A facade is bought per square metre — but not all of it

Cladding is the job that changes a house's face — and its durability class: the boards replacing tired render, the ventilated wall protecting the masonry, the front that stops asking for maintenance every season. The quote presents itself «per square metre», and the square metres do tell the main item. But around the boards work two items that do not count metres: the context — the upper storeys, the openings to trim one by one, the corners, the removal of the old skin — and the fixed block every facade carries: the site setup, the starter and closure profiles, the head flashings. This calculator breaks the quote into its three forces and sums it up in two honest numbers: the effective cost per square metre and the index ι.

The formula: square metres, context and fixed block

The model is the decomposition of the cladding job. The bare bill is A·c: the area net of openings times the installed system cost — boards, substructure, fixings, labour. On that bill acts the context surcharge h: from the 10-15% of the low, smooth front to over 60% when the storeys climb, the windows multiply and the old cladding must come down first. Outside the product stays the fixed cost F: the fixed block disguised as an accessory item, eleventh appearance of the geometry — setup, profiles and flashings do not count the square metres they will serve. The index ι = C/(A·c) is dimensionless and holds in any currency.

The facade scale: the small front pays the big one's fixed block

A 60-per-square-metre system, 30% context, fixed 1,200; only the area grows:

On the single front the fixed block is worth almost three tenths of the price and the effective square metre climbs to 108; on the small building it dilutes to 3.7% and the metre falls to 81. And the last row hides a connoisseur's detail: its index is exactly 1.35 — the model's low boundary, touched and shown: the whole facade is the site that buys cladding closest to its list price.

A complete numeric example

A typical job: 120 m² of facade — the two-storey detached house, net of openings — at 60 per square metre of installed system, context at 30% (one upper storey, ordinary windows), fixed block of 1,200 between setup, profiles and flashings. The bare bill is 120 × 60 = 7,200; the context brings it to 9,360; the fixed block closes at 10,560. The index is 10,560 / 7,200 = 1.47: every clad square metre costs 88 — not the 60 of the list — and the fixed part weighs 11.4%. Whoever compares two quotes «at 55 and at 65 per metre» without reading context and fixed block is comparing the wrong item.

How to read the quote index

The four bands tell four sites. Below 1.35 the large facade buys at list price: the real comparison is on system quality. Between 1.35 and 1.60 the cladding is well quoted: the physiology of the accessible facade. Between 1.60 and 1.95 the context climbs with the storeys: heights, trims, removals — survey territory. Beyond 1.95 you buy worksite, not boards: the work on the building dominates. No band is «wrong»: ι says where to point the lens before signing.

The cost per square metre: what it really contains

The variable c sums up the installed system. Inside live the boards with their thickness and class — from budget vinyl to fibre cement and engineered wood — the substructure that keeps everything flat and creates the air gap, the fixings and the labour that keeps the joints straight. The 30-150 range tells the real market: vinyl that dresses fast, fibre cement that lasts decades, wood that asks for its treatment. The item to inspect with a lens is the ventilated wall: the chamber behind the boards is what dries the masonry — cladding without ventilation is a damp blanket nailed to the facade.

The context: the facade gets harder as it climbs

The variable h is the survey turned into a number. The low, blind front travels at 10-15%; you climb with the storeys (every metre of height is scaffolding and handling), with the openings — every window is four trims, a sill, a junction — with corners and geometries, and with the removal of the existing when the old skin must come down before the new one goes up. It is the item that produces distant quotes on houses equal on paper — and the reason the window-filled facade costs more per metre than the blind one, even with fewer metres.

International perspective: siding, bardage and the same wall

The cladding is universal, the names are not. North America lives siding as the standard skin of the house — vinyl and fibre cement counted in hundred-square-foot squares — and replaces it the way others replace a roof; Europe says bardage, Fassadenverkleidung, ventilated facade, and mounts boards on substructure as the finish of insulation systems or the skin of extensions; everywhere the push is the same: less maintenance, more envelope. The structure of the count never changes: metres, system, context, fixed. And the index ι compares quotes across markets on the same scale, because a ratio needs no exchange rate.

Limits of the model and proper use

The model photographs the facade cladding: it does not cover the remediation of a damaged substrate, nor the thermal insulation that often travels along — the insulated jacket is another item, with its incentives — nor the windows worth replacing while the scaffolding stands. The perimeter must be written: which fronts, with which system, with which trims. And the facade lives in an envelope: the insulation cost calculator says how much the layer the cladding can dress returns, and the window replacement calculator does the maths of the opportunity the scaffolding gifts — because the facade is opened once every thirty years, and everything mounted together shares the same setup.

Inside the quote: the context scale and the fixed scale

The six sections that follow put the model on the test bench over the two items that do not count square metres. The first is the context: the same house, clad under ever more demanding conditions. The second is the fixed block: from the minimal set of profiles to serious flashing work. The two tables use the example facade — 120 m² at 60 — and move one knob at a time: the cleanest way to see where the final number really comes from.

