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Masonry Construction Information

2907 Views 15 Replies 9 Participants Last post by  heavyc
New to masonry construction for bearing walls. Have a few questions. May seem obvious but want to be sure before I bid out. Any help would be appreciated. Thanks.

1: Drawings on floor plan show darkened out sections of the CMU ext. wall, assuming this is the fill cell requirements? Detail sections calls for this.
2: Drawing on floor plan show open sections of CMU ext. wall, assuming this is not filled? Detail section does not state solid fill. However, seems to show a vertical #5 bar (in a dashed vertical line contained in the CMU). Does this represent a #5 vertical bar contained in this section?
4: At the top of the ext. wall calls for K.O. Block w/ (1) #5 bar cont. I assume this is the bond beam with a horizontal bar through the ext. perimeter of the wall.

Any basic info on block ext. wall construction would be helpful. Thanks ahead of time.
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Also forgot to mention, assume I need a clean out at each fill cell block to identify the vertical #5 bar.

*Best process is to build the wall and pump in the filled cells at the same time as we grout the bond beam?

Yes. The clean out is to allow the inspector to see the steel is tied to the steel in the footing. Make sure there is enough overlap where the steel meets. I would hire a block crew.

Pump the whole house , assuming its a single story, at the same time. The masons should make sure the headers have enough room in the ends for the concrete to get down in past all the steel. We used to just cut larger the ends on 50% of them just to make the pump guys life easier. Put a leg under the garage header or it can sag.

Thats about it.
Your verticals should lap 5x rebar diameter. On a #5 the lap should be 25" min.
Most likely the roofing sub or general will want to embed a number of hurricane ties when you grout. Are you building in a high wind area?, no added steel around windows and door openings? Extra durawall in shear walls? Inspections(inspectors) required during pours, grout/mortar tests? who pays? you, GC or Owner?

salt resistant coatings?
I'd develope a check list when estimating, a spread sheet with all the possibilities listed, such as: eye tye wire for veneers, stainless bump ups, High test grout, etc...

Most likely plans will say local Codes prevail... CYA check the wind and sesmic zones. lot of snakes and gators in Florida, some even have briefcases.

First glance, there are two wind Zones, and another big bump up area within a mile of the coast? You have to have approval from the City/county to do non-permitted work....WOW! land of the free, not so much.....

The Florida state Building code (it is online) actually has some pretty good drawings and tables for a state code.
just make sure your using the right one for the building's wind and frost zones, If there is a gable end rake wall there are quite a few more hoops, anchor bolt size and spacing , maybe even a poured in place raked cap beam.

If the plans are stamped by a P.E. for that address, Call him with your questions, he or she will be pleasently suprised. Take notes.

I do tap on my keyboard, Hmmm...
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Is this residential or commercial?

If it's commercial, all your answers are in the specs and structural drawings. If something is missing submit an RFI.
This is certainly a lot of scary information on masonry construction. The residential buildings seem to be way over designed because of the poor construction methods, so the engineers cover themselves by over-designing since there is little little inspection and and the methods do not meet the normal masonry standards and it cheaper and easier for the engineer to cover himself based on the local residential methods. Quick and dirty and arbitrarily dumping grout 8' or 12' is not good construction.

Clean-outs (if really required) are to check if the bottom of the cores are relatively clean and ar not large enough to see if the lap on the steel is sufficient.

Take a look at the real standards or links that can be found by going to the MCAA (Masonry Contractors Association of America) site or the NCMA (National Concrete Masonry Association) for TEK notes(over 120 water down enough to be easily used).

Some other places in the world routinely do some great masonry construction. Brazil has some projects of 4 to 20 buildings that are 8 to 22 stories with 6" partially filled block for load bearing walls with NO steel or concrete columns. The site inspection is minimal and there are no clean-outs. The grouting is usually scheduled in 2 lifts to avoid splices and do proper grouting procedures and allow for consolidation and let the block absorb to water required for a 8" to 11" slump grout. - The also do not use the old-fashioned "knuckle buster" block with flush ends or the 2 core block with small 1/2 end cores. - All block are color coded and approved at the plant before delivery and the "guts" of the masonry drawings for the multi-building projects are clear only only about 7 pages. It is all done in compliance with U.S. codes and standards
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Just don't tap the block in place :whistling:
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Next block lead I build im going to tap my level with my brick hammer....
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lol tyb,JBM :)

Clean-outs (if really required) are to check if the bottom of the cores are relatively clean and ar not large enough to see if the lap on the steel is sufficient.
exactly right. The inspector has already approved the footing and the lap based on how much the steel sticks up above the concrete.

