Basement foundation

[ncbuckeye]

Any advice on building basement foundation for my garage. Engineer says either poured or block will work as long as they are reinforced in the same manner. Garage is 24' x 26' with 2nd floor walk-up. Cost looks like it will fall somewhere between 30K and 35K to get to the point I can begin framing. Includes excavation, footings, walls, steel beams, decking and both slabs. Has anyone had experience in building a suspended slab?

 

[KMR Construction]

Where are you located? Frost has a big part in a foundation

 

[ncbuckeye]

Located in North Carolina so frost shouldn't be a problem. I'm still weighing the pros and cons between poured vs. block. Cost looks as though it will be 15% less with block. Is there an advantage to either when waterproofing?

 

[PAToyota]

Do you actually mean a basement under the load supporting first floor of the garage? Or just the foundation walls with no room below the floor?

Either block or poured can be made waterproof. Block is done with exterior coatings. Lately we have been using a crystalline waterproofing for poured walls that an ad-mixture to the concrete. It isn't exactly cheap, but if you're serious about wanting to keep things dry and know that there is the potential for water issues it is good insurance. You can check out more information here on one of the typical products.

 

[ncbuckeye]

I'm looking at using the room below for a workshop/storage. Our existing basement to our house is block with no water issues after 7 years. The garage will be located at the end of our drive which slopes from front to back. I know get the water directed away from the foundation is the key to keeping things dry. Looking at putting in drain grates in several location to help with that.

 

[JimShortz99]

Off topic...what part of NC are you in?

 

[rinny_tin_tin]

I'm looking at using the room below for a workshop/storage. Our existing basement to our house is block with no water issues after 7 years. The garage will be located at the end of our drive which slopes from front to back. I know get the water directed away from the foundation is the key to keeping things dry. Looking at putting in drain grates in several location to help with that.

Poured is stronger than block. Since you have a habitable space underneath the slab - I would use full passive water-proofing means with the 4-inch perf PVC pipe/gravel, etc. I'm not crazy bout the corrugated wall membranes and instead prefer two coats of Sonneborn HLM 5000 - liquid rubber and backfill with #57 gravel, etc. By a floating lab - I assume you mean no dowels or no other ties to the walls - in theory, floating is supposed to be better to allow movement w/o cracking, etc. I floated mine and so far no cracks - however, it is only about 6 mo old yet. One item - I used no vapor barrier under the slab and instead poured atop 4 inches of sand that sat on 8 inches of #57. In theory - this is supposed to offer better performance with respect to cracks - as per the attached

http://www.stegoindustries.com/docs/Vapor Barriers Under Concrete Slabs.pdf

Instead of using drain grates in the slab - we sloped the slab forward and are installing Class E ACO zipper drains along the front of the slab to catch rain/wash water from either the garage or grade

http://www.acousa.com/drain/klassikdrain.htm

 

[ncbuckeye]

Off topic...what part of NC are you in?

Apex, just south of Raleigh.

 

[ncbuckeye]

Poured is stronger than block. Since you have a habitable space underneath the slab - I would use full passive water-proofing means with the 4-inch perf PVC pipe/gravel, etc. I'm not crazy bout the corrugated wall membranes and instead prefer two coats of Sonneborn HLM 5000 - liquid rubber and backfill with #57 gravel, etc. By a floating lab - I assume you mean no dowels or no other ties to the walls - in theory, floating is supposed to be better to allow movement w/o cracking, etc. I floated mine and so far no cracks - however, it is only about 6 mo old yet. One item - I used no vapor barrier under the slab and instead poured atop 4 inches of sand that sat on 8 inches of #57. In theory - this is supposed to offer better performance with respect to cracks - as per the attached

http://www.stegoindustries.com/docs/Vapor Barriers Under Concrete Slabs.pdf

Instead of using drain grates in the slab - we sloped the slab forward and are installing Class E ACO zipper drains along the front of the slab to catch rain/wash water from either the garage or grade

http://www.acousa.com/drain/klassikdrain.htm

Garage slab will sit on decking which is tack welded to I beams. Have any pics of your project? Also, would a monolithic slab work for the footings and basement slab?

