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new cmu replacing load bearing 1800's deteriorating brick on interior basement footing
2

new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

(OP)
tl;dr (summary): I need to know how to replace an 1800's era interior brick load bearing basement wall most cheaply and most long lasting way with existing water migration issues that have deteriorated brick over time, hopefully keeping this all on an unknown footing.

Details:
I'm a licensed SE with a little experience in residential work and construction. I need some help for some pro bono advice for a friend in an old old house. I won't need to sign or stamp anything for them.
I am advising them to replace old crumbling brick 8" load bearing interior basement walls. Groundwater migrates up into the brick walls and evaporates, deteriorating the walls from years of the effects of efflorescence on old soft weak brick. The brick crumbles enough to need to sweep up daily. There are many sections of the walls that were broken out to duct AC through and I believe the plaster walls are bridging load to better supports in places. They have shored certain joists at the ends at those openings to provide some peace of mind while they decide what to do. They bought the abandoned house after the county and a structural engineer gave them the go-ahead (nothing stamped, maybe a letter to the bank and a $500 charge to the owners), I think they got bad advice and they feel betrayed.
This is a 3 story (including basement) house built in the 1800's in Michigan with a tall 45 degree roof.
Brick is deteriorating rapidly from efflorescence, and many areas have been knocked through for AC ducts.
The existing foundation could be brick itself or stone and mortar like the perimeter basement walls.
A slab was more recently poured in 2/3 of the basement on top of the dirt before they bought it.

Best idea so far?:
For the best bang for their buck (cost is a huge issue), I feel an ungrouted cell CMU half wall will be important to retain the existing system stiffness and benefit of spreading the point loads out on the original foundation. The upper half of the wall will be studs and plywood for ease of construction in replacement.

Problem:
Per https://www.eboss.co.nz/assets/Uploads/2010/07/Eff... I believe that efflorescence could continue be a structural problem gradually causing the breakdown of the cement matrix in the mortar. To prevent primary efflorescence on the new CMU half wall, I will recommend low alkali grout, washed sand, etc., but I don't know how best to prevent secondary efflorescence to prevent the new wall from similarly deteriorating.
They also showed me an exterior wall areas where new brick repairs seemed to deteriorate adjacent original softer bricks. I read Dik's article on http://slideruleera.net/Historic_Brickwork.pdf which perhaps addresses a similar issue in repairing with modern materials.
So long term, I don't know where or if it's okay to stop removal existing materials and build on top.. at TOS, TOF, or replace the whole footing (would seem unnecessary, super expensive/ or difficult if they DIY)

a few questions:
1) The footing may be brick.. will placing CMU above it be a terrible idea for shrinkage/expansion? (or even some chemical compatibility issues)
2) Is it possible the new mortar chemistry could react somehow with the original foundation in an undesirable way?
3) Can epoxy be used at the bottom of the new wall on top of the existing material to prevent groundwater migration into the wall?
4) Would EffLock or similar admixtures also be useful to prevent secondary efflorescence permanently in the new wall or is that a sacrificial type solution to the problem that will eventually be overcome?
5) Would it be okay to leave the brick flush with the top of slab and build on top of that?

There will certainly be other ideas:
Another engineer they have contacted much prefers to preserve the existing brick, but this is expensive too and there are some trouble spots full depth that need some serious repair.
Co-workers have said it would be best for them to replace the foundation of the wall line as well. Due to very limited funds, they would certainly want to only replace the wall. I feel since the existing foundation is carrying the loads already, if I recommend a stiff enough wall there won't be a big risk of new settlement.

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

Revised for JAE's comment; I missed that it was an interior wall and have not encountered this on interior walls. I suspect that if this is moisture 'wicking' up from the soil that there may be other health issues due to moisture (mold, mildew and possibly wood deterioration).

You are not avoiding any liability... you bought the baby... Some engineers are of the opinion that if they don't prepare sealed documents that they are 'off the hook'. If you are the only technical dude offering advice you are even more exposed. Important and still OK

Three options, as I see... and none of them cheap... You can treat the entire wall or a part of it.

Option 1
You have to remove the existing brick wall and reconstruct it with masonry or concrete. Can you frame the support provided by the removed wall with beam and posts? The posts supported on new spread footings. This may be the least costly.

Option 2
You can remove damaged portions of the historic brickwork and reconstruct them with masonry or concrete. This may reduce some costs.

Option 3
You can maintain the heritage of the existing brickwork and repair using existing brick and historic mortar (this is much softer than Portland cement mortar)... somewhere on the site, there is a paper I developed for historic brickwork. I can re-post it. This is the most costly. I'll have to send SRE an update on historic brickwork... the paper is now about 15 pages and not 5.

Efflorescence is a problem, but, not likely one that will cause you heartburn if you have the proper materials.

In response to your questions:

The footing may be brick.. will placing CMU above it be a terrible idea for shrinkage/expansion? (or even some chemical compatibility issues)

This is not likely an issue... your bricks have likely expanded all they will; you have to check the material properties. Is there a local mason that has experience in historic brickwork that you can talk to? You have to know what the bricks are: hard or soft, composition, strength, whatever.

Part of dealing with historic brickwork is studying the existing bricks to determine what issues you may have. Biggest problems are usually the ingress of moisture. You can create several problems if you don't appreciate the materials you are dealing with.

