Is the best way to waterproof this condition with a negative side product, similar to xypex? The elevator pit is part cast in place, part precast, making it difficult to use an integral product.
Robin,
Why is part of the elevator pit be precast?
Generally they have to be fully cast-in-place.
I normally specify crystalline (Xypex) waterproofing at the elevator pit.
I think they need to get rid of the precast.
I’ve don’t ever remember seeing one in the 40 years I’ve been doing this. They’ve always been cast-in-place, especially from a structural standpoint.
Well Rich, I am not going to tell the Structural Engineer how to design their parking garage. I just spec 'em as I see 'em! Or, at least, I pick my battles! Hope you are doing well!
The lot of the independent spec writer.
In that case, you’re going to need to provide some type of watertight joint at the precast, if the SE hasn’t already done so, and then use the “Xypex”
I agree with Richard, we normally do cast-in-place for elevator pits and use either cast in vinyl or bentonite clay waterstops at any construction joints. This may be difficult to do with precast but I would make my preference known. After that I think crystalline WP is definitely the way to go.
Robin: Two suggestions:
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Old timers may remember metallic waterproofing. It consists of a parge coating of mortar with a mixture of iron filings which expand [rust] when moist [works on the same principle as Bentonite]. Mixture is 20# metallic per bag of 1:2 cement/sand. “Ironite” by Western Waterproofing is still available as are products by Euclid, Master Builders, and Sonnenborn. MW goes on at 3/4" to an 1" thick.
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A little known product are the surface bonding cements originally designed for dry-stack CMU applications. The original product was introduced by Owens Corning Fiberglass as a structural component under the name of “Block Bond” [contains fiberglass fibers] but it was never accepted by the masonry industry. “What? Yo’ can’t build a wall without no mortar!” The product repackaged and sold as a negative-side waterproofing compound because of it’s superior tensile strength. Over the years the product formulation was bought and sold several times. Bonsal sold it as “SureWall” then as “Surface Bonding Cement” under the Sakcrete brand. Unfortunately, Sakcrete is mostly marketed through the residential market [ie, Home Depot] and will no longer support the technical testing. Ash Grove Cement Company is the one company that I know of that uses a formula close to the original Block Bond and does provide the technical testing and quality controls. Their product is called “Surface Bonding Cement.” [www.ashgrovepkg.com]. SBC goes on at about an 1/8" thick.
Both of the products above are cementitious and should bond well to both cast-in-place and precast concrete and will bridge small cracks.
I would ask first: is there a hydrostatic load?
If there is no hydrostatic load, why use waterproofing?
If the pit is located well within the footprint of the building, the likelihood of water penetration from surface water is probably nonexistent, so the only possible source of hydrostatic pressure would be from ground water.
If there is a moisture issue:
A similar joint condition would be the precast vault lids we have on a current project on cast-in-place concrete utility tunnels that are backfilled and covered with landscapping.
Our waterproofing consultant requested “BackerSeal” by Emseal as a secondary behind a single component silicone.
The lids are to facilitate (make possible) eventual transformer and other EQ replacement.
according to Civil Engineer, there is hydrostatic pressure.
What are thoughts on using a membrane on the vertical walls and an integral waterproofing in the concrete on the horizontal (CIP)? This is Structural Engineer’s suggestion.
The Architect is concerned about using crystilline products on the negative side and doesn’t feel this will be “to little, to late”.
If you have hydrostaitc pressure concerns about the elevator pit, then you must also have hydrostatic pressure issues at the slab, I would venture to guess. If that were truly the case, then you would more than likely have a waterproofing system already at the plane of the slab and a continuation of this at elevator pits.
Crystalline waterproofing for elevator pits that are not submerged below the water table (again, I am guessing that yours are not) is way more than you need and not something the rocket scientist - er, architect - need be concerned about. I like Kryton much more than Xypex and the others, because Kryton has a better warranty, better technical service, and better information about about how/when/why to use their crystalline products for various conditions.
I have used this system for many, many below grade elevator pits and never had a problem.
Good luck…
Robin:
I assumed from your initial post that the application was to an existing pit. That is why I advised the negative-side WP.
If the pits have not been constructed yet and the exterior side of the wall is accessible and there is a hydrostatic pressure, then by all means a membrane system should be used on the outside of the walls and possibly under the slab. All joints between the different substrates should be properly bridged prior to application of the membrane. A WP membrane should NOT be used on the inside of the wall. Slabs should have a complete membrane under the slab; or, as a minimum, a HD water-resistant vapor retarder under the slab with a Bentonite waterstop around the edge and a backer rod and quality sealant around the slab perimeter. Use of integral waterproofing is problematic in that it would such a small pour.
In regard to the post-construction applications, I have absolutely no hesitation recommending a good quality and tested surface bonding cement as previously posted. Remember it was originally designed as a structural product. I have successfully used SBC in retrofit water applications for over 30 years. As an example, I successfully used SBC over a 200-year old historic structure foundation wall constructed of loose-laid, irregular shaped stones. The SBC bridged the gaps and actually retained water behind the membrane system. The water could be seen [by dark splotches] behind the membrane. The spaces were tested with a hygrometer and had reading acceptable to accept a law library full of books.
Not only is the SBC a superior application choice, it is the least expensive.
Before using a product such as Xypex as an integral product in the concrete mix for hydrostatic loading I would check with the manufacturer. I think it is a good product and likely to provide the performance you need but it is my understanding that Xypex stops short of recommending it for that use in new construction.
Regardless of hydrostatic pressure, I’m not certain but I believe that the ASME A17.1 Code on elevators calls for waterproofing and a sump pump; specifically Part 2, 2.2.2.
ASME A17.1, 106.1b (3) states: “Drains connected directly to sewers shall not be installed in elevator pits. Sumps may be installed. Where drains are not provided to prevent the accumulation of water, sump pumps shall be provided”.
Hope this helps.