Floor Area Ratio - Lot Coverage

[Joe_Carrick]

OK, so depending on the jurisdiction there can be a lot of difference in what the Building Dept can require in terms of the FAR and LC calculations.

 

Generally, the FAR is simply the Gross Floor Area (All Floors) / Total Site Area

 

The LC is generally the Total 1st Floor Area of all Structures plus Parking Pads & Driveways / Total Site Area

 

Sometimes a jurisdiction also wants a Main Building Footprint Coverage which includes Deck, Porches, Paved Courts, Sidewalks, etc.

 

What are the most common in your areas and are there any additional items required?

[kMoquin]

Usually lot coverage here. Some municipalities it is just the building, but most include building, decks, driveway, patio, etc..

[HumbleChief]

FAR. Gross floor area all floors - plus garage area - in San diego.

 

Lot coverage - all structures, patios covers etc. Not driveways parking pads - City of Coronado.

[Kiwideziner]

Our site coverage is rthe area to the gutters plus hard surfaces.

[Richard_Morrison]

Some areas have FAR, some just have lot coverage, some cities use both depending on what zoning district the subject property is actually in. The biggest issue is what is actually included in FAR or lot coverage. For example, some municipalities include stairs at both levels, some just at one. Some have "floor area equivalents," meaning if the space is very tall, you might get additional square footage assessed. Some include floor area or lot coverage for porches depending on how many sides are open, and some include decks only if above a certain height above grade. Certain architectural features like fireplaces or bay windows may or may not get counted.  Paving often gets calculated differently if permeable vs. impermeable.

 

Why do you ask?

[rlackore]

Some areas have FAR, some just have lot coverage, some cities use both depending on what zoning district the subject property is actually in. The biggest issue is what is actually included in FAR or lot coverage. For example, some municipalities include stairs at both levels, some just at one. Some have "floor area equivalents," meaning if the space is very tall, you might get additional square footage assessed. Some include floor area or lot coverage for porches depending on how many sides are open, and some include decks only if above a certain height above grade. Certain architectural features like fireplaces or bay windows may or may not get counted.  Paving often gets calculated differently if permeable vs. impermeable.

 

I agree with most of this for my area. Plus, some jurisdictions will count a suface as pervious, while others will count the same surface as impervious.

[Joe_Carrick]

Why do you ask?

I have been working on a macro system that automatically keeps track of all Building Areas by Room, Floor, Room Type, and a variety of other factors.  It works invisibly and can calculate the Total Areas, Sub-Totals by Room_Type, FAR and Lot Coverage.  I can even go so far as to have it provide sub-totals for the Bedrooms, Master Suite, Baths, etc.

 

In order to have as complete set of macros for FAR and LC I need to know what needs to be included and what should not.  I know what the jurisdictions that I do work in require but I also know that they are not all the same.

 

If I have a macro that covers each variation as required by the jurisdictions then anyone could use it to get an automatic display of those things - calculated accurately.

[DRAWZILLA]

There all different around here, you have to look it up online.

[Joe_Carrick]

It appears that the best bet would be to start with the Wikipedia Standard - then add additional macros on a custom basis depending on the local requirements.

 

So maybe I end up with:

 

FAR

FAR - San Diego

FAR - Anaheim

FAR - Riverside

FAR - Big Bear Lake

 

LC

LC - San Diego

LC - Anaheim

LC - Riverside

LC - Big Bear Lake

 

Each macro customized to meet the needs of that particular local.  It's doable - and having a basic starting place makes it easy enough.

[fangelo]

I find that every jurisdiction is different  based on the language in the zoning code.

[Gawdzira]

Building area also for me sometimes. That would be the FAR + decks over 24" above grade or overhangs/eaves that project farther than 18". Fireplace footprints go into the building area and FAR.

[Nicinus]

Where I'm at it is coverage of all buildings including garage and guest houses. Second floor has it's own rules, max 7.5% of the lot size. The first 500SF of porches open on 2 sides or less are excempt.

[dshall]

All of these comments reinforce my notion that we need to be able to use PLINES to describe different areas. I think it's is too complicated and cumbersome to expect that CA will give us the tools for all of the different variables that have been defined in previous posts.

Conclusion: we need boxes with labels, and within these labels there is an area calculation, and we should then be able to take this area calculation and put this value in any number of formulas.

[Kiwideziner]

Scott that sounds the easiest to cover any and all possibilities.

[lbuttery]

yes, when I worked in the DC metro area ,we had DC, MD, VA and the 8 counties within these states to deal with

plus more if he branched out to Baltimore and Fredericksburg and Richomond

 

they all seemed to want something different concerning the codes

 

I doubt if you will be able to cover "everything"

so code for the common and do the "outliers" as needed

 

Lew

[Joe_Carrick]

Scott,

 

I agree that PLines with Labels are needed.  My main concern with PLines is that they do not automatically adjust when the building and site features change.  That means the user has to manually adjust the PLines to match those other items.

 

I'm trying to get a more reliable method - one that is always in sync with the Plan.

 

Terrain Features such as Driveways, Sidewalks, Roads, etc should also have Labels.  All these things are potentially needed for such calculations.

 

Rooms - including Courts, Decks, Balconys, Porches, Garages, etc - already have names and types that can be used to accurately calculate building areas.  I know that in general you do not like to use Room Types but I'm sure that you do use them for some things.  I personally use them because they provide more information. 

[GerryT]

For what it’s worth (who **** cares) I agree with both Scott and Joe on this one but both are wrong in not considering the remaining problem areas - IMNOHO. Polylines w/label would only uncover a new range of limitations which would make area analysis still impractical in Chief.

 

Notably, is the lack of a readable ID or name field to uniquely identify the object, as is available with rooms? Also the lack of a default label to allow one common default macro to read all similar objects. Lacking that, a macro for every object is required on every new plan and/or plan revision. Which is totally impractical? The other point is that roads, streams, gardens, fenced areas, overhangs do not lend themselves easily to polyline outlines. And polylines on top of polylines create an enormous amount of confusion. And they can’t turned off since their macros would then not execute.

 

And in practice, using individual polylines, writing to global memory, requires as much "hook-up" effort,upon each new revision, as just the " pencil and paper" method.

 

Also required, is the ability to quickly group select several objects together as one identity.

To accomplish this:

1. We need the ability to tag any object or selected object group, and establish a permanent connection to their attribute accessor methods in memory in a designated location and have those connections automatically re-established upon saving and re-opening the plan.
2. The ability to execute a single macro or sequence of macros on demand from an icon similar to the library place icon.

 

Using the above one could simply place a series of tables which would contain the calculation macros in your library, one for each different scenario. When the table is added to the plan, the appropriate macros are also brought in and the only remaining effort is to select and connect the appropriate objects/areas to global memory location.

 

You might be surprised to know that this ability already exists, under the hood, as I have demoed, but has yet to be made available to us. – WHY NOT???

[Doug_Park]

You make some very lucid points.

[Joe_Carrick]

I think the KEY POINT that Gerry made is that not only do we need the Polylines to have Labels but that they also need to have unique identifiers (aka Names).  This should also be done for the Terrain Features such as Roads, Terrain Paths, Driveways, etc. 

 

Another item that would be really helpful would be a floor_number for Rooms.  I am currently using a couple of different methods to identify the floor a room is on but neither of these is 100% fool proof. 

 

Gerry's other points regarding persistence of data, grouping & execution of a sequence of macros on demand are also valid.  I will say that I can already perform a sequence of macros on demand very easily - but it would be nice to be able to assign those to a Toolbar Button.  The Tables can be done by having them stored as Rich Text Boxes in CAD Detail Windows.