Clean outs are required here only if you want to grout higher than 5'4" they will often let you go 6' if that's the top of wall. Check your local codes, or as NJ said, check the notes on your plans.
There is an acceptable method of high lift grouting that was developed by the mason contractors, engineers and some code representatives. - Definitely not a "quick dump" but is good construction and gets more masonry used.

Clean-outs are a big problem for contractors and engineers. The job I was on in Brazil used a mini camera (suggested by the masons) to allow random checks of walls for the quality of masonry and amount of droppings/slop and speed things up since waiting for inspections was a problem on a job that had to go a floor or two a week. Not likely in the U.S. because of the layers of contractors, designers and inspection/verification, but the owner of the buildings was the general contractor that also did the masonry work. - A little different situation than the U.S.
I personally think the emphasis on perfectly clean grout cells forgets the purpose of the top of the "Engineered" CMUs walls being thicker than the bottom of the sides, so every course is mechanically bonded together even when the suction bond between the mortar and units has failed... Walls not completely grouted laid sans any mortar projections are weaker in torsion, and due to less surplus moisture,lower tensile bond, to statisfy just one parameter, decades of existing knowledge is kicked to Kerb to gain a few lbs on the compression strength of a grouted cells.

On the other hand I've seen alot of mud slinger's cavities un groutable due mortar droppings. I issue them a plastic Pot spoon to remove the excess from their grout cells. I've never had much luck filling 8"CMUs 100% for Hi lft grout when ever there are intermediate horizontal bars... the more rebar holders/positioners the worse it gets.

The current 50 dia bar lap spec was the result of rebar connector manufacturers sand bagging the ASTM committees with "volunteers" of people whose paychecks depend upon selling more rebar connectors.... Further increasing the cost of Unit masonry in the USA without much increase in building strength. Similar to when Brick manufacturers(ASTM comittee filled with Manufacturer reps, no end users) got to have more then 25% cores in a "Brick", they save a penny a brick in energy costs, the masons have to buy 2 cents more mortar every brick to fill the larger void, the wall assembley costs another 25 cents a foot, fewer brick now sold....
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personally think the emphasis on perfectly clean grout cells forgets
Personally, what you think matters not one bit to me. I build them according to code and give my inspector what he asks for. No problems.

I think worrying all the time about what everyone else is doing and thinking you know better than everyone else is not healthy, have you had your blood pressure checked lately?
Fourthgeneration -

If you have trouble getting 100% grouting you are doing something wrong. Unreinforced cells should not be filled. Since the strength of the masonry unit determines the wall strength in the end, except for wind loading on reinforced walls.

1. Not using the right grout (8" to 11" slump) with the right maximum size of the aggregate for the steel spacing or core spaces. The grout does not need to be very high stength and some engineers put a limit of the maximum strength allowed.

2. Just dumping and not consolidating as you go is definitely poor workmanship and laziness.

3. The wrong units being used that do not have cores aligned. If the "bottom" of the block is wider, you are laying the block upside down. The minor core tapers do not have an effect. It is not necessary to use block with flared tops/mortar beds (hand holds). The best units for engineered masonry are symmetrical and have 2 webs 8" on center (1 core "H" block) that align to form vertical cells that can be isolated if desired in either running bond or stack bond. For 2 core block, the worst are the units with small partial encores followed closely by the 2 core flush end "knuckle busters". Obviously, 3 core are worthless because of the tight cores and often the pear shaped cores. For most partially grouted construction the 16" long block with 2 webs each 4" off the centerline stacks well and gives the easiest walls to reinforce and grout.

