On a replacement job the opening is a fact. It is already in the wall, it has been in the wall for years, and the whole exercise is a matter of measuring it accurately enough to put something new into it. On a new build the opening does not exist. It is going to be designed, then drawn, then framed, then rendered, and every one of those steps is a decision taken by a different person at a different time.
That single difference drives everything else. It is why a new build can have four different glass specifications on four elevations at no extra cost, and it is also why a new build can arrive at week twenty with sixty openings framed to a number nobody wrote down. We have written elsewhere about replacing windows in a building that already stands; this piece starts where that one cannot go, with the building that does not exist yet.
The argument in one sentence: a new build is the only project type where you can still change the wall, and that is exactly why the window has to be decided before the wall rather than after it.
Both jobs end with a window in a hole. Almost nothing before that point is shared.
| Question | Replacement | New build |
|---|---|---|
| Where the opening comes from | It is already built. You survey it. | Somebody has to decide it, on paper, months earlier. |
| Who owns the dimension | The existing wall. | The structural drawings, then the framer, then nobody in particular. |
| When it freezes | At the site survey. | In practice when the elevations are issued; in law often not until the lintel is ordered. |
| Cost of a wrong dimension | One unit remade, or a made-to-measure filler. | The opening, the lintel, the facade and the programme. |
| Frame depth | Whatever fits the wall you have. | A wall-design decision made before the wall exists. |
| Glass specification | Usually one build-up for the whole house. | Can differ per elevation, and in most climates should. |
| Colour consistency | Match what is already there, or accept a visible difference. | One coating batch can cover the whole project, if you ask for it. |
| Thresholds and floor levels | Work around a finished floor that is not moving. | Decided together, and the floor is structural. |
| Who walks past it afterwards | The client. | Six more trades, none of whom were at the handover meeting. |
The last row is the one that costs the most money and gets the least attention. On a replacement job the window is among the final things to happen. On a new build it is among the first, which means it is among the first things on site that the rest of the site has to live with.
Of every number on a window schedule, the depth of the frame into the wall is the one that stops being negotiable earliest. Once the wall is built, you can still change the glass, the hardware, the colour and the handle. You cannot easily change the depth of the hole.
Our published frame wall widths run from 90 mm to 182 mm. That is not a range to pick from at random; each number belongs to a specific series and a specific track count.
| Series | Published frame wall width | What that number is |
|---|---|---|
| AW90 Passive Window | 90 mm | Depth of the frame into the wall. Not the visible frame face, not the opening. |
| C113 Outward-Open Window | 113 mm | Same definition. The 57 mm glass sash thickness is a different measurement entirely. |
| C116 Outward-Open Window | 116 mm | The 28 mm press line and the 22 mm mullion face are sightline numbers, not depth. |
| C120 Outward Opening System Window | 119 mm | Same definition again; the integrated mesh adds an interior layer. |
| TS130 Side Press Window | 130 mm | Track heights published as 53 mm and 31 mm are two tracks on one frame, not a tolerance band. |
| SL126 / 182 Sliding Door | 126 mm two-track, 182 mm three-track | One series, two depths. The track count is a depth choice. |
| SL112 / 167 Heavy-Duty Sliding Door | 112 mm single or two-track, 167 mm three-track | The same profile system in two track counts. Not two products. |
| SL155 Thermal Break Sliding Door | 155 mm four-track | Four tracks and still shallower than the three-track 182. Depth is a series property, not a function of track count. |
That last row is worth pausing on, because it is the kind of thing a schedule gets wrong: the four-track door is shallower than one of our three-track doors. Anyone specifying "more tracks means a deeper frame" is carrying a rule that our catalogue does not obey.
Now the arithmetic, which anyone can check. Public North American guidance gives standard window jamb depths of 4-9/16 in for a 2x4 wall and 6-9/16 in for a 2x6 wall, built up from a 3.5 in or 5.5 in stud plus half an inch of sheathing and half an inch of drywall, plus a sixteenth of an inch so that the frame sits very slightly proud of the finished interior surface. Converted, 4-9/16 in is 115.888 mm and 6-9/16 in is 166.688 mm.
Our C116 is published at 116 mm. Our three-track SL167 is published at 167 mm. The first is about a tenth of a millimetre from 4-9/16 in, the second about a third of a millimetre from 6-9/16 in.
