huangyhg

masonry below & at grade
i review structural drawings for a design/construction firm. architects & structural engineers, often detail cmu/brick being used below grade, without being waterproofed.(not talking about basements) this is especially disturbing when cmu stem walls are supported on spread footings extending to finish floor grade, when reinforced concrete would seem a better choice. the brick industry association in their technical notes 28b 鈥?brick veneer does state, 鈥淚f the soil immediately adjacent to the brickwork is not free-draining the brick wythe exterior should be waterproofed below grade.鈥?however; i have found nothing in the national concrete masonry teks concerning this and their details use cmu extensively below grade without waterproofing. to me this does not seem to be good engineering practice and i would like to see waterproofing masonry below grade be addressed better by the masonry societies, due to the environmental problems of algae, mildew, mold, staining, and efflorescence.
another problem i do not see addressed is cmu walls being placed at floor grade without masonry/brick ledges.
this joint often becomes unbonded from the foundation, losing the shear strength, and creating a crack which often causes water penetration in blowing rains. therefore, masonry/brick ledge should be installed, which is more accepted for brick than cmu.
please provide your recommendations and thought on these two subjects, as i often feel i am the only one concerned about these two problems. known code or technical references would be helpful. i posted a similar thread and received no replies.
i have worked for several companies and the masonry stem walls have never been waterproofed. i'm not sure i understand the necessity of this given the wall is just a stem wall. typically the stem walls below grade are fully grouted. besides, does it make a difference if the water seeps through the masonry if it is not open on the other side? as for walls that extend above grade to the finished floor level, a lot of wicking action would have to occur to cause any major problems.
as for the second problem, i only see this being a problem if the cmu is the exterior cladding. the joint between the bottom cmu and the slab on grade would have the potential to leak. if their is a brick veneer in front of the cmu, i don't see how blowing rain can be a problem to the cmu. the brick would stop it. although, if the brick veneer doesn't drain properly, water could collect between the two wythes and potentially seep under the cmu.
i always grout all cells and the cavity between brick and cmu solid below grade. do the problems you describe happen below grade only? if so i don't see this as a problem. it is really more of an architectural issue.
rgerk; thanks for your reply.i did not intend for you to have to read between the lines.
usually the details i am referring to the below grade reinforced cmu stem wall extends up to grade and the exterior cmu wall extends from there (often single wythe) which i tried to cover in my last post. therefore, i am concerned with the wicking you noted & environmental problems noted in thread. it seems architects also like to extend masonry(brick & cmu) below grade as they do not want the foundation exposed.
yes, cmu is the exterior clading mostly single wythe. i have personally investigated carpet getting wet and tile becoming unbonded from the floor due to leaks at perimeter walls caused by blowing or rain wetting the walls where the joint between the reinforced concrete foundation and first course of cmu had become unbonded, which often does occur. has anyone else experienced this?
it is my further opinion that single wythe cmu walls should only be used in austere facilities like pump houses, warehouses etc. where no interior finises are provided as they are prone to leak as there is no way to effectively flash them.
i've never detailed the masonry below grade solid poured and don't see any real necessity as to why. perhaps someone from this group can enlighten me to the benefits this added cost provides.
well, there may be pressurized water acting on the soil side of the hollow cells. the water would more easily penetrate into the hollow cells if they were not solid as that is usually a problem even for solid grouted block. and if the hollow cells that had water froze, i would think busting of the cells and deterioration of the block. it is likely code required that cells below grade are filled solid, i am surprised a building inspector hasn't written you up on that one.
the only reason i can see why you wouldn't waterproof the wall is if that space is exposed to the elements, such as a parking garage.
just like concrete isn't waterproof, a cmu wall, even fully grouted, isn't waterproof. the architect should specify a waterproofing on the outside of the wall. don't stick you head in the sand if he doesn't show it. tell him he needs it.
also, check the ibc for the exact requirements, but in the cmu empirical design section, you aren't required to grout solid if the wall height is less than something like 5'. as almost all basement walls are higher than 5', they need to be grouted.
i guess i should have stated i'm an engineer in florida (use the fbc for design) so we don't have any freezing issues. with that said, aggieyank above basically stated my point that a cmu wall, even fully grouted, isn't waterproof.
do they normally apply waterproofer to hollow foundation walls in florida?
based on the jobs i've seen (commercial stemwalls with floating slab on grade), i would say they normally do not apply a waterproofer.

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