Is this support for a wood girder ok? The lower portion was mortared but the top block was not. There were 3 columns like this in the crawl below a 1 story add-on (den) to a 1959 ranch house. Should all block have been mortared?
NO! They should have been installed parallel not lateral to provide full support under the beam or girder not across the beam. They will snap in the middle 1/3 of the CMU if not supported correctly underneath.
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I should have include this in my post: I am not sure if it is a CMU or solid cement block since there was no access. The entry was blocked by a hopper window that I reached over to snap the photo.
Into the vault that one goes!
Marcel, thank you. I am still a little confused and need verification of my interpretation. My structure did not exactly meet any of the fig. 10 examples. So, since mine are lateral and not interleaved like brick even though doubled I think I interpret this as not according to standards of practice. Yes? Also I am planning on disclaiming that they may not be resting on any footers since I could not access the crawl to observe them.
Unless you are in a high seismic/wind risk area, where all supports need to be tied down, I don’t think just the top block not being mortared in place is such a big deal at all. For most houses, piers are only resisting vertical gravity loads, and there are no lateral loads … like on exterior walls which need to have fully mortared joints up to the sill plate, with sill plate anchors.
I can see why they didn’t mortar the last course as it likely would have made the top of the pier just a little too high. Another option would have been to build up the top of the pier with mortared brick (see attached), which is less stable over time in my opinion. In either case however, the top course/block should be filled solid with mortar or have at least 4" of solid masonry (“pier cap” per IRC R606.6.1). It’s not likely that was done.
Intermediate piers typically have a shim or spacer without tie downs, and uplift loads are at the perimeter where anchor bolts tie down the structure to the foundation. So essentially that last block is acting like a large shim. And the pier blocks do not need to be orientated parallel to the joists unless the spans are marginal, and you want to reduce the span a little.
About the footing, I think it’s a good thing that you cant see it. You typically shouldn’t be able to see that, except maybe for a deck. And that doesn’t look like a Harry Homeowner “fix” for sagging floors where I would suspect no footing. Just look for possible signs of no footings (e.g. uneven floors or sagging beam).
One concern I do have is that the wood beam appears to be in direct contact with the masonry pier, and there should be something to separate the masonry and the wood (which is likely not treated, and it doesn’t appear to be). Was there a thin metal plate/shim or some type of tar paper between the two?
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**606.5 Piers.
**The unsupported height of masonry piers shall not exceed ten times their least dimension. When structural clay tile or hollow concrete masonry units are used for isolated piers to support beams and girders, the cellular spaces shall be filled solidly with concrete or Type Mor S mortar, except that unfilled hollow piers may be used if their unsupported height is not more than four times their least dimension. Where hollow masonry units are solidly filled with concrete or Type M, S or N mortar, the allowable compressive stress shall be permitted to be increased as provided in Table R606.4.
606.5.1 Pier cap.
Hollow piers shall be capped with 4 inches (102 mm) of solid masonry or concrete or shall have cavities of the top course filled with concrete or grout or other approved methods.
excellent replies! gentlemen
Correct
Yes marcel, those are the correct references for what I was talking about.
The unsupported height appears to be just under 3 block courses or 24", for a hight to least dimension ratio around 3, which is less than 4 for a required solid grouted pier per IRC R606.5
And R606.5.1 is the reference for the cores of the top block to be filled (“pier cap”), so that the masonry contact bearing stresses are not excessive. By the time the load gets to the first joint, bearing stresses have distributed to the point where grouting is not needed.
The pic reminds of a “dry stack” built home. Only difference is there should be a ‘bond coat’ applied. Perhaps they filled the cores instead.
http://www.drystacked.com/sequence.html
Yes Jeff, Dry Block and surface boding cement (SBC) have been around for a long time. Seen and used it before.
We call it Structural Skin Mortar.
Here is another link on the subject.
Never really like dry stacked block walls, cause the bending strength relies primarily on just the grouted rebars. Grouting is very tricky sometimes, and you can end up with grout voids (can pick those up with an IR camera). And its much weaker than a mortared block wall with the same rebar.
In any event, I wouldn’t flag the piers for repair unless you saw indications of poor performance (e.g. crushing or deterioration of the beam indicating excessive bearing stress or cracked pier blocks). Assuming it’s performing well, just make a note of it … and you could also recommend monitoring if you couldn’t verify adequate bearing or separation.
Is there a code you can cite that specifies the direction of the CMU in relation to the beam?
Hollow block is a highway for termites.
2009 IRC R606.6 Piers. The unsupported height of masonry piers shall
not exceed ten times their least dimension. When structural
clay tile or hollow concrete masonry units are used for isolated
piers to support beams and girders, the cellular spaces shall be
filled solidly with concrete or Type M or S mortar, except that
unfilled hollow piers may be used if their unsupported height is
not more than four times their least dimension. Where hollow
masonry units are solidly filled with concrete or Type M, S or N
mortar, the allowable compressive stress shall be permitted to
be increased as provided in Table R606.5.
R606.6.1 Pier cap. Hollow piers shall be capped with 4 inches
(102mm)of solid masonry or concrete or shall have cavities of the
top course filled with concrete or grout or other approved methods.
Joe:
The reason I do not use code is for this very reason.
Marcel points out exactly what our IRC has in it.
No code as to proper orientation so you must evaluate the pier with this in mind. Since I have seen the cement block split in the middle due to improper weight distribution I always inform people according to good practice today they should be bearing fully under the beam unless for some reason the cement block has been laid this way because of local practice.
Take three styra foam cups and place them on a table upside down. Place a board on top the same width as the cups and push down on the top. now take the same board turn it perpendicular and put force against the one cup in the middle.
Which can hold more support?:eek:
The key to orientation of a hollow cell masonry unit is commen sense more than a code specific. The common standard compressive strength of a cmu is about 1900 psi over the net area. Now if the bearing is only traverse to the center web of the block as a whole, what do you think will happen when there is an axial loading above the net area of the unit?
Hollow core block should always be positioned to maximize the net surface area of the block to obtain the most value. I would think that is a standard of practice in using cmu masonry for bearing units.
I call it “ca mon” sense. LOL
Il est sensé, n’est-ce pas ? :mrgreen: