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Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

(OP)
I have a 12" thick (nominal) unreinforced brick masonry wall 6' from base to ground floor joists that needs to support gravel fill. The basement needs to be filled to comply with FEMA insurance regs. I am surprised that the bending stress is so high in the masonry wall fb=40psi. There will be a gravity load as follows: Dead = 2500lbs, Live = 500lbs

I am using a phi of 36 degrees so Ka=0.25 and a weight for gravel of 150pcf.

The building is a row home and the adjacent buildings have similar basements. The walls are not party walls but independent. There is no guarantee that the neighbors are also filling in their basements so there is no passive pressure.

I am surprised that the wall is inadequate and the homeowner is not really in a financial position to spend money on reinforcing the wall.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

Is there a question here?

EIT
www.HowToEngineer.com

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

(OP)
Ha...you are right there was no question. I guess my question is am I missing anything? Or is there a way I can justify the load.

I don't think there is. Bad news upon bad news for homeowner.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

KevinChez:
A 6' clg. ht. in a basement, what’s that all about? What was this bsmt. used for? Is the FEMA Ins. intent that this lower level not be habitable. Is this bsmt. 4 or 5' down in the ground on the two walls, and then no external soil support on the walls at adjacent units, the problem walls? You should be careful to use a low estimate for the D.L., and is that 2500lbs./ft. or per mile? You probably shouldn’t use any L.L. If you use gravel fill, 150lbs./c.f. is probably a little high since there is considerable void volume. But, in a flood, won’t you have to design for water pressure? Can’t you use this space as storage space, but not inhabited space. Could you fill this space with lean concrete, in 2' lifts, and pretty much keep 5' of water out of there?

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

Please don't post in multiple forums.

Regarding your situation: If the basement is going to be abandoned you could build a gravity wall along the existing walls. Use concrete blocks; just stack them up; no need to mortar or grout them.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

I would think 150pcf would be very high to be using. 150pcf is what I use for the density of concrete. I understand the point about flood water filling the voids of the gravel, but wouldn't the flood water also be on the other side of the wall causing equal pressure? Bridgebuster's idea of adding a gravity wall to the inside of the wall is a good idea if you still have a problem. Probably will not be easy getting the material into position, but neither will the gravel fill.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

why does the neighbor not have to do this, but your client/side does???

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

I typically use 100 pcf for washed stoneand an active pressure of 30 - 35 psf

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

(OP)
Thanks to everyone for the comments. The house was built in the early 1900's. It is located in Red Hook Brooklyn NY. The flood elevation is 13ft. To get FEMA flood insurance there can be no inhabitable space below the 13ft. The basement needs to be filled to meet the flood insurance requirements and the first floor can only be retail space (zoning allows for this - but it can't be a living room, etc.) The first floor will most likely be concrete slab on the gravel fill although the architect and homeowner want to put wood sleepers on the gravel and have a deck which I am advising against.

The neighbors are not getting the insurance so they can do whatever they want. I guess there is no mortgage on their homes so they do not care. Or if you do not fill in your basement the rate would be so high to be prohibitive.

I will refine my weight of stone and look at the friction angle.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

I was reading that in Brooklyn the cost for premiumns will be about $500/year if the owner complies vs. $10,000 for not. 30 years no one would have cared about Red Hook and the surrounding neighborhoods.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

Sorry, I meant 110 pcf.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

(OP)
bridgebuster,

where i live on LI people by the water need to raise their homes to avoid $24k/year premiums. there is a lot of work to be done.

it is not possible to raise this home in red hook which is an up and coming area although very much industrial.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

Where does it say in a FEMA document that you have to fill in the space? I am fairly familiar with FEMA and retrofit requirements but have not come across that one.

And I think you said it was a basement, but then do the basement walls extend above grade to form stem walls and this is the lateral pressure you are worried about? Just a little confused about the actual construction.

You could also look into flowable fill in lifts. Maybe do it in 1-2ft lifts, and then once it cures it will shrink slightly and you should end up with almost no lateral pressure.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

Consider converting this to a MSE wall with geotech grids. Securing to the wall could be by bringing each grid layer up along with layers of earth fill by wrapping the grid around an object, such as a horizontal pipe. The pipe can be secured to the wall with galvanized bolts through the wall to plates on the outside. Geotech professionals that regularly work with MSE should be contacted for the details. Fill material between the grids probably should have better frictional properties than single size gravel, such as a typical sand-gravel mix for concrete. A lot of crawling around inside as this is done, but I think feasible.

RE: Unreinforced Brick Masonry Foundation Wall Needs to Support New Gravel Fill Due to Flood Ins Regs...

KevinChez I know the area. High school, college, worked nearby. For what people pay for a brownstone today in Fort Greene you could have bought the whole block when I was in high school.

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