Those two near-collisions are the most dangerous numbers in this article, because they are pure coincidence and they will be read as equivalence. The imperial jamb depth is derived from one particular stud-plus-sheathing-plus-drywall stack, and your wall is probably not that stack: masonry, brick veneer, external insulation, service battens and thicker board all move it. The metric figure is the depth of our frame into the wall, which is not the same thing as the depth of the finished wall. If they happen to agree on your project, good. If they do not, you need a reveal, an extension, or a different series, and you need to know that before the wall is built rather than after.
The practical instruction that follows from this is simple and almost never done: do not send us a single depth number. Send the wall build-up layer by layer, from the outside face inwards, with each layer's nominal thickness. We can then tell you whether the frame lands where the drawings expect it to land, and where the reveal will fall.
One specialist source on preparing door and window schedules states the problem plainly: the architect may schedule a nominal unit size, the manufacturer may quote a frame size, and the framer may build the rough opening from a note or a shop drawing, and these are not always the same number. It adds that a half-inch misunderstanding repeated across twenty windows becomes a real framing problem.
That is the whole of it. On a new build nobody is lying and nobody is careless; three competent people are each using the correct number for their own purpose, and the three purposes do not meet.
| The number | Who writes it | What it is | What it is good for |
|---|---|---|---|
| Nominal or schedule size | Architect, on the elevations and the schedule | A design intent, usually a round number | Framing the opening, energy compliance, consent drawings |
| Manufactured or frame size | Manufacturer, on the approved drawing | The unit we actually cut and assemble | The purchase order, and nothing else |
| Rough or structural opening | Structural engineer or framer | The hole, including the fixing and movement gap | Building the wall. It is not a thing you can order from a window factory. |
A schedule line that reads 34 x 80 entry door is a design intent, not an order: it tells the framer what to build and tells nobody what to manufacture. For that reason we ask for the purchase order to carry only one of the three, the manufactured size in millimetres, and for the schedule to state in writing which of the three it is quoting. Another published guide puts the same point as a warning against letting an early planning dimension be mistaken for a final order dimension, which is a polite way of describing a very common and very expensive mistake.
This is also the reason the version number matters. On a new build, an enquiry is very often priced from a drawing set that is going to be superseded, and the superseding happens quietly, in a revision cloud that nobody sends to the supplier. We have written about drawing approval and version control elsewhere; on a new build the only thing worth adding is that the revision has to reach the factory, not just the site.
A new build has one advantage that no other project type has: time to decide well. It loses that advantage in an extremely consistent way, by treating the window package as a finishing item that gets ordered once the building is standing.
One glazing contractor describes the most common mistake on new home construction as treating windows as a punch-list item, and notes that they are not one: they are ordered to fit framed rough openings, and a late order pushes back the entire dry-in schedule. Another builder-oriented source gives typical lead times for windows and exterior doors as eight to twelve weeks with a range of six to sixteen or more, and advises ordering three to four months before framing starts. A Scottish glazing company gives eight to ten weeks for both standard windows and large sliding doors, and warns that late design changes, even small ones, are one of the biggest causes of delay and cost increase.
The reason a window holds up so much of a build is not the installation day. It is that windows are what turn a frame into a closed building. One supplier's advice puts insulation firmly after glazing: the shell is built, the roof is on, the windows are installed, and only then can insulation proceed without interruption. Everything that follows, plastering, screeds, joinery and decoration, waits behind that.
| Stage | Who freezes it | What happens if it slips | What it actually costs |
|---|---|---|---|
| Elevations and glazing ratios | Designer and client | Every later number moves with it | Redesign, and in some jurisdictions re-consent |
| Structural openings and lintels | Engineer | The hole is built to the wrong number | Structural work, not window work |
| Wall build-up and finished floor levels | Designer and builder | Frame depth or threshold no longer fits | Extensions, packing, or a new unit |
| Schedule issued with a stated size basis | Designer | The framer guesses which number it is | A small error multiplied by every opening |
| Enquiry sent with the data block | Buyer | Two quotations are not comparing the same thing | Re-quoting, and the lead time starts again |
| Order placed against approved drawings | Buyer | The production slot goes to another project | Weeks, not days |
| Delivery to a site that can receive and store | Site manager | Units sit outside, or in a wet ground-floor room | Damage, and an argument about whose it was |
| Installation, then protection | Installer, then builder | The following trades mark or etch the units | Glass replacement late in the build, when it hurts most |
| Film removal and final clean | Builder | Adhesive cures and bonds | A restoration job rather than a clean |
| First adjustment and commissioning | Named in the contract, in advance | Nobody owns it, and normal settling gets reported as a defect | A warranty argument about an adjustment |
Ten rows, and only two of them are about the window itself. That is the point. On a new build you are not buying a product, you are buying a place in a sequence, and the place matters more than the product.
