If the joists are a full 2 inches by 8 inches they are probably not overspanned. Any modern span table is based on the reduced size of modern lumber. A 2x8 is actually only 1.5 x 7.25 inches. If you have full dimension lumber it is about 1.33 times stronger by being 2 inches instead of 1.5 inches (goes directly with thickness), and about 1.34 times for being 8 inches vs. 7.25 (goes as the cube of height) The inadequate bearing area is a separate issue. A ¼ or ½ inch bearing is way to low. You need to get up and carefully measure this, but adding sisters of modern 2x8 with adequate nailing can easily solve that problem. A good PE with wood design experience can provide the nailing schedule and confirm the span. Framing a wall to provide support (unless you want one for other reasons) will just reduce floor space and transfer the load to the floor at a place that may not be suitable for bearing since it may not be over a footer.

sullidc, Thanks for your post... I contacted Aeratis about this issue... I felt I had to because I have made recommendations to contractors and homeowners about this product and i continue to recommend it... They put me in touch with the sales rep that went to your house. His name is Roy. I spoke with Roy to find out if it was possible that A) the boards were a different width and B) if the boards were a different width, if they really just left you out in the cold. What i found out was very interesting... It seems that Aeratis like most manufactures, do not make a specific length of board. When the boards are manufactured, they are made from a constant string of product and they are cut to a length by a moving saw. The material never stops moving and it is almost impossible for multiple boards to be wider or narrower at a consistent point on any length of board. I also found out that Roy measured almost every board on your porch and he found that they were exactly 3-1/8" in the areas that you stated they were a different width. I also found out that they offered you some free boards for your porch if you had decided to take the boards up and fix the un-square boards on your porch. I went through all of this with them because I take porch restoration and my work very serious. The products I recommend have an effect on my reputation. I have to tell you here, I cannot call foul on Aeratis. They visited your jobsite, they offered a solutions and on top of this, they offered to give you FREE board. I am not one to stand up for a manufacture, but it sounds to me they went above and beyond on this one for you.. I pushed Roy on this just to make sure he was not just giving me a good story so I would continue to use and recommend the product. He sent me the report and photo's from his inspection. I removed your name to not cause an issue... Roy's email to the manufacturer STARTS HERE......I went to job last week, measured several boards, found consistent 3-1/8" widths. Porch is 10' x 32'. Traditions, painted. Tried to lay down a straight edge / level and confirmed that most of the boards have a slight bow. They were installed staring at the right side (facing house) of the porch. It was difficult to determine if the starter board was bowed but from about 3' in from the right, the bow is apparent. To best see it, you crouch down and view from a position almost level with the floor. There is a very slight raised area about 4' in from the front edge, not consistent across the entire porch. I spoke with Mr. Ssullidc who said he understands the holidays could delay a response from Aeratis but said that if, in a month or so, there is no response/ resolution, rather than go to legal methods, will publish a negative review on every web site dealing with Areratis. REPORT ENDS HERE.... sullidc, Posting negative reviews is a good way to get resolution with a stubborn manufacturer. It forces folks like me to call and question their business practice. However, when they have gone above and beyond to work with you on a mistake you made, seems to me you are not the one who should be shouting FOUL!

Look around ad see if there is a repair plate for that size joist made of metal.

Hey all, thanks for the replies! Sorry for misspelling "joist" as "joint" about 5 times! I did some research based on the replies and I have learned a lot. Thanks for pointing me in the right direction. I was wrong about the sill plate. There is one, but it is recessed into the foundation wall, being proud of the top by about 1/4". I just didn't see it. The floor joists sit on the sill plate. The rim joist does not appear to be load bearing. It is not on the sill plate. It only appears to hold the joists from twisting. I suppose that explains the lack of joist hangers. Still, my guess is some sort of hangers/fasteners would be advised. I was wrong about the floor drop. I re-measured, and it is more like 1/4" rather than 3/8". Also, the house sheathing is some lousy particle board and the siding is horizontal boards and also particle board. There is not even any house wrap. House was build in the early 80's. It is turning into quite a project! So I guess I'll be re-sheathing, wrapping, siding the house as I redo all these windows and doors. This remodel keeps growing! The house is a one story. The roof is asphalt, with trusses which are parallel with the floor joists. @Sye Phommachanh: The floor is not in a plane. It drops 1/4" from one floor joist to the next under the sliding door area. Floor joists are perpendicular to the gliding door with about 5 joists spanning the door area. On either side of this drop the floor joists are pretty level and in a plane. I'd say the left 2 joists are the low ones and the right 3 joists are the high ones, with a 1/4" inch rise between the 2nd and 3rd joist. The door closes on the left/low side. The current patio gliding door has the closing side jacked up high (via wheel adjust) so that it is level when it closes. When the sliding door is open it is totally crooked since both wheels are sitting on the high portion of the floor. @ksc36: Thanks for that! I checked and found the gloding door I plan to install has similar instructions. It is supposed to sit right on the floor, and caulked in with three beads of silicone caulk over the sill pan. I guess I'm looking for my solution to "Correct as necessary" with respect to leveling the bottom of the opening. I think I need to raise the two floor joists on the low side of gliding door area.. This will move the 1/4 floor drop left of the door. After that I'll probably raise the joists in a tapered fashion to spread the 1/4 drop over a few joists. That part of the wall will have a window where I can shim the bottom if necessary. I plan to shim the floor joists with metal shims between the joist and the sill plate. The shims will be the width of the sill plate and long enough to screw to the sill plate on either side of the joist they are raising. If this is not legit, somebody please stop me! The wall top-plate/roof-line will get pushed up a bit, but I'm re-framing the window and door openings to widen them, so I can fix that if it is an issue. @joseph_corlett: I think my shimming option would be to create some sort of long wide shim that I could install on the floor in the door track area to make it seem like the floor is level. The shim would need to be 1/4" tall tapered to zero, 4-9/16" wide, and about 29" long. Basically, a super-shim that simulates a level door opening. Maybe just nail/glue down 1 /4 thick board on the low side, and then sand it level with a belt sander. Then install the flexible sill pan on top of that. Of course, the rest of my floor would still have this drop between two joists, which could become and issue when I eventually install new flooring, depending on the product. Thanks again!