garden all winter, that matters more than people expect.
Cost
For a like-for-like opening the two are broadly comparable, with slim-framed premium sliders usually costing more than a standard aluminium bi-fold. We fit bi-folds in aluminium only — uPVC is not rigid enough to stay true over folding spans.
Thresholds and access
Both are available with low or flush thresholds, which is worth specifying if you have children, use a pushchair or need level access. Flush thresholds need proper drainage detailing outside, which we allow for at survey.
Everyday use
Sliders are easier for quick everyday use — one panel glides open. Bi-folds are a small operation to fold fully back, which suits summer and entertaining more than nipping out to the bin. Many customers spec a bi-fold with a 'traffic door' — one leaf that opens on its own like a normal door — to get both.
Our recommendation
Choose bi-folds if you entertain, have a usable patio, and want the whole wall open. Choose sliders if you want maximum glass and the cleanest view, or if the opening is very wide. Either way, go aluminium and specify a low threshold.
FAQs
Are bi-folds draughty?
Good quality aluminium bi-folds with modern gaskets and multi-point locking are not. Cheap ones can be — the hardware and installation matter as much as the product.
Do I need building regulations approval?
Replacing an existing door like-for-like generally doesn't. Forming a new opening does, because it's structural. We'll flag it at survey.
How wide can a bi-fold go?
Commonly up to six or seven panels. Beyond that, a slider or a fixed panel combination is often the better answer.