# Reinforcing 8" block wall



## PaulPrice (Nov 20, 2010)

I just purchased a house to re-build and re-sale, the house was badly damaged in a fire, and from the foundation up, will be completely dismantled and re- built.... The foundation seems alright except for the fact that its built with 8" block and has 6' of unbalanced fill pushing on it.

The basement is partially finished, so I have not been able to put eyes on all of it, but what I can see looks good, no noticable cracks or anything.
As far as the county is concerned, I can just go with it..... However, I would like to bring everything up to current standards, or at least as close as possible.... I will definatly be re-doing the footing drains and sump

Any ideas, I was thinking maybe some pilasters? every 12' or so?


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## Walraven (Jan 24, 2014)

Get an engineers opinion on it.


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## PaulPrice (Nov 20, 2010)

yea, I will, but I'd like to have the opinions of people who have actually constructed these types assemblies and their opinions..... and he'll probably ask if I have a preference


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## superseal (Feb 4, 2009)

Can you rod and grout it? Pilasters are and excellent idea as well. 8" is a no no around here these days...many failures out there.


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## JBM (Mar 31, 2011)

Might put some of them carbon fiber straps epoxied to the walls with a beam on the top course., assuming even the sills are coming off.


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## PaulPrice (Nov 20, 2010)

Rod and grout, sounds like a good idea, I've just never seen it done....the straps do too, my big thing about the straps, is it a rated assembly, like would my engineer even be able to give me a stamped approval with those..... have you used them?

with the rod and grout, how much has to be cut away to get the steel pinned into the footing?


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## heavyc (Jul 2, 2013)

It would depend on how long of a masonry bit you could aquire.
And what you might find in the cells you intend to reinforce. 
Not sure if you already have horizontal
Reinforcing? Could be a factor. 
Open a can of worms or crapp shoot.
Maybe a do over? Let engineering expert put his stamp on it. I wouldn't want to be liable.


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## mako1 (Sep 1, 2013)

When I was doing that type work we would place a piece of # 5 rebar every 4 foot and pour those cells.Your problem with that would doweling into the footer.


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## cleveman (Dec 28, 2007)

Photos?


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## heavyc (Jul 2, 2013)

Not sure how fire effects the strength of cmu's. I would assume it weakens them. There is a lot of unknowns. Photos would aide in a hypothesis. 
Might pay to clear lot start over?


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## heavyc (Jul 2, 2013)

PaulPrice said:


> Rod and grout, sounds like a good idea, I've just never seen it done....the straps do too, my big thing about the straps, is it a rated assembly, like would my engineer even be able to give me a stamped approval with those..... have you used them?
> 
> with the rod and grout, how much has to be cut away to get the steel pinned into the footing?


You said basement? How do you know there's no reinforcing in place already?


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## JBM (Mar 31, 2011)

Would cut it up 3 courses and drill 6" into the footer. Put the dowel in and bend an angle on it and slide it up and in. Nail or screw plywood on it and pour. Simple enough.


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## heavyc (Jul 2, 2013)

JBM said:


> Would cut it up 3 courses and drill 6" into the footer. Put the dowel in and bend an angle on it and slide it up and in. Nail or screw plywood on it and pour. Simple enough.


Wouldn't want to forget to epoxy the rods of course. Blow all debris out from drilling too. Then use a quality epoxy making sure you get enough in each hole twist as you insert to form contact as much as possible.


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## mako1 (Sep 1, 2013)

We used Parabonds.They are epoxy in a glass capsule.You buy them according to the size hole.Blow it out,drop the parabond in,juke the rod in the hole breaking the glass and your done.No mixing and no mess.


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## JBM (Mar 31, 2011)

heavyc said:


> Wouldn't want to forget to epoxy the rods of course. Blow all debris out from drilling too. Then use a quality epoxy making sure you get enough in each hole twist as you insert to form contact as much as possible.


Oh sure, but will he know to use a 3/4 bit instead of 5/8 lol.


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## fjn (Aug 17, 2011)

mako1 said:


> When I was doing that type work we would place a piece of # 5 rebar every 4 foot and pour those cells.Your problem with that would doweling into the footer.





You read my mind.:thumbsup:


Without the dowels in the footing ,you will create what engineers call a moment.


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## fjn (Aug 17, 2011)

Another thing regarding the busting cells,drilling,plywood dams etc;that only addresses the vertical steel,still no opportunity for horizontal.


Like another mentioned,possibly best tack would be clear the lot. Among other perks to that approach,you are not committed to working with the existing building footprint.


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## heavyc (Jul 2, 2013)

fjn said:


> Another thing regarding the busting cells,drilling,plywood dams etc;that only addresses the vertical steel,still no opportunity for horizontal.
> 
> 
> Like another mentioned,possibly best tack would be clear the lot. Among other perks to that approach,you are not committed to working with the existing building footprint.