All grouted walls must be allowed to consolidate and let the excess water from the grout to be absorbed by the block and the grout to be sucked into the block and create a tight masonry section.

Most masonry units are far beyond the ASTM requirements because the existing ASTM standards are too low and have not increased (if at all) nearly as fast as the manufacturing processes. CMU are typically 25% to 50% over minimums because a lower strength to not cheaper (material cost) and is too difficult to handle and deliver. If you need higher block prism strength it is easy for a manufacturer to make higher strengths. I have seen 8500 psi block laid with 2200 psi mortar test at 4800 psi in a 8" - 2 block high ungrouted prism (which is the standard used by engineers).
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dbrons, That is nice, Don't ever question authority, keep your head down and go with the herd when they are loading the cattle cars...
BP fine, thanks for asking.

I don't care what everyone else is doing unless they expect me to comply with a silly idea, such as laying CMUs with out enough mortar to from a mechanical bond between units. I do clean out the grout cells to the statisfaction of the inspector, but my ungrouted cells have mortar fingers. Any one who has demoed a wall with bed joints that aren't extruded into the cells knows they are weaker, easier to unbond, and much easier to displace, in more severe examples one can knock units out of the wall sideways with out any great effort.

Concrete Masonry, I respect your opinions here and on other forums.
I might not made myself clear, With 50 diameter laps, # 5 bars are lapped ~65% of length vertically with 4 ft grout lifts, any horizontal bond beam crossing them creates congestion that even a tiny bit of dead mortar worsens, add a 90 degree corner bar for a sesmic/hurricane window detail, you 've something very hard to insure grout is flowing downward to fill all the voids below.

If I'm the decider, we grout at every horizontal beam...
I try to get my grout to test as close as possible to the CMUs strength, the higher the test, the shorter the laps needed for the iron, the cheaper the wall is to construct, saving labor and materials.

I mastered the slump part about 25 years ago... Pea rock should flow, except when it doesn't... Aligning the webs, that was the week after the slump lesson.:surrender:

#2. Again you are preaching to the choir brother, If I'm getting paid. its done right.

I understand that particularly in high rise construction, no unreinforced cells should be filled, the surplus weight alone could rapidly consume safety margins of lower load path components. Some times more isn't better.

I humblely submit your opinion about CMUs produced without the tops being slightly larger than the bottom as having no effect as false, Test a panel with all the units laid upside down... The wider top allows the mortar to make legos instead of remaining Jenga style smooth units. Any one who has laid "Menards" straight sided CMUs knows by lunchtime the 8 oz of material used to produce the "handles" is money well spent.
H block are lovely,just about eliminates congestion, now if they could figure out the corners... I'd like to see 24" long lightweights with the Army (H) style webs, similar to the haydites 24" scored CMUs used out East. Additionally three web block are much easier to one hand than the "Army" H block. That considerably cuts the weight advantage of the two web blocks.

Having had the priviledge of working on a Super Target that had bastard walls with a mix of 3 and 2 web block where different color Rock face blocks were used, H block still have some unresolved issues...

The now old school "engineered" CMUs were a giant step up from the old old school 3 holers..

Sorry about the rant about ASTM standards being preverted by biased panel members--any suggestions to evolve them to more rational rules?

Kickler, Every print and spec I read will say,..."Contractor is required to meet all applicable laws, regulations, statutes, zoning,....etc.." It is on you to find out if the specs meet the codes for this location, use and TIME.
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Clean Out is a term or requirement in some jobs for masonry veneers. Anyone familiar with masonry has knowledge of the process. What I believe most are referring to is correctly called inspection blocks. Commonly used or required in high lift grout placement. These block also come with an accessory package. That contains the complete inspection cover kit. The old covers were not transparent usually yellow or orange. The latest I have used are clear Plexiglas. Now to the reason for these block. They allow a window so to speak in to the success of the grout placement. This is a tool for inspectors and masons performing the grout fill. Obviously no grout behind inspection cover means unsuccessful grout placement. One of the biggest headaches to the high lift grout method is patching the dang inspection hole itself. Referring to interior load bearing cmu's that are viewed from both sides.
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