Replies

1. 
   agm413 | May 17, 2022 12:53pm | #1

   You can definitely do a 26' ft span with I joists. They will be fairly deep depending on what your preferred joist spacing is. You can do a BCI 90 Joist with 12" centers, and it is rated to 26' 7" on the span table I looked at for their "3 star floor" which is L/480. From one website I can see pricing one from a material provider, those joists are about 260/piece, so your floor joists will come in at around 11-12k depending on taxes, deliveries, etc. Maybe a touch more or less. Also, I don't know how much these advertised prices would differ if a contractor or whoever is buying them.

   If you wanted less deflection you'd need a deeper joist. On that same table for L/960 you can just eek by that 26' span with a 16" depth joist.

   As far as vibrations or "bouncy" goes here's what BC says about it:

   "The most common methods used to increase
   the performance and reduce vibration of wood floor systems is to
   increase the joist depth, limit joist deflections, glue and screw a
   thicker, tongue-and-groove subfloor, install the joists vertically
   plumb with level-bearing supports, and install a direct-attached
   ceiling to the bottom flanges of the joists."

1. 
   jayhawkcrna | May 18, 2022 10:02pm | #3

   Thanks so much for this info. It has been very helpful

2. 
   windwash | May 25, 2022 06:48pm | #6

   Floor trusses would be my choice. Unless you use solid sawn lumber or LVL/LSL/Parallam lumber for the joists you may be required to install sheetrock on the bottom of trusses or I-joists to get your certificate of occupancy.

2. 
   unclemike42 | May 17, 2022 02:06pm | #2

   I would look at trusses. My brother has them in his condo, and the floor is like a rock.

   Plenty of access for utilities as well.

   May complicate your elevations, but such is life.

1. 
   jayhawkcrna | May 18, 2022 10:03pm | #4

   Thanks. I am not sure if budget will allow but I would love trusses as I am finishing the basement myself/diy and the ease of running mechanicals would be nice.

1. 
   unclemike42 | May 19, 2022 05:38am | #5

   Think of it this way, If you raise the floor level, and use trusses for a free span floor, and include daylight lights in the basement, you have more attractive space for not much more money.

3. 
   ct_yankee | May 25, 2022 08:38pm | #7

   Here's a crazy thought:
   install (2) steel beams spanning the 26' direction, bearing on the 40' walls. Beams would be 13'-4" c/c. Run wood floor joists parallel with the 40' foundation walls. It is possible to make the wood joists flush with the top of a nailer on the top flange of the steel beams. Joists would likely be 2x8s. Floor 'bounce would be controlled by the depth of the steel beams (and not by the wood joists) as their depth can be increased enough to tame the potential bounce. The major drawback is running any plumbing lines or ductwork thru/around the steel beams.

4. 
   jayhawkcrna | May 25, 2022 09:57pm | #8

   I’m leaning toward asking for trusses if it would work. But now I have a question about the sub flooring. I’m thinking about asking for 1 1/8” Advantech. Is this overkill?

1. 
   greg_e | May 26, 2022 09:20am | #9

   You will probably be able to design floor joists with 24" spacing so 1 1/8 subfloor will be a great option. Personally I don't think advantech is worth the premium over warehauser edgegold subfloor. It's about a 30% upcharge for me.

1. 
   jayhawkcrna | May 26, 2022 10:21am | #10

   Thanks. I will look into that option. I mainly was meaning to looking at the thicker 1 1/8” option

1. 
   windwash | May 26, 2022 01:27pm | #11

   3/4" Advantech will be fine for most applications at 24" on center. You're only spanning 20-1/2" with the floor truss.

5. 
   ChelsieOakey | May 26, 2022 01:51pm | #12

   When choosing insulation for the floor on the first floor, several factors are usually taken into account. If on top of the thermal insulator is supposed to arrange a cement screed, the work will require protective materials of high density, capable of withstanding significant mechanical stress.