Masonry guru help needed-Use of an FHA masonry block

[Ron247]

I saw a house where all the interior piers are made with a masonry block on top that looks upside down to me. A builder told me that is what they are doing now but really can't cite a standard or detail that shows this. The masons appear to be the ones who are doing this. He stated this is an FHA block but beyond that had no information. All the interior piers are built like this and the top course of the perimeter masonry wall is built the same except they then put the anchor bolts into the solid top of the unreinforced block. I saw some pictures on the internet of an FHA block and a few of the pictures had the solid flat side up but the caption says "solid bottom" not "solid top".

I have not seen any details where the block is part of a wall or pier system, just individual blocks with dimensions. The cell layout varies in the different drawings I have seen. None of the blocks I see in the walls have been reinforced or filled with grout.

Are the blocks being used correctly?

 

[dhengr]

Ron247:
That is not a proper use of that top blk., it is upside down. That’s a bond beam blk., with the cross shells cut off/formed, in height, to support a couple longitudinal rebars, and then it is intended to be filled with conc. to make a bond beam at the top of a wall or a light lintel. That mason is misusing that blk., and misunderstanding its intended use, to his advantage, to get a good flat bearing surface for the wooden beams and joists, assuming he has set it so that the top surface is truly level. Potentially, he gets good bearing btwn. the wood and the conc. blk., if level, but now check the net area for that blk’s. bearing. It is 4(1.25 or 1.5” squared), at best, but puts the blk. in bending in the least favorable orientation. I would like to see it turned upright and filled with conc. An A.B. into that top shell is almost useless, it only has to move one blk. which weights 20lbs.

The chimney blks. pilaster blks. or col. blks. make good piers, particularly in crawl spaces. They are easy to install, act as forms and can be filled with conc. for greater strength, etc. A good mason can adjust the thickness of 3 or 4 joints to get a proper top elevation.

Edit: What the heck is an FHA blk., and by who’s terminology? This is the builder’s old saw…, ‘we’ve always done it that way,’ as they look for a cheaper, quicker, dirtier way to make their life a little easier without any understanding of what they are really doing, and at the same time negating the engineer’s effort to meet ever more complex code requirements.

 

[Ron247]

Thanks dhengr,
That is what I thought. I told them it looked like a bond-beam block. I think the manufacturer calls it an FHA block and I think there is some type of block with that name but I felt it was not supposed to be used with the solid face up. As I stated, they are also doing the entire top row of a basement or crawl space with them turned upside down and then drilling a hole and putting some type of an anchor bolt in it. Not sure how the anchor bolt actually secures. The entire pier sets on about a 1.25" thick shell setting across the 3 cell dividers of a standard12" block.

I was there looking at the fact the pier sets about 8" from a 7' drop off when I noticed the top block upside down.

 

[kipfoot]

Yeah, that's not what that block is for. I found this reference the the knock-out block that refers to the (US) Federal Housing Authority:

 

[Ron247]

As I said, I found several drawings where it showed an FHA lock drawn upside down but the drawing said "Solid bottom". I think people are seeing these upside down drawings and think this is the correct way to install this block.

From what the contractor said to me, this has become very common where I live. I think there is one hell of a mistake here.

 

[JLNJ]

If the load is small and you need just the face shells to carry it, then what’s the big deal? The block doesn’t care which side is up.

 

[dhengr]

JLNJ:
I agree, if loads and bearing stresses allow. However, when the blks. are used up-side down on foundation walls, just to achieve a nice flat top surface, this negates the real structural benefits of having a bond beam, with a couple longitudinal rebars, tie the top of the whole found. wall together, both for vert. and lat. loads. The conc. filled bond beam also allows some almost real means of installing A.B’s., although their embedment is not deep enough to really be meaningful. You do imagine having to lift or shift some length of bond beam, and maybe a few blks. below, when the A.B. comes into play. I do understand that this detail is not particularly liked by most builders, it’s just more work to them.

As an aside, the sketch provided by Kipfoot does not call that conc. blk. an ‘FHA blk,’ it says it is approved by the FHA. And, that begs the question, are all the other blks. not approved by them? I’ve also watched a guy tightening A.B’s. down; He stopped tightening (turning the nut) when he reached the end of the thread, and the nut tightened up and would go no further. In the process he had actually pulled the poorly placed A.B. up out of the bond beam by an inch or so.

 

[JLNJ]

dhengr:

I agree about the bond beam, but I didn’t see anything in the OP about a bond beam. If there is a bond beam, the block cores should go clear through, otherwise it’s a lintel block and not a bond beam. True bond beam blocks can be installed with the bars at the bottom if that’s what you desire.

If the piers have 100 sq ft tributary area and 60 psf total load, you get 100x60/(16x2.5) or about 133 psi.

Anchor bolt pullout/breakout in unreinforced CMU is going to be pretty lousy no matter what, but obviously much worse in the 2 or 3” “solid” portion of an upside-down lintel block.

My only point was that the arrangement didn’t necessarily need to be dismissed out of hand.

 

[phamENG]

Here's my question - what' is the Federal Housing Administration's role in "approving" certain CMU shapes, and why are all "FHA Approved Blocks" apparently some kind of combination knock-out web/lintel block?

Quick google search didn't help - just got a bunch of references to mobile home foundations. Best I can tell is that these are produced to go on the top of a CMU pier to create a closed top without having to use a solid block or grout - references to up and down notwithstanding.

 

[Ron247]

The FHA block upside down is the top course of the wall so there is no bond beam present at the floor level. The floor sets on it but it is difficult to concentrically load the block. Since the wall above is a 2x4 wall, it never sets centered on the block and the floor joists tend to load the inner edge. I know my biggest problem is the unreinforced vertical leg. If you could load it concentrically, you still have an issue with beam bending of the flat unreinforced top.

My main point is whether the design of the block itself ever intended it to be used with the legs down. I think people seeing the details where it is drawn upside down think it was intended to be used that way. A google search for FHA block keeps showing me at least 3 drawings of it upside down. The contractor explaining the block to me was not the contractor for the house I was looking at.