Locating Post-Tension Cables
I'm a forensic structural engineer in Colorado and would like
to comment on the Q&A item "Demo Near Post-Tension
Cables" (3/05). I have repaired numerous slabs with both
post-tension systems and embedded hydronic heating systems and
have found the most reliable method for locating "hidden"
components in slabs to be the use of ground-penetrating radar
(GPR). We typically mark the slab to outline the extent of our
work, then use GPR with great success to locate any conflicts
within the slab. Although this costs some money up-front, it's
worth it to avoid serious problems later.
Bruce Barnes, P.E.
Repairing Fire Damage
I read the article "Repairing Fire Damage" (3/05) with
interest. I would caution your readers that using the Uniform
Building Code's notching standards for assessing the residual
strength of charred wood frame members might not be a good
practice. Besides the depth of notches, there are specific
requirements for their length and position on the member. If a
framing member is charred and its utility is questionable,
replace it or get a design professional to okay it. This would
make the repair code-compliant. You'll find that an extra stud,
joist, or header is the most cost-
effective way to go.
Assistant Building Inspector
West Seneca, N.Y.
Author Fernando Ruiz responds: Thanks for the letter. The
point is to avoid tearing out framing needlessly when the
tear-out can create more damage than the fire itself did. But
if you're in doubt, always ask for a qualified opinion. The
design professional does the same thing I do — looks
with the eyes of experience. The code notching guidelines I
mentioned in the article are a good starting point for
assessment; they include all requirements for size and location
of acceptable holes and notches.
Note that the fire photographed in the article charred the
joists from below. Fire rarely burns from the top down, which
makes it easier to assess the damage. Besides sistering joists,
you can sometimes use a plywood gusset. I've also used
structural steel C-channel, bolted in place, to reinforce
Wrong Railing Test
From my perspective as a working carpenter, the key sentence
in the article by the folks from Virginia Tech concerning deck
post connections ("Strong Rail-Post Connections for Wooden
Decks," 2/05) was "rather than look at the entire guardrail
system, we decided to narrow our testing to post
Testing posts in isolation in a lab is interesting and no
doubt valuable, but the code implications strike me as highly
exaggerated. I've never built a deck that featured stand-alone
4x4 posts as a guardrail. Call me crazy, but I've always
thought that the odds of a tumbling customer being stopped by
hitting a 4x4 post dead-on, rather than falling through a 5- or
6-foot-wide open space, were a little too risky. So, to be on
the safe side, I connect my posts with railings and
My point is the test that would be meaningful to me would be
one performed on a complete assembly, not one particular
component. To say that conventional post connections amount to
a code "failure" seems highly questionable.
It's my sense that most builders settle on a preferred set of
design details and techniques for building decks, and, unless
instructed otherwise by a customer or designer, tend to repeat
those details. In my case, I always run a continuous 2x6 top
railing over my posts and fasten it securely to the tops of the
posts. I'll add finials or cups that line up with the posts if
the customer wants more of a sense of the railing fitting
between the posts, but I avoid cutting the railing and piecing
it. Also, I always try to span a complete run of posts, from
corner to corner, with one piece of lumber.
I'm no engineer, but in the case of a drunken "party animal"
acting crazy on a deck, I regard my 2x6 top railing as a kind
of horizontal joist. A person flung against my railing is like
a person jumping up and down on a 2x6 joist. Of course, the end
connections (corners) are important in my scenario, but it
seems clear to me that a series of posts tied securely together
at their tops will do a far better job of resisting the kind of
concentrated stresses described in the article than a lone post
The best experiments try to accurately replicate the "real
world" in the lab, and I don't think the guys at Virginia Tech
did that. However, as I said, the article contained a lot of
interesting information, and if I'm ever required to deviate
from my usual practice in a manner that seems risky, I'll
definitely consider using the metal hardware that was
suggested. I wasn't aware of that hardware, so thanks for the
Radiant and Geothermal
I enjoyed the article on ground-source heating and cooling
(2/05). Given the current popularity of radiant-floor heat, I
would like to have seen a discussion of geothermally driven
radiant-floor systems. To date, they haven't been widely
discussed. If you could direct me to a source of information on
this subject, I would be very grateful.
