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This help desk is a free resource intended for discussion purposes only. Neither BOMA, its chapters, affiliates, or Extreme Measures Inc.® are responsible for the information, comments or opinions expressed herein. For complete information, refer to the official publications of the standards themselves.

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Mixed-Use Common area line

Susan Tang
Studio in Labour
June 15, 2014

I am doing a Mixed Used Project so I am just going through you example 1 in the 2011 standard. In the first step where the EGA is broken down to use components on each floor, the line of measurement between use component and MUCA-A ( ie stairs & elevator) seems to be in the centre of wall always. So then when it comes to actual floor rentable area calculation on each floor, for Office Use, there is IGA/EGA ratio, which is clear. My concern is for retail, I thought the rentable area is measured to the exterior side of common area wall( corridor, stairs), because MUCA is never added to the rentable area. So should I be doing a RA/EGA factor??
My project has a kindergarten. Can you tell me if I am going to the exterior side of wall, and if MUCA is assigned to it?
Your help is much appreciated!

David Fingret
Extreme Measures Inc.
June 16, 2014

Hi Susan

There is no requirement to calculate an RA/EGA ratio. MUCA allocations should be determined using MUCA and EGA. Since the Office Standard does not use EGA, BOMA has developed the Office IGA/EGA ratio to overcome this.

For the Retail portion, the Retail Standard applies, so you will be measuring to the exterior walls. The MUCA allocations for the retail portion will be either Common Area or Non-Leasable Area, so there is no impact on the Gross Leasable Area. Nevertheless, it is necessary to accurately calculate the MUCA for each Use Component regardless of whether it will affect the rentable area of a particular Use Component or not.

Susan Tang
Studio in Labour
June 16, 2014

Since it's not in the standard, the small discrepancy may not matter.
But truly to be accurate about assigning MUCA as you said. It has to be adjusted...
The exterior wall is not the issue. It is the Units against the common spaces. For example, the office again a stair, the EGA line & IGA line is different and it's adjusted thru EGA/IGA ratio. Where a retail is against a stair, the EGA line for Retail use component (centreline) is also different from the GLA line (including entire stair wall), then the GLA + MULCA adds up more than the Use component EGA
Do you get what I mean?
This creates discrepancy in the excel chart that is hard to double check.

Susan Tang
Studio in Labour
June 16, 2014

Forgot to thank you first for your help. Sorry I was a bit frustrated to figure this out. I went back to read the Office Standard, and I am even more confused.
So IGA is to the dominant surface of exterior, centreline of other unit & building common space, and inside finished surface against corridor. But if the elevator in a stacked mixed use is MUCA-A, is the IGA line at the the centreline as per building common, or the finished surface as per MVP? Secondly, am I correct to say it's inside finished surface again all Floor common space (vs. centreline with all Building common space?)
And the retail issues are somewhat opposite of these...
Thanks again. It's a bit difficult to combine standards...

David Fingret
Extreme Measures Inc.
June 18, 2014

I'm sorry but I'm finding it difficult to interpret and answer all of your latest questions.

One thing I think you might be confused with is that notwithstanding the special "IGA/EGA ratio" for the office component, EGA is used simply to determine the proportionate share of MUCA to the various building types. EGA is a separate calculation as per the Gross Building Areas standard. It doesn't matter that the retail GLA + MUCA adds up to more than the EGA because they are completely independent from the EGA.

If you have correctly calculated the areas, there should be no discrepancies in your Excel chart. Make sure that everything you've inputted is also being outputted so that there is no loss of areas or extra areas being added to the various charts.

Please note also that Mixed-Use Components on the same floor are separated by the centerline.

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