Our Ad in Today’s Gazette: Slab-on-Grade Foundations Raise Questions of Durability

Here is our ad as it appears opposite the editorial page in today’s Daily Hampshire Gazette (download a high-resolution PDF, 265 KB). This ad focuses on slab-on-grade foundations, a construction technique Kohl Construction wants to use for its proposed condos off North Street. In this article we reproduce the text of the ad and provide links so you can explore the issues. The Planning Board will take up Kohl’s proposal again on May 14, 7pm in City Council Chambers. Concerned citizens are urged to attend.

Kohl Construction, operating as Tofino Associates and Northern Avenue Homes, currently proposes to build 23 condo units plus roads in the woods, grassy areas, and wetlands buffer zone between North Street and the new bike trail in Northampton. The North Street Neighborhood Association has previously raised objections regarding the close encroachment to wetlands, the experience of flooding on this property, the loss of trees, and the cookie-cutter design that is a poor fit with the neighborhood. Let’s now explore the drawbacks involved in slab-on-grade foundations, a construction technique Kohl proposes to use. Slabs raise concerns about durability and energy efficiency, core values of the Sustainable Northampton Plan.

Slab-on-Grade Foundations

On some areas of this site, seasonal high groundwater rises to within 14-16” of the surface, according to Kohl’s own test pit data (PDF report, 735KB). Scientific studies suggest the proposed removal of numerous large trees could cause groundwater to rise several inches higher. (A single large tree absorbs as much as 150 gallons of water from the soil per day. Trees also intercept a portion of rainfall before it reaches the ground.)

Because of this high groundwater, Kohl proposes to avoid basements and place the condo units on “slab-on-grade” foundations. Wikipedia notes this technique is less common in cold climates and describes the drawbacks:

“Slab-on-grade foundations are…most often seen in warmer climates, where ground freezing and thawing is less of a concern and where there is no need for heat ducting underneath the floor…

“The disadvantages are the lack of access from below for utility lines, the potential for large heat losses where ground temperatures fall significantly below the interior temperature, and a very low elevation that may expose the building to flood damage in even moderate rains. Remodeling or extending such a structure may also be more difficult. Over the long term, ground settling (or subsidence) may be a problem, as a slab foundation cannot be readily jacked up to compensate…”

Monster Constructors (Fort Worth, TX) echoes these concerns:

“…slabs come with some baggage. Frequently, plumbing drainage and water supply lines are buried beneath the slab. If something goes wrong or a leak develops, repairs can be costly. Heating or cooling ductwork buried underneath the slab can sometimes fill with water during wet seasons. Should this happen, mold can form and spores might be blasted into the home each time the air conditioner fires up. Thermal conduction issues are always present. Slabs poured in colder climates can conduct cold back into the house unless special precautions are taken. Homes built on slabs often offer little protection during tornadoes or hurricanes, unless a special masonry or concrete safe room is built within the house.”

Bruce Maki, editor of HammerZone.com, is so concerned about slab foundations that

“…[q]uite frankly, you couldn’t give me a house built on a slab foundation. With no easy access to any of the ‘environmental systems’ (electrical, plumbing, HVAC) maintaining these structures is a nuisance at best, and a nightmare at worst…

“Builders will say that slab foundations are cheaper… I don’t buy into that argument. It only saves money up front, and almost certainly adds costs later, costs in maintenance and repair…

“Another issue that nobody talks about is structural longevity. Long ago I heard a rule-of-thumb for carpentry: keep all wood at least 6 inches above the soil so the splashing water doesn’t get on the house and cause decay of the wood. Around here most houses are plenty high off the ground, but many garages and sheds are built low. And I’ve seen many of these buildings get structural damage, typically rot but also termite infestations, from rain dripping off the roof, onto the ground, and splashing onto the building. The houses around here with basements usually have 18” to 24” of masonry directly above the soil, and no problem with rotting sill plates. …I have absolutely no confidence in the long-term structural integrity of slab-foundation houses. I have to wonder what all these fancy slab houses will be like in 30 or 40 years. I won’t be doing repairs on them, that’s for sure. Maybe they’ll be knocked down to return the land to farming…”

It takes more than a downtown location to qualify a development as Smart Growth. Kohl’s proposal falls far short.

Kohl’s latest proposal, concept “D” [download a high-resolution PDF, 1.1MB], calls for 23 units (two units at the end of Northern Avenue not shown). Over half of these units have a footprint that intrudes within 100 feet of the wetlands around Millyard Brook. The safety margin against flooding and wetlands disturbance may be even less than it sounds, because the wetlands boundary on this site is “particularly difficult to delineate…there were indicators of hydric soil almost anywhere we looked” (8/21/07 report of environmental scientist Alec MacLeod). Hydric soils are those that are saturated, flooded, or ponded long enough during the growing season for the development of anaerobic conditions in the topsoil. The 10 units at the bottom of this diagram gave particular concern to Conservation Commissioner Paul Wetzel. Their relatively low elevation close to the water table motivated him to say, “to me, getting rid of these guys…is a big help” (3/12/09 public hearing, video recording available at www.northassoc.org).