Horseshoe Bend Development
Smith Mountain Lake, Va.
Author John Vastyan responds: The two systems are
compatible because of the relatively low water temperatures
that radiant systems typically require. Most geothermal systems
can provide temperatures of 110°F to 115°F
without backup heat, whereas radiant heating systems, depending
on the climate, typically have design temperatures ranging from
85°F to 140°F. In colder climates, where the
higher design temps are required, a geothermal system may not
be able to keep up. But in more moderate climates, radiant
systems can typically be designed to heat with water
temperatures of up to 115°F.
Geo is probably not ideally matched to staple-up radiant
installations, which often require water temperatures as high
as 130°F or even 140°F.
For more information, visit the International Ground Source
Heat Pump Association Web site at www.igshpa.okstate.
edu or the Geothermal Heat Pump Consortium at
Skilled Workers for Hire
Regarding the "shortage" of skilled workers in the
construction trades (Letters, 2/05 and 4/05), I find the entire
discussion laughable. There is no shortage. Oh, there may well
be a "shortage" at the wage you want to pay — but
raise your wage, raise it again, and I guarantee you will find
Witness the Chicago market, where I am a carpenter. Here, a
journeyman union carpenter makes around $34 per hour, plus full
benefits and pension, which puts us comfortably in the middle
class. And guess what? Many would argue that there are too many
skilled carpenters here in both commercial and residential
work, since most of us face some periods of unemployment. Also,
the carpenter's union apprenticeship program generally has a
one- to two-year wait to get in, in spite of a strict screening
process and virtually no publicity. The situation with all the
other trades is similar.
And what about the "skill" part of the equation? Employers
here seem to find that men and women who are accepted into and
manage to complete a formal four-year apprenticeship in a trade
(which includes extensive classroom and on-the-job training)
are dedicated and talented, and make pretty good employees.
Beyond apprenticeship, many of us continue to take classes at
night at our carpenter training center on our own time and at
our own expense.
As an employer, you get what you pay for. The organized labor
system we have in place here in northeastern Illinois has
worked well for both contractors and tradespeople for over 100
years and continues to do so. If you have any doubts, come and
see for yourself.
After reading your report "Florida Builders Group Issues
Waterproofing Guidelines" (In the News, 3/05) and
being concerned about references to the failure of brick
masonry in the recent hurricanes, I downloaded the report,
looked at the pictures and diagrams, and read the scope of the
work, the summaries, the recommendations, and the remainder of
the document, trying to find some reference to "brick." Clearly
the authors of the FHBA study believe that brick masonry was
not any part of their study, since the first sentence of the
second paragraph states that "the specific focus of the review
was on the water management details associated with stucco
claddings." While I could not find the word "brick," the
authors of the FHBA study did talk about one masonry unit:
concrete block. Bricks are not concrete blocks.
This story unfairly stains the reputation of brick masonry
veneer wall systems, when the actual materials and
circumstances addressed and condemned by the FHBA report
involved the capabilities and detailing of applied faux stone
systems and stucco systems.
Ronald J. Hunsicker, P.E.
Manager, Architectural Services
Editor Don Jackson responds: You're right. The article
should not have referred to brick claddings. We regret the
CO Detectors Required In Rhode Island
The article "Carbon Monoxide Death Spurs New Look at Old
Problem" (In the News, 4/05) states that
carbon-monoxide detectors "aren't required by any of the major
model building codes. Only the state of New York and a few
dozen municipalities across the country have enacted
legislation mandating their use in single-family residences."
Please note that Rhode Island mandated CO detectors about four
Rhode Island Builders Association