huangyhg

foundation for cmu wall
up north, i have never seen a foundation for cmu wall showing cmu below grade. is there a problem if we start to lay the cmu from top of the pad below grade? thanks

you can but if it is a frost wall, i recommend it be grouted solid so that water does not enter the cores and freeze.
if it a basement wall or a retaining wall, make sure that it is reinforced for the lateral soil loads.
it is done all the time in residential construction in the midewest and northeast...can't stress enough waterproof it!!!!
thanks. my wall is fully grouted. do we need waterproof it and why? where shall put the flash? thanks
masonry is porous, waterproof it!
the best way to test something is to squeeze it, slowly, until it breaks!
waterproof it 6'' - 8'' above grade - then paint it a pretty color
is this a basement or a "frost wall" to get below frost?
if it is a basement, you design it with block on the strip footing and the interior slab poured on the footings with 3.5" of concrete in contact with the wall. reinforcement in the wall may not be required according to the irc which is based on the ibc emprical design method (chapter 5).
if it is a frost wall with masonry above, waterproofing may not be required, but the reinforcement pattern must continue. grouting is of no benefit to "waterproof" a frost wall. basement waterproofing is first accomplished by water control, then by coatings.
anyone that makes a blanket statement that masonry is "porous" should think a little more. the absorption of concrete masonry units canbe rediculously low to the point where they are difficult to lay.
you do not "paint" waterproofing.
if you are concerned about the "flash" (flashing?) look at your engineers plans or one of the genally accepted details published by various associations and material suppliers.
dick
it is a frost wall. basicaly it is ok to have a cmu frost wall. i mean to lay cmu below the grade as a frost wall as long as the bottom of the strip footing is below the frost line.
there is no problem and it is done every day for frost walls if you are talking about construction when it is cold, the main thing is to make sure the subgrade or footing does not freeze before the cmus can be laid.
dick

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