Walkout basement stuff

[GeneDavis]

A walkout basement design in a winter climate is a hybrid affair, isn't it?

 

The front of the house, the uphill side, has a foundation under, while the rear, the walkout side, has its lower exterior walls built atop the basement slab, which is brought to bear upon the frost-wall foundation below.  

 

So that basement slab is part inside the walls and part outside.

 

I built a model for a friend that wants to build such a house, and floor 1 is the main or upper floor.  The foundation floor under has the out-of-ground exposed walls as wood framed, while the buried walls, in this case, are 11" ICF.

 

What is my best route to getting the frost walls built in Chief, and getting that basement slab modeled accurately?

 

 

[DavidJPotter]

Gene, I have designed many such homes and you just set the walls as seems proper. I don't exactly understand what you are asking "What is my best route to getting the frost walls built in Chief, and getting that basement slab modeled accurately?" . I mean the exact design will be determined by a State Licensed Local Structural Engineer, not you, me or anyone else.

 

From your posted image (if it were mine), I would step the stem walls along the gradient in the terrain for the purpose of looks, the actual design will fall to a Structural Engineer who has inspected your design and the intended property.

 

DJP

[GeneDavis]

It ain't Texas, David. Us mere mortals do foundation design in vast parts of the north country.

[Kbird1]

Generally the stem wall Foundation is stepped to follow the terrain but 10"-12" above to meet code requirements,( 8" to bottom of siding here) and the slab is inside the stem walls not sitting on top of them .... The Slab will be 6" + above "grade", as at least here, you need a 4" step down at the entry with a drainage pit so the basement cant flood during heavy rain.

M.

[Kenoeightspot]

Place Basement on First Floor if you build a separate foundation plan (reads better). Add pony walls as needed around the building(I use three different types at this level.

In elevation cut your foundation walls to lower the footings at the walkout side at meet the frost depth.

Most of my residential project have walkouts.

[NRST8TRKR]

Gene,Here when we do a daylight basement we step the footer back on the sides to a point that will get them below frost line, 30" in our county and pour a footer then 12" block to slab grade. Or in some cases just pour  solid concrete from footer to grade and form for slab. In chief either pony wall or block foundation wall lowered to desired elevation for slab.

 

Hope this is a little clearer than mud. Not as bad as it sounds.

 

Have a great Memorial Day weekend and thanks to all veterans out there,Ken

[GeneDavis]

Here are two details that represent how we will build.  Taken together, one can see how the floor slab sits within the foundation when the walls above the slab are ICF, and atop the foundation wall when the wall above the slab is wood-framed.

 

I can model the stepping.  Thanks to Bill Page for reminding me to do the lower floor not as Floor 0 Foundation, but to make that floor Floor 1 and do the part-foundation below it (the stepped down frostwalls) in Floor 0.

 

But now that it can be modeled in 3D, sort of, there still exists two problems.

 

1.  How to get a foundation drawing to layout, in that part of it is on Floor 0 and part on Floor 1.

 

2.  How to dismember the floor slab so it places both inside foundation wall and atop foundation wall, where needed.

 

[Kenoeightspot]

Gene,

Dtl. 1 - I Pour the stem wall first then compact the soil against the conc. wall  before pouring the slab. ICF. or conventional pour then compact. Use the rebar stubs to attach the slab to the foundation.

Dtl. 2 - Are you going to continue the upper sheathing down over the ICF form so you have something to nail the siding to.

[CJSpud]

Gene:

 

I do my basements as Foor 0 and just drag the walkout wall and two side walls down in elevation views with breaks in the bottoms of the side walls where needed to get the footings set at the right frost elevations.  If the walkout is going to be a framed wall, then I would make the walkout wall a pony wall with the upper part (above slab level) your framed wall and the lower "foundation" wall your ICF wall type.  I "always" specify foam insulation under the whole slab as opposed to only doing insulation around the perimeter as most codes have required (the minimum).  If a basement is to have a design temp of ±70°F and the ground temp under the basement slab is ±55°F, then it is easy to see where the bigger thermal energy leak in the basement is going to be if there isn't "complete" insulation under the whole slab area.

[joey_martin]

Looks like everyone has the answer you need. I always do basements on floor 0 and step the foundation as needed per lot slope. And to add info for Mr. Potter...I have designed my own foundations here in Indiana for 20 years. I think if I called an engineer to do a residential foundation for me he would ask why I am crank calling him.

[GeneDavis]

Well, I tried Bill Page's technique, and while it got me into a mode in which I can get the 3D model pretty close to reality, I am not happy with the mechanics of things.

 

Here it is in X6, for those that want to look.  https://dl.dropboxusercontent.com/u/17835038/Jack%20Grouse/Chalet%202800%20walkout.plan  I have retired the plan for now, awaiting answers to some questions, and did not step the footings accurately.

 

I don't like having the main (upper) floor not at elevation zero.  Something I did in inserting the new foundation level under the old, caused my main floor to go from zero to +46-1/8".

 

I don't like having my foundation on two different floors.  The full depth ICF walls are on floor 1 and the frostwalls are on floor 0.

