Post #1087: Do you want bigger houses in Vienna, VA?

Posted on April 1, 2021

And I don’t mean, “more houses of the size currently being built.”

I mean, do you want the Town to change the zoning rules to allow new houses to be, say, 25 percent larger than the ones currently being built?

The Town is in the process of doing just that.  And here’s the thing.  Nothing that you will see from the Town of Vienna will ever let you know that this is (part of) what the revised zoning will do.  Instead, if you look at what’s available from the Town, you’ll get the impression that this is some harmless revision to allow more outdoor living areas.

But if you step back and actually look at the law, and the simple economics of it, the main impact of this law is going to be to increase the size of new houses in Vienna.  Materially.

It’s not rocket science to understand this.  Heck, it’s not even hard to visualize what this proposed change will do.  (At least, for the most common case where the current lot coverage rule limits the size of the house.)  Look at any large new house, and imagine putting up a full-height addition on the house, covering the entire driveway.  For typical new house construction in Vienna, that larger house will become the standard.  And this is an immediate, logical, and (to an economist) inescapable consequence of this one small aspect of the proposed change in zoning.

And, because nobody in the Town of Vienna government will say that, these days, I feel that I should.  Although, as cited below, some Town Council members did say that, in the past.  So that’s what I’m going to do in this post.  In effect, I’m just reminding you of a now-forgotten Town Council debate that included this exact issue.

To be clear, I really don’t care about this issue one way or the other.  Instead, what got me started on this topic is that, as with the now-repealed MAC zoning,  when it comes to development, all we seem to get out of our Town government is cheerful, upbeat, and often misleading information.  Cute pictures of little front porches on houses.  And, somehow, we never get an unvarnished and unbiased presentation of the facts.

Finally, what does the title of this post have to do with the May 4 Town election?

We rarely have Town Council candidates that are clear about any one issue.  Instead, in most but not elections, in most but not all cases, we tend toward being fed bland statements around election time.  This gives you the option of voting for whichever flavor of motherhood-and-apple-pie you find most appealing.  But nothing meatier.

But this particular change in the zoning is the creation of Councilmember Patel.  (Reference, Reference).  As I understand it, at least initially, she was merely trying to solve a problem for some neighbors.  But it’s now clearly on track to become permanent change in the residential zoning of Vienna. And, as shown below, it will have consequences for the town.

And so, unlike so much of what happens with Town Council, this is one issue that is clearly owned by one Town Council member.  If you favor this proposed change, you should vote for Councilmember Patel in the May 4th election.  If you don’t, you should vote for someone else.

But above all, you should at least be given an opportunity to understand what’s being proposed.  And vote based on clear information.  And you won’t really get that if all you rely on the Town as your sole source of information.

Details follow.

Cut to the chase.

Let me skip a lot of stuff that would provide much of the context.  I don’t think it really matters that this was a well-intentioned attempt by one Town Council member to accommodate some Vienna residents’ wants, in their existing homes.

I think it’s more important to point out to Vienna citizens what this will do to all future home construction in Vienna.  And so, rather than dwell on the past, or even mention the existing residents who would be helped by this proposal, I’m just going to explain what this proposed change would do to the size of new houses in Vienna.

Current lot coverage rule

To understand what’s going on, you first need to know what limits the size of houses now.  Vienna currently allows single-family homes to cover no more than 25 percent of the area of the lot they sit on.   That’s for the house, driveway, any outbuilding, patios, and so on.  Pretty much the sum total of everything that’s paved or under roof.

(There are other limits — height, number of stories, setbacks from lot lines, and so on.  But the main one that would be affected by this proposed change is the 25 percent lot coverage limit.)

You can read the law at this link, but here’s the key part of that for one of those residential zones:

Sec. 18-15. - Area requirements.

F.   Lot coverage. Not more than 25 percent of a lot shall be covered by buildings, accessory buildings, automobile parking spaces and access, sport courts, tennis courts, patios and terraces. Decks, as regulated in section 18-169, may not cover more than five percent of the total area of a lot.
(Code 1969, § 18-15; Ord. of 6-6-1988; Ord. of 4-17-1989; Ord. of 8-19-1991; Ord. of 10-7-2002)

And, sure enough, pretty much every new home built in Vienna covers the full 25%.  (See last line in this reference.)  Which is no surprise to anyone who has been watching the ongoing tear-down boom in Vienna.

So, more precisely, a house, driveway, and any outbuildings (e.g., detached garage) and other paved areas can cover no more than 25% of the lot.  (Decks don’t count toward that 25%, but instead are limited to an additional 5%.)

The key here is that the sum total area of all of those has to fit within the 25% limit.  The practical result of that is that the footprint of new houses in Vienna is currently limited to less than 25 percent of the lot.  That’s because you have to fit the house, driveway, and every other paved or roofed surface into that 25% limit.

I think that’s clear.

Proposed lot coverage rule.

The Patel proposal would raise the total lot coverage to 30%, and would allow the house to cover a full 25% of the lot.  The remaining 5% could have to be used for screened or covered porches, patios, driveways, and such.

You might not think that an additional 5% of the lot could matter much.  But, based on a sample calculation below, that will translate to roughly a 25% increase in the size of the typical new house, as I demonstrate below.  So it’s really quite a material change.

