Adding Foundation Under A Slab. - Building & Construction - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 01-28-2010, 11:38 AM   #1
Newbie
 
Join Date: Jan 2010
Location: Michigan
Posts: 8
Rewards Points: 10
Default

Adding foundation under a slab.


I am adding a addition onto the back of a garage which will have a basement. Can I put the foundation wall under the slab just were the basement will be ajoining and have the basement tie into it for support. The basement will have a 8ft ceiling height and this area is mosthly sand.

Advertisement

bob grube is offline   Reply With Quote
Old 01-28-2010, 11:54 AM   #2
Member
 
Join Date: Mar 2007
Location: Long Island, NY
Posts: 9,519
Rewards Points: 2,000
Default

Adding foundation under a slab.


Quote:
Originally Posted by bob grube View Post
I am adding a addition onto the back of a garage which will have a basement. Can I put the foundation wall under the slab just were the basement will be ajoining and have the basement tie into it for support. The basement will have a 8ft ceiling height and this area is mosthly sand.
Are you going to dig out under this slab for the basement space? If that's the case, this is not something you would(should) do.
You should break up the slab and dig your hole and install the forms for the walls.
Ron

Advertisement

Ron6519 is offline   Reply With Quote
Old 01-31-2010, 05:45 PM   #3
Newbie
 
Join Date: Jan 2010
Location: Michigan
Posts: 8
Rewards Points: 10
Default

Adding foundation under a slab.


No I am not digging underneath the slab for the basement. I just want to add the foundation under from the edge of the slab inboard about the width of the footing and secure the slab to the foundation then butt the basement wall to the new garage foundation and figure out how to secure it. The basement wall will be poured cement. Thanks for your response.
bob grube is offline   Reply With Quote
Old 01-31-2010, 07:38 PM   #4
Licensed P.E./Home Insp
 
Aggie67's Avatar
 
Join Date: Dec 2008
Location: New Jersey
Posts: 587
Rewards Points: 500
Default

Adding foundation under a slab.


I wouldn't, if it were my house. You may think you can excavate into the soil like a knife through cheesecake (with the walls of the exavation staying put), but that rarely happens. One rain storm, and you might find yourself building a new garage. Also, I don't see how you could properly insulate the outside of the foundation, or install drain tile. You should also tell whoever is designing the foundation that the one wall will be very close to a garage. That might play into how much soil pressure will bear against the wall.
Aggie67 is offline   Reply With Quote
Old 02-01-2010, 05:26 PM   #5
Newbie
 
Join Date: Jan 2010
Location: Michigan
Posts: 8
Rewards Points: 10
Default

Adding foundation under a slab.


Thanks for your advise. Is there a way that this can be done without adding a foundation under the entire garage?
bob grube is offline   Reply With Quote
Old 02-01-2010, 06:28 PM   #6
Wire Chewer
 
Red Squirrel's Avatar
 
Join Date: Jun 2009
Location: Ontario, Canada
Posts: 3,221
Rewards Points: 2,020
Default

Adding foundation under a slab.


I'm no engineer but I'd be worried that the garage may want to "tip over" right against the new structure. The ground pressure of the weight will make it so the wall of the basement needs to take lot of side/diagonal pressure compared to the other side of the garage.

Then again I'm no expert. I'd be curious to see how this would be handled by a pro. I'm sure it's been done before, but there is probably a very specific process to it.
Attached Thumbnails
Adding foundation under a slab.-untitled.jpg  
Red Squirrel is offline   Reply With Quote
Old 02-01-2010, 08:11 PM   #7
Licensed P.E./Home Insp
 
Aggie67's Avatar
 
Join Date: Dec 2008
Location: New Jersey
Posts: 587
Rewards Points: 500
Default

Adding foundation under a slab.


Now that I see a rendition on screen, I'm going to keep my nose out of this. I have a firm I call when we need to do things like that. I stay away from that kind of work. A little too risky.

My recommendation is to call in an unbiased professional to come up with a design and construction scheme, and have some folks bid it. Leave all the risk in their lap.
Aggie67 is offline   Reply With Quote
Old 02-01-2010, 09:36 PM   #8
Wire Chewer
 
Red Squirrel's Avatar
 
Join Date: Jun 2009
Location: Ontario, Canada
Posts: 3,221
Rewards Points: 2,020
Default

Adding foundation under a slab.


Keep in mind my pic might be wrong, I'm just making some assumptions as to what seems would make sense from a physics point of view.
Red Squirrel is offline   Reply With Quote
Old 02-02-2010, 10:08 AM   #9
Newbie
 
Join Date: Jan 2010
Location: Michigan
Posts: 8
Rewards Points: 10
Default

Adding foundation under a slab.


your picture is correct except it is missing the footing under the slab that the basement wall will butt up against. I had several builders tell me it can be done but it's hard to get a answer as to how and how much.
bob grube is offline   Reply With Quote
Old 02-02-2010, 12:08 PM   #10
Member
 
Join Date: Mar 2007
Location: Long Island, NY
Posts: 9,519
Rewards Points: 2,000
Default

Adding foundation under a slab.


Quote:
Originally Posted by bob grube View Post
your picture is correct except it is missing the footing under the slab that the basement wall will butt up against. I had several builders tell me it can be done but it's hard to get a answer as to how and how much.
Contractors are more likely to give estimates if they're given a set of blueprints to work from. It shows the homeowner has officially started the process and has himself invested in the project.
Estimates take time and nobody wants to waste time on vague drawings and descriptions that might get more involved(pricier) once plans get drawn up based on an experienced, professional eye.
Ron

Advertisement

Ron6519 is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Extending slab foundation for bigger bathroom newimaging Building & Construction 1 07-02-2009 11:27 PM
Is this a high quote? Price of a slab foundation pauls Building & Construction 8 10-29-2008 08:49 AM
Darn. A leak in my main supply from street, Galvanized. In foundation under slab? twilightcall Plumbing 2 07-31-2008 01:22 AM
I need help Re: Poured Slab Foundation - Moved to Plumbing alextina Plumbing 6 04-19-2007 05:35 PM
slab foundation jorguez1167 Building & Construction 2 06-27-2006 12:42 PM




Top of Page | View New Posts