Control joints in concrete foundation walls

fjn · Mar 24, 2015

From the responses in the previously locked out thread,there appeared to be considerable surprise regarding the need for control joints in concrete foundation walls. While I have to admit they are not seen often does not in any way diminish the need for their usage.

We as an industry almost universally understand that "new" concrete shrinks. That is why we utilize control joints in CMU walls. Who among us would think of pouring a 50'--60' long concrete driveway without jointing it ? A concrete foundation is nothing more than a real thick driveway stood on edge.

The same good practices utilized in commercial work should also be implemented in residential applications,no exceptions.

The locked thread originated as a result of the concrete contractor not adhering to possibly little known but non the less trade standards. The Portland Cement Assoc. publishes a 7 page paper that is a guide to placing trouble free concrete foundations. Their report is titled Concrete Basements For Residential & Light Building Construction. Try as I may,it seems non available on line.

Here is a brief excerpt on joints in basement walls. "Proper jointing is of great importance if uncontrolled cracking of concrete walls is to be avoided. A control joint provides for expansion and contraction movements in the plane of a wall or slab.It is used to prevent unsightly,unwanted random cracking caused by drying shrinkage".

While cracks in slabs are unsightly,in foundations besides being unsightly,provide a pathway for water intrusion. We all know how much fun wet leaky basements are.:no:

Eaglei · Mar 24, 2015

I agree 100% with placing control joints along poured foundation walls . Why it's not done , I think you'll get a few different answer's . My cousin has been in the poured foundation business for over 30 years and is highly regarded in the industry .Currently pouring a few foundation's across the street from me so I asked him why he doesn't do it. His answer was that if the footing's are done properly , on top of virgin soil ,the correct amount of re-bar ,depth and width of footing and the correct psi and slump of the concrete . He also waits at least a week before pouring the walls . That's the way he was taught and said he never saw anyone in the industry putting in control joints .To me it doesn't make sense , the city checks the sidewalks we pour for control joints but not for foundations .

Fancis Casini · Mar 24, 2015

I have 10' high by 12'' concrete foundation walls with rods... I put 5/8'' every 3' vert into the footongs and 3 runs of 1/2'' horz.
For about 15 years no cracks....but now at both basement windows a vert crack is developing. this is in a 30' by 20' L shaped section the walls being those lengths.

I thank god I put the rods as I poted the footings..I wish I did more now but it's now 22 years. Also I have 4'' slabs with rods on blueboard with infloor heat. Not a hairline in 1o years but eever so slight cracks are developing off the oustide corners at jogs. I have exp joints at all perimeters.....I have an ungle whoe's a good crpeneter mechanic...he said I should have rounded the corners to stop the cracks. He compared it to formica..ie and interior corner rounded will not split...but square will.

IMO that only aplies to flexible material..??

fjn · Mar 24, 2015

Eaglei said:
I agree 100% with placing control joints along poured foundation walls . Why it's not done , I think you'll get a few different answer's . My cousin has been in the poured foundation business for over 30 years and is highly regarded in the industry .Currently pouring a few foundation's across the street from me so I asked him why he doesn't do it. His answer was that if the footing's are done properly , on top of virgin soil ,the correct amount of re-bar ,depth and width of footing and the correct psi and slump of the concrete . He also waits at least a week before pouring the walls . That's the way he was taught and said he never saw anyone in the industry putting in control joints .To me it doesn't make sense , the city checks the sidewalks we pour for control joints but not for foundations .

Your mentioning your cousin with 30 years experience and the way he was taught made me chuckle a bit. When I see a guy doing something in the trades that is truly not up to trade standards and he gives me the I have 30 yrs. experience line,I just laugh and say,no you don't you have 1 year experience replicated 30 times.:laughing:

The virgin soil,correct re-bar,correct PSI ,slump etc.is all well and good,however,as we all know water is a part of the equation. The control joints are needed to address the volume change that has to take place as the water leaves the mix. In other words,to control shrinkage cracks and allow them to take place at a predetermined location so they can be caulked prior to backfilling and not require digging around the exterior of the building at a later date. It boils down to the old adage,an ounce of prevention is worth a pound of cure.

fjn · Mar 24, 2015

Fancis Casini said:
For about 15 years no cracks....but now at both basement windows a vert crack is developing. this is in a 30' by 20' L shaped section the walls being those lengths.

