So, I wondered if anyone had insight into finishing an attic space if my joists are 8x2 spaced 16" apart.  Now, I have heard that this only allows for "office space" rating, but my intention is to put in a full 2 bedroom unit with kitchen and bathroom with bathtub. 

Anyone have experience?

It will not be a formal unit, it will simply be an extension of the second floor unit in a duplex, so I do not need to get it permitted. 

I suspect that this is something that people often do, and typically suffer few if any negative consequences, but I wanted to see if folks had hands-on experience. 

@Margie Pierce I would encourage you to dig deeper into the permitting issue. I can't imagine a locality that would not require a permit for the work you described, and the cost of violating permit regulations can be a huge expense.

Hi, @Margie Pierce . 

@Matt Clark is absolutely right. You will definitely need a permit to do this kind of work. Not only for the structural work but the plumbing and electrical. 

8x2 joists are most likely undersized to carry a living space, especially bathroom or kitchen. The other important part is the span of the joists. 8x2s may be fine with 6ft of span, but woefully undersized at a 12ft span.

@Jaysen Medhurst If you study your joist table, you will find that most 2x8 graded lumber down to a number 2 is adequate for a span of 12ft.

where can I find a joist table??

Originally posted by @Margie Pierce :

where can I find a joist table??

See link below:

http://www.awc.org/pdf/codes-standards/publication...

You did not say anything about rafters. The size of the rafters will set the thickness of insulation you can install; for R-38 as required by code, to use fiberglass batts, you would need 12 inch rafters. If your rafters are not 12 inches (or more) then you might have to consider spray foam insulation, and that costs way more than fiberglass.

@Robert Hudson , I'll take your word for it. I was just trying to point out that there is a lot more to consider when figuring out the load capacity.

@Margie Pierce https://bct.eco.umass.edu/publications/articles/understanding-loads-and-using-span-tables/

I would consult an architect or structural engineer.  Also look to city code.  Do this right.

From my experience, a lot of the buildings have 2 x 6 joists in the ceilings (smaller buildings).  So to build in the attic, they double the existing joists with another 2 x 6.  This is called "sistering" the joists.

There are many ways to get this accomplished that do not add a lot to the overall budget of the project, but I agree that at the very least you should consult with your permitting office. More often than not I see the circulation up to the space become an issue (considering that you have the required headroom). Generally, this requires design of space above and below the new floor assembly, as well as the structural load path. 

If a 2x8 joist isn't large enough you can merely install a 2x10 beside them.

@Margie Pierce From my perspective as a Pittsburgh-area home improvement contractor in good standing with the PA Attorney General's office, with one million bucks worth of insurance on every job I do:

The bathroom and kitchen you're planning are what you should be really worried about.

The city of Minneapolis issues plumbing permits and licenses plumbers -- it says so on their website. The city of Pittsburgh proper and the boroughs of greater Pittsburgh do not -- plumbing permits and licensing plumbers is handled by the Health Department of Allegheny County, where Pittsburgh is located. We do 3rd party paid electrical inspections, and everything else is handled by local code enforcement and the quality of that varies sharply across the boroughs. It's a mess, except for those plumbing permits. We all mind our P's and Q's when it comes to those.

As Napoleon once put it, "In this country, it is wise to kill an admiral from time to time to encourage the others." The health department has a ferocious reputation for going after small offenders and issuing draconian penalties when they find them. I'd bet a significant sum that the city of Minneapolis has much the same reputation when it comes to plumbing permits. Illegal sanitary water work destroys property, hurts people (typically children and the elderly), leads the news, and makes top local politicos look like they can't get their thumbs out.

So the problem with not pulling building permits (with special attention given to plumbing permits) if you're in this business for keepsies is that sooner or later, the odds catch up to you, and once they do, your name is mud and your career as a landlord is over. I maintain the absolute best possible professional relationships with the building inspectors who typically check my work, but I am ready to drop and shine an Allegheny County plumbing inspector's shoes if he wants me to. Over time, several have come to trust I will always do the right thing because I know the score. This makes my life easier in turn.

The simple construction reality is that if you sister your 2x8s, as indicated elsewhere in this thread, you can do whatever you want up there and the floor will hold. The plumbing work to cut into the stack and put in the fixtures you talked about isn't impossible hard even for a DIYer. But my recommendation is that before you do anything at all, call the plumbing department and indicate your intentions, call the office responsible for issuing building permits in your area, AND DO WHATEVER THEY TELL YOU TO DO. Or hire a contractor who knows the score. Pulling permits is more than a bit stressful but is an absolutely integral part of being in this business -- you've got to learn the process sometime. As an starting investor who owns a single duplex (as indicated on your profile), with the desire to get a few more, this is the best time to learn even though, perversely, it's the time when you can least afford the expense of it.

Politicos LOVE shafting and shaming us, Margie. If they could shaft one of us every day and give a speech about how "the good people of our fine city need not worry about predatory slumlords doing their tenants wrong on this administration's watch," they'd stay in office forever. Perp-walking one landlord in handcuffs on camera is worth kissing a hundred full-diaper babies for a politico. There's no downside for them, whatever party they belong to.

Good luck to you, whatever you choose to do.

Just did a renovation where we took it to the studs and sisters all the 2x8 2 me fl- floor joists with 2x10's for strength, also replace 2nd fl headers as they were insufficient- had a structural engineer come in for the weight calcs for headers and submitted with the revised permit- sounds like you aren't a GC and advise you hire one so it's done right- you have too much work to not do that and understand code.  It has to do be done right or you will have even more issues.    You absolutely have to permit this.  you don't know what you don't know.

Hi Bruce Runn. I am absolutely hiring a contractor. The issue is that not all of my GCs are mentioning the joists and I'm trying to determine if I am being taken for a ride. 

Also Bruce Runn, may I ask you what the cost of this was? Sistering is exactly what we may end up doing. 

Just curious if you ended up moving forward with the project? 

What area of minne is it in?

 I'll also echo what everyone else said you 100% need to permit this in minneapolis.