If you were concerned with the horizontal. Don't see much in residential, but if your mud sill, green plate has to come off? You could take chop saw cut your own bond beam, block off the cells with no vertical reinforcing add horizontal bars add grout and anchor bolts?


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## Framer53 (Feb 23, 2008)

How old is the house?
How long has it stood with existing foundation?

My experience with engineer is that the CBU is not affected with the fire.
Lastly, exactly how do you know there is no horizontal or vertical support existing?


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## fjn (Aug 17, 2011)

heavyc said:


> If you were concerned with the horizontal. Don't see much in residential, but if your mud sill, green plate has to come off? You could take chop saw cut your own bond beam, block off the cells with no vertical reinforcing add horizontal bars add grout and anchor bolts?






True,however,that gets you one bond beam. And that one is at the very top of the wall,more than likely above the unbalanced fill.....the place where it is needed the least and does the least good.


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## concretemasonry (Dec 1, 2006)

fjn -

The moment at the base of the wall is only created if it is connected to the footing by grout and rebar. Otherwise it is simply supported wall that has horizontal resistance at the top and bottom. Usually the joists parallel to walls are blocked well between them for the first couple of spacings get the floor system to resist at the top of the wall.

If it is a wall on a strip footing with the typical basement floor cast over the footing, which is suggested/required in many ares, it is a simply supported wall that has no "moment" at the base and the moment of maximum stress in the wall is moved up to near the center of the wall area from the soil, so reinforcement can be required depending on the amount of retained soil. This stress is reduced somewhat by the vertical load from the walls and above floors and compressive strength of the masonry or concrete is usually not a factor of a home.

The bond beam on a masonry walls is just there to provide masonry continuity at the top of walls with no joists on it and a level area for bearing on all masonry walls.

In many areas where 12" masonry basements are used, a special filled top is used on the top course of the wall for good bearing and they can be grouted at down to 16" increments for anchor bolts. - A common historic term for those block is "FHAs" since they were required by the Federal Housing Authority (FHA).

Sorry for the engineering and code slant.


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## dom-mas (Nov 26, 2011)

I agree with concretemasonry (I think...not sure what a moment is in engineering). The major problem with block basements is soil pressure/hydrostatic pressure. reinforcement that doesn't join with the footing will still resist that soil pressure which is fairly low at the bottom near the footing. At the top where soil pressure is strongest the masonry should be tied in via the floor system so the area where it's going to be effected the most is in the middle and reinforcement every 4 cores should be plenty to deal with that. Personally I don't think horizontal re-enforcement is particularly necessary in this situation. Dead loads are pretty constant and fairly light

remember that the foundation has been doing it's job without ANY re-enforcement for 40-50 years


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## heavyc (Jul 2, 2013)

fjn said:


> True,however,that gets you one bond beam. And that one is at the very top of the wall,more than likely above the unbalanced fill.....the place where it is needed the least and does the least good.


That's why you have vertical reinforcing? 
Never seen horizontal reinforcing called out for at grade or an intermediate bond beam if you will at grade?
Although I would think that in conjuction with vertical reinforcing a continuous or more commonly called structural bond beam would provide more stability and continuity to the vertical reinforcing intention than none at all?


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## PaulPrice (Nov 20, 2010)

I dont know that its not already re-inforced, I don't really know anything at this point, other than, from what I can see , it doesn't look bad, and would like to save some money by re-using the foundation.....I would say that the footing drain is a definate. I'd be hard pressed to build a new house on top of a potentially wet basement

The purpose for my inquiry, is simply to gain knowledge and prepare myself


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## dom-mas (Nov 26, 2011)

The foundation was built outside of California 50 years ago. It doesn't have any reinforcement. Almost a guarantee


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## heavyc (Jul 2, 2013)

PaulPrice said:


> I dont know that its not already re-inforced, I don't really know anything at this point, other than, from what I can see , it doesn't look bad, and would like to save some money by re-using the foundation.....I would say that the footing drain is a definate. I'd be hard pressed to build a new house on top of a potentially wet basement
> 
> The purpose for my inquiry, is simply to gain knowledge and prepare myself


PHOTO'S Would greatly aide in your request.
And I would also think the engineer
would be quite knowledgeable as that is his forte?
Seems a whole lot of brain power is being wasted? Without more information on your part?
As most some or all replies and input of knowledge may be mute?


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## PaulPrice (Nov 20, 2010)

I'll get some photos, but the basement interior partitions have to be demoed first..... I was planning on using the structural engineer who does everything for me , for framing.... I don't know any masonry specific engineers, anyone got any suggestions.... As far as wasting knowledge/ input, I have nothing better to while my wife watches some award show, and don't incinveniance yourself on my behalf, but I do appreciate the advice


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## Walraven (Jan 24, 2014)

In my experiance with block retaining most situations require specific engineering from the footings up. Footing width,amount of bars in the cages, diameter of starters, centres of starters....etc etc.
As far as retro fitting reinforcing i know theres some cool new products out there as mentioned earlier they have been used over here abit for earthquake strengthening.


