How We Calculate Building Condition

A guide for property owners and managers

This document explains, in plain language, how the condition figures in your
report are produced: the condition of each individual building part, the
condition of each part group, and the condition of the whole building.

1. What "condition" means

Condition is a percentage between 0% and 100%.

Condition describes technical condition — how much technical life a part
still has — not market value and not how pretty it looks.

Why condition never reaches 0%

Every building part has a wear limit: a floor below which its condition is
never reported. A worn-out roof is still a roof. It still keeps most of the rain
out, and the parts underneath it are still there. The wear limit reflects that
residual usefulness.

Different parts have different wear limits. A foundation might have a wear limit
of 40% (it essentially never becomes worthless), while a ventilation unit might
have a wear limit of 10% (once it fails, very little is left).

Consequence: a building can never be reported at 0% condition, and often
cannot even be reported at very low percentages. See section 7.

2. The three levels

Conditions are reported at three levels, and each level is built from the one
below it:

                  WHOLE BUILDING
                        |
        +---------------+---------------+
        |               |               |
   STRUCTURAL         HVAC         ELECTRICAL
        |               |               |
   foundation      heating system    electricity
   base floor      heat distribution  lift
   sitework        ventilation        automation
   outer wall      pipes              fire protection
   facade          cooling system
   windows
   floors
   roof
   balconies
   interior

Only the parts that actually exist in your building are included. If your
building has no lift and no balconies, they simply do not appear anywhere in the
calculation or in the report.

3. Level 1 — the condition of a single part

Each part ages along its own curve. Three numbers define that curve:

• Technical lifecycle — how many years the part is expected to last

(for example, 50 years for a roof).

• Wear limit — the floor described above.
• Age — how many years the part has been in use since it was built or last

replaced.

The condition of a part is:

Condition = 100% − (age ÷ lifecycle)² × (100% − wear limit)

…and never lower than the wear limit.

Why the curve is squared, not straight

A part does not lose condition evenly over its life. A new roof barely changes
in its first years; an old roof deteriorates quickly. Squaring the age fraction
reproduces this: wear starts slowly and accelerates.

Example — a roof with a 50-year lifecycle and a 30% wear limit:

After the roof reaches its wear limit at 50 years it stays there. Meanwhile
other parts with longer lifecycles keep ageing. Each part follows its own
clock.

Repairs and renovations

If a renovation is recorded for a part, we add the value that renovation created
back into the part and continue ageing from that improved level. A partial
renovation lifts the part part-way back up; a full replacement resets it to
100% and restarts the clock at zero years.

4. How parts are combined — weighting by renewal cost

A group condition is not a simple average of its parts. Averaging a €900,000
facade with a €9,000 balcony railing as if they mattered equally would be
misleading.

Instead, every part is weighted by its renewal value — essentially what it
would cost today to renew that part, in today's prices. Expensive parts move
the group figure more than cheap ones, in proportion to how much of the
building's technical value they represent.

Group condition =
(sum of: each part's condition × that part's renewal value)
÷ (sum of: all those renewal values)

Worked example — a structural group with three parts

Assume the building is 20 years old and nothing has been renovated:

Weighted sum:

0.888 × 100,000  =  88,800
0.800 ×  60,000  =  48,000
0.667 ×  40,000  =  26,667
                   -------
                   163,467

Group condition = 163,467 / 200,000 = 81.7%

The facade is in clearly the worst shape (66.7%), but because it is the
cheapest of the three to renew, it pulls the group figure down only modestly.

Prices are always expressed in the report year

Renewal values are restated into the prices of the year you are looking at,
using a construction-cost index. This means a part installed in 1995 and a part
installed in 2020 are compared on equal terms, and the weighting is not distorted
by inflation.

5. Level 2 and 3 — group and whole-building condition

Group conditions (structural, HVAC, electrical) use exactly the formula in
section 4, applied to the parts of that group.

Whole-building condition uses exactly the same formula again, applied to
every part in the building at once:

Whole-building condition =
(sum of: every part's condition × its renewal value)
÷ (total renewal value of the building)

Because the same weighting is used at every level, the whole-building figure can
equally be calculated from the three group figures, weighted by each group's
total renewal value. Both routes give the identical answer. This consistency is
deliberate: the numbers you see always add up.

A practical consequence: the structural group usually dominates the
whole-building figure, simply because structural parts are usually the most
expensive to renew. A building with excellent HVAC and a tired facade will still
report a mediocre overall condition.

6. When you enter a condition yourself

Often you know the real condition of something better than a calculation does —
because you have an inspection report, or you have simply been in the building.
You can enter a condition at any of the three levels, and the system works
backwards from what you entered.

6a. Entering one single part ("the windows are at 55%")

This is the most targeted edit.

1. The part you named gets exactly the condition you entered.
2. Every other part is left alone. Any condition you had already recorded for

that same year stays exactly as it was. Parts you never recorded keep their
calculated condition, based on their age and their renovations.

3. The group containing that part is recalculated from its parts.
4. The whole-building figure is recalculated.

The other two groups will not move at all, because none of their parts changed.
Only the group you touched, and the building total, will move.

