Unsupported Stem Concrete Wall Max Height

[longevity]

I am hoping to build this stem wall with a light frame wood on it. However the county is giving me an issue that it needs to be engineered since she can't find the table to support the rebar placement. It is 5'6" from the bottom of the footing to the top of the stem wall with 2 feet of backfill on the inside and 4'6" of backfill on the outside. So there is 2' of unbalanced fill on the wall. There is a 8' 2x6 light framed wall above on the stem wall making the inside wall height 10' however there is no concrete floor just compacted gravel. I pointed out 404.1.1 Design required. · 1. Walls are subject to hydrostatic pressure from ground water. · 2. Walls supporting more than 48 inches (1219 mm) of unbalanced fill and she came back with this: This is just a tractor shed but the previous shed was below grade on two sides as its on a hill.

You can build to the approved plans with a maximum of 4’ tall concrete wall or provide engineering. I have included the code sections reviewed below.

404.1.3.2.1 Concrete foundation stem walls supporting above-grade concrete walls.​

Foundation stem walls that support above-grade concrete walls shall be designed and constructed in accordance with this section.

1. 1.Stem walls not laterally supported at top. Concrete stem walls that are not monolithic with slabs-on-ground or are not otherwise laterally supported by slabs-on-ground shall comply with this section. Where unbalanced backfill retained by the stem wall is less than or equal to 18 inches (457 mm), the stem wall and above-grade wall it supports shall be provided with vertical reinforcement in accordance with Section 608.6 and Table 608.6(1), 608.6(2) or 608.6(3) for above-grade walls. Where unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the stem wall and above-grade wall it supports shall be provided with vertical reinforcement in accordance with Section 608.6 and Table 608.6(4).

We do not have the highlighted standards. These would typically come from an engineer.

Does anyone know how to use the table in this chapter to demonstrate rebar spacing requirement. My engineer says he is 6 months out on doing anything. She approved my permit but i need my wall a little taller than 4' to get proper drainage.

Thanks,

Ted

 

[classicT]

What thickness concrete wall are you wanting to use? 6"? 8"?

 

[longevity]

8" stem wall with a 20x8 footing under it. I don't understand this reasoning basically what she is saying is every deep spread footing or every wall with a deep frost depth would require an engineer to design.

 

[classicT]

I'd go with an 8" wall given the proposed conditions. If so...

Follow the table below for vertical reinforcement.


And follow this for horizontal reinforcement.

 

[classicT]

8" stem wall with a 20x8 footing under it. I don't understand this reasoning basically what she is saying is every deep spread footing or every wall with a deep frost depth would require an engineer to design.

What is your SDC?

 

[longevity]

C is the Category, She says since its a stem wall and light frame combo it is a pivot point at the connection of the two walls and that these tables aren't applicable. Using the table the max unsupported wall would be 10ft (just under) and under 4 ft of unbalanced fill.

 

[longevity]

She says it should have a floor or ceiling joist at the top of the concrete to prevent lateral movement of the wall, but somewhere there has to be a provision for a daylight basement in the code as in a since this is what it is.

 

[classicT]

Your plans examiner may be confused. The foundation wall is not the issue.

I do believe that you have an issue with the story height.

2018 WA-IRC R301.3 Story Height​

The wind and seismic provisions of this code shall apply to buildings with story heights not exceeding the following:

1. For wood wall framing, the story height shall not exceed 11 feet 7 inches (3531 mm) and the laterally unsupported bearing wall stud height permitted by Table R602.3(5).
2. For cold-formed steel wall framing, the story height shall be not more than 11 feet 7 inches (3531 mm) and the unsupported bearing wall stud height shall be not more than 10 feet (3048 mm).
3. For masonry walls, the story height shall be not more than 13 feet 7 inches (4140 mm) and the bearing wall clear height shall be not more than 12 feet (3658 mm).
   Exception: An additional 8 feet (2438 mm) of bearing wall clear height is permitted for gable end walls.
4. For insulating concrete form walls, the maximum story height shall not exceed 11 feet 7 inches (3531 mm) and the maximum unsupported wall height per story as permitted by Section R608 tables shall not exceed 10 feet (3048 mm).
5. For structural insulated panel (SIP) walls, the story height shall be not more than 11 feet 7 inches (3531 mm) and the bearing wall height per story as permitted by Section R610 tables shall not exceed 10 feet (3048 mm).

