Bifold doors in London, surveyed, made and fitted

What to get right before you buy bifold doors in London

Bifold doors in London are usually chosen at the worst possible moment: the extension is half built, the budget has already been eaten by groundworks, and someone needs an answer by Friday. The doors are the part of the room you touch every day and the part that gets blamed when the kitchen is cold in January, the track fills with grit, or rain finds its way over the threshold. Nearly all of that is decided weeks before anyone arrives with a drill, in the specification and in the sequence of the build.

We cut, toughen, laminate and make up our own sealed units in our Wembley workshop and we fit with our own teams, so we also see what comes back. The problems are rarely exotic. They are a door that was measured before the opening existed, a threshold detail nobody designed drainage for, a cheap quote that quietly excluded making good, or a six panel set stacked across the one part of the opening the family actually walks through.

How do you compare three bifold quotes line by line?

Most homeowners get three quotes and compare the bottom number. That tells you almost nothing, because the three quotes are usually not describing the same job. Put them side by side and compare them item by item instead. If a quote does not state these things, it is not a quote, it is an estimate with a price on it.

• Overall structural opening size the price is based on, and whether that is a surveyed dimension or a figure you gave over the phone
• Panel count and the exact configuration, written as something like 3 left and 1 right, including which panel is the traffic door
• Whole door U value for the finished set, not the centre pane figure for the glass on its own
• Glass specification: unit make up, whether the outer pane is toughened or laminated, any solar control or acoustic interlayer, and which panes are safety glass
• Threshold type, and who is designing the drainage below and in front of it
• Whether the price includes removal and disposal of the existing door or window, or whether that is extra
• Making good internally and externally: plaster, reveals, sill, and what finish you will actually be left with
• Who supplies and fits the lintel or structural support, and who is paying the structural engineer
• Scaffolding, access equipment, glass lifting equipment, parking charges and permits
• Lead time from signed survey, and what happens to the price if the surveyed opening differs from the assumed one
• What the guarantee covers: frames, glass units, moving parts, and the finish, each with its own period
• Whether the installation is FENSA registered and a certificate will be issued

Once you have that list filled in, the price gaps usually explain themselves. A quote that is a few thousand pounds cheaper is often a thinner aluminium system, a centre pane U value quoted as if it were the whole door, a weathered threshold where the drawings showed flush, and a line at the bottom saying making good by others. That last phrase can add a plasterer, a decorator and a fortnight to your project. Ask what making good by others means in your specific opening, and get the answer in writing.

Be equally suspicious of the most expensive quote. Paying for triple glazing on a north facing utility door, or acoustic laminated glass on a garden wall facing a quiet alley, is money that would be better spent on a wider opening or a better threshold. We will tell you when a cheaper specification is the right one, because arguing you out of glass you do not need costs us a little and saves you a lot more.

Who is responsible for the structural opening?

This is where most bifold projects come unstuck. The doors are fitted into an opening somebody else forms. If a builder is on site, the structural opening is their responsibility: the lintel or steel, its bearings, the padstones, the propping during the works, and the opening being square, level, plumb and the size the drawings say. The lintel specification itself comes from a structural engineer, not from us and not from the builder, because the load above a four metre opening in a Victorian rear wall is a calculation, not an opinion.

What we are responsible for is the door set fitting that opening correctly, weathering properly and working for years. The two responsibilities meet at a set of tolerances. If the opening is 15mm out of square across four metres, the frame can be packed and the doors will still run. If it is 40mm out, you have a choice between a visible wedge of packer and silicone or cutting the structure, and neither is a decision to make on a Tuesday morning with the room open to the weather.

So the honest sequence with a builder involved is: engineer specifies the steel, builder forms and props the opening, we survey the formed opening, we manufacture, we fit. Anyone offering to compress that sequence is moving risk onto you.

Why does it matter when the survey happens?

