Code Requirements for Retaining Wall Drainage

[Smoot24]

I phave an issue where my builder constructed a retaining wall without a footing drain or weep holes.

The City uses 2018 International Building Codes. Are there any codes I can reference to require proper drainage and backfill to to put in place since the builder does not want to do it?

 

[Mark K]

Do not believe this is a problem/concern that the building code is well suited to resolve.

Talk to an attorney.
.
Was drainage required by the building permit? What current problems are you dealing with that are the result of a lack of drainage.

 

[Yankee Chronicler]

At 11 courses of 8-inch blocks, the wall is 7'-4" high. Is the soil on the high side fairly close to the elevation of the top of the wall?

Any retaining wall that retains more than 4 feet of earth requires a permit. Retaining wall construction falls under IBC 2018 section 1807.2:

1807.2.1 General. Retaining walls shall be designed to
ensure stability against overturning, sliding, excessive
foundation pressure and water uplift.

1807.2.2 Design lateral soil loads. Retaining walls shall
be designed for the lateral soil loads set forth in Section
1610. For structures assigned to Seismic Design Category
D, E, or F, the design of retaining walls supporting more
than 6 feet (1829 mm) of backfill height shall incorporate
the additional seismic lateral earth pressure in accordance
with the geotechnical investigation where required in Section 1803.2.

1807.2.3 Safety factor. Retaining walls shall be designed
to resist the lateral action of soil to produce sliding and
overturning with a minimum safety factor of 1.5 in each
case. The load combinations of Section 1605 shall not
apply to this requirement. Instead, design shall be based on
0.7 times nominal earthquake loads, 1.0 times other nominal
loads, and investigation with one or more of the variable
loads set to zero. The safety factor against lateral
sliding shall be taken as the available soil resistance at the base of the retaining wall foundation divided by the net
lateral force applied to the retaining wall.

IBC 1807.2.2 sends us to IBC 1610:

1610.1 General. Foundation walls and retaining walls shall
be designed to resist lateral soil loads. Soil loads specified in
Table 1610.1 shall be used as the minimum design lateral soil
loads unless determined otherwise by a geotechnical investigation
in accordance with Section 1803. Foundation walls
and other walls in which horizontal movement is restricted at
the top shall be designed for at-rest pressure. Retaining walls
free to move and rotate at the top shall be permitted to be
designed for active pressure. Design lateral pressure from
surcharge loads shall be added to the lateral earth pressure
load. Design lateral pressure shall be increased if soils at the
site are expansive. Foundation walls shall be designed to support
the weight of the full hydrostatic pressure of undrained
backfill unless a drainage system is installed in accordance
with Sections 1805.4.2 and 1805.4.3.

Basically, a retaining wall of this height has to be designed -- you don't just build it. Without drainage at the base of the wall, water in the soil greatly increases the lateral pressure on the wall and must be accounted for in the design calculations. My view is that this wall should have been designed by a licensed structural engineer or civil engineer (in some states these share the same license). As the owner, I believe you have a right to review the calculations for the design of the wall and have them checked to verify that the design is adequate without drainage. If not, the wall builder has a problem.

 

[Smoot24]

At 11 courses of 8-inch blocks, the wall is 7'-4" high. Is the soil on the high side fairly close to the elevation of the top of the wall?

Any retaining wall that retains more than 4 feet of earth requires a permit. Retaining wall construction falls under IBC 2018 section 1807.2:



IBC 1807.2.2 sends us to IBC 1610:



Basically, a retaining wall of this height has to be designed -- you don't just build it. Without drainage at the base of the wall, water in the soil greatly increases the lateral pressure on the wall and must be accounted for in the design calculations. My view is that this wall should have been designed by a licensed structural engineer or civil engineer (in some states these share the same license). As the owner, I believe you have a right to review the calculations for the design of the wall and have them checked to verify that the design is adequate without drainage. If not, the wall builder has a problem.

I will look up the IBC codes you provided. I will also ask the City's Building Department for a copy of the structural calculations. The builder had an engineer sign off on the structural aspects of the wall. The letter basically says that if the builder used the footing, rebar and spacing as they were told then the structural calculations show that the wall was built properly. I looked up the engineer on the State's Board of Technical Registration website and they hade their license suspended for a year in 2021. The case against the engineer involved improper retaining wall design.

 

[Smoot24]

Do not believe this is a problem/concern that the building code is well suited to resolve.

Talk to an attorney.
.
Was drainage required by the building permit? What current problems are you dealing with that are the result of a lack of drainage.

The house is still under construction an there are no current issues with the retaining wall but I do not want a long term problem. The stem wall next to the house has already leaked after the first snow/rain and ruined insulation and drywall that were installed. The stem wall is being addressed under IRC 405.1. Also, from the photo below the neighbor's roof downspout is directing water right behind the retaining wall. I want to give the builder the opportunity to correct the issue before we close on the house but they are pushing back. It would have been so easy for them to install the proper drain, backfill and weep holes during construction of the wall.