The zipper drain system looks like the way to go.

 

[rinny_tin_tin]

Garage slab will sit on decking which is tack welded to I beams. Have any pics of your project? Also, would a monolithic slab work for the footings and basement slab?

The zipper drain system looks like the way to go.

Try this link for some pics

http://www.kodakgallery.com/ShareLa...mail-_-site_share-_-core-_-view_photos_button

I'm not sure what you mean when you say the slab will sit on decking - please explain a bit more. And - yes - a mono slab will work fine for the basement slab - just make sure you install your expansion joints/reliefs. Footings are usually poured at once - so I'm not sure what you mean here either.

 

[ncbuckeye]

Sorry, guess I could be more specific. The engineer has the garage slab being poured on 1 1/2 " wide rib 18 gage (wr18) composite decking. I'll try and get a pic posted.

The mono slab consists of both thicker footing and 4" slab. All done in the same pour. Correct?

 

[Torque1st]

"Decking" -Probably steel bridge deck just like I am using for a structural slab.
http://www.metaldek.com/

Structural slabs are required whenever a slab is placed over a void like a basement or over fill more than a specified depth.

 

[ncbuckeye]

"Decking" -Probably steel bridge deck just like I am using for a structural slab.
http://www.metaldek.com/

Structural slabs are required whenever a slab is placed over a void like a basement or over fill more than a specified depth.

Yep, that's it. The plan also calls for W18x40 beams. (5) 24 ft long.

 

[Torque1st]

Yep, that's it. The plan also calls for W18x40 beams. (5) 24 ft long.

I hope the engineer knows what he is doing but that sounds real heavy on the beams. What is your PSF and point loading for the slab? Can you get away with some support columns in the basement?

 

[rinny_tin_tin]

Yep, that's it. The plan also calls for W18x40 beams. (5) 24 ft long.

ok ok ok....between Torque's and your stuff - I got ya now...its that corrugated steel stuff...sittin on your W18x40 grade beams...Gotcha...Yes - I was going to go that route too ---to permit a space beneath the slab in my project (which was all filled in with dirt) -- but it was too late in the game and I already had the plans approved etc and I didn't want to delay - but I did brace the walls extra in case I wanted to later cut into the walls and excavate (That will be an interesting project if it ever comes to pass - it took 38 Quads to fill the cavities)

I'm not sure what is done when you pour on decking - how does the water drain out, etc? Are there holes in the decking? However, the decking should provide excellent added tensile strength to the cement slab....In my slab - I used #4 rebar 1-foot on center in both directions, steel mesh ontop-- but no dowels to tie the slab into the walls. Its floating as far as I can tell.

 

[rinny_tin_tin]

Sorry, guess I could be more specific. The engineer has the garage slab being poured on 1 1/2 " wide rib 18 gage (wr18) composite decking. I'll try and get a pic posted.

The mono slab consists of both thicker footing and 4" slab. All done in the same pour. Correct?

That sounds like what they call a turned down footing --

Lets get a pic or some dwgs if you can as I'm getting a bit confused as to how this all works with the decking and all.....

But here is a site that may help in the interim

http://searchwarp.com/swa321790.htm

 

[ncbuckeye]

ok ok ok....between Torque's and your stuff - I got ya now...its that corrugated steel stuff...sittin on your W18x40 grade beams...Gotcha...Yes - I was going to go that route too ---to permit a space beneath the slab in my project (which was all filled in with dirt) -- but it was too late in the game and I already had the plans approved etc and I didn't want to delay - but I did brace the walls extra in case I wanted to later cut into the walls and excavate (That will be an interesting project if it ever comes to pass - it took 38 Quads to fill the cavities)

I'm not sure what is done when you pour on decking - how does the water drain out, etc? Are there holes in the decking? However, the decking should provide excellent added tensile strength to the cement slab....In my slab - I used #4 rebar 1-foot on center in both directions, steel mesh ontop-- but no dowels to tie the slab into the walls. Its floating as far as I can tell.

