huangyhg

below grade masonry walls
i was recently in a meeting with an arch. and said something stupid and had to fumble to recover. i wanted to get some opinions on this. my background is primaraly commercial buildings. at my old job we alwalys detailed all masonry walls below grade to be filled soild. im assuming this was just detailing practice that had been passed down. i raised this issue for a small retaining wall in a house and then realized that there was really no reason to fill the wall solid. im comfortable provided the wall meets the structural requirements. does anyone else detail below grade masonry walls in commercial buildings as filled solid? why? how does this apply to residential applications?
one reason to fill solid below grade is to impede water intrusion and to be able to create weep holes above grade. structurally, usually not necessary unless earth pressures are sufficiently high (not likely).
below grade, i spec. as grout full.
jjeng-
i believe this question was discussed in a previous thread, please try a search. my personal preference is to always grout all cells below grade solid, even where there is earth on both sides of the wall. don't want any water collecting in the cells and freezing, or causing corrosion in the horizontal joint reinforcement. i have this approach for both residential and commercial.
recommend you specify grout for filling the cells, and not concrete as some do. properly mixed grout will have a higher slump and will likely fill the cells more completely. regards.
i dont believe it is standard to fill house basement walls solid. correct? where would i draw the line on what to spec. filled solid and what not to?
the florida building code for instance requires masonry walls retaining earth to be filled solid in section 1815.4. this is the "retaining wall" section. it then becomes a point of debate whether stem walls holding back earth are considered retaining walls. personally i say fill them solid period and most definitely always fill basement walls solid. here at my firm standard procedure is to fill all cells below grade.
i have done it both ways. i am very familiar with florida building code the ucfse mentioned. it is specific to retaining walls. florida does not have many basement walls. the most common type is stem walls that are two to three courses of block bellow finish floor.
regarding ron’s comments about water intrusion, filling cmu solid with grout will not stop moisture or water intrusion. you have to have a vapor barrier (mopped on or applied to the exterior face of the walls). vapor barriers are those with permeance of 1 perm or less. moisture will travel as water or vapor. masonry is very permeable material, even when filled. that is why you need to apply vapor barrier coating. i do lots of moisture intrusion simulations and modeling. i actually spend lots of time debating and educating architects about this very issue. when i ask them where the vapor barrier is, they look at me like a deer caught in the headlights! often times they place it on the inside.
stem walls are not retaining walls. at least the stem walls i deal with. often times they have soil on both sides of the stem. hence, you are retaining nothing! soil pressures negate each other for the most part.
if it is a retaining wall, then fill them solid. the extra mass helps with the rightening moment. filling cells is cheap. no forms are required. just make sure that the masons rod the cells well.
in a basement wall, i would grout the cells solid. apply the best water/vapor barrier. i like the mopped on or sprayed on coating. be generous with it. slope grade to drain away from the building. do not place sprinklers any where near the basement wall.
my two and half cents worth
lutfi
lutfi-
agree with the gist of your post, but would like to comment on something. grouting a masonry wall solid will not prevent water vapor or liquid from intruding if there is something driving it through the wall, but having the horizontal reinf and any vertical reinf completely encapsulated in grout and/or mortar will have some passivating effect and surely must help prevent corrosion.
i normally would not damp proof or waterproof either face of a wall that has earth on both sides.
best regards.
i agree with the concept of covering and protecting rebars.
i would not damp proof stem walls where earth is present on either side. however, if you have a basement wall and or exterior wall for an office or some structure, i think vapor barrier is essential, especially if you live in the hot humid south.
regards,
lutfi

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