Looking for some advice here… I’m a DIYer considering hiring a contractor to frame in a 2nd story addition. Right now, I’m just trying to assess the feasibility of the project. My house: 1924 28’X 28′ bungalow with basement foundation. My walls are 2×4’s 16″ OC, ceiling joists are 2×6 24″ OC, floor joists are 2×8, 16″oc. Foundation is 6-7″ thick (not reinforced), 7′ deep. I don’t know how wide and deep the footings are… For the most part the foundation is in good shape (only one area with noticeable cracks and settling of an inch or so.
The tentative plan is to span the width of the house with 2nd story floor trusses, then frame in a steep pitched roof with shed dormers in the front and back. It would be a true 2 story house disguised as a 1 and a half story.
The biggest question I have is whether or not the existing walls and foundation are sufficient to support a second story. If not, how could they be reinforced? I know this questions needs to be eventually answered by an engineer and architect so I’m just looking for any anecdotes of contractors or other DIYers that have done a similar project with similar constraints – esp. the 2×4 walls and
Thanks,
Gossett
Replies
Gosset,
I don't know where you’re from but around here in NJ, a foundation for a one story house is built the same as a foundation for a two story or three story houses.
The 2x4' studs can handle a two story or three story additions. You don't have to worry about the 2x4's at all.
What you do have to worry about on the outside walls are the existing headers for windows and doors if they can handle the second floor. Some houses don't even have headers above the windows and doors.
Some houses have 8' and 10' windows in there with small headers that are already sagging up to 3/4". Those have to either be replaced or you put a flush header on top.
Your center walls might have to be beefed up if there are any big openings on the first floor. These are just some of the things that the Architect or Engineer will have to look at.
If your second floor calls for any big supporting beams above the center wall, they might have to be supported underneath and the load might have to transfer down to the basement girder and a footing and column has to go in.
If there’s a beam above an outside wall, you’ll have to transfer the load down to the foundation. Sometimes a beam lands above a window header on the first floor, so you either have to put a flush beam or take out the existing header and replace it a beam or steel depending on whether you have a cantilever or not.
There are a lot of things going on that has to be looked at but as far as your 2x4 walls handling a second floor, that's not one of them and is never an issue. As far as foundations being able to handle a second floor, that's never been an issue either around here anyway. Maybe by you it is. Either way, you have to have it looked at by an Architect or Engineer. If you don’t need either and can draw your own plans, then you have to have a professional come in there and check everything out.
If you can clear span I-joists from front to back without depending on the center wall to support them, then it doesn't matter what's underneath.
Thanks for your reply Joe. I'm from Portland, OR if that adds any relevance to the discussion. Portland is kind of a wanna be San Francisco so they tend to have fairly stringent code requirements for earthquakes but that's what engineers are for...My hope is to span the entire width of the house (28ft) with I-joists or floor trusses and have the load of the second floor sit on the outside walls through to the foundation. I'll be replacing and moving some windows on the first floor so I will bring the headers up to snuff during that process.Thanks again,Gossett
Gosset, I'm going to offer a bit different opinion than Framer and it probably won't be quite as popular.
Around here, (MA) not all foundations are created equally. It's very common for an old rubble foundation to be incapable of supporting a new second floor without some additional shoring and general 'beefing up' being done.
My personal opinion is that your very first phone call needs to be to a residential structural engineer who is qualified to assess your foundation. If you were in MA, you'd need to do that anyway before you could get your permits. So before wasting any money on construction drawings that may never get built... I'd spend a couple hundred on an engineer.
If you said you had a 10" poured concrete foundation from 1960 or something then I'd say go for it, because you're probably ok. But your situation sounds a bit more complicated than that to me.View Image
Brian,I'm talking about block foundations. I've done some add-a-levels over stone foundations also.I've talked to masons and Architects about this and they say the block is the same for one story or two story.Joe Carola
Sorry 'bout that Joe.... I meant to address the post to the OP and instead directed it at you. My bad. View Image
I have 2 sets of prints on my desk 2to bid on right now for the same as you are describing, (at least the second story addition part) .
Bolth had engineers come by and take a looksy Before any design work was done.
Until you get the ok for your foandation from an engineer it doesnt realy matter how your going to do the addition above.