Because the windows go in early, they are present for everyone else's work. Render, plaster, tile, screed, paint, welding and the final clean all happen after the units are in, and all of them produce residue that bonds to glass and to coating in ways that ordinary cleaning does not touch.
One post-construction cleaning specialist lists the four residues that account for most of it, and is explicit that post-construction cleaning is a restoration process rather than a routine clean. The same source notes that a post-construction clean costs two to four times a standard clean on the same property, and that using the wrong blade on coated glass can scratch it permanently.
| Residue | How it attaches | How it comes off | Risk to the unit |
|---|---|---|---|
| Paint and texture overspray | Fine droplets settle and cure into a hard film, travelling further than the trade expects | Water-based is manageable if caught early; solvent-based and texture coats need solvent and careful blade work | Medium. Blades scratch coated glass. |
| Mortar and concrete splatter | Alkaline material dries to a porous crust and can begin to etch if left | Diluted acid, described by the source as hazardous and not a do-it-yourself item | High if delayed. This is the one that does permanent damage. |
| Silicone smears | Cross-links into a rubbery film that resists solvent | Mechanical removal with a blade | Medium |
| Protective film adhesive | Ages under heat and ultraviolet, bonding harder over time | Alcohol or a dedicated remover, gentle heat, plastic scraper only | Low if early, high if late. Can lift coating if pulled hard. |
The same source also makes a scheduling point that is easy to ignore: wait until all trades have finished before scheduling the final window clean, or the clean simply gets re-contaminated. Which brings us directly to the contradiction in the next section.
Two pieces of advice about the same piece of plastic are in direct conflict, and both of them are correct within their own context.
| Who is giving the advice | What they say | Why they are right |
|---|---|---|
| Window and installation companies | Take the film off within one month, two at the very most | Adhesive ages under ultraviolet and heat. Leave it and removal becomes difficult to impossible. |
| Manufacturer-side and trade guidance | Three months is the hard ceiling; in hot sun, fifteen to thirty days | The film becomes brittle or leaves residue, and aggressive removal can take coating with it. |
| Builders and independent inspectors | Keep protection on through plaster, fixing and painting; take it off near final clean and handover | Replacing glass late in a build means ordering panels, removing trims and delaying completion. |
Both cannot be followed on a build that runs long, and most builds run long. The way out is to stop treating the film as an attitude and start treating it as a product with a rated exposure life. Ask the supplier, in writing, for the film's rated exposure life and the removal deadline, then put the removal date in the programme as a task with an owner. If the programme is longer than the film's life, which it usually is, the answer is not to argue about it: it is to plan for the film to be replaced, or for the frames to be protected by a covering that does not age the same way.
Two small details that save real money. Use a plastic scraper and warm heat, never a metal blade on coated glass. And when the film comes off, go around and clear the drainage slots and track channels, because the same debris that blocks a weep hole is the debris that turns a correctly detailed sliding door into a leak six months later.
On a replacement job you almost always buy one glazing specification for the whole house, because anything else creates visible mismatches between old and new. On a new build there is no such constraint: the south and west elevations are usually fighting solar gain while the north elevation is fighting heat loss, and those are different problems requiring different glass. A schedule that says "double glazed, low emissivity" tells the factory nothing and the energy assessor nothing. One specialist source warns of exactly this failure mode: the drawings say one thing, the quotation says another, and the submittal quietly changes a third.
This is the single most under-asked question on a multi-unit or phased development. Coating is applied in batches, and two batches of the same named colour are not guaranteed to be identical. On a new build you can require the entire order, or an entire phase, to be produced in one batch, and you can require the batch reference to be recorded against each unit mark so that a replacement in year three can be matched deliberately rather than hopefully. Ask for it at quotation stage. It is very hard to arrange after the first container has shipped.
A sliding door threshold is not a door decision, it is a floor-level decision, and floor levels are structural. Our published options differ by a wide margin, and the choice has to be made while the slab and the external drainage are still lines on a section.
| Published option | Series | What it means on a new build |
|---|---|---|
| Low track, 8 mm | SL126 / 182 | Near-level access. The internal finished floor and the external drainage both have to be designed to meet it, in the same drawing, before the slab is poured. |
| High track, 43 mm | SL126 / 182 | More water capacity at the track. It is a step, and the step has to appear on the section. |
| 45 mm high-ｄｒｏｐ bottom track, optional 85 mm water barrier | SL112 / 167 | The step is the design. It cannot be removed after the slab is poured, and it is not a threshold the floor can be built up to afterwards. |
The outer track of a sliding door is designed to hold water and drain it to the outside. Water in the outer track is the system working; water past the inner upstand is a leak. That distinction is easy to state and impossible to retrofit, which is why it belongs in the drawings and not in a conversation on site.