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## dom-mas (Nov 26, 2011)

Figuring out steel requirements for a residential or light commercial block wall isn't all that tough. You need 0.002 of the gross cross section of the wall to be steel and for some to be horizontal and some to be vertical with a minimum of 1/3 in either direction. 

In this situation it would be very difficult to add any horizontal steel and since the wall is already under built those steel requirements would change but for new work that is the method


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## fjn (Aug 17, 2011)

heavyc said:


> Although I would think that in conjuction with vertical reinforcing a continuous or more commonly called structural bond beam would provide more stability and continuity to the vertical reinforcing intention than none at all?





Exactly,that is why belts work really good around our mid sections.:laughing:


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## fjn (Aug 17, 2011)

This article sheds some additional light on the subject. Of particular interest is the chart depicting the unbalanced fill,which is always a concern. The soil type is also a very large factor,I.E. clay vs. sand or gravel.


http://www.masonryconstruction.com/Images/Building Residential Block Basements_tcm68-1374431.pdf


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## heavyc (Jul 2, 2013)

fjn said:


> Exactly,that is why belts work really good around our mid sections.:laughing:


FYI I prefer and use suspenders as I also need the vertical reinforcing they
provide.


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## dom-mas (Nov 26, 2011)

Just because I'm an ass...another paper saying that joint reinforcement counts as horizontal reinforcement


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## dakzaag (Jan 6, 2009)

You guys are all messed up...

The main concern would be if the basement walls were exposed to fire or not. If the temp of the walls went over 600 F, the mortar and block will be ruined beyond repair and require replacement. I would basically assume any burn marks are over 600 and replace those sections. 

If you're digging out the perimeter for a new footer drain, then by all means check out the wall and reinforce as needed. Pins and grout will do the most for the least and personally I would not get too concerned about drilling into the footer. 

Helicoil could be added to the bed joints on the outside wall for extra measure. The manufacture probably has some data on tensile strength. 

Get the deck back on before back fill. If it ain't broke, don't kid yourself into thinking you need to fix it.


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## heavyc (Jul 2, 2013)

I think if you read the 9th. post made after the starting thread. I most definitely made the statement your referring to? So I don't know that we're all messed up?


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## muskoka guy (Nov 16, 2013)

If you wanted to install rebar into the wall and pour the wall solid, you would probably have to remove the top course or maybe two as these are usually poured solid or laid with semi solid block on the top course. 
Unless the wall looks like it sustained very high heat, it will probably be fine if it has lasted 50 years in its present state. In Ontario, you could probably only be allowed to backfill about three feet on eight inch block. We use 12 inch block with rebar every hole, poured solid with concrete and we can only backfill about seven feet. Buttress walls on the inside are a great idea. As already stated, if the basement floor is poured a good portion up on the bottom block, it would help stop the bottom of the wall pushing in. Therefore rebar would help even if it cannot be drilled into the footing. If the floor isn't at least half way up the bottom block, the rebar will be fairly ineffective unless pinned to the footing somehow.


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## dom-mas (Nov 26, 2011)

muskoka guy said:


> If the floor isn't at least half way up the bottom block, the rebar will be fairly ineffective unless pinned to the footing somehow.


Yes it will. Soil (same as hydrostatic) pressure increases with height. There is little to no force at the bottom. and it would need to move all that soil to swing outward


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## fjn (Aug 17, 2011)

dom-mas said:


> Yes it will. Soil (same as hydrostatic) pressure increases with height




Yes this is correct. One other important fact to keep in mind,the pressure exerted with an increase in height is exponential.Six feet of fill exerts considerably more than double the pressure of three feet of soil etc..


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## Fouthgeneration (Jan 7, 2014)

Ask the local inspector if you have to retrofit reenforcement meet current codes

Cover it up before it freezes.... hope it isn't to late.....

Many CMU basements only work because the weight of house keeps both faces under compression. thus removing the weight of the superstructure will allow the basement walls to cave in.....even using 2x4 instead of 2x8 sillplates can allow the block roll more easily.

Worse case, its already cracked.... Hire a PRO, that knows masonry to inspect it.


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## muskoka guy (Nov 16, 2013)

dom-mas said:


> Yes it will. Soil (same as hydrostatic) pressure increases with height. There is little to no force at the bottom. and it would need to move all that soil to swing outward


Why do they make us pin the bottom course to the footing if it has no benefit. Just asking.


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## dom-mas (Nov 26, 2011)

muskoka guy said:


> Why do they make us pin the bottom course to the footing if it has no benefit. Just asking.


Oh there's a benefit of course...it's just that there is still a huge gain even if it isn't pinned


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## JBM (Mar 31, 2011)

I would strap it with the epoxy straps before I wasted my time pouring cells without pinned dowels.


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## superseal (Feb 4, 2009)

Properly done, the floor will pin the base course. I don't think pinning the footing is absolutely necessary in this case. Just make sure rebar extends the full height of the block before grout.


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