How many openings and how many square metres of glass does your Berwick house have?
A three bedroom Casey house usually has 9 to 12 window openings plus a glazed door. A four bedroom estate house runs 12 to 16 plus one or two doors. Total glazed area lands between 18 and 28 square metres, which is about 10 to 15 per cent of the floor area. Count the openings first, because the opening count drives the price far more than the glass area does.
Job size estimator.
Set the number of openings you actually have, then the size band and the glazing. The quantity shows beside each slider and the dollar range updates underneath. This sizes the job: for per-window rates see the Berwick pricing page.
What this estimate assumes.
- Every opening stays at its existing structural size, so no lintel work, brick cutting or engineering.
- Branded residential aluminium to AS 2047, standard powder coat colour, removal and disposal of the old frames included.
- Single-storey, reasonable access along each elevation, and one mobilisation rather than several visits.
- Flyscreens on opening sashes, and safety glass wherever AS 1288 requires it, both already in the base rate.
- Excludes painting, curtain and blind refitting, and any structural repair found behind the render once a frame comes out.
- This is a 2026 guide for sizing the job. A fixed price needs an on-site measure of every opening.
How to measure it properly with a tape and a phone.
Measure the structural opening, not the old frame. This is the whole ball game. On a brick veneer house, which is nearly every house through Berwick, Narre Warren South, Hampton Park and Cranbourne East, the number that matters is the hole in the brickwork: from brick face to brick face across, and from the underside of the lintel down to the top of the sill brick. The old aluminium frame sits inside that hole with a fitting gap around it, so measuring the frame gives you a number 20 to 40mm too small.
Three measurements each way, take the smallest. Width at the top, the middle and the bottom. Height at the left, the centre and the right. Openings in a house that has been moving on Casey clay for twenty years are rarely square, and the smallest dimension is the one the window has to fit through. Write both sets down rather than only the smallest, because a 15mm difference between top and bottom tells the installer something useful about the building.
Then take four more numbers. The reveal depth from the outside brick face to the internal plaster, which decides the frame depth. The sill height above the finished ground outside, which decides whether the opening needs a restrictor or a screen. Which way each sash currently opens, and which way you would prefer. And the head clearance to the eave or the gutter, which decides whether a taller door will physically fit.
Photograph everything. One photo per opening from outside with the tape extended across it, one from inside showing the reveal and the architrave, and the room name written on a scrap of paper in the shot. Thirteen openings all called window.jpg is how measurements get transposed. If you send us those photos with your numbers we can give you a ballpark the same day, though we still measure on site before anything is ordered.
Rather we counted them?
The free measure takes 45 to 90 minutes for a whole house and every opening is measured twice. You get the count, the glass area and a fixed price in writing.
The allowances to build in, and the ones not to.
Do not add a fitting tolerance. This trips up more people than anything else on this page. The manufacturer deducts the clearance for you, normally about 10mm in total across the width and the height, so a window ordered at your raw opening size arrives too big. Give the true opening dimension and let the factory take the tolerance off it.
Do add a budget allowance. Five to ten per cent on top of the quoted figure covers the reveal make-good you decide you want after all and the one opening in a 1990s house that turns out to have soft framing behind the render. On a $24,000 job that is $1,200 to $2,400 set aside, and most of the time you keep it.
Check the minimum areas before you change a window style. The National Construction Code sets minimums for habitable rooms: light transmitting area of at least 10 per cent of the room floor area, and openable ventilation area of at least 5 per cent. A 16 square metre bedroom therefore wants about 1.6 square metres of glass and about 0.8 square metres that actually opens. The trap is that an awning sash typically opens only 45 to 60 per cent of its own area, so replacing a full-width slider with a fixed panel and one awning can quietly drop a room under the ventilation minimum. There is more on how the styles behave on the awning windows page and the sliding doors page.
Allow for the small openings you keep forgetting. Toilet, laundry, ensuite, the hallway highlight and the robe window. They add maybe 2 square metres of glass between them but they are five separate openings, five strip-outs, five make-goods and five lots of sealant. On the opening count that is a third of a small house.
A typical 1999 Berwick four bedroom, added up.
Single-storey brick veneer, 198 square metres of floor, the standard estate plan with the living area facing west. Walking it room by room with a tape: lounge 2400 by 1500 at 3.6 square metres, family 1800 by 1500 at 2.7, meals 1500 by 1200 at 1.8, kitchen 1500 by 900 at 1.35, master 1800 by 1200 at 2.16, ensuite 900 by 600 at 0.54, bed two and bed three both 1500 by 1200 at 1.8 each, bed four 1200 by 1200 at 1.44, bathroom 900 by 900 at 0.81, laundry 900 by 600 at 0.54, hallway highlight 900 by 600 at 0.54, and the toilet 600 by 600 at 0.36. That is 13 window openings and 19.44 square metres of glass.
Add the alfresco slider at 2400 by 2100, which is another 5.04 square metres, and the house totals 14 openings and 24.5 square metres of glazing. Against 198 square metres of floor that is 12.4 per cent, right in the normal band, which tells you the house was designed to the code rather than generously glazed.
Run those numbers through the estimator above at 13 windows, one door, mostly medium, double glazed, with reveal make-good ticked, and it lands around $15,900 to $36,100. The reason that band is so wide is the size mix and the hardware, which is exactly what a site measure resolves. On a house like this a real quote normally comes in around the middle, and if the budget will not stretch, the sensible cut is the west elevation done properly now and the south side in a later year rather than dropping every window to single glazing.
Three sizing errors, and the honest note.
1. Ordering to the old frame. The most expensive error we get called to. The new frame lands 20 to 40mm short of the brickwork on each side, which is a gap no sealant bead can honestly bridge. Fixing it means packing, flashing and re-rendering the reveal if you are lucky, and a new window if you are not.
2. Assuming an opening can be widened. Everyone wants the 2.4 metre slider to become a 3.6 metre stacker. Past the existing lintel span you are into a new lintel, brick cutting, propping and often an engineer's sign-off, at $900 to $2,500 per opening on top of the door. Sometimes it is absolutely worth it, and the stacker door upgrade page works through when. What it is not is a free change of mind at check measure.
3. Losing openable area. Swapping sliders for fixed glass with a single awning looks better and ventilates worse. Check the 5 per cent openable rule room by room before you sign the style selections, particularly in bedrooms.
The honest note. You do not have to do any of this. We measure free, we measure twice, and we do not price installation off photographs, so nothing on this page is a prerequisite to getting a number from us. It is here because knowing your own opening count makes every quote you receive comparable, and it stops the classic conversation where one quote covers 11 openings and another covers 14. One more thing worth saying plainly: if your house was built after about 2012 with double glazing already fitted and the frames are straight, sizing a re-window is probably the wrong exercise. Read signs you need new windows first, and if it turns out to be glass rather than frames, the retrofit versus replacement page is the cheaper road. Whichever way it goes, our Berwick service page covers the area and the lead times.
Send us your opening count and we will price it.
Give us the numbers you took, or none at all, and we will book a free 45 to 90 minute measure and return a fixed written quote within 7 days.
How much glazing, answered.
How many window openings does a typical Berwick house have?
How do I measure a window opening properly?
How much window area does a room actually need?
Do I add a tolerance or wastage allowance to window measurements?
What is the most expensive sizing mistake on a window job?
Can I get a quote from measurements I take myself?
Know the count. Now get the number.
Free measure across Berwick, Cranbourne, Narre Warren, Hampton Park and Endeavour Hills. Fixed written quote within 7 days.