One exception: if you enter a value below the part's wear limit, the wear
limit is reported instead. We do not report a part as being in worse shape
than its floor allows.

6b. Entering a whole group ("HVAC overall is at 65%")

You are describing the group as a whole, not any individual part, so the system
has to decide how to distribute that figure across the parts inside it.

It does so by finding a single equivalent age — one age that, if all parts of
that group had been ageing for that long, would produce exactly the group figure
you entered. Each part is then read off its own curve at that age.

This is the key idea, and it is worth stating plainly:

We do not apply your percentage to every part. Entering "HVAC is at 65%"
does not set all five HVAC parts to 65%. It sets them to the mix of values that
genuinely averages out to 65%, given their different lifecycles and wear limits.

So a part with a short lifecycle comes out well below 65%, and a part with a long
lifecycle comes out above it. Some short-lived parts may already have hit their
wear limit and sit at their floor.

Continuing the worked example from section 4, if you enter 70% for that
group:

Equivalent age found: about 25.6 years

Roof     (50 yr life, 30% floor)  ->  81.6%
Windows  (40 yr life, 20% floor)  ->  67.2%
Facade   (30 yr life, 25% floor)  ->  45.4%

Check: (0.816 x 100,000 + 0.672 x 60,000 + 0.454 x 40,000) / 200,000 = 70.0%

The other two groups are untouched: their parts keep their recorded or
calculated conditions. The building total is then recalculated from all three
groups.

6c. Entering the whole building ("the building is at 60%")

Same mechanism, applied to everything at once. One equivalent age is found for
the entire building, every part in every group is read off its own curve at that
age, the three group figures are rebuilt from those parts, and the building
figure is rebuilt from the groups.

This is the broadest edit available: it overwrites every part condition in the
building for that year. Use it when you have an overall assessment and no
part-level detail.

Which edit should I use?

Prefer the most specific level you have real information for. A single-part edit
disturbs the least and is the easiest to explain later.

7. Why a condition you enter may not be accepted

Because every part has a wear limit, a group has a minimum reachable
condition: the figure you get when every part in it is sitting on its floor.

Using the section 4 example again:

Minimum = (0.30 x 100,000 + 0.20 x 60,000 + 0.25 x 40,000) / 200,000
        = 52,000 / 200,000
        = 26%

That group can never be reported below 26%, no matter how old the building gets.
If you enter 15%, the system does not silently pretend to comply. It puts every
part on its wear limit — the worst state that is physically meaningful — and
reports the resulting 26%.

If a figure you entered comes back higher than what you typed, this is why.
Nothing went wrong. You asked for a condition the building is not able to have,
and you were given the closest attainable one. The report also carries the
minimum condition for every line, so you can always see the floor you were up
against.

8. Frequently asked questions

Why did my building condition change when I only edited the windows?
The window condition feeds its group, and the group feeds the building. Both
totals are recalculated from the parts. The size of the shift depends on how
expensive your windows are to renew relative to the whole building — this is
usually a small nudge, not a jump.

Why is one group so much worse than the others?
Groups contain parts with very different lifecycles. HVAC and electrical parts
typically last 20–35 years, while structural parts last 40–80. In a 30-year-old
building, the HVAC group is often near the end of its life while the structure is
barely middle-aged. This is normal and expected.

I renovated the facade. Why didn't the condition go to 100%?
A repair adds back the value that repair created; only a full replacement resets
the part to new. A €200,000 repair on a €900,000 facade restores part of the
lost condition, not all of it. Record it as a part replacement rather than a
repair if the element was genuinely renewed in full.

I entered a condition for last year. Why is this year's figure different?
Conditions are recorded against a specific year, and they are only used for that
exact year. For any other year the calculation starts from what you recorded and
ages the part forward from there. A part you recorded at 80% in 2024 will be
slightly below 80% in 2026 — as it should be.

Some parts show a condition but no cost. Why?
A part that exists in the building but has no renewal cost recorded is still
listed, and flagged as having no cost, so you can see that it is there. But
because the whole weighting is based on renewal cost, such a part carries no
weight at all in the group and building averages, and its own condition cannot
be derived either. If you see this on a part that clearly does have value, the
renewal cost for it is most likely missing from the building data — that is
worth fixing, because it also means the part is missing from your repair debt.

Does condition affect the repair debt figures?
Yes. Condition and technical value are two views of the same underlying number.
The gap between a part's current value and its as-new value is what drives the
repair backlog, so editing conditions changes repair debt as well.

Summary

1. Each part ages on its own curve, defined by its lifecycle and its wear limit,

and wear accelerates over time.

2. Each part has a floor it never goes below.
3. Groups and the whole building are cost-weighted averages of their parts —

expensive parts count for more.

4. The same weighted-average formula is used at every level, so the figures

always reconcile.

5. When you enter a condition for a group or the whole building, we solve for the

single equivalent age that produces it, and distribute it across the parts
realistically rather than applying it flatly.

6. When you enter a condition for a single part, nothing else you have recorded

for that year is disturbed.

7. A figure below the minimum reachable condition cannot be honoured, and the

minimum is reported instead.

Updated on: 18/09/2026