Yeah, my neighbor had his 3rd bay slab done this way. I'm still going back and forth on fill or basement. Not the cheapest way to add storage, but will keep the rest of house quiet when I'm in the shop. I'm assuming that rebar will still be required on the top slab... not sure though.

 

[ncbuckeye]

That sounds like what they call a turned down footing --

Lets get a pic or some dwgs if you can as I'm getting a bit confused as to how this all works with the decking and all.....

But here is a site that may help in the interim

http://searchwarp.com/swa321790.htm

Have the plans on PDF. What's the best way to upload??

 

[rinny_tin_tin]

Have the plans on PDF. What's the best way to upload??

I guess using the attachment manager - or whatever they call it here. If its too large - you need to find a host - like Kodak or any of the million Hosts out there.. I have not used any other than the Kodak site - but maybe Torque or on of the others can make a rec.

 

[Torque1st]

I use ImageShack for pictures but AFAIK they are not set up for file hosting.

In my case the basement decision was easy. I had two huge 30" and 36" diameter silver maples cut down. The were rotten & hollow inside so they were a menace to the house. The roots would have to be dug out for the garage. I would have to go down 6-8' just to find virgin soil and there will be two huge holes, -so why not square it off and place a basement floor... The only real cost difference will be for the basement floor. A structural slab would have been needed for the garage floor anyway. It would have been a simpler structural slab since the earth fill could provide the bottom form.

The metal deck does NOT allow water to drain away from the concrete mix into the fill which improves the strength of the mix. Concrete needs water to cure since it is a hydration or water addition chemical reaction. The metal decking is considered part of the reinforcement but additional wire or rebar is usually required depending on the load. There are many different choices to be made when the metal deck is used regarding construction spans and shoring etc.

 

[ncbuckeye]

I use ImageShack for pictures but AFAIK they are not set up for file hosting.

In my case the basement decision was easy. I had two huge 30" and 36" diameter silver maples cut down. The were rotten & hollow inside so they were a menace to the house. The roots would have to be dug out for the garage. I would have to go down 6-8' just to find virgin soil and there will be two huge holes, -so why not square it off and place a basement floor... The only real cost difference will be for the basement floor. A structural slab would have been needed for the garage floor anyway. It would have been a simpler structural slab since the earth fill could provide the bottom form.

The metal deck does NOT allow water to drain away from the concrete mix into the fill which improves the strength of the mix. Concrete needs water to cure since it is a hydration or water addition chemical reaction. The metal decking is considered part of the reinforcement but additional wire or rebar is usually required depending on the load. There are many different choices to be made when the metal deck is used regarding construction spans and shoring etc.

With the slope of the lot being a 6ft drop in 26 feet, it makes the decision of a basement a bit easier. There are several large trees that also need to be removed.

I've been told that the use of fiber mesh in the concrete will allow us to forego using the wire mesh. Does that sound right?

http://www.fibermesh.com/application.aspx?ID=2173

 

[Torque1st]

With the slope of the lot being a 6ft drop in 26 feet, it makes the decision of a basement a bit easier. There are several large trees that also need to be removed.

I've been told that the use of fiber mesh in the concrete will allow us to forego using the wire mesh. Does that sound right?

http://www.fibermesh.com/application.aspx?ID=2173

I have heard that fibermesh is OK for controlling shrink cracks but as far as real reinforcement it does not work. I like real steel in my concrete. There have been advances in the composition of rebar and epoxy coated rebar is a plus. Coated metal deck is also a good thing in areas where salt is used on the roads.

 

[rinny_tin_tin]

With the slope of the lot being a 6ft drop in 26 feet, it makes the decision of a basement a bit easier. There are several large trees that also need to be removed.

