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RE: Water Proof Membrane

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Ever since you joind CRSI the quality of your postings on this LIST has considerably improved and do show the colors of a person engaged in Research. Keep up the good work!
Syed Faiz Ahmad; MEngg, M.ASCE
Senior Structural Engineer
Saudi Oger Ltd
Riyadh, Saudi Arabia
-----Original Message-----
From: GSKWY(--nospam--at) [mailto:GSKWY(--nospam--at)]
Sent: Thursday, October 16, 2003 5:30 AM
To: Seaint(--nospam--at)
Subject: Re: Water Proof Membrane

I don't mean to discourage people from asking questions, but if you don't know anything about either concrete repair or waterproofing,  how do you propose to write specifications for the work?  Even more importantly,  how are you going to ensure the work is done correctly?

Perhaps this is squabbling over words, but "epoxy repair mortars" are not used for crack repair.  The ones I am familiar with at least, for example Epocem, are used as surfacing to create abrasion or chemical resistant floors.  

Epoxy resins (not the same thing as epoxy repair mortars) are used for crack repair but usually not for somewhere like a sidewalk which is subject to volume changes due to temperature.  

You also typically don't route cracks when you use epoxy.   Epoxy is usually either injected or gravity feed.  You rout cracks when you use an elastomeric sealant, in order to create a sealant width that can support the expected movement.  One of the main reasons to use epoxy in crack repair is that you don't want to make the crack any more visible than it already is.  Routed cracks are pretty ugly unless covered with a membrane.  Even when covered, you can still see them.

Another reason to use epoxy is that the crack is somewhere that sealant replacement is either impossible or unlikely.  Sealants age and eventally fail.  Epoxy tends to last alot longer.  

Epoxy injection is about an order more expensive than routing and sealing with a urethane, so there has to be a pretty good reason to recommend it be used.  Cracks very seldom, like almost never, need to be repaired with epoxy for structural reasons.

With respect to waterproofing, there are dozens of  products on the market.  Selecting an appropriate product requires a little more than just calling the Sika (or Tremco or Sonneborn) man.   Elastomeric membranes can be pedestrian membranes or vehicles membranes. Two coat systems or three coat systems.  With sand or without sand.  Low VOC or not.  Fast cure, slow cure, or no cure.   Similarly,  there are many, many kinds of sealers.  Some are better than other for certain applications.  Some are not good for any application.  No waterproofing product is any good unless installed correctly.

There are also probably some other concerns you need to think about.  If water has been penetrating into the slab and you put a water proofing membrane or sealer on, you are likely to get ponding or water infiltration into other places, unless the slab is sloped away from the building.

It is kind of curious  that the sidewalk is actually part of the building.  This type of construction, referred to as "vaulted sidewalks", is common in places like New York, Chicago, and DC.  I have never seen the sidewalk be the roof of the basement, though.  I have only seen standard city sidewalks constructed as a separate element over the roof.  The basement roof typically has a waterproofing membrane which also serves as a bond breaker that separates it from the sidewalk.

Gail Kelley