See also:

Our Guest Article at Northampton Redoubt: “The Kohl condo proposal and the Struggle Over the Meaning of Infill”

Valley Advocate: “Bogged Down – Doug Kohl runs into trouble with plans for his subdivision off North Street in Northampton”

Tree Loss and Slab-on-Grade Foundations: A Poor Fit with the Sustainable Northampton Plan
First, let’s review some of the goals of the Sustainable Northampton Plan:

Facilitate the increased energy efficiency
and use of renewable energy in public
and private buildings (page 17)

Encourage development that maximizes
building orientation and landscaping to
increase energy savings (page 17)

Add standards in City’s street tree and open space programs to help reduce fossil fuel use
(e.g. provide summer shade to reduce use of
air conditioning) (page 22)

Minimize the loss of tree canopy throughout
the City and increase tree canopy in
urbanized areas to maintain a higher
quality environment in all areas… Target: 2% increase in area or number per year (page 23)

[Glossary:] Sustainability: “Meet[ing] the needs of the
present without compromising the ability of
future generations to meet their own needs”
– former Norwegian Prime Minister Gro Harlem
Brundtland. A sustainable community
manages with a balanced set of integrated
principles: Social Equity, Environmental Respect,
and Economic Strength, that preserve
a high quality of life for future generations.

A Northampton Schools Strategic Planning document (PDF, 803KB)  suggests that the Planning Department views durability as part of its Sustainable Northampton vision:

Although most of the actual policy, regulatory, and investment changes to implement Sustainable Northampton have yet to be initiated, the first changes are already underway:

  • All new subdivisions now require concrete sidewalks, granite curbs,
    and sufficient water pressure or sprinkler systems to fight fires.
    These expensive features will both lower future city costs and make it
    far more likely that development will occur closer to downtown and
    Florence, where street lengths per unit are shorter, and not in
    outlying areas…

At a March 26 hearing, Conservation Commission member Paul Wetzel also raised the issue of durability and longevity of materials.
He questioned Smith College’s commitment to sustainability in light of
its proposal to replace turf with a synthetic field that would need to
be torn up, discarded and replaced every 15 years.

Durability is an important value in Envisioning Sustainable Northampton, the book recently produced by the Notre Dame School of Architecture:

The Notre Dame School of Architecture’s guiding ideal is a built
environment that is convenient, durable and beautiful;
and we contend that by being convenient, durable and beautiful, the
built environment will necessarily also be sustainable. (page 1)

Durable Construction: In promoting sustainable building construction in Northampton, rewarding builders for
using a limited palette of low-embodied energy building materials–e.g., integral masonry bearing walls, heavy
timber frames, slate or clay tile pitched roofs; no steel reinforced concrete or steel lintels–will result in an
environment of beautiful buildings that will last for hundreds of years, an essential component of a sustainable
human settlement… (page 7)

Tasha Lucas…from Monster Constructors, adds:

Slab-on-grade foundations are constructed with reinforced concrete and
are usually shallow, quickly built, and inexpensive. For a builder that
doesn’t have to live in the homes that he builds, slab foundations are
a dream. Slab foundations are used with homes that do not have
basements. A major disadvantage to slab-on-grade foundations is that
they are not resistant to seasonal movement changes and moisture
disbursement due to root growth. In other words, slab foundations are
not a long-term option for homes in North Texas…

We’ve previously noted how the area at the end of View Avenue, at a relatively high point on Kohl’s land, reported flood damage
from Tropical Storm Floyd in 1999. It’s also still an open question
whether some of the condos would be built on filled wetlands, which is
disfavored by the 2004 Flood and Natural Hazard Mitigation Plan (PDF, 1.5MB):

Many areas of the City were developed before the passage of the
Massachusetts Wetlands Protection Act of 1972. Historically filled
wetlands are commonly related to problems with wet basements, flooding,
shifting foundations and failed septic systems. Development in
historically filled wetlands should be discouraged through zoning in
order to protect health and safety. (page 24)

Combined with the high water table, there is ample reason to be
concerned about water intrusion damaging the condos, reinforcing the
overall concern about the durability of the proposed structures. The
condos would likely face several tests over their lifetime. The latest Hazards Mitigation Plan
estimates that tropical systems hit the Massachusetts coastline every
six years on average. Since Floyd struck in 1999, the next one is