I've been told that the use of fiber mesh in the concrete will allow us to forego using the wire mesh. Does that sound right?

http://www.fibermesh.com/application.aspx?ID=2173

Your circumstance sounds like mine as I also built on a hill. The fiber only checks small surface cracks - while the wire mesh checks deeper cracks while the rebar checks even bigger cracks. Use the wire mesh in addition to the re-bar - its relatively cheap. You can also use the fiber too - it won't hurt, and its not expensive. When you remove a tree - just be prepared to deal with a stump hole effectively as big as the canopy - that is, the ground is going to be real soft and either you need to dig your footers deeper (maybe step it) or fill it with rock and tamp. I'd also go with a 6 inch slab in lieu of a 4 inch.

 

[ncbuckeye]

Your circumstance sounds like mine as I also built on a hill. The fiber only checks small surface cracks - while the wire mesh checks deeper cracks while the rebar checks even bigger cracks. Use the wire mesh in addition to the re-bar - its relatively cheap. You can also use the fiber too - it won't hurt, and its not expensive. When you remove a tree - just be prepared to deal with a stump hole effectively as big as the canopy - that is, the ground is going to be real soft and either you need to dig your footers deeper (maybe step it) or fill it with rock and tamp. I'd also go with a 6 inch slab in lieu of a 4 inch.

It's interesting having the different viewpoints from contractors when it comes to what the foundation needs and what it doesn't. I think I've had close to 8 bid the job and none are the same. Would it be wise to have the engineer on site to check on correct construction? You don't get a second chance at this stuff.

 

[Torque1st]

You will have to pay the engineer to do the inspections but if you are getting a line of BS from the contractors the money for the engineer will be well worth it.

I use rebar in all my projects. Wire mesh has a tendency to disappear in the concrete after a few years plus it gets mashed down when the concrete is placed and ends up who knows where. A good man on the hook can get it placed fairly well but they are few and far between. Places where wire was used around here usually only ends up with a little rust stain somewhere down in the concrete.

I have used old chain link fence as mesh in a few places for "home projects" and the galvanized coating makes the wire hold up well.

 

[rinny_tin_tin]

It's interesting having the different viewpoints from contractors when it comes to what the foundation needs and what it doesn't. I think I've had close to 8 bid the job and none are the same. Would it be wise to have the engineer on site to check on correct construction? You don't get a second chance at this stuff.

You would be wise to enter into this with a design stamped by a PE or architect - and not a design developed by the contractor. During construction, it would also be worth it to have the PE perform conformity assessment on your behalf to audit compliance. That is, have the engineer do the design and the contractor do the building.....

 

[Torque1st]

A structural slab around here requires a PE stamp.

 

[Tim M]

Are you working with an engineer?

Your costs are right on target.

I am about to pull a permit for a 26x42 garage with basement using W18x46 ibeams. I am building on a slightly steeper slope and am shooting for a 9' - 10' ceiling in the basement.

And many thanks to this forum for inspiring this project and Utah997 in particular. Great group.

I am going with 10" poured walls with a 6" thick elevated slap on 18 gauge decking using #3 rebar 18" oc. Actually I think the decking corrugations are about 1.5" so the slab will vary between 6" and 4.5" thick. Footers are 12" deep x 24" wide. Walls have #5 rebar 16" oc.

The engineer said I could use welded wire fabric in the slab, but rebar is better.

I am putting in a large garage door in the "walkout" side of the basement as well with gravel road access to it.

Another thing I did was have the engineer draw up the plans to the maximum I might want (28'x48'). In that way I can reduce dimensions to fit my lot layout (big trees) without requiring a bunch of drawing updates. I won't know my dimensions for sure until I start to excavate.

This is my first project like this so I am looking for inputs as well.

BTW I am just north of Raleigh and interestingly I grew up in MI... ncwolverine.

 

[ncbuckeye]

Are you working with an engineer?

Your costs are right on target.

I am about to pull a permit for a 26x42 garage with basement using W18x46 ibeams. I am building on a slightly steeper slope and am shooting for a 9' - 10' ceiling in the basement.