:

Do not beat yourself up regarding the vertical cracks adjacent to the windows. The means and methods to prevent such cracks only came into vogue around the time you did the foundation (at least that is approx. the time I read of the remedy ):laughing:

The prescribed method is to place a short rod on a 45 degree angle at the window corners.

superseal · Mar 24, 2015

The simple solution for control joints in foundations is using chamfer strips vertically 2ft off corners, at window header apexes and sills and 20 ft runs along walls.

Your right, nobody does it and I'm forever fixing irregular cracking at these locations.

fjn · Mar 24, 2015

superseal said:
The simple solution for control joints in foundations is using chamfer strips vertically 2ft off corners, at window header apexes and sills and 20 ft runs along walls.

Your right, nobody does it and I'm forever fixing irregular cracking at these locations.

Exactly ! Those two articles I referenced prescribe placements of joints very near the locations you mentioned.:thumbsup:

The one I was able to provide a connection to the publication,the one from the PCA to the best of my knowledge is not available on line. Both of them clearly lay out the guidelines to give one a fighting chance for a crack free foundation providing one follows all the other good trade practices.

NYCB · Mar 25, 2015

Oddly enough I see them more on agricultural work than on residential.

I don't really know why, but the inspectors for residential don't seem to mind to much when they aren't put in.

fjn · Mar 25, 2015

sitdwnandhngon said:
I don't really know why, but the inspectors for residential don't seem to mind to much when they aren't put in.

There is probably a real good chance the inspectors are not up to speed. Also,even though they are not noted on the plans,litigation can be brought against the architect (anyone can sue anyone else) they are not mandated by code. They are in the process of making them code,but who knows how long that will take.

duburban · Mar 25, 2015

this is all new to me. Does anyone have diagrams/ drawings to help educate me?

fjn · Mar 25, 2015

duburban said:
this is all new to me. Does anyone have diagrams/ drawings to help educate me?

Here is one article,however the one I referenced by the PCA is not available on line.

http://www.concreteconstruction.net/Images/Joints in Poured Walls_tcm45-342541.pdf

superseal · Mar 25, 2015

Another important note to mention would be the use of slip dowels as opposed to continuous reinforcement across the locations.

Without internal relief, the wall stands no chance no matter how many chamfers or saw cuts you put in.

I'll usually pack grease in copper pipe which is sized one size larger than the rebar.

JBM · Mar 25, 2015

My pal built me a house and as I was flipping through the contract it stipulated in there that up to *i believe* 1/4 inch cracking in the foundation was acceptable and not covered under warranty.

Maybe unless it leaked, he would have dug it out if it did so I didnt pay any attention to it...

I should note this was an ol timer pal of mine, not some young whipper snapper. Been building houses since early 80's.

pritch · Mar 25, 2015

I always put in control joints when I was doing res foundations. It's how I was taught, and it is what I teach the kids.

JBM · Mar 25, 2015

I agree, just never thought about it before. Good info!

Fancis Casini · Mar 25, 2015

superseal said:
Another important note to mention would be the use of slip dowels as opposed to continuous reinforcement across the locations.

Without internal relief, the wall stands no chance no matter how many chamfers or saw cuts you put in.

I'll usually pack grease in copper pipe which is sized one size larger than the rebar.

The rods at a 45 at windows is bull. I said I have 3 - 1/2'' rod horizontally. The top one is just below the window sill about 8'' or so. There is also another fine vert hairline at a beam pocket.....ie any spot that is a bit weaker will give ...however these took every bit of 10 years to show up.
I was taught in school concrete hardens up to ten years then gradually disintegrates and it sure is behaving that way.

As to the grease pockets they arent new. My wife's uncle was a super for a large const co....he told me stories how they did the greaseed rod and sleeve. The crack ended up adjacenet

IMO the main thing is stopping the cracks rom opening with rods but cracks will happen no matter!