Because a survey taken before the opening is formed is a prediction. We can take it, and sometimes we have to, but then the dimensions come from drawings and from a builder saying it will be 3,600mm. Brickwork, blockwork, steel packing and plaster thickness all move that number. When it moves outward you get a gap and a lot of filler. When it moves inward, the doors do not go in and you wait for a remake.

Our preference is simple and it is worth planning the build around. Let the builder form the opening, prop it, get the steel in and the bearings loaded, then let us measure the real hole. If the room needs to be watertight before that, a temporary hoarding for two or three weeks is cheaper and far less stressful than a remanufactured four metre door set. If you genuinely cannot wait, we will survey off drawings and we will tell you in writing which dimensions are assumed and what the consequences are if they change.

Does the direction the doors face change what you should buy?

Yes, and it changes the decision more than the brochure suggests. A south or west facing bifold on a rear extension turns a kitchen diner into a greenhouse by mid afternoon in June. That is the case for solar control glass, which reflects and absorbs part of the solar heat before it reaches the room while keeping the glass looking clear. It costs more per square metre and it earns that back in a room you can actually use in summer.

A north facing bifold has almost no solar gain to control, so solar control glass is largely wasted money there. What a north facing opening needs is a good whole door U value, warm edge spacers and a thermally broken frame, because that elevation is losing heat all winter and never getting any back. East facing openings sit in between: hard morning sun, cool afternoons. We ask which way the wall faces before we specify glass, and if a supplier has not asked you that, they are specifying by habit.

How many panels, and what does bespoke actually mean?

Panel count is driven by the opening width, the weight each leaf can sensibly carry and where you want the stack. Wider leaves mean fewer joints and more glass, but each leaf gets heavier and the stack gets deeper when folded. Narrower leaves are lighter and easier on the hardware but you look at more frame. Somewhere around 900mm to 1,100mm per leaf is where most domestic sets land, and it is a conversation about the room, not a rule.

Bespoke is a word worth interrogating. Genuinely bespoke means the frames are cut and fabricated to your surveyed opening, so the sightlines are even and the packing is minimal. The other version of bespoke is a standard size set, dropped into a larger opening with a timber sub frame and a generous bead of silicone. Both can be weathertight. Only one looks right. Ask any supplier whether the frame is made to your measured opening or to the nearest stock size, and ask how much packing they expect at the head and jambs.

How wide is too wide?

There is a point where a bifold stops being the right answer. Past roughly six or seven metres you are dealing with a very large stack, a heavy run of hardware, a long threshold to drain and a structural opening that needs serious steel. The folded panels have to go somewhere, and a seven panel stack can swallow a metre of wall, which is often exactly where the sofa or the bin store was going. Very wide openings also move more in the frame, so alignment and regular hinge adjustment matter more, not less.

For some of those openings a sliding system, or a bifold on one side with a fixed pane alongside, gives a better result for less money. We would rather tell you that at survey than fit a set you fight with for a decade.

If a quote for bifold doors is dramatically cheaper than the others, something has been left out of the scope, taken out of the specification, or assumed about your opening. Find out which before you sign.

How do you budget sensibly for bifold doors?

We will not put a from price on a website, because a number without an opening size, a panel count, a glass specification and a threshold detail is marketing, not information. What we can tell you is where the money actually goes, so you can build a realistic allowance into your project before you have a quote in your hand.

The cost of bifold doors in London is driven by overall glazed area first, then panel count, then glass specification, then threshold and access. Area is the big lever: going from three metres to four metres of opening costs more than adding a panel within the same width. Glass is the second lever, and that is where solar control, acoustic laminated interlayers and triple glazing live. Threshold choice is smaller in material cost but can carry real cost in the groundworks around it. Access is the one people forget: a terraced street with no side gate and a controlled parking zone adds time and sometimes lifting equipment.

A sensible approach is to set an allowance for the doors early, specify the frame and the whole door U value properly, and treat glass upgrades as the adjustable part. Then get a written fixed quotation against a surveyed opening rather than a ballpark against a hope. Our survey is free across London, the quotation is fixed and written, and if the answer is that you should spend less with us and more on your threshold detail, we will say so.