 

David Potter can be excused for his deferring all foundation design to engineers.  He is in the TX hill country, and from my experience with the way residential building works there, a combination of shoddy building practices and unstable soils have caused enough foundation failures, such that builders all hire engineers to detail the reinforced slab foundations, and they all get overdesigned.  The engineers, all with TX professional registration, are carrying insurance.  Use Google and do a web search for "Austin foundation repair" or "San Antonio foundation repair" and the number of business feeding off the result of all that shoddy work will make you understand things.

[Kbird1]

It aint just Texas ,anywhere considered an earthquake zone in particular is the same from my experience .... here we have geotech/ foundation/structural(framing)/Air/trusses etc. too depending on the project.

M.

[DRAWZILLA]

for me ,I would make the lowest floor, level 1, so you can do a foundation below that.

[dshall]

for me ,I would make the lowest floor, level 1, so you can do a foundation below that.

I concur,  and if you can combine the foundation with the basement plan do so.......  and don't even use LEVEL ZERO.  Nothing magic about that layer...... 

[lbuttery]

two schools of thought on floor 0

 

some, including CA, use it for foundation and basement

 

others use it for foundation only

 

toss a coin -  take a choice

 

Lew

[DRAWZILLA]

I couldn't even think of combining the foundation plan with any floor plan, with all the earthquake stuff we have to put on the plan out here. It would look like Godzilla stomped it down.

[GeneDavis]

Here is one problem with the way I did it, in putting the lower walkout floor on Floor 1, and the frostwall foundation under the exposed walls on Floor 0.

 

I am unable to send a "clean" foundation plan to layout.  I'll either have to send one like shown and CAD-draw the rest, or come up with another solution.

 

The pic attached is of Floor 1, with a layerset done to shown footings and foundation wall main layer only.  This is an ICF job.

 

 

[ebdesign]

 

 

I don't like having the main (upper) floor not at elevation zero. 

 

Yup.

Multiple floors below #1 would be nice.

[lbuttery]

I don't like having the main (upper) floor not at elevation zero

 

Chief can have 30 floors

 

even floor 30 can be set to elevation zero

 

Multiple floors below #1 would be nice

 

you can put the "main level" on floor 30 if you want

 

thus you can have all 30 floors below grade if desired

[Kenoeightspot]

This is how My plans show on level (1) Basement and on level (0) 

[ebdesign]

The default for Floor 1 is 0'-0". That cannot be changed as far as I know.

I suppose I could have multiple floors at 0'-0".

Tho I can't imagine why.

Just one flr (-1) & the foundation level would be great.

[lbuttery]

yes, but floor 30 can be 0' 0"

 

with all the other floors having negative values

 

Lew

[dshall]

yes, but floor 30 can be 0' 0"

 

with all the other floors having negative values

 

Lew

Thank you Lew, you are absolutely correct. Put the foundation on level 25 and have 24 floors below plus foundation. There is nothing magical about LEVEL zero if you build your own foundation.

BTW, auto foundations would never work for 97% of my projects. Yes, auto foundation can get me started but I would always need to edit.

[ebdesign]

Another idea to help solve some of these issues is to be able to show the upper or lower wall of a pony wall by layer set.

[GeneDavis]

I believe that houses with this design feature, meaning a walkout basement with part of the walkout floor walls wood-framed, with frost-wall foundations below, are being built all across the country from I-70 to the Canadian border.

 

Wherever there are basements.  Wherever it snows.  Wherever there are sloping lots.  A lot of wherever.

 

And that is a lot of houses.  The Chief software should be able to handle this better.

 

Here are some of the things that ought to be requested in software features to handle this right:

 

1.  "Build stemwall with footing under this wall."  These stemwalls, which many of us call frost-walls, should be built on the same level we are using for the rest of that lower walkout level of the house, and it should be Level 0.  The spec dialog should allow us to specify a beginning wall depth, and as we can now, we should be able to break and drag up or down the footings and their walls as needed for stepdowns.

 

2.  Separate layer for the stemwalls.  Just as we have for footings, we need to be able to turn the stemwalls on and off, depending on what we are sending to layout in construction documents.  This is a variant on what Jim suggested above.

 

3.  Main layer or layers only, but show fill.  A foundation wall in a walkout basement job or in a non-walkout, may have finish layers on both outside and inside surfaces.  The foundation plan drawing should not be showing these finish layers, but it is, for some, a drawing convention that foundation walls shown in the plan drawings have a fill.  Now all we have is "main layers only," but that option does not show fills.

 

4.  Extend floor slab atop stem wall.  A lot of houses are getting built this way, with the basement slab poured to sit atop the frost wall parts of the foundation, where wood-framed walls sit atop the slab.  See the typical detail I attached in an earlier post to this thread.

 

5.  Stop exterior wall sheathing and finish layers at floor level.  Chief does this when walls have monoslab foundations under.  We ought to get same for the walkout walls that are sitting atop the basement floor slabs.

 

If Chief had these features and options, we would not have to do the workarounds we now do.  I am going to copy and paste this post in the Suggestions section, and would appreciate some cheerleading here, so Chief people pick up on the issues.