Flashing reistant to corrosion

[ajk1]

Is there any flashing that is particularly resistant to corrosion from de-icing salts? The situation is a public library where the existing deteriorated flashing extends from ahout the 4th brick course above the sidewalk down to the sidewalk. We are removing the sidewalk, sounding the garage roof slab below to detect delaminations and repairing, re-waterproofing the garage roof slab, placing a high stength drainage board, then re-pouring the sidewalk and putting in new flashing to replace the existing deteriorated flashing. I am not sure that galvanized steel flashing would be as resistant to corrosion in the salt environment as would be wanted.

QUESTIONS

Is there a PVC flashing, or any other non-metallic flashing, that could be used?
If so, are there any disadvantages to it?
Does it come in brown colour?
Is it UV resistant?
How should it be specified (thickness, etc.)?

If a metal flashing is deemed to be corrosion resistant in a chloride environment, how should it be specified...how thick, etc?

 

[XR250]

Why not stainless?

 

[JedClampett]

I'd call Hohmann and Barnard (

http://www.h-b.com/).

I had a question on brick ties the other day and got to talk with one of the Hohmanns. They have about a dozen different flashing materials, like copper, membranes, etc.

 

[cvg]

copper would be better than galvanized

 

[hokie66]

Stainless would be my choice.

 

[ajk1]

Would stainless blend in with the colour of the brick or would its appearance clash>

Can I be sure that itwiukd not be excessively expensive?

 

[JedClampett]

No matter how expensive it is, it's cheaper to do it right once than replacing it.

 

[ajk1]

Agreed

 

[hokie66]

Nothing is going to look like brick, but stainless looks like you are serious about flashing. A disadvantage is that it is not as easy to form on site, as compared to a softer flashing material like copper or lead. The material is not that expensive...most of our flashings and rainwater goods in commercial buildings in Australia are fabricated from stainless.

 

[MikeHalloran]

Stainless that's fed a steady diet of salt, guaranteed in the US Rust Belt, is going to corrode, but probably not to a nice uniform brown like Cor-Ten (and salt wouldn't do the Cor-Ten any good, either).





Mike Halloran
Pembroke Pines, FL, USA

 

[ajk1]

The stainless is also vulnerable to salt (something I expect that you don't use much as winter a road deicer in Australia)..the Nickel Institute told me this about 10 years ago when I was researching things out...but it is still better than most other metals. Somone has recommended to me that we specify the following...any comment?

.1 Prefinished sheet metal flashing: Galvanized steel, 0.71 mm [24 ga.] core nominal thickness, Z275 zinc coating to ASTM A525M. Finish to Stelco's 8,000 series or an approved equivalent, applied both sides. Colour to match existing and be approved by Owner from the 12 standard colours listed in CSSBI's General Colour Card.

 

[ztengguy]

Put heated sidewalks in so you dont have to salt them.

 

[CELinOttawa]

Galv isn't a bad idea, but this directly exposed to deicing salts it will fail...

Stainless, particularly 316 with a specified maintenance routine of semiannual washing, may be a much better performer in this situation.

See if you can find a comparative report for materials in your exposure conditions; A good report I've got in my reference materials is "Deicing Salts - Recognising the corrossion threat".

 

[ajk1]

I'll soundout our client about whether they are willing to pay for the cost of s/s. I expect it is at least double the cost of galvanized steel and harder to work with...maybe that is why it is seldom used? The original flashing which is most likely galvanized steel is 40 years old...I will double check its condition before reaching a conclusion. Heated sidewalks are expensive and hard to justify from an energy use point of view ...particularly since this is not the main enrance to the building. As far as copper goes, I have seen copper skylight flashing totally corroded away, not exposed to salt, but it was 80 years old and in contact with steel rafters so it may have created a galvanic corrosion cell. I am dubious that copper will do well against salt, but if anyone has some specific experience with that, it would be interesting to hear about it. Thnaks for al the advice and commens to-date.

 

[Ron]

ajk1...take a look at a PVC through-wall flashing:

http://www.polyguardproducts.com/products/architectural/masonryflashing.htm

 

[ajk1]

Ron - yes that looks very interesting for thru-wall flashing. In my case the flashing is all exposed (it starts about 4 brick courses above the sidewalk and extends down the exterior face of the brick and ends at the bottom with a short turn-out away from the brick) so I am not sure if the exposed polyethylene based flashing will resist bumps and impacts against it over the years. I don't see that they are promoting it for exposed wall flashing. But it is what I had in mind for something really corrosion resistant.

 

[a2mfk]

I was at Lowe's the other day and walked by the flashing which was mostly aluminum, stopped to look and thought of this post. Aluminum not an option because of contact with steel?

 

[cvg]

stainless or copper would be far better than aluminum. Aluminum has been banned in some locations for deck flashing because the design life is so short. you got 40 years out of galvanized which is very good.

why not aluminum or galvanized?

http://www.deckmagazine.com/wood/beyond-aluminum-flashing.aspx

comparison of types of flashing

http://www.maconline.org/tech/materials/Flashing_for_Masonry/flashingtypes/flashingtypes.html

 

[smb4050]

It appears you are trying to solve multiply conflicting issues with a single magical material. Could a 2-piece metal flashing similar to a roof curb detail be utilized with the difference being it is fastened at its top and bottom? Install PVC flashing which will provide the chemical resistance workability needed. Over the PVC flashing install a colored metal flashing which will protect the PVC from physical damaged and UV deterioration. The metal flashing can be removed and replaced as needed.

 

[hope9010]

a2mfk - I don't think there is contact with steel (except perhaps at the door frame), but I wonder how aluminum would do in resisting corrosion from de-icing chemicals.

cvg - I am not sure what material the existing flashing is. I will try to look at it again on the weekend. Thanks for the information in the links. Very interesting indeed.