topic Re: Zones driving me insane in Documentation

Zones driving me insane

alexliz — Mon, 26 Jan 2026 14:09:35 GMT

I have an automatically generated Zone (used Inner Edge) surrounded by simple walls. Floor to floor height is 4m. No doors on any wall.

Why is it calculating the correct zone area, correct wall perimeter, but incorrect wall surface?

I have confirmed that all four walls are part of the zone - look at wall parts in the right-most column.

As per the dimensions in plan view, area is correct at 34.49², also confirmed by the fill at right.

Perimeter P is also correct, 24.9228m

Ceiling Height CH is correct, 4m

Zone Volume ZV is correct, 34.49 x 4.00 = 137.97m³

Why is Walls Surface Area in column 4 wrong? It shows 95.29, it should be 99.6912, i.e. 4.40m² more than showing. It's like it's ignoring 1.10m of wall length.

The zone heights are correct, both floor and ceiling linked to the stories elevations.

This is happening with a few although not all of my project's zones. What am I missing, guys?

Re: Zones driving me insane

alexliz — Tue, 27 Jan 2026 08:26:02 GMT

Seeing there are no replies here yet, I was wondering - does anyone use Zones to calculate wall surface areas? Or do you prefer Wall schedules, instead?

Or even internal elevations and then measure manually, using fills?

Re: Zones driving me insane

Mathias Jonathan — Tue, 27 Jan 2026 08:30:24 GMT

If you change the thickness of walls, is the result the same?

Re: Zones driving me insane

Barry Kelly — Tue, 27 Jan 2026 08:43:51 GMT

Do the bottoms of the walls line up with the bottom of the zone and the tops of the wall line up with the top of the zone?

Personally I don't calculate surface areas, but if I did, I think I would use the surface schedules.

Barry.

Re: Zones driving me insane

alexliz — Tue, 27 Jan 2026 09:26:29 GMT

Thanks Mathias, interesting. I changed the two different-thickness walls at right, to make them a single wall of the larger of the two thicknesses, like this:

Without updating the Zone, I simply selected it and right-clicked on the schedule, to view only that one. This resulted in Walls Surface Area now had jumped to 121.00 (from the original 95.29).

I updated the Zone in plan view, and the 121 dropped back down to the previous 95.29.

I played around with various walls and their thicknesses and reference line direction, it stayed at 95.29. If I broke a wall in two parts of different thickness (while maintaining the floor area the same), then it may spike to 121m² but then, after updating the Zone, it always drops back down to the 95.29.

As a reminder, all walls and the zone itself are set at 4m height. No reductions enabled (due to roof/door/window/wall/column/fill etc). Since the perimeter is (correctly showing in the schedule) 24.92m, I would expect the walls surface area to be 24.92 x 4 = 99.69, not 95.29. It seems that it's always 'missing' 4.40m² (or 1.1m of the 4m-high wall).

What am I doing wrong?

Re: Zones driving me insane

alexliz — Tue, 27 Jan 2026 09:48:08 GMT

Hi @Barry Kelly ,

Yes, they do. All walls and the zone itself are set at 0.0000 bottom, with a 4.000m height. There are no slabs, no roofs, no beams, no columns, no doors, no windows, no openings to interfere with. Just a room made of 9 walls and a zone inside.

FWIW I have also deleted all 'ignore element holes if' and all 'ignore component holes if' rules in Project Preferences > Calculation Rules.

Very odd.

Re: Zones driving me insane

CIA20 — Tue, 27 Jan 2026 10:04:30 GMT

Did you check whether the issue comes from the wall’s reference line?
Try setting the wall’s reference line to the interior side only and see if that fixes it

Re: Zones driving me insane

alexliz — Tue, 27 Jan 2026 10:25:50 GMT

Hi @CIA20 , thanks. No, reference line isn't fixing it. Plus, it'd be impossible to do that - if it was the case and it did fix it on one side, you'd have the issue with the zone on the other side of the wall.

But no, it isn't the issue.

Re: Zones driving me insane

Mathias Jonathan — Tue, 27 Jan 2026 10:31:24 GMT

I'll speak from memory.

I had to create a wall surface schedules a long time ago, and I had problems with the results when using a schedule by element for wall surfaces. The exterior surface area was calculated wall by wall, without taking into account the increased/reduced surface area due to the connection. I think the solution was to switch to a surface schedule rather than an element schedule.

Re: Zones driving me insane

Gabor Szelei — Tue, 27 Jan 2026 10:46:09 GMT

Hello,

Check the thickness of the floor structure in the zone settings. It is not included in the wall surface area!

Regards

Gábor

Re: Zones driving me insane

alexliz — Tue, 27 Jan 2026 10:47:52 GMT

@Gabor Szelei Thanks - no slabs or anything other than zones and walls in this project.

@Mathias Jonathan Thanks again, I will try with surface schedules.

Re: Zones driving me insane

Gabor Szelei — Tue, 27 Jan 2026 10:52:15 GMT

I thought of this:

bottom right corner

It gives me good value with these settings.

It took me a long time to solve this problem too.

Gábor

Re: Zones driving me insane

alexliz — Tue, 27 Jan 2026 10:56:35 GMT

All my zones are set with the 'Subfloor Thickness' set to zero, as well. This is not it, Gábor : (

But, you say you solved it.

So, is it now returning the correct Walls Surface Areas in the schedule for you?

Re: Zones driving me insane

Gabor Szelei — Tue, 27 Jan 2026 11:03:35 GMT

this is very strange!

gives me a good number for the area of the walls

((5+4)x2)x3=54

Re: Zones driving me insane

alexliz — Tue, 27 Jan 2026 11:27:24 GMT

I also get *some* zones showing correct data. But most do not. In the screenshot here, only one of the four (WETROOM 03) generates correct data for the Walls Surfaces Area column - the other three show a smaller number than what it is.