Fouthgeneration · Mar 28, 2015

frank: I think the latest "confined fiber stress" theory of concrete design would interest you. All those vertical rods need j hooks at the ends to work better
the "sharp corners" creating stress 'risers' is old news. the nicked wire breaks at the tiny scratch.

Remember a basement has a slab to restrain the bottoms of the walls, and mostly a constant inward thrust on all faces to push many cracks closed. The use of control joints is generally for appearance, most basements are mostly out of sight.

Fancis Casini · Mar 28, 2015

Fouthgeneration said:
frank: I think the latest "confined fiber stress" theory of concrete design would interest you. All those vertical rods need j hooks at the ends to work better
the "sharp corners" creating stress 'risers' is old news. the nicked wire breaks at the tiny scratch.

Remember a basement has a slab to restrain the bottoms of the walls, and mostly a constant inward thrust on all faces to push many cracks closed. The use of control joints is generally for appearance, most basements are mostly out of sight.

The vert rod on a 10' high 12'' wall isn't sliping. Have you ever demoed a roded wall and inserted a frost wedge into a series of holes to counter the rod's grip.....it wont give,,,the concrete around the wedge crumbles. I can see prestressed conc beams doing so.
I know the round corner thing has been around ...I did my foundtion 22 years ago..lol.

As to the exp joint for the basement perimerter I actually thought about it hindering the stabilization of the wall bottoms,however all the slabs I see shrink from the walls anyhow. And I did use super plasticizer.

Those wire nicks at acute corners?? I placed 3/8 rod at 30'' squares atop blueboard. The heat tubes were tied to the rod..except one f..n spot where we poured down thru a window,..the tube came up and was touching the back of my shoulder. I pushed it back down and re-rounded the kink [they say it has a memory] however I have a dead zone ....memory my ass.:no: I should of marked the spot:whistling

The slab is very nice still, as I said the cracks [ever so minute] are at two corners both where the slab either lengthens or shortens.
I really think its inevitable....

oh and I think you are forgetting I have a heated basement floor....ie that's a call for expansion at the perimeters..no?

The latest confined fiber stress?? I know about the mesh, is that the same?

fjn · Mar 28, 2015

Fouthgeneration said:
Remember a basement has a slab to restrain the bottoms of the walls, and mostly a constant inward thrust on all faces to push many cracks closed. The use of control joints is generally for appearance, most basements are mostly out of sight.

While random cracks are aesthetically unsightly and not appealing,they are also a pathway for water intrusion. It makes sense to me that at least with the utilization of control joints one has a fighting chance to predetermine where the crack will occur and take the necessary steps to minimize water intrusion BEFORE the building is backfilled,when it is the absolute most economic proposition to do so.

Fouthgeneration · Mar 28, 2015

Frank, Re Confined fiber stress, is a theory of concrete design that represents the internal stress loads on a piece of concrete structure, to me its similar to magnetic flux diagrams or EMF fields--lines of force.

Use of this theory has lead to some change in design and location of "stirrups' etc used in beam & columns to increase load capacities and reduce failures. and the common practice of post tension floor slabs out West.

Next basement just run a couple of tension strands in every panel to keep any cracks from opening up. Kind like a boxing ring.

Any techniques we develop to eliminate cracks in concrete/CMU basements would just be used to reduced the thickness of the walls until they start to fail again.

I just laid my basement out 12" CMus grouted on 32" centers and a bond beam below the windows. Some small cracks from I assume differential settlement..

I hope my dampproofing would cover an 1/8th inch crack...
I can't see low bid houses GCs using water stops and other costly products to ensure a 'dry' control joint.
Just sealing the poured walls ASAP would reduce the # and size of cracks.

Control joints in concrete foundation walls

fjn

Eaglei

Fancis Casini

fjn

fjn

superseal

fjn

NYCB

fjn

duburban

fjn

superseal

JBM

pritch

JBM

Fancis Casini

Fouthgeneration

Fancis Casini

fjn

Fouthgeneration

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