Pushing out a exterior wall

Question Icon
Posted by: from North Sydney
6/11/2012 at 10:52:55 AM

We want to push out an exterior wall to gain just about 18 inches for a kitchen dining area. It would hold cabinets but the problem is the floor joists run with that wall not into it... can we still join this pushout into our home?

User Icon
Cassidy Residential Design in Gloucester
Date/Time6/11/2012 at 12:11:43 PM

Exterior walls are ALWAYS load bearing and will require lintels over and new openings together with posts each side in wall to support the posts. You will also need a building permit for this work.


Frank Cassidy IMAATO

OMMAH Registered Designer

Cassidy Residential Design

phone: (613) 834 1857

fax: (613) 834 4597

User Icon
Date/Time6/11/2012 at 12:32:56 PM

Unfortunately this is not my specialty.

User Icon
Michael from General Carpenter in Ottawa
Date/Time6/11/2012 at 1:00:58 PM

It is still possible to join your extension to the existing exterior wall. You have several options available for supporting the extension.

1) Sonotubes with 4x4 posted embedded in them

2) Pouring a new foundation wall beneath the extension

3) Using cinder blocks to create the new wall beneath the extension.

I recommend using cinder blocks because

1) Pouring a new foundational wall is expensive

2) Sonotubes would not provide the best support in case of any unexpected movements such as earth quakes. However, extending your kitchen space would be costly. Gaining more than 18" would help justify the expense.

Are you interested in hiring a professional to do the work for you or do you hope to do the work yourself?

General Carpenter


User Icon
Date/Time6/11/2012 at 2:05:06 PM


Yes, There are special brackets you can have.



User Icon
Date/Time6/11/2012 at 5:19:28 PM

Yes you can, it's called cantilever's.

Use straddles to extend the floor joists, Sheath the new josts, add a header in the area that you are cutting out, then build you new wall, and small roof to shead the water.

Don't forget to install s/m on the bottom of the cantilever to keep the floor in this area warm.

User Icon
Date/Time6/11/2012 at 5:51:16 PM

If your basement is not finished, you can still cantilever the joists. If you extend 18" out then 36" in of the floor joists will have to be re framed. You'll need a structural engineer and permits. Concrete sono tubes with 4x4's is the cheapest option.

However the best option is to use concrete blocks at least 4' down to create a crawl space and frame the extension on top of that. With the cost of this extension, if you can go out further than 18" the better. It won't add much to the total cost.

User Icon
Kimble & Jamie from JKS Custom in London
Date/Time6/11/2012 at 11:22:48 PM

Dear Home Owner,

I have done a few similar projects & the very first thing you need to do is have an engineer come in & design the addition with the proper specifications. You will find the engineer will insist on a full foundation to support the structure as it is a load bearing wall. The existing foundation will be left in place & the new footing and foundation will support the new structure. The roof structure would more than likely have to be modified to ensure proper snow load & run off from my previous experience.

A building permit is a must & if you work with a reputable Engineer you will find the experience much easier and less stressful.

I would strongly recommend that you think about increasing the size of the addition to take advantage of the opportunity as a new foundation, pushing out the wall & the roof will be rather costly. It wouldn't cost much more to go4', 6',8' or even larger as it actually gets cheaper when you go bigger. It would cost approximately $1200 to excavate18" as you have to take the new foundation down to the same level as the existing in most cases. Once the excavator is on site it wouldn't cost much more to go bigger. The footing and foundation would be in the $2500 to $3500 range as a ball park, please keep in mind that it is a difficult task to estimate a project site unseen but I will do my best to help you with this.

Demolition would cost the same big or small & be in the $800 to $1400 range including a bin.

Rebuilding the floor@ 18" would be around $1500 for new floor joists and sub floor and the new code requires you would have to insulate the new floor joists & foundation, 8' about $3000.

Rebuilding & reworking the roof would be $2000 to go 18" and around $4500 range to go 8' . If the engineer required the entire roof be reworked it would cost more.

Walls around $3500 to frame the 18" & approx $5500 to go 8' , includes insulating to the new code of R24 which requires 2"x6" construction, drywall, paint, house wrap, exterior cladding, & for budget purposes siding, the amount includes labour but not windows or doors.

Finished flooring cost would depend on your taste & going from 18" to 8' would just be a simple multiple. The advantage of going bigger is that the sub trades are already on site.

Electrical & plumbing would follow the same formula & I would budget $3000.

Think it through & best of Luck.

User Icon
Ricky in Quebec
Date/Time7/16/2012 at 9:52:14 AM

I think you should need permission for that. In my opinion the exterior wall gains all the weight of home, So be careful while remodel ling this.

Search the TrustedPros directory and discover the best contractors in your area.

Find your home service pro
Great renovations start with a great contractor.

Since 2004, TrustedPros has been helping homeowners find the right contractor for their home improvements and repairs.

Post Your Project

Within hours you'll be comparing offers from top-rated professionals. It's free to post and you're under no obligation to hire.

Trustedpros Inc. does not warrant the accuracy, completeness, safety, legality or usefulness of any Content, or Whether Content is Current and up-to-date, and TrustedPros Inc. Shall have no liability whatsoever with respect to your use or reliance upon any content or for content being removed or otherwise ceasing to be available. Please refer to the terms and conditions of use of this websites for more details.

It appears you may be located in the US

TrustedPros is designed to deliver results targeted to your location.

Get Free Estimates

Post your project and compare offers from top-rated pros.