Floor area to include siding?

[Alchemyjim]

Hello everyone,

 

I have been in construction for 20 years and I had the first building department say that the floor area is measured to the exterior of the siding. For every project I've ever been on I have measured to the exterior face of the framing (essentially to the edge of foundation). This is a new one to me but sure enough it is in their code (Santa Clara County, CA). Has anyone else run into this?

It is kind of a big deal. For example a 30' x 30' house should be 900sqft. But if you add sheathing, house wrap, siding etc., it is 912 sqft. 

I am working on a 5,000 sqft residence with a convoluted shape and thick stucco cladding. This would add another 77 sqft.

 

Thanks and appreciate the feedback.

[Alaskan_Son]

Never had anyone ask for square footage using those parameters.  I could see why certain departments could potentially want that information though.  It may not be a usable living space number, but it could definitely be a valid number for lot coverage or other overall footprint/building envelope information.  As a more extreme example, around here we occasionally use something called the REMOTE Wall System which is comprised of

• Framing
• Exterior sheathing
• Building wrap
• Exterior Foam Insulation
• Furring strips
• Siding

That could mean an extra 5-1/2" or more of conditioned space or building envelope around the entire perimeter (energy code stuff), and if we use 6" of foam, up to an extra 8" of building footprint around the entire perimeter (lot coverage stuff)...so again, it could make sense that certain departments would want this information under certain circumstances.  Not at all normal in my experience though especially for standard construction.

[DRAWZILLA]

Never been asked that either and I'm in Calif. As usual all the cities want to milk you for as much money as they can.

[VisualDandD]

Actually I used to think this way, but I realized there are differing ways of measuring sqft.   I would often notice that appraisers would do a home I drew and it would always be 100-200+ sqft larger than what I drew.  I just assumed they were not good at doing thier job

 

Turns out, I was the one that was wrong.   There is actually an ANSI standard published on how to calculate square footage.   Appraisers are required to use this standard when calculating 'living area'.  It goes to the outside of the envelope.  Outside of siding or brick.  With brick, it adds approx 200-300sqft to a home.  Always notice brick homes appraise for more, part of it is they measure more!

Also the odd one is stairs are measured on BOTH levels.

 

This is quite different than the construction standards which have always been face of stud and stairs on one level.

 

Here is a link to the standard:

https://www.homeinnovation.com/-/media/Files/Standards_Development/Square_Footage/2020_Z765/ANSI_Z765_-_DRAFT_20200207_-_no_cover_art.pdf

 

 

[Alaskan_Son]

1 minute ago, VisualDandD said:

Also the odd one is stairs are measured on BOTH levels.

 

Absolutely makes sense.

I have always counted stairs twice myself.  Not only is there commonly usable space beneath the stairs but they require at least twice as much of everything  that occupies said space, and to say they double the time required to design and build that space would be a gross understatement.  

[Gawdzira]

Carmel by the Sea counts the building area to the outside of the siding. I believe Monterey County does as well. 

[Gr8trim4u]

So here is one for you. We calculate to the outside of the sheathing. Stairs do not count. Any rafter or truss top chord that intersects from the finished floor to the 7' mark is counted. They also include the footage inside an unfinished attic from the top of the bottom chord to the 7' mark. When i provide as builts to my architects. I have to provide a really spot on frame model of the house. 

 

The jurisdiction is the City of Alexandria VA. This is for FAR calculations. The rules seem to change 3 to 4 time a year.

[CharlesVolz]

Here is the latest ANSI Z765 I have which is 2021.

ANSI Z765-2021 - SQUARE FOOTAGE print.pdf

[Alchemyjim]

Thank you everyone, 

This has been very informative. I think many of us in the industry (including building officials) have been using different methods. It sure complicates matters because this means a 10' x 10' shed is actually 100.7 sqft. But ANSI Z675 clears it up. It is indeed 100.7 sqft. Wild but true.

