Download PDF version (105.8k) Log In or Register to view the full article as a PDF document.

Leak-Free Chimney

I enjoyed reading “Cricket Retrofit” (1/09) by John Carroll; we also receive calls about improper or nonexistent chimney flashings. We add some extra measures to ensure a leak-free chimney and have had great success.

At the chimney corners, we brake the copper and solder the joint to make it watertight (see photo). When installing the counterflashing, we make a continuous cut above the step flashing parallel with the roof surface. We then brake a continuous counterflashing for each side of the chimney and once again solder the joints.


Finally, we waterproof the masonry surfaces to prevent water infiltration through the brick or through cracks in the chimney cap. Using a bug-sprayer, we seal the vertical surfaces with Conpro Shield MX, an alkoxysiloxane-based water repellent manufactured by Conproco. This helps keep out wind-driven rain and reduces the effects of freeze-thaw cycles. We treat the chimney cap with Geocel’s Pro Flex, a clear brushable coating that seals hairline cracks in the surface as well as around the flue liner. These two waterproofing steps are easy to do while you are already on the roof, and may prevent a callback.

Ryan Fetter

R.T. Fetter General Contractors

Bedford, Pa.

Don’t Use Stainless Steel Screws With Copper

I enjoyed Mr. Carroll’s article on constructing a cricket, with its origami-like copper folding (1/09). However, his use of stainless steel screws with the copper is bad practice, since iron-based stainless steel is 3 on the galvanic scale while copper is 6. At 7, lead (as the author correctly notes) can live comfortably with copper, as their immediate adjacency in the series indicates. The greater the distance between the two numbers, the greater the electrolytic corrosion. Although the dab of silicone on each stainless screw might forestall the inevitable, physics suggests that any close relationship between steel and copper is doomed for failure. Good practice would be to use fasteners made of brass (a copper-based alloy) or to solder, as recommended in “Copper and Common Sense,” which is holy writ on anything about sheet copper.

Milton W. Grenfell, Architect

Charlotte, N.C.

Subslab Vapor-Barrier Details

I noticed that the drawing in the article “Adding to an Existing Slab Foundation” (12/08) shows the vapor barrier buried in the middle of 4 inches of sand. I also noted that the author is in California, which brings to mind a document called “Concrete Floor Problems,” published at, in which the author, Joseph Lstiburek, P.E., makes a good argument against using a sand layer between a vapor barrier and a concrete slab — a practice he claims is common in California because of the involvement of soils engineers. He also argues that puncturing holes in a vapor barrier (which the sand is intended to prevent) has no effect on its performance.

Joe Parchesky, P.E.


Author Alon Toker responds: In fact, local practice is changing in the direction that Mr. Lstiburek’s article recommends. The city of Los Angeles, for example, used to require a layer of sand between the vapor barrier and the slab, but no longer does. The county, however, still maintains this requirement. Architects, structural engineers, and builders do not typically make the call regarding the slab assembly; they do so only when the municipality where the project is being built has no input on the matter — which is a rare occurrence!

Credit Card Warning

I wanted to share my experience with one of your newer advertisers, Advanta Bank. Until recently, they were a partner with NAHB and regularly solicited NAHB members with credit card offers similar to the ads running in the e-mailed JLCUpdate. In the NAHB solicitation, they promised cardholders a fixed rate of 7.99 percent on carried balances.

This card was targeted at smaller builders, and about two years ago I signed up. I was very happy with their services and used the card for most of my charge expenses. I gave a duplicate card to one of my field employees to carry for his expenses.

For 18 months, I used the card and carried a balance, happily paying the “fixed” interest rate of 7.99 percent — always on time and never for the minimum. Then, a couple of months ago, they raised my “fixed” rate without explanation from 7.99 to 27 percent!

I assumed that it must have been a mistake and called customer service when my statement arrived. They told me that they had sent me a letter in the mail, separate from my statement, that notified me that if I used the card after a certain date, I was agreeing to the rate change. This letter must not have passed the “junk mail” filter and did not register on my end.

When I asked for an explanation, they gave none and noted that it was a business decision and did not necessarily reflect on my actions as a customer. It became obvious to me that they either wanted to fleece me or didn’t want a small —albeit profitable — builder as a client.

I am an avid JLC reader and have been a subscriber for a few years. I would hate to see this happen to someone else who gets caught by the “bait and switch” tactics of Advanta. To my knowledge, they are no longer an advertiser or partner with NAHB. I just mailed them a check to pay off my balance and will be cancelling my account.

I understand that advertising is a precious commodity in this precarious economic environment, but I thought it might be helpful for me to share my experience with this organization.

Tom Sims, CGB, LEED AP Buckhead Building Co. Winter Park, Fla.

Thank you for your letter; we share your concern and have forwarded your message and others like it to our publishers at Hanley Wood, LLC, the corporation that owns JLC. — The Editor