On a retrofit, escape and ventilation requirements are constraints you work around, and the result is often a smaller opening or an awkward one. On a new build they are inputs: they are known before the elevations are fixed, and the opening can be sized to satisfy them rather than argued about afterwards. We have written about escape sizes elsewhere; the only new-build point is that the requirement has to reach the person drawing the elevations, not the person ordering the windows.
Covered in section 2, and listed here only because it is the one of the five that stops being available first.
A new build does not have a window-and-door purchase. It has at least three, bought by different people at different times and frequently discovered to be inconsistent with each other only when they arrive on site together.
The word "folding" illustrates the trap. 30 inch bi fold doors for a wardrobe and a six-metre folding wall to a terrace are the same three words on a drawing and two entirely different products, bought by two different people from two different supply chains. We make neither of them: our folding-door category is currently empty, and we would rather say that in week two than quote it and disappoint you in week twenty. What we can do for a large opening is a sliding configuration, and we will say so plainly rather than pretend a folding door is on the way.
If a new build produces one document, it should be the schedule, and it should exist while the elevations are still changeable. One published guide to custom schedules describes its job as turning design intent into information that the homeowner, the architect, the builder, the installer and the supplier can all use, and recommends a unique mark for every opening that is then used on the plan, the elevations, the schedule, the quotation and the site notes. Another lists the fields worth carrying, and is careful to specify that dimensions must identify whether they refer to the unit, the frame, the masonry opening or the framed rough opening.
Below is the version we would like to receive, with the entries as they should look. If you can fill fewer than fifteen of these rows, what you have is a quotation with pictures attached rather than a specification, and the price you get will be a guess.
| Field | A good entry looks like | What a blank does to the order |
|---|---|---|
| Mark, unique and used everywhere | W-07, matching the plan, the elevation, the quote and the crate label | Nobody can discuss a specific opening without walking to it |
| Size basis, stated in words | "Manufactured frame size. Rough opening by others." | Three people build three different numbers, all in good faith |
| Manufactured size in millimetres | ____ mm wide by ____ mm high | No production can start, and any quote is provisional |
| Wall build-up, layer by layer | ____ outside to inside, with each layer thickness | Frame depth is guessed, and the reveal lands somewhere unexpected |
| Finished floor level, internal and external | ____ mm internal, ____ mm external, datum stated | The threshold is wrong and cannot be fixed on site |
| Opening type and configuration | Fixed plus one movable, movable on the ____ side viewed from ____ | The door arrives mirrored |
| Series and track count where relevant | ____ series, ____ track | Frame depth and net opening are both undefined |
| Threshold option | Low track / high track / high-ｄｒｏｐ, ____ mm | A step appears where none was drawn |
| Glass build-up per elevation | ____ mm glass, ____ mm cavity, coating ____ , per elevation | Sash weights change and every hardware rating becomes provisional |
| Safety glazing flag | Yes or no per opening, against the local rule | A unit fails inspection at handover |
| Egress and ventilation flags | Yes or no, with the required clear opening in mm | The bedroom window is the wrong size and the wall is already up |
| Screen requirement and which side | ____ mesh, on the ____ side | A second sash appears in a reveal that was sized for one |
| Colour, inside and outside, and batch requirement | ____ outside, ____ inside, one batch per ____ | Two elevations are two slightly different greys |
| Hardware set and finish | ____ system, ____ finish, handle height ____ mm | Handles do not match the rest of the ironmongery |
| Delivery phase and site contact | Phase ____ , week ____ , named recipient | Everything arrives at once on a site that cannot store it |
| Who performs the first adjustment | Named company, before handover, signed off | Normal settling gets reported as a defect and nobody owns the fix |
Fifteen rows. None of them is exotic, and every one of them is cheaper to fill in at design stage than to argue about on site.
Delivery is where a good package becomes a damaged one. Our packaging is designed to get units across an ocean; it is not designed to sit in a puddle for a month.