Video: Conservation Commission Meeting of 3/12/09; Deadlock on Kohl Condo Proposal
3:11:40… Wetzel: “So to me, getting rid of these guys [points
to condo units 1-10]…is a big help” because they are at a relatively
low elevation close to the water table. He wants more room to be made
for the development’s normal operations, such as snow clearing and snow
storage. He believes that violations of wetlands protection covenants
are likely to occur over time…

3:51:13…: Meyer: “This has been the problem with this
project from the beginning… When the footprint of the project
impinges on the wetlands, there’s no other place to do improvements…
If you had the project heavily concentrated in one end of the site,
going right to 35 feet, but nothing was happening down at the other end
of the site, then there’s some place where you can do significant
mitigation in the 35 to 50 foot zone… I don’t think that the
difficulty is something that is set in stone. I think it’s generated to
a certain extent by the design of the project.”

Mike Kirby: “The Meadowbrook Chronicles Part One”
The developers built 255 units
of affordable apartments there. They crammed them in everywhere they
could, pushing them up into the bluffs, and close to the creek and
wetlands. No backyards to speak of. One third of the buildings were
built within 50 feet of the wetlands, 63% of the buildings are within
the customary 100 feet of wetlands.

None of the buildings have
cellars under their apartments. If they have cellars, there are people
living in them. The cellar floors in the basement apartments in
Buildings #4 and #2 are lower than the surrounding swamp. Some slabs
have cracks in them. People have been flooded out. No moisture-proof
barriers between the surrounding earth and the foundations. Moisture
and mold percolate up into people’s apartments via the chases that hold

Cellars are a wonderful thing;
you’re away from the groundwater and dampness. Our first big purchase
after we bought our house in 1983 was a top-of-line Sears submersible
pump. For twenty-five years it has been working without human
supervision. The float goes up, it goes on, the float falls, it shuts
off. Whoosh-whoosh in the cellar, all is right with the world.

Our Ad in Today’s Gazette: A Review of Our Objections to the Kohl Condo Proposal
Some claim that because Kohl’s proposed condos are within walking distance
of downtown and have a high density, they are a good example of Smart
Growth. However, there’s more to it than that, according to the Urban Land Institute (ULI).

True Smart Growth respects green infrastructure, such as trees and wetlands. These greenspaces filter the air, reduce the urban heat island effect, enhance property values and moderate stormwater flows, and they do it inexpensively. Urban greenspace is associated with improved physical and mental health and greater social cohesion in neighborhoods.

True Smart Growth preserves a community’s character, unlike development that
“bears little relationship to a community’s history, culture, or
geography.” ULI says homebuyers are increasingly attracted to
vernacular and historical house styles that characterize their
immediate area or region. Quoting Jim Constantine, a market specialist
who does “curb appeal” surveys for developers, “Consumers are turned
off by cookie-cutter subdivisions and the homogenous look of houses.”
Unfortunately, that’s exactly what Kohl Construction is offering the

Smart Growth vs. “Smart Growth”

…developers often seize on convenient aspects of Smart Growth that
align with their profit goals and disregard others. A common result
appears to be overlarge developments, inapt developments, and/or
excessive density. These are major bones of contention in Los Angeles and Berkeley, to give two examples…

The problems with Kohl’s condo proposal include:

  • It threatens green infrastructure by putting roads and structures as close as 35 feet or less to a wetland. Scientific evidence
    indicates that substantial disturbance within 50 feet puts wetland
    ecology at risk and threatens water quality. In addition, the condos
    themselves appear to be at risk of flooding.
  • It goes against the existing character and diversity of housing stock in the neighborhood by offering a monotonous, cookie-cutter design scheme with little sense of place.
  • As Daryl LaFleur
    observes, “the Kohl North Street area development proposal includes row
    house condominiums set to the rear of parking lots, not free standing
    detached single family homes that front the ‘street’, which would
    better match the existing neighborhood and is also a tenet of Smart

Smart Growth is most palatable when it’s
implemented as a whole. When public and private actors are allowed to
cherry pick aspects that suit their convenience, the “Smart” can be

Good Cul-De-Sacs and Bad Ones
…the cul-de-sacs in Kohl’s latest condo proposal give reason for concern:

  • The roads would not be straight
  • The space would be visually broken up
  • The homes would be isolated from North Street
  • Many units would be difficult or impossible to see from North Street
  • Footpaths (shown in pink) and the woods would give easy secondary access to the units
  • Homes would only be present on one side of the street

…the proposed road layout in Kohl condo
proposal “D” presents new reasons to be concerned about this project.
It raises security issues and reinforces its disconnection and
disharmony with the surrounding neighborhood. It is easy to imagine
that neighbors would feel uncomfortable walking through the roads and
paths of the development. Instead of public ways, these would feel like
private spaces.

Planning Board Debates Kohl Condo Density – Quotes from the March 26 Hearing