Re: [BP] Question about waterproofing products

[Hammarberg, Eric]

Where to begin…   The metal is probably terne coated stainless (TCS)   I think the inboard side of the parapet is wet because most of the moisture drive through a façade escapes thru the parapets and since the exterior side may be “clogged” with a waterproofing coating, this moisture path is thru the back.   How old is the façade waterproof coating? Most coatings don’t last much past 5 years so if you coat the backside of the parapet and “if” you get improved performance from that coating you will need to reapply it every 5 years or so. The problem with that is repeated applications can reduce the permeability of the coating. Eric Hammarberg Director of Preservation Senior Associate Thornton-Tomasetti Group LZA Technology Division 641 Avenue of the Americas New York, NY  10011 Telephone: 917.661.8160 Fax: 917.661.8161 Mobile: 917.439.3537 email: [EMAIL PROTECTED] From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Tuesday, March 15, 2005 10:37 PM To: BULLAMANKA-PINHEADS@MAELSTROM.STJOHNS.EDU Subject: Re: [BP] Question about waterproofing products   In a message dated 3/14/2005 7:57:48 PM Pacific Standard Time, [EMAIL PROTECTED] writes: Absolutely no spray on applications to masonry, ever, under any circumstances (for the most part, which is to say 99.999999% of the time, and I can't think of any legitimate exceptions.)     Spray-on applications are cheap-shit, half-assed attempts to avoid doing things the RIGHT way, and will eventually (and possibly immediately) bite you in the ass, wallet, and historic fabric.  Have the parapets disassembled, flashed properly (using SHEET flexible-membrane flashing, not schmear-on crap with the potential for holidays which will leak) and rebricked. Make sure that flashing is installed under whatever the coping material is, also. OK. I'd like some further discussion if possible on this one. Here's the deal. This isn't a quickie re-roof proposal. The building is a huge Richardsonian Romanesque monster in the center of town-- used to be one of the state government buildings (courthouse I think) later became the Post Office (now known as the Old Old Post Office) currently inhabited by a well-heeled law firm. The proposal was from an architectural firm I haven't worked with previously, but was professionally presented, and they seemed to know the terrain. (I'll explain that comment presently)   So the proposal is to remove the entire (clay tile) roof, repair any structural and underlayment issues, and rehang the existing clay tile. The tiles are an unusual shape, an older European variant, from what the architectural firm has said, so they are proposing to utilize a similar tile as a replacement tile on the roof. They will use the old tile on as many faces of the roof as they can tile with the existing/remaining tile after the repairs, and use new tile on a face or faces as necessary. If I were writing the thing myself, that is probably the conclusion I would reach. They are doing the flashing in a terne coated metal-- I think it is aluminum, but I can't remember off the top of my head. All in all it was a thoughtful presentation, and a clever way to retain as much historic fabric as possible.   So this is why the water-proofing question bothered me. It is a very high quality proposal, and a huge job. I don't have the impression that it is a quick and dirty job at all. I researched the silane waterproofing materials, and most of them said that the coating was breatheable, so there shouldn't be any damage done to the parapet as a result of the application, in terms of water retention and freeze/thaw issues.   I was reviewing the Preservatio Brief on water-proofing treatments, and while they pretty much say to avoid waterproofing materials, there is a comment that they can be useful for areas that are exposed to extreme or unsual weather conditions, as in the case of the parapet roof here.   I questioned the architect on the waterproofing pretty thoroughly, and his response was that the rest of the building had been waterproofed, and the parapet has been a continuing problem. Furthermore, he mentioned that the interior face of the parapet seemed to be very wet in contrast to the exterior sides of the parapet that had been waterproofed in previous work.   Thanks for comments-- I wouldn't have asked if I didn't want an opinion, so if you have any further thoughts after reading this, let me have 'em. What questions should I be asking?   -Heidi <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> The information in this email and any attachments may contain confidential information that is intended solely for the attention and use of the named addressee(s). This message or any part thereof must not be disclosed, copied, distributed or retained by any person without authorization from the addressee. If you are not the intended addressee, please notify the sender immediately, and delete this message. <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>