 

[Smoot24]

At 11 courses of 8-inch blocks, the wall is 7'-4" high. Is the soil on the high side fairly close to the elevation of the top of the wall?

Any retaining wall that retains more than 4 feet of earth requires a permit. Retaining wall construction falls under IBC 2018 section 1807.2:



IBC 1807.2.2 sends us to IBC 1610:



Basically, a retaining wall of this height has to be designed -- you don't just build it. Without drainage at the base of the wall, water in the soil greatly increases the lateral pressure on the wall and must be accounted for in the design calculations. My view is that this wall should have been designed by a licensed structural engineer or civil engineer (in some states these share the same license). As the owner, I believe you have a right to review the calculations for the design of the wall and have them checked to verify that the design is adequate without drainage. If not, the wall builder has a problem.

Here is a photo of the wall from behind looking into the neighbor's backyard. There is some room above the adjacent grade but not much. Also, the neighbor's roof downspout is directing water right towards the back of the wall. I assume the builder will do the same with a downspout on my house which has yet to be installed. There was no retaining wall or stem wall on the original plans. The area between the two lots was to be left open and drainage would flow between the lots. In order to make up the difference in grades in the field the builder installed a stem wall retaining wall without approved plans. They had an engineer sign off on the structural components of the retaining wall after the fact (see response to another comment in thread). The stem wall has already leaked and damaged insulation and drywall during construction. The stem wall issue is being handled under IRC 405.1. I will look at the Coe sections you provided and speak to the City's Building Department.

 

[ICE]

In order to make up the difference in grades in the field the builder installed a stem wall retaining wall without approved plans. They had an engineer sign off on the structural components of the retaining wall after the fact (see response to another comment in thread). The stem wall has already leaked and damaged insulation and drywall during construction.

It must be difficult to have confidence in the builder and the inspectors. I do not see evidence of water proofing on the house stem wall.

 

[Mark K]

Here is a photo of the wall from behind looking into the neighbor's backyard. There is some room above the adjacent grade but not much. Also, the neighbor's roof downspout is directing water right towards the back of the wall. I assume the builder will do the same with a downspout on my house which has yet to be installed. There was no retaining wall or stem wall on the original plans. The area between the two lots was to be left open and drainage would flow between the lots. In order to make up the difference in grades in the field the builder installed a stem wall retaining wall without approved plans. They had an engineer sign off on the structural components of the retaining wall after the fact (see response to another comment in thread). The stem wall has already leaked and damaged insulation and drywall during construction. The stem wall issue is being handled under IRC 405.1. I will look at the Coe sections you provided and speak to the City's Building Department.

The more I hear the more I believe you need to talk to an attorney. There are problems that the contractor is not interested in addressing so how do you provide pressure?

The building code has requirements for obtaining a permit but does not address how to resolve these problems. Thus you need to make use of civil law which leads to retaining an attorney. Don't expect the building department to take responsibility, you will have better luck trying to teach a mule to sing.

You will probably need to hire an engineer and an architect to advise you and your attorney. The builder's engineer will not be responsive to your concerns.

 

[e hilton]

I looked up the engineer on the State's Board of Technical Registration website and they hade their license suspended for a year in 2021. The case against the engineer involved improper retaining wall design.

Unfortunate that you didn’t know that in the beginning. Has the builder had any disciplinary issues?

 

[Smoot24]

Unfortunate that you didn’t know that in the beginning. Has the builder had any disciplinary issues?

I looked up the builder on the Registrar of Contractor's website and they have 6 closed/resolved complaints and 2 open complaints. I did not see how to get detailed info on each case. I will look into it some more. Since the home is still under construction and we have not closed on it yet I do not think there is much I can do through the legal route.

 

[Smoot24]

It must be difficult to have confidence in the builder and the inspectors. I do not see evidence of water proofing on the house stem wall.

View attachment 12949

Here is a photo of the stem wall and retaining wall prior to backfilling. The City's Building Department told me that "waterproofing" used was not intended for this use.

 

[ICE]

Here is a photo of the stem wall and retaining wall prior to backfilling. The City's Building Department told me that "waterproofing" used was not intended for this use.

Who made the decision to accept it?

 

[Smoot24]

Who made the decision to accept it?

The stem wall and water proofing has not been accepted yet. The builder keeps pushing back against the City's Building Department. The Building Department is looking into the issue further. The City Building Department feels the retaining wall is acceptable. There is no specific code requiring waterproofing or drains other than sound engineering design. As noted above, IBC 1807.2 covers the design loads for retaining walls. I am going to get the "post construction" structural calculations for the retaining wall to see if they took into consideration hydrostatic pressure from water since a drain was not put in.

