Garage Foundation with Clay soil conditions

[gladiatorxx]

We are in the process of having removed the right side and back wall of an existing garage. The material is clay silt. This garage is set back into the land and the area is tiered. Thus the right side back fill would come up about 4ft against the right side garage wall at finish grade and the back side back fill would be about 6 ft at finish grade. We intend to use 3/4" stone against the new walls. It is the intent to use 12" block, filled with concrete and #4 rebar every 24" inches. Wall that was removed was 12" hollow, and had a 6 - 8" concrete wall poured against it fron the bottom of the footing to finish grade of the back fill.

Thoughts on what we now propose??

I can privide pictures if this will help

 

[concretemasonry]

Do not fill the wall with concrete!!! - The proper material is grout with an 8" to 11" slump and definitely not 3" to 4" slump concrete.

Filling the wall completely provides minimal extra strength, but can the allowed if it is easier and the extra material cost in not excessive.

You would be better advised to locate the rebar properly, consistant with the design, to get much more strength.

Where will the 3/4" stone be placed? - how far out from the wall and is it full height?

Dick

 

[gladiatorxx]

The 3/4" would be placed up against the wall from the bottom of the footing, up to about 6" below finish grade where then loam would be placed. The 3/4" is for drainage.

What would you suggest for a wall, concrete, instead of cinder block?

 

[hokie66]

A reinforced concrete masonry wall, properly designed and constructed, will work fine. If you want the interior to be dry, the wall will have to be waterproofed on the exterior face. Where will the water behind the wall drain to? You need a perforated drainage pipe with a geotextile sock around the pipe to prevent blockage in the long term, and the pipe needs to daylight somewhere. Geotextile fabric should also be used against the excavation to prevent blockage of the gravel drainage layer.

This is all quite simple, but not just any builder will be willing or able to do it right.

 

[gladiatorxx]

Above concretemasonry stated blocks filled would provide minimal additional benefit for strength.

hikie66 are you refereing to a poured concrete wall or cinder block?

 

[hokie66]

I only talked about a wall constructed of concrete block. I don't think cinder block is made anymore.

Concretemasonry's statement about minimal additional benefit for strength referred to filling all the blocks rather than just those with reinforcement. He is correct for bending strength of the wall, but I would never leave cores unfilled below grade.

 

[concretemasonry]

Hokir - You are correct about the old "cinder block" not being made since trains stopped using coal. Lighter weight units are made using lihtweight aggreagte, but usually at a higher cost and corresponding benefits.

An engineer does not design or build with "cinder block" since they are not made and there is no way they might fit into any ASTM or ACI standard or code. CMUs, or concrete masonry units, are controlled by ASTM C90 minimums and referenced in ACI 530. The compressive strength of the masonry units is a minimum of 1900 psi (net area) but I have seen 8700 psi units used with 2500 psi mortar to make 4850 psi ungrouted prisms.

A reinforced (partially or fully grouted) wall can be as strong and resist the same loads as a reinforced concrete wall.

Below grade it might be more economical to fully grout a wall since pumping may not be required, but the problem of filling too fast still exists. The block is really a high strength loadbering form that is left in place.

For above grade, especially in high rise or in seismic areas, excess grout is conunter-productive and uneconomical. - Why fill every core on a 15 story loadbearing block block structure just because the lower 3 or 4 floors are completely filled? When you go up, the cost of moving materials increases time and construction costs. The effect of the excess weight can also be penalty in the design of the structure.

Dick

 

[hokie66]

The OP was asking about a wall below grade, and I just offered my advice to fill all those cores. I know all the arguments about core filling on multistorey buildings.

 

[gladiatorxx]

Sorry guys, when i said cinder, I simply meant block.

Also can you guys accept pictures on here?

 

[hokie66]

Yes, just follow the instructions for attachments.

 

[MiketheEngineer]

I would design it as a retaining wall and don't forget to place drain pipe at bottom

 

[gladiatorxx]

Here are some pics

http://files.engineering.com/getfil...56d4-45a1-893d-ef63b0fb5d1f&file=DSC00111.JPG

http://files.engineering.com/getfil...3887-4f62-99a5-4848343c2d83&file=DSC00112.JPG

 

[hokie66]

Looks like you will need a footing for the wall to start on, and your wall starters will come out of the footing. Suggest you need a structural engineer to design this for you.

 

[gladiatorxx]

Do you suggest removing some clay under the footing even though the disturbance is minimal, and put some 3/4" stone pack under the footings?