Being explicit about the gaps is more useful to a new build than filling them with adjectives, because a new build is the one project type where a gap discovered early is free.
| Item | What we publish | Why there is a gap |
|---|---|---|
| Alloy | 6060-T66 across the range | It is the same for every series, so it is a floor, not a differentiator |
| Profile thickness | A range, for example 1.8 to 2.5 mm on SL112 / 167 | The range is a list of permitted specifications, not a tolerance band on one product |
| Thermal performance | K values on three series, for example 1.3 on AW90 | It is a system value, not a whole-window value for your size and your glass |
| Sliding series thermal performance | Not published | Unpublished is not worse. It means there is nothing to compare, so ask for a calculated value in the same standard |
| Air, water and wind ratings | Not published for the window series | Without a declared class, "non-compliant" cannot be defined, and deviations have no threshold to be measured against |
| Salt spray and shear | 240 hours and 5,000 N on AW90 | Published test results for one series. They do not transfer to other series and they are not a project qualification. |
| Hardware cycles | Cycle figures on specific hardware brands | They are rig tests on a component, not a service life for a window |
| Roller capacity | 400 kg on SL155, 220 kg driving capacity on SL112 / 167 | Rated per sash and dominated by the glass. Change the glass and the number is void. |
| Maximum sash size | Published for some door series | It is published against an assumed glass build-up. Heavier glass moves it down. |
| Glass rebate | Not published | Sash thickness is a stack-up, not the opening that takes the glass. Ask the section drawing for the rebate. |
| Protective film life | Not published | It is a consumable with a rated exposure life. Ask for it in writing and programme against it. |
| Rough opening, anchoring layout, drainage route, sash order | Not published, and not ours to publish | These belong to your building, not to the unit. They are what the approved drawing is for. |
The right-hand column is the useful one. On a new build you will receive a great many answers that are courteous, prompt and completely empty.
| What to ask | Why you are asking | An answer that sounds reasonable and tells you nothing |
|---|---|---|
| Which of the three size systems is your quotation using? | To find out whether you are comparing like with like | "We will confirm sizes before production." |
| Show me the section with my wall build-up drawn on it. | Frame depth and reveal position are the earliest-freezing decisions | "Our frames suit all standard walls." |
| What is the threshold height at my finished floor levels? | The floor is structural and cannot be adjusted later | "We have low threshold options." |
| Give me the roller rating per sash, at my glass build-up. | Glass dominates sash weight, and the rating is per sash | "Heavy-duty rollers, four hundred kilograms." |
| Which standard, which class, and was the test piece the opening configuration? | A fixed light almost always tests better than an opening sash | "Tested to international standards." |
| What is the protective film's rated exposure life? | So you can put the removal date in the programme | "Please remove before handover." |
| Will my whole order be one coating batch, and will the batch be recorded per mark? | Colour matching in year three depends on it | "Same colour code throughout." |
| Can you deliver in phases, and what is the storage requirement per phase? | A new build site is the worst possible warehouse | "We ship whenever you need." |
| Who performs the first adjustment, and is it in the contract? | Settling is normal; an unadjusted window is not a defect but looks like one | "Fully adjustable hardware." |
| Which items on this schedule are not your products? | A supplier who names what they do not make saves you a month | "We can supply everything." |
Yes, and you should ask us to, because a budget figure early is worth more than an accurate figure late. What we will not do is treat that number as final. Quote it as a budget, mark the drawing revision it came from, and re-price once the openings and the wall build-up are fixed.
Earlier than feels comfortable. Public guidance for other markets suggests windows and exterior doors run six to sixteen weeks and should be ordered several months before the opening is needed. Do not take that as our lead time; take it as a reason to ask us for ours, in writing, against your drawing revision.
For colour consistency, one batch is better. For site reality, one delivery is worse. The usual answer is to order the whole project as one production batch and to agree a phased delivery schedule, with the storage requirement for each phase settled before the first crate moves.
Not at present. Our folding-door category is empty, and we would rather say so at enquiry stage than quote it and disappoint you later. For a large opening we can usually offer a sliding configuration instead, and we will tell you what changes when you do that: no swing arc, a different net opening, and a threshold decision you have to make before the slab.
Whoever the contract says, which is why it should say. Damage in transit, damage in storage and damage by following trades are three different events under three different responsibilities, and the only thing that makes any of them quick to resolve is photographs taken at the handover points and a written statement of when risk passes.
No. We can tell you what our frame needs, and we can draw it, but the opening, its lintel and its deflection belong to your structure and to the engineer who signs it. We are happy to be told the number and to build to it.