 

[ICE]

The stem wall and water proofing has not been accepted yet. The builder keeps pushing back against the City's Building Department. The Building Department is looking into the issue further. The City Building Department feels the retaining wall is acceptable. There is no specific code requiring waterproofing or drains other than sound engineering design. As noted above, IBC 1807.2 covers the design loads for retaining walls. I am going to get the "post construction" structural calculations for the retaining wall to see if they took into consideration hydrostatic pressure from water since a drain was not put in.

There's a place for everyone to start from... it's called the beginning. Cause the builder to hire as real engineer. Get plans and cause the builder to submit the plans to the building dept. and obtain a permit. The plans will include a drainage system. The plans will include a specific water proofing method and material. Make it clear to everyone you expect the plans to include Earth sloping to a drainage inlet located near the wall.

The foam that has been sprayed on the wall is not coming off... at least not without a fight. Your neighbors, and that's a square block's worth, will be under duress for a solid week. You had better warn the neighbors about the dust and noise from a sand blaster. Honestly, if you want them to like you after this is over... ya know Hawaii is nice this time of year.

You have mentioned the building department several times. I'd rather not say anything too strong but gosh, golly, this job should have never passed a first floor framing inspection before fixing the mistake.

If I could give you just a single bit of advice it would be, "It''s never too late to start over."

 

[Yankee Chronicler]

The stem wall and water proofing has not been accepted yet. The builder keeps pushing back against the City's Building Department. The Building Department is looking into the issue further. The City Building Department feels the retaining wall is acceptable. There is no specific code requiring waterproofing or drains other than sound engineering design. As noted above, IBC 1807.2 covers the design loads for retaining walls. I am going to get the "post construction" structural calculations for the retaining wall to see if they took into consideration hydrostatic pressure from water since a drain was not put in.

For retaining walls, that's true. But sound engineering design for a retaining wall involves accounting for the weight of the retained material behind the wall. Soggy, wet soil weighs a lot more and exerts a lot more pressure than dry soil. If the design doesn't provide for the proper drainage of water from behind the wall, then the wall has to be designed to retain the weight (and resulting lateral pressure) of the water in addition to the soil. That's pretty basic.

Retaining Wall Design to American Standards: Structural Considerations | ClearCalcs

This comprehensive guide aims to assist structural engineers, building designers, and architects in the United States by focusing on American standards and key structural considerations for retaining wall design.

clearcalcs.com

 

[e hilton]

If I could give you just a single bit of advice it would be, "It''s never too late to start over."

Might be time to “lawyer up”.

 

[redeyedfly]

I don't see anything wrong with the retaining wall from the information provided in this thread. Most modular walls will not require a dedicated drain in many soil types. They drain through the rock backfill and through the blocks just like the first picture shows.

 

[ICE]

I don't see anything wrong with the retaining wall from the information provided in this thread. Most modular walls will not require a dedicated drain in many soil types. They drain through the rock backfill and through the blocks just like the first picture shows.

Did you catch the part about water ruining drywall? Water draining through the block as you see in the first picture tend to discolor the block and leave unsightly deposits. I would not anticipate that failure of the wall due to hydro-static pressure is likely given the 7.5 inches of annual rainfall at Phoenix, AZ.

 

[redeyedfly]

Did you catch the part about water ruining drywall? Water draining through the block as you see in the first picture tend to discolor the block and leave unsightly deposits. I would not anticipate that failure of the wall due to hydro-static pressure is likely given the 7.5 inches of annual rainfall at Phoenix, AZ.

I didn't read that as an issue with the construction of the retaining wall. There was a separate waterproofing of the foundation issue. Retaining walls like this are not waterproof(able). Water drains through the block on all modular retaining walls.

 

[ICE]

Retaining walls like this are not waterproof(able). Water drains through the block on all modular retaining walls.

We have had nearly a foot of rain in the past few weeks.. It' raining now. No water has made it through the block and there's no weep holes. There is a drainage system with waterproofing on the wall.

 

[redeyedfly]

We have had nearly a foot of rain in the past few weeks.. It' raining now. No water has made it through the block and there's no weep holes. There is a drainage system with waterproofing on the wall.


View attachment 12971

Cool story bro. That's not a modular retaining wall. It has almost nothing in common with the OP's wall.

 

[ICE]

Cool story bro. That's not a modular retaining wall. It has almost nothing in common with the OP's wall.

I didn't pay attention to your use of the word "modular." It appears to be CMU. What is odd is the water pattern so perhaps you are correct and the blocks are stacked without mortar.

 

[Smoot24]

I am still waiting for the retaining wall calculations and geotech/soils report from the Building Department so I can verify is water was considered in the calculations. Below are some photos from the other day showing the wall and nieghbor's drainage behind the wall.

 

[SCBO1]

Is this retaining wall a common wall, if so, who pays for the repairs when if fails?

Most retaining walls here have drain tile in the design with gravel coverage.