When to Choose Windows and Doors for a New Build

Windows get treated as a late decision on a new build, and they are not one. The sizes and the configuration are locked at the drawing stage because the openings get built to them, and the glazing specification is settled well before anyone is standing on site talking about colours. This article sets out when each part of the window decision actually has to happen, where it sits in the build sequence, what the code and the site decide for you before taste comes into it, and what a supplier needs in front of them to quote your build properly. If you are partway through and wondering whether you have left it too late, the sequence below will tell you quickly.

The window decision happens earlier than most people expect

It helps to treat this as three separate decisions with three different deadlines, because they do not close at the same time.

Configuration and sizes close at the drawings. The window schedule on the plans is what the openings get built to. The draftsperson or architect sets the sizes, the engineer sizes lintels and structural openings around them, and the carpenter frames to those dimensions. Swapping a slider for a pair of awning sashes later is sometimes workable. Changing the size of the opening is a structural change, not a window change.

The glazing specification closes before manufacture, usually at or just after slab. This is where the energy assessment does its work, because the performance it models has to be the performance that turns up on site.

Colour and hardware close last, but still before manufacture. Foils and non-standard colours can carry a different lead time from white, which is worth confirming before you commit to one.

The practical upshot is that by the time the frame is standing, the configuration is already fixed. The measure at frame stage confirms real dimensions, it does not reopen the design.

The build sequence, and where windows sit in it

1. Drawings and development approval. Sizes and configuration are set here, in the window schedule, and approval is given on that basis.
2. Engineering. Lintels and structural openings are sized around the windows that the drawings specify.
3. Slab. A good point to lock the glazing specification, because the energy assessment is settled and nothing is waiting on it yet.
4. Frame. The openings exist physically for the first time, and they are now measurable.
5. Window measure at frame stage. A measure is taken off the built frame, with the openings checked for square and for real dimensions.
6. Manufacture. Units are made to the measured sizes. The lead time varies by specification and colour and needs to be confirmed for your job rather than assumed.
7. Delivery and installation at lock-up. Windows and external doors go in so the building can be closed up and made weathertight.
8. Internal linings. Insulation, plaster and the rest of the internal trades follow once the building is closed.

The point worth making explicitly is step five. Windows are measured off the built frame, not off the drawings, because timber moves, openings end up fractionally out of square, and a frame built to a plan is not identical to the plan. That is why the measure cannot happen before the frame is up, and why manufacture cannot start before the measure. Manufacture therefore sits directly on the critical path to lock-up: the date the frame is finished and the lead time on your specification together set the earliest date the building can be closed.

What compliance sets for you

Three things are decided by the site and the code rather than by preference, and they narrow the options before anyone talks about taste.

The energy efficiency provisions of the National Construction Code. The energy assessment for your home, usually a NatHERS rating, models the building envelope with assumed window performance. Whatever glazing the model relies on is what has to be installed, so changing the glass later means the assessment no longer describes the house that was built.

The bushfire assessment for the site. If the land is in a bushfire prone area, an assessment sets a bushfire attack level, and the BAL determines the glass, the seals and in some cases the screening. It is a property of the site, not a choice. Bushfire rated windows and doors are supplied to meet the level the assessment sets. The assessment and the certification sit with your assessor and certifier; a window supplier supplies to the specification, it does not set it or certify it.

Council and development controls on appearance. In heritage areas and in some estates there are controls on sightlines, frame colours and the look of the facade. These vary by locality, so they need checking against the consent for your site rather than assumed.

What a supplier needs to quote your build properly

Gather these before you ask anyone for a number, and you will get a quote you can actually compare.

• Stamped drawings with the window schedule. The schedule is the document the quote is built from.
• The elevations. They show how each unit sits in the facade, which the schedule alone does not.
• The BAL assessment, if the site has one. It sets the specification, so a quote prepared without it may price the wrong product.
• The energy assessment or NatHERS certificate. This is what the glazing specification has to satisfy.
• Site access details. Whether a crane or scaffold is needed, where a truck can park, and what the path to each opening looks like.
• Your target lock-up date. This is what the manufacture lead time has to be worked back from.
• Whether you want supply only or supply and install. Decide it before you ask, rather than after the quotes arrive.

Two things follow from that list. A quote given without the window schedule is a guess, however neatly it is presented. And a quote that does not state whether it covers supply only or supply and install cannot be compared with another one, because the two are not describing the same job.

Doing the whole house at once

On a new build the whole envelope is usually done together, and the reasons are logistical rather than promotional. One measure covers every opening in the house, at the same stage, by the same person. One delivery arrives, one installation crew works through the building, and the trades who need to attend are there once rather than returning for a second round.

The specification stays consistent too, which matters more than it sounds. The energy assessment models the envelope as a whole, so a house glazed to one specification at the front and a different one at the back is no longer the house the assessment describes.

The other benefit is accountability. Where the same team manufactures and installs, the sizing and the sealing sit with one party. If an opening is tight or a sill is not draining as it should, there is one conversation to have, not an argument between a supplier who says the fitting was wrong and an installer who says the unit was out of size. On a build with dozens of openings and a lock-up date to hit, that single point of responsibility is worth more than it appears on paper.

Five things that cost builders time on windows

1. Ordering before the frame is measured. Units made to plan dimensions have to be packed out, trimmed around or remade when the real openings differ.
2. Changing an opening size after manufacture has started. At that point the change is structural at one end and a remake at the other, and it moves the lock-up date.
3. Leaving the bushfire assessment until late. The BAL changes the specification, so finding it out after the glazing is settled means pricing and ordering the job twice.
4. Choosing a colour without checking its lead time. Foils and non-standard colours can run differently from white, and nobody notices until the delivery date is confirmed.
5. Not agreeing who clears the packaging and protects the openings. Window packaging is bulky and install day is busy, so settle before the truck arrives who removes it and who protects the finished units for the rest of the build.

Start the conversation at the drawings

The window decision is made at the drawings, confirmed at the frame, and delivered at lock-up. Those are three distinct moments, and the first of them is the one that sets everything after it. A conversation that starts at lock-up is a conversation about what can still be fixed. A conversation that starts at the drawings is about getting the schedule, the glazing specification and the lead time to line up with the date you need the building closed.

If you are specifying a new build, send us the drawings and the window schedule and we will quote the whole envelope. See how we work on new home builds.