The article "Building a Block Foundation" (5/06), by Rob
Corbo, shows "dampproofing" below grade in the wall
In my opinion, dampproofing is the wrong material for this
application; waterproofing should be indicated. I define
"dampproofing" as a product used above grade in the absence of
hydrostatic pressure, in applications like the outer surface of
CMU backup for a brick and block cavity wall.
"Waterproofing," on the other hand, is a product used below
grade in the presence of hydrostatic pressure, in applications
like the foundation wall in the wall section.
Whether one uses dampproofing or waterproofing on a foundation
wall, it won't keep water out for long without a drainage
protection board to keep the membrane from being punctured
I'd like to hear Mr. Corbo's response to my suggested
Rex Garton, AIA
Hart Freeland Roberts
Author Rob Corbo responds: We simply followed the
specifications presented to us in the architect's drawings. I
agree that "dampproofing" is an appropriate description of the
method used on this job. I keep my fingers crossed, but I
usually find that parging and asphalt coating in conjunction
with perimeter drainage, sump pits where needed, and
surface-water controls — proper grading and ground
cover, as well as gutters, leaders, and dry wells —
will keep the basement walls dry.
We explain the differences between waterproofing and
dampproofing to the client, but bid projects per the
I also prefer a waterproofing membrane, for two reasons: It's
a fairly straightforward process and can easily be
subcontracted (whereas we can't find a sub willing to parge and
coat), and the waterproofing subcontractor assumes
responsibility for the basement staying dry.
More Door-Hanging Tips
Regarding the question "Do Door Jambs Need Shims?"
(Q&A, 5/06), there is no need for a shim at the top
hinge: The force at this point is outward, not inward. Not
shimming behind the top hinge allows for a little adjustment
later by tightening the 21/2-inch screw going into the
We have also had good experience with foaming between the jamb
and stud instead of shimming.
We have provided acoustical engineering on many single and
multifamily home projects, and we found the article
"Innovations in Sound Control" (3/06) to be one of the more
comprehensive and accurate articles that we've encountered in a
building-trades publication, especially regarding residential
Nevertheless, we do have a few additional comments.
While an STC rating is a good guideline for the control of
many types of sound sources encountered in residences, in cases
where very low frequency sound is concerned (such as in
home-theater applications), this descriptor is limited.
The STC rating is based on test data that extends only down to
100 hertz (Hz), whereas theater sound systems can often produce
considerable sound energy down to the 30-Hz range.
A single-stud wall assembly (with some type of isolation
device or proprietary sound-control sheathing) may have an STC
rating comparable to a staggered-stud or double-stud assembly,
but the sound-insulation performance below 100 Hz will be
considerably less and is not reflected in the STC rating.
Also, there are no isolation devices that could connect any
two building elements that will outperform an actual structural
This probably makes intuitive sense to most readers. Staggered
2x4 studs on 6-inch plates with standard fiberglass-batt
insulation will outperform any single-stud assembly of the same
overall thickness, regardless of the devices involved.
Finally, the "loaded vinyl limp-mass barrier" noted in the
article is indeed effective. When the material is unconstrained
("limp"), it is free to convert sound energy to mechanical
Adding the limp-mass barrier in the air space of the
staggered-stud assembly noted above, for example, will provide
added sound insulation. Adding the mass barrier between layers
of sheathing, however, will provide only a small increase in
sound insulation, proportional to the mass added. (It is no
longer "limp," as it is constrained between rigid
Thomas Schindler, PE
Charles M. Salter Associates
Protecting Fascia From Ice
I'm a home inspector and roofing-project estimator in the
western New York region, and have followed your debate on roof
waterproofing membranes (Q&A, 1/06; Letters, 6/06). Over
the last 20 years, I've solved all types of problems relating
to ice-dam leakage.
The eaves waterproofing membrane should be folded down over
the finished fascia. If the home is to have formed aluminum
fascia, it can be installed first. Next, the leading edge of
the membrane can be folded down onto the fascia 1 to 2 inches,
then the drip edge installed.
Installing membrane on top of the drip edge or stopping it at
the edge of the roof sheathing will give no protection where
the fascia and the decking meet. This area is tested first and
is very prone to leakage as the gutter fills with ice and
The membrane should also extend up the roof a minimum of 24
inches horizontally over the heated area of the home.
Concealed Splices? Proceed With
I wrote to one of the companies listed in your article about
electrical connectors that can be used to tap conductors and
then concealed behind drywall (Q&A, 4/06). The company
denied having any. Could you please clarify?
Editor Don Jackson responds: The electrical code is very
specific about leaving access to splices in Romex, so I can
understand the reluctance of a manufacturer to encourage the
use of this kind of product without fully understanding your
There are two key points to keep in mind. First, you should
speak with your electrical inspector before proceeding with
this strategy. Second, the device in question must be listed as
meeting NEC 334.40(B), which excludes its use in new
The price for a 9-foot straight-run NexStep stair (Products,
5/06), including shipping, is around $540, depending on volume,
not $120 as stated.