We are in process of designing our home. The home is going to be a modern style “farmhouse”. Think 3 “monopoly” houses connected by atriums. The main sections are going to be the garage, great room/kitchen then a bedroom wing. It will be on a basement with 9’walls. The great room/kitchen section will be 26’x40’. One story that is going to be wide open. The basement is going to be left unfinished at first. We would love to have it be completely open but also want to balance that want with budget and ease of construction. Would floor trusses or I Joists or LVL be your favorite choice in this instance? We are worried about “bounce” on the main floor. We plan to put solid hardwood on first floor but possibly looking at Laminate/LVP.
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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."
Thanks so much for this info. It has been very helpful
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.
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.
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.
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.
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.
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?
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.
Thanks. I will look into that option. I mainly was meaning to looking at the thicker 1 1/8” option
3/4" Advantech will be fine for most applications at 24" on center. You're only spanning 20-1/2" with the floor truss.
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.