Is it possible the new mortar chemistry could react somehow with the original foundation in an undesirable way?

This is unlikely; the original mortar is likely a burned lime material with pozzolanic properties. Portland cement concrete didn't become established until about the 1900s and I'm not aware of it ever being used for historic brickwork; there have been some disastrous repairs using the Portland cement material. Strip footing foundations could be masonry or stone. It was also common for the wall to be thick enough that a footing was not used. For durability brick masonry was not often used below grade.

Can epoxy be used at the bottom of the new wall on top of the existing material to prevent groundwater migration into the wall?

Not likely a good idea... if you have water issues, then best to provide a positive means of providing drainage.

Would EffLock or similar admixtures also be useful to prevent secondary efflorescence permanently in the new wall or is that a sacrificial type solution to the problem that will eventually be overcome?

Efflorescence is generally caused by impurities with the brickwork or mortar caused by a source of water. Have to check the materials and look for the water source. You may want to deal with the issue than try to use a bandaid.

Would it be okay to leave the brick flush with the top of slab and build on top of that?

Can you post a sketch showing what you are planning?

Dik

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

dik - I think it is an "interior" brick wall.

One idea would be to sequentially remove small portions of the wall - shoring on either side of the wall to support floor, etc. Perhaps 4 ft. sections at a time.

Then remove the footing (is it an old brick corbeled footing perhaps?) and install a concrete footing sized for the load coming down from above.
Then install a heavy, treated wood stud wall system on top of the concrete footing, using a vapor barrier below the sill plate to inhibit moisture from coming up.
I doubt that a concrete footing will wick up water as much as a brick foundation will but the vapor barrier can't hurt.

Progress this replacement method down the length of the wall. I would recommend sheathing both sides of the wall with marine grade plywood.

Alternatively you can do the same thing with a CMU wall instead of the stud wall...just more pricey but definitely more durable.



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RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

JAE... missed that, thanks... I'll check tomorrow and see if any revisions are in order...

Dik

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

(OP)
as for option 1, replacing the wall with a beam would be worth considering. Thank you for the idea!

Shoring will be a challenge under a concentrated load the way things are framed. It's like a game of tetris there after the top of the wall was removed for AC ducting. A cracked header and posts installed around the ducts under this point load was sad to see. The parallel wall above is on the joists framing into the wall in one bay, and the adjacent bay has joists running the other way blocking access for easy shoring of the concentrated load (10.5 k DL, 9.9 K LL estimated, unreduced)

We are still in the talking and schematic phases of this. If they feel they can't safely do the work themselves their options would be to rely on the kindness of friends and community to raise support for a contractor to do the work, or to find recourse with the original engineer who gave the okay to the bank for the loan. I can't imagine the difficulty of the latter route for all involved.

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

Can you dig down and determine what type of foundation you have? How thick is the masonry wall 12"? or more?

Dik

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

(OP)
The brick wall is 8" and CMU replacement would be 8"

I called the owners. I don't think we can easily check what kind of foundations exist under the interior walls. I was mistaken about one side being a dirt floor in areas, one side is just a slightly lower concrete floor and water during a rain had carried dirt to cover the floor in that area. They would have to get a jack hammer to know any more.

The perimeter foundation walls are large stone and mortar, so that is a possibility for the interior wall footings.

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

Rather than beam and post, can you replace it with a 2x6 stud wall? Provide temporary shores, remove wall construct a small concrete strip footing PT bottom plate and 2x6@16 studs with gypsum wallboard?

Dik

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

(OP)
That is about what JAE suggested too. If they stick frame the wall, it would definitely need to have a new footing underneath because the loading would be more concentrated in places on the footing.

I was just hoping to keep the original footing for cost and effort, since it is carrying all the loads already. I don't see settlement issues currently, and building a CMU replacement would keep stiffness high and spread out the loading in a similar way to the ftg. I've worked with residential civil engineers who don't consider existing footings a factor if loads aren't increased. Would that be too big of a risk for them if that's the direction they choose to go?

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

maybe you can still use the original footing...

Dik

RE: new cmu replacing load bearing 1800's deteriorating brick on interior basement footing

Sorry I'm so late to the party, but I was away for a couple of weeks & haven't looked at the site. "1800s" encompasses 100 years and a huge change in building technologies, but assuming you mean the first half & not the 2nd half of the century, it is very unlikely that there is a footing of any sort, even under a brick wall. If the wall's issues are deterioration, not settlement, then you can conclude that the footing or lack of is not a problem, but you're right, you can't change the loading from distributed to concentrated without asking for trouble. That doesn't mean you can't use wood framing, a double bottom plate will distribute the loading as well as loose-laid bricks, which is what you basically have. For the el-cheapo solution, use JAE's method above minus the footing but look carefully at what you really need for studs & sheathing to carry the loading. Instead of a footing, remove the brick to just below the level of the slabs, grout to a level surface that you can continue in the next section, install a moisture barrier (min. 2 layers of 10 mil poly but Blueskin TWF or equal is preferable) then install your double bottom plate, staggering the joints, and frame the wall in sections. This is not as good as new masonry with the proper support and moisture treatments but is a fraction of the price.

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