Individual walls or wall studs shall be permitted to exceed these limits as permitted by Chapter 6 provisions, provided that story heights are not exceeded. An engineered design shall be provided for the wall or wall framing members where the limits of Chapter 6 are exceeded. Where the story height limits of this section are exceeded, the design of the building, or the noncompliant portions thereof, to resist wind and seismic loads shall be in accordance with the International Building Code.

[RB] HEIGHT, STORY. The vertical distance from top to top of two successive tiers of beams or finished floor surfaces; and, for the topmost story, from the top of the floor finish to the top of the ceiling joists or, where there is not a ceiling, to the top of the roof rafters.

 

[longevity]

I APPRECIATE YOUR TIME AND REPLIES!

Sorry, the concrete wall steps down and is 8' max where the wall turns to a low stem wall. The wood framing is reduced at the 5' wall to make the finished floor to truss height 10'. We are still on 2018 IRC not sure if that matters. I don't think we are over height here. Her issue is that there isn't a table to use she says to determine the 5' wall rebar spacing.

My plans called for a 6' max stem wall on the foundation and she reviewed that page and didn't stamp but on the elevations page she says "48"max concrete wall from top of footing to top of stem wall or provide engineering".

I want to comply with the code I just don't have months to wait for an engineer and it seems unneeded here. It's just a 24x32 tractor shed.

 

[classicT]

I APPRECIATE YOUR TIME AND REPLIES!

Sorry, the concrete wall steps down and is 8' max where the wall turns to a low stem wall. The wood framing is reduced at the 5' wall to make the finished floor to truss height 10'. We are still on 2018 IRC not sure if that matters. I don't think we are over height here. Her issue is that there isn't a table to use she says to determine the 5' wall rebar spacing.

My plans called for a 6' max stem wall on the foundation and she reviewed that page and didn't stamp but on the elevations page she says "48"max concrete wall from top of footing to top of stem wall or provide engineering".

I want to comply with the code I just don't have months to wait for an engineer and it seems unneeded here. It's just a 24x32 tractor shed.

Absolutely! Glad to be of help.

I am here in WA as well, so everything I have posted is the current WA-amended 2018 code.

So long as you follow the tables above for reinforcement and the max unbalanced fill is less than 4-ft, I don't think you have an issue.

Worst case soil type, vert reinforcement is not required, although I would provide #4 at 16"oc (just my opinion). Horizontal, you need at minimum a #4 bar at mid height, and a#4 within the top 12" of the wall. Again, in my opinion, I would provided #4 at 16"oc.

 

[longevity]

Absolutely! Glad to be of help.

I am here in WA as well, so everything I have posted is the current WA-amended 2018 code.

So long as you follow the tables above for reinforcement and the max unbalanced fill is less than 4-ft, I don't think you have an issue.

Worst case soil type, vert reinforcement is not required, although I would provide #4 at 16"oc (just my opinion). Horizontal, you need at minimum a #4 bar at mid height, and a#4 within the top 12" of the wall. Again, in my opinion, I would provided #4 at 16"oc.

I planned #4 18" vert and 12" hor. I would do a tighter grid if needed but I don't know how to get her to use the table you provided as she said the wood and concrete create "pivot point".

I made a mistake she said 48" from bottom on footing to top of stem wall. This wouldn't even allow me a 36" stem wall on my 15" deep spread footing and would prevent any low wall where there is a deep frost depth.

 

[classicT]

I would just be very clear in indicating that the unbalanced fill is less than 48". Ask her for the code section she is referencing in issuing the correction item.

Also, going back to your first post, take note that Section R404.1.3.2.1 does not apply. The section applies to above-grade concrete walls.

2018 WA-IRC​

R404.1.1 Design Required​

Concrete or masonry foundation walls shall be designed in accordance with accepted engineering practice where either of the following conditions exists:

1. Walls are subject to hydrostatic pressure from ground water.
2. Walls supporting more than 48 inches (1219 mm) of unbalanced backfill that do not have permanent lateral support at the top or bottom.

R404.1.3.2.1 Concrete Foundation Stem Walls Supporting Above-Grade Concrete Walls​

Foundation stem walls that support above-grade concrete walls shall be designed and constructed in accordance with this section.