 

Perhaps this is a good suggestion for Chief as it measures sqft area from exterior framing which is not the code. Maybe an option to create a polyline that includes siding?

 

[DBCooper]

It's already there.  In general plan defaults, you can set your living area to either surface or main layer.  Also, you can control which rooms are included or not and then you can use the "make living area polyline" tool to generate the polyline that was used for the living area.

 

[Chrisb222]

15 hours ago, VisualDandD said:

Also the odd one is stairs are measured on BOTH levels.

 

To my reading, any unfinished area under stairs would not be counted, nor would finished area under stairs with ceiling lower than 5'. So in most cases, the full area occupied by stairs would not be measured on each level.

 

 

 

 

 

[VisualDandD]

18 minutes ago, Chrisb222 said:

 

To my reading, any unfinished area under stairs would not be counted, nor would finished area under stairs with ceiling lower than 5'. So in most cases, the full area occupied by stairs would not be measured on each level.

 

 

 

 

 

 

Nope.  Clearly shown in graphic example of sqft envelope that they fully count them on both floors.    They then have a break out to show specifically how stairs are measured on 2nd floor.   to where you only count the actual area of stairs and NOT the open to below area. 

 

The old....picture is worth 1000 words is easy on this one.  Look at their examples.

 

[Chrisb222]

1 hour ago, VisualDandD said:

The old....picture is worth 1000 words is easy on this one.  Look at their examples.

 

Yeah I saw that, but the example diagrams are not part of the Standard. I'm going by the language of the Standard, which clearly states that unfinished area is not counted, and finished area with lower than 5 ft ceiling is not counted. It seems their drawings are not a very accurate representation of the language of the Standard.

 

It's interesting that the drawing shows finished space in the basement with no access to the space beneath the stairs, yet it indicates that that space should be counted, which clearly violates the language of the overriding Standard.

 

Maybe I'll write to the commission. 

[Alaskan_Son]

15 minutes ago, Chrisb222 said:

...and finished area with lower than 5 ft ceiling is not counted.

 

Section 3.7 clearly states that under stairs there is no specified height requirement. 

 

I could see an argument for any enclosed or inaccessible area beneath the stairs as being considered unfinished but But BUT...considering that the area is typically both minimal and inaccessible just like any other areas covered by interior partitions, exterior walls, siding, chases, furred walls, etc. then I'd say the intent of the code makes it relatively clear that it should be measured.  Its inside the finished footprint and not unlike any other finished area of the house where there exists areas covered by unusable voids, trim, wall framing, wall surfaces, etc..  If you leave it out of the calculations then you head down a path to leaving other inaccessible areas out as well (chimney chases, thick walls, cabinet voids, etc.)

[Chrisb222]

4 minutes ago, Alaskan_Son said:

Section 3.7 clearly states that under stairs there is no specified height requirement. 

 

Thanks, I see now that all finished area under stairs counts. I read that section but the wording was a little unclear to me. My apologies to @VisualDandD

 

4 minutes ago, Alaskan_Son said:

If you leave it out of the calculations then you head down a path to leaving other inaccessible areas out as well (chimney chases, thick walls, cabinet voids, etc.)

 

Actually, I was thinking specifically of usable space beneath stairs, which is not only accessible, but usable - although often unfinished. 

[Joe_Carrick]

For stairs, the area is the actual surface area.  Under stairs usable space is also included.  

Assuming a 1 story stair the "open below" area isn't counted because there's no floor.  If it's a 2 story stair then you have to count the 2nd floor stair but not the "open below" of the 3rd floor.

Note that the "Open Below" area may not be the same as the stair area.

 

[ValleyGuy]

In my area, the county isn't as concerned about the few dollars/sq ft for a permit, they are pretty relaxed here so it doesn't effect the plan measurements. However, for the purposes of taxes, they come out and physically measure to the outside of the corner boards! Greedy buggers tax me for a couple hundred extra sqft year after year!