The context scale: the same facade, different sites

120 m² at 60 per square metre, fixed 1,200; only the surcharge h grows:

From the smooth front to the constraint-filled site the total grows by more than half — from 9,120 to 14,160 — without one extra square metre of boards. The index crosses all four bands (1.27 → 1.97) and the effective square metre goes from 76 to 118: it is the price list of the how, the column phone quotes cannot see — and the reason the serious survey counts the windows before the metres.

Reading the scale: openings are the context you do not see

Inside the surcharge, the surprising item is the openings: every window subtracts square metres from the bare bill but adds four trims, a sill and two junctions to the work. It is the facade's mocking arithmetic: removing surface can add cost — the window-filled wall has fewer metres and more site than the blind one. The operating lesson: when two quotes on the same house sit far apart, the difference almost always lives in how each one counted — or did not count — the trims.

The fixed scale: from profiles to serious flashing work

Same 120 m² at 60, context held at 30%; only the block F grows:

The last row travels with the flag lit: more than a third of the quote in the closures. But here too the flag must be read intelligently: on facades with rich geometries — heads, copings, junctions with roofs — custom flashing work is often what separates the cladding that lasts thirty years from the one that leaks at the first autumn. The share turns on the lens; the specification decides the judgement.

The flashings: the details that decide the lifespan

Cladding lives or dies at its edges: the starter keeping the boards off the plinth, the head closures stopping water from entering from above, the junctions with sills and roofs. They are linear metres of folded sheet, not square metres of boards — which is why they live in the fixed block — and they are where savings take revenge: the makeshift trim does not show at handover, it shows at the first driving rain. The trade rule: the flashings are drawn before the boards, because they decide where the system begins and ends.

Before signing: the three-item checklist

A readable quote always breaks out the model's three forces. Demand in writing: the square metres net of openings with the measuring criterion; the surcharge justified — storeys, openings, corners, removals, item by item; the fixed block itemised — setup, profiles, flashings with their developments. Then two questions worth more than any discount: how the wall behind the boards is ventilated, and what happens to the price if a surprise appears under the old skin. Whoever answers with numbers is selling a facade; whoever answers with adjectives is selling a photograph.

Frequently asked questions

How much does siding cost?

With the decomposition C = A·c·(1+h/100) + F: the area net of openings times the installed system cost, increased by the context, plus the fixed block of setup, profiles and flashings. A 120 m² house at 60 per metre with 30% context and a 1,200 fixed block closes at 10,560 — an effective 88 per square metre.

What is the cladding quote index?

It is the ratio ι = C/(A·c) between the total and the bare system bill. Below 1.35 the large facade buys at list price; between 1.60 and 1.95 the context climbs with the storeys; beyond 1.95 you are mostly buying work on the building.

Why does the small front cost more per square metre?

Because setup, profiles and flashings cost the same on 40 and on 400 m²: on the single front the fixed block is worth 27.8% and the effective metre climbs to 108; on the small building it dilutes to 3.7% and falls to 81. It is the fixed block disguised as an accessory — the flashings do not count metres.

What does the cost per square metre include?

The boards with their thickness and class, the substructure creating the plane and the air gap, the fixings and the labour. The 30-150 range tells the market: from budget vinyl to fibre cement and branded engineered wood.

How much does the context weigh on the price?

It is the surcharge h of the model: 10-15% for the low, smooth front, over 60% with upper storeys, many openings to trim and the old skin to remove. Every window is four trims: the window-filled facade costs more per metre than the blind one.

What does the fixed block include?

The site setup, the starter and closure profiles, the head flashings and the junctions. They are the items that do not grow with the square metres — and the ones that dominate the small front's quote.

Vinyl, fibre cement or wood: how do I choose?

Vinyl costs less and installs fast, but fears impacts and strong sun; fibre cement lasts decades with minimal maintenance and is the reference choice; wood is the most beautiful and the most demanding. The model's variable c puts them on the same scale: at equal context and fixed block, the comparison becomes a system comparison.

What is a ventilated facade and is it really needed?

It is the air chamber behind the boards, open at the bottom and the top: it circulates air that dries the wall and carries away summer heat. It is needed: cladding without ventilation is a damp blanket nailed to the facade — and the substructure creating it is part of the cost per metre, not an extra.

Does the calculator work for American siding counted in squares?

Yes: one square is about 9.3 m², and the structure of the count is identical — area, system, context, fixed. The index ι stays comparable across markets because it is a ratio: the geometry of the quote does not change language.

Is it worth insulating together with the cladding?

Almost always yes, if the envelope asks for it: the scaffolding and the setup are paid once, and the cladding becomes the finish of the insulation layer. It is the item to decide before signing: adding it later means rebuilding the site.

And the windows while the scaffolding stands?

Same logic: the open facade is the chance to replace the windows without paying twice for access and protections. The cladding trims join new windows better than old ones: doing them together also avoids makeshift junctions.

What does the computed cost NOT include?

The remediation of a damaged wall under the cladding, the thermal insulation, the windows, the building permits where needed and the surprises behind the old skin. It is the photograph of the installed cladding: the rest is added item by item, with the perimeter in writing.

Updated July 2026