Now, this is not how that proposal is written or described.  It’s described as allowing 5% more lot coverage for those “outdoor” uses, including (I think) screened porches.  It really doesn’t mention the size of the house at all.

But unless I’ve missed something, that’s exactly how it would work.  Assuming builders could squeeze the necessary driveway into no more than 5% of the area of the lot, this would now allow houses to cover a full 25% of the lot.  (More properly, I guess, it’s “everything enclosed by roof and walls” that would have to fit into the 25%, but in almost all cases, that’s the house.) As long as the builder could fit all that other stuff into the remaining 5%.

Let me be clear that this isn’t a secret, and I am far from the only one to have noticed it.  When this proposal was first brought forward, Town Council members immediately raised the possibility that builders would just use this to increase the size of houses so that they would cover 25% of the lot.  (That’s discussed on this Facebook page, by a Town Council member.)

Let me also say that this higher level of lot coverage appears perfectly normal for the Northern Virginia suburbs.  For example, Falls Church says that all the buildings on a lot used as a private residence can cover no more than 25 percent of the lot.  Separately, total impervious surface (which would include driveways) cannot exceed 35%.   City of Fairfax (.pdf) also limits total building coverage to 25 percent, except that affordable housing units can cover up to 30 percent of the lot.  Total impervious area cannot exceed 40 percent.  (Fairfax County (.pdf), by contrast, seems to have much stricter rules.  For their housing zone with three houses per acre, houses are restricted to a 25 percent floor area ratio.  That would effectively limit a two-story house to covering no more than about 12.5 percent of the lot.)

But what seems clear to me is that nobody is now saying what should be obvious:  That by voting in favor of this as part of the overhaul of all the coding in Vienna, Town Council members will be voting in favor of a large increase in the size of new houses in Vienna.

Other aspects of the proposal — such as allowing covered porches to protrude beyond the normal setbacks — I don’t think I’ve seen those anywhere else.  But it’s not as if I’ve looked, or even care to look, to find out.  There’s also a storm water hold-harmless provision, but in my experience, those are unenforceable over the long run.  (Nobody bothers to check if (e.g.) infiltration trenches are still functioning years after they are built, and with our clay soil, most will eventually fail without considerable periodic maintenance.)

A simple numerical example.

For this, I’m just going to take my across-the-street neighbor’s house and try to do some simple measurements via Google Earth.  You have to be a little bit careful, because part of the driveway is actually on the Town of Vienna right-of-way.

Per Fairfax County tax records, the parcel is 16,050 square feet.  The full 25% coverage would then work out to be more-or-less 4000 square feet.  Google Earth says the footprint of the house clocks in at just a bit less than 3200 square feet under roof.  And, sure enough, excluding the part I estimate to be on Town land, the driveway is just about exactly 800 square feet.

Plus or minus a little measurement error, then, the house and driveway cover the 4000 square feet that is allowed to be covered under current rules.  But the house only covers 3200 square feet, because they needed a large driveway to serve the multi-car garage.

Under the new rules, the builder of that house would now have an additional 800 square feet to play with (another 5% of the 16,050 square foot lot).  Which, by coincidence, is exactly the size of the driveway.  Now the builder can build the house out to a full 4000 square foot footprint.  And the driveway fits neatly into the additional five percent, allowed for outdoor spaces, under the Patel proposal.

And so, in this real-world example, a house that maxed out the new rules would be 25 percent larger than the house that maxed out the old rules.  (I.e., 4000/3200 = 1.25).  It would be 4000 square feet (25% of the lot), with an 800 square foot driveway (5% of the lot), for total lot coverage of 30% of the lot, of which 5% is for outdoor surfaces.


I think my across-the-street neighbor’s house is fairly typical for new construction around here.  And if you think developers wouldn’t max out the new rules, you clearly haven’t paid attention to the tear-down boom so far.

Councilmember Patel herself said that the intention of this change is not to allow for bigger houses.  (Cited here.)  But I think we learned with MAC zoning that the intention doesn’t count, at all, when it comes down to what’s legally allowable under the zoning, and what is most profitable to build.  What counts is what’s spelled out in the rules.  And the revised rules would allow for new houses to be significantly larger than they are now.

If, for whatever reason, the Town wants to allow for more outdoor living space, so be it.  Or if it wants to make exceptions for existing homeowners who somehow didn’t realize that they were buying the largest house that would legally fit on their lot, likewise.  But if the intention is not to have larger houses, then, as we learned from MAC, you’d damned well better write the law so that it doesn’t allow for larger houses.  Because, right now, as proposed, that’s surely going to be the result.

The Town has hired lots of top-drawer consultants to assist the rewriting of all the zoning in Vienna.  With all that genius talent on tap, surely, if they wanted to, they could find a way to do that.

Or, alternatively, at least admit that you’re going to get bigger new houses from this.  Don’t disguise that fact with a lot of happy talk and pretty pictures.  Just have a realistic discussion.

As I said up front, I don’t much care one way or the other about this.  But I’d bet  that some residents do.  And I think the citizens of the Town should be allowed to form an opinion about this proposed change based on what it will actually do.  Not based on cute little drawings, or even based on good intentions, but based on the actual letter of the proposed law.