And many thanks to this forum for inspiring this project and Utah997 in particular. Great group.

I am going with 10" poured walls with a 6" thick elevated slap on 18 gauge decking using #3 rebar 18" oc. Actually I think the decking corrugations are about 1.5" so the slab will vary between 6" and 4.5" thick. Footers are 12" deep x 24" wide. Walls have #5 rebar 16" oc.

The engineer said I could use welded wire fabric in the slab, but rebar is better.

I am putting in a large garage door in the "walkout" side of the basement as well with gravel road access to it.

Another thing I did was have the engineer draw up the plans to the maximum I might want (28'x48'). In that way I can reduce dimensions to fit my lot layout (big trees) without requiring a bunch of drawing updates. I won't know my dimensions for sure until I start to excavate.

This is my first project like this so I am looking for inputs as well.

BTW I am just north of Raleigh and interestingly I grew up in MI... ncwolverine.

I'm working with Southern Engineers out of Raleigh. I've spoken with them several time about the project.

I'm leaning towards 10 in poured although the engineer says 12 inch solid filled block (w/ rebar) would suffice. I'd be fine with 8 1/2 feet in the basement.

Do your plans call for lug footings at the beam ends? Mine has 30"x30"x10"

Glad to someone nearby is in the same boat.

 

[Tim M]

No extra footing at the beams, but the footings and wall have an extra vertical run of rebar directly under the beam pocket. And each beam will be welded to a bearing plate with studs pointing down, inserted at the bottom of the beam pocket during the pour... need to think this through a bit.

My engineer also gave me the option of 12" block. I just like poured walls.

Anybody know if a elevated slab will support a lift? I imagine if you lined it up correctly you could tie right into a beam below.

Anybody know where I can find loading/installation details on a lift to provide my engineer?

Thanks,
Tim

 

[ncbuckeye]

How concerned should I be about the trucks destroying the existing driveway (3000psi) when the pour happens? I hate to think about installing a new one. The garage is about 100 feet from the street.

 

[rinny_tin_tin]

No extra footing at the beams, but the footings and wall have an extra vertical run of rebar directly under the beam pocket. And each beam will be welded to a bearing plate with studs pointing down, inserted at the bottom of the beam pocket during the pour... need to think this through a bit.

My engineer also gave me the option of 12" block. I just like poured walls.

Anybody know if a elevated slab will support a lift? I imagine if you lined it up correctly you could tie right into a beam below.

Anybody know where I can find loading/installation details on a lift to provide my engineer?

Thanks,
Tim

You'll need a reinforced pier/column to translate the load to its own footer.

 

[rinny_tin_tin]

How concerned should I be about the trucks destroying the existing driveway (3000psi) when the pour happens? I hate to think about installing a new one. The garage is about 100 feet from the street.

You may be able to use a articulating pump situated some distance away from your driveway. In fact -if you go the pour route - you'll likely have the pump anyway

 

[PAToyota]

How concerned should I be about the trucks destroying the existing driveway (3000psi) when the pour happens? I hate to think about installing a new one. The garage is about 100 feet from the street.

Concrete trucks destroy residential driveways.

 

[ncbuckeye]

You may be able to use a articulating pump situated some distance away from your driveway. In fact -if you go the pour route - you'll likely have the pump anyway

Yep, just heard back from the foundation contractor who say's they'll be pumping from the street.

 

[rinny_tin_tin]

Yep, just heard back from the foundation contractor who say's they'll be pumping from the street.

Make sure they use a concrete ******** and they not just rely on the high velocity of the pump discharge to compact the concrete - else you may get voids. Also - make sure you take cylinder samples and that the concrete supplier know beforehand that you are taking samples - that way - they are less likely to pull a fast one.

 

[Torque1st]

Get your sample towards the end of the pour so they don't add water after the sample is taken. Don't let them hurry up and empty the truck before you get it either. They know all of the tricks.