1. Stem walls not laterally supported at top. Concrete stem walls that are not monolithic with slabs-on-ground or are not otherwise laterally supported by slabs-on-ground shall comply with this section. Where unbalanced backfill retained by the stem wall is less than or equal to 18 inches (457 mm), the stem wall and above-grade wall it supports shall be provided with vertical reinforcement in accordance with Section R608.6 and Table R608.6(1), R608.6(2) or R608.6(3) for above-grade walls. Where unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the stem wall and above-grade wall it supports shall be provided with vertical reinforcement in accordance with Section R608.6 and Table R608.6(4).
2. Stem walls laterally supported at top. Concrete stem walls that are monolithic with slabs-on-ground or are otherwise laterally supported by slabs-on-ground shall be vertically reinforced in accordance with Section R608.6 and Table R608.6(1), R608.6(2) or R608.6(3) for above-grade walls. Where the unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the connection between the stem wall and the slab-on-ground, and the portion of the slab-on-ground providing lateral support for the wall shall be designed in accordance with PCA 100 or with accepted engineering practice. Where the unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the minimum nominal thickness of the wall shall be 6 inches (152 mm).

 

[mtlogcabin]

but somewhere there has to be a provision for a daylight basement in the code as in a since this is what it is.

Read through this section. The majority is for seismic zone D, so if you follow the requirements for a "D" zone it will work for the "C" zone you are in.

R403.1.6.1 Foundation anchorage in Seismic Design Categories C, D0, D1 and D2.

5. Stepped cripple walls shall conform to Section R602.11.2.

 

[SDS]

There is a 8' 2x6 light framed wall above on the stem wall making the inside wall height 10' however there is no concrete floor just compacted gravel.

R404.1.1 Design Required.

yadda yadda yadda....

#2 blah blah blah...that do not have permanent lateral support at the top or bottom.

Is this perhaps what she is questioning?

There does appear to be a pivot point in play where stem wall meets wood-framed wall that has no lateral support, thereby restricting max wall height to 48 inches, no?

edit: unbalanced backfill still does not exceed 48"

 

[longevity]

She told me it relates to this section but when i read it it says:​

R404.1.3.2.2Concrete foundation stem walls supporting light-frame above-grade walls.​

Concrete foundation stem walls that support light-frame above-grade walls shall be designed and constructed in accordance with this section.

1. 1.Stem walls not laterally supported at top. Concrete stem walls that are not monolithic with slabs-on-ground or are not otherwise laterally supported by slabs-on-ground and retain 48 inches (1219 mm) or less of unbalanced fill, measured from the top of the wall, shall be constructed in accordance with Section R404.1.3. Foundation stem walls that retain more than 48 inches (1219 mm) of unbalanced fill, measured from the top of the wall, shall be designed in accordance with Sections R404.1.1 and R404.4.

Since i am retaining less than 48" i then need to construct to

R404.1.3Concrete foundation walls.​

Concrete foundation walls that support light-frame walls shall be designed and constructed in accordance with the provisions of this section, ACI 318, ACI 332 or PCA 100. Concrete foundation walls that support above-grade concrete walls that are within the applicability limits of Section R608.2 shall be designed and constructed in accordance with the provisions of this section, ACI 318, ACI 332 or PCA 100. Concrete foundation walls that support above-grade concrete walls that are not within the applicability limits of Section R608.2 shall be designed and constructed in accordance with the provisions of ACI 318, ACI 332 or PCA 100. Where ACI 318, ACI 332, PCA 100 or the provisions of this section are used to design concrete foundation walls, project drawings, typical details and specifications are not required to bear the seal of the architect or engineer responsible for design, unless otherwise required by the state law of the jurisdiction having authority.

This leads me to believe that Table R404.1.2(3) is the table as classticT said.

What i cant find is where does the code say that a stem wall height is max 48" from bottom of footing to top of wall or engineering is required?

 

[longevity]

R404.1.1 Design Required.

yadda yadda yadda....

#2 blah blah blah...that do not have permanent lateral support at the top or bottom.

Is this perhaps what she is questioning?

There does appear to be a pivot point in play where stem wall meets wood-framed wall that has no lateral support, thereby restricting max wall height to 48 inches, no?

edit: unbalanced backfill still does not exceed 48"

The max wall height or unbalanced backfill height? What i am thinking about is deep frost depths or deep spread footings. They would have to have engineering in these cases to even come out above grade.

 

[classicT]

What i cant find is where does the code say that a stem wall height is max 48" from bottom of footing to top of wall or engineering is required?

It doesn't.