huangyhg

foundation waterproofing
i am working on an existing office building with a basement. the basement extends out beyond the face of the building to the street curb line. a pedestrian sidewalk is the roof of the basement in this area. the sidewalk slab sits on 1/2 the wall thickness. the street curb sits on the outer half of the wall thickness. it looks like before they poured the curb they put down about 1/2" thick asphalt to waterproof the joint.
the city is reconstructing the street and wants to remove the curb. the owner is concerned about water leaks into the basement due to disturbing the curb. the city has come back and said they will consider putting a waterproof membrane down before installing the curb.
i have a couple of questions i would like help with. first, i think the right material is a prefab membrane that is laid down on the wall, verses some kind of canned mixture that hardens in place. would this be a correct assumption? any words of caution of preparation of existing concrete for the membrane application?
second, i have a question about what material might be best. you see the joint is a 'z' shape. the foundation wall is vertical till you reach the top. then you go horizontal the width of the curb, then you go vertical again to the top of the slab. it is like a brick shelf, only for the curb. i know bends will be weak points. any suggestions for the best way to do this?
third, usually there is a protection board on top of a membrane. i am wondering what is best to do here. there will be differential movement between the curb and the walk slab/foundation wall. should there be some kind of protection board that wraps horizontally under the curb and then vertically between the curb and the slab?
fourth, what kind of warranty should te building owner ask for?
my gut feeling is to leave the curb alone since there presently is little leakage. the city is pushing to replace the curb so it matches the rest of the project.
i appreciate any helpful suggests i can get!
thanks!
rich
normally both the "adhesive" and membrane solutions may work, at least as well or nearly so is the case with the present situation. in fact, membrane solutions also will need some "adhesive" or mastic part.
the main concern in general is not being able to produce a complete impermeabilization. if the structural floor under the exposed sidewalk could acommodate a membrane as well, and the weight of a stiff enough mortar or better rc slab concrete base to support the actual pavement the result would be of better prospect. if not, the biggest care needs be given to the line where the running water needs to pass from the sidewalk to the curb, for beyond will have proper impermeabilization.
respect warranties, here 10 years is common, and some go 15 or 20, but far less in number.
thanks for your input.
i can't touch the slab. i believe it is a single slab system, ie. no membrane at all. fortunately it is under a canopy and the walk has a good slope to it. unfortunately, you're right, the joint between the curb and the sidewalk is the most vunerable spot and all wind blown water will have to roll over it. obviously i would have it caulked with a good sealer, but eventually it will wear out. we are adding a traffic bearing membrane to the slab surface, but that will not eliminate the joint between the slab and the curb.
any other thoughts would be appreciated!
jimbo (staff)23 oct 03 16:15
for the joint last mentioned, have you considered using silicone sealer such as dow 890 sl or crafco equivalent.
(please, do not criticze the suggestion that dow has an equivalent)
a typical joint can be used as in pavement, with blocker below the silicone.
is ther a specific reason you recommend using a silicone sealant verses a polyurethane-based, elastomeric sealant?
thanks.
i would contact the technical services department of w.r. meadows co. and also sonnobone co. they both produce very good waterproofing materials and will surely have solutions. you should have digital pictures and perhaps a sketch or two of the existing condition available to send them.

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