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Building a Home
pinebaron1

Floor Joists: Lumber, I-Joists or Trusses

Pinebaron
hace 7 años
última modificación:hace 7 años

For those who are building or have recently built a home with large rooms/spans over a crawl space or basement, what was your choice of floor joists/material/type and reasoning for your decision?

Our home in NJ used I-Joists and we had zero squeaks. New code for standard I-Joists requires covering lower surfaces with gypsum board for fire protection (like in crawlspace or unfinished basement).

Respuesta destacada
  • Andy
    hace 7 años

    In my line of work, if somebody comes to me and asks me a question where it is clear their assumptions have not been well founded, I ignore their question and ask them questions about their assertions until they spot the error. So don't be upset when you come here and get similar treatment from professionals in this industry.

    Comentarios (37)

    • mushcreek
      hace 7 años

      We used I-Joists, and they are an excellent choice. Open trusses are better for running the various utilities, and solid lumber is more fire resistant, at least for maintaining its structural integrity. They do now make all of the choices with fire retardant treatment. My plans are to install a double layer of 1/2" drywall, which has a one hour fire rating.

      Pinebaron agradeció a mushcreek
    • Pinebaron
      Autor original
      hace 7 años

      Mushcreek, Thanks; it is reassuring. I'd love to install open trusses but expect it's cost would be prohibitive due to size; am currently waiting for an estimate for I-Joists. Subfloor would be above a 4' or higher crawl space and may not need drywall protection since we will have fire sprinklers. Another contender is TJI I-Joists with Flak-Jacket for fire protection.

    • User
      hace 7 años
      Última modificación: hace 7 años

      Open web joists may cost more initially, but they SAVE when it comes to the plumbing, electrical, and HVAC because it makes those jobs much easier to do. Talk to those trades first before making your decision. It is worth the cost upgrades on the front end for that quickness and ease. And possible cost reduction. Also for easier access and alterations down the road should that be needed.

      Pinebaron agradeció a User
    • Pinebaron
      Autor original
      hace 7 años
      Última modificación: hace 7 años

      Hi Live wire, I'd love to install open web joists; with over 5000ft of joists needed for 16" OC longitudinal install (not including rim joists etc.), may explain why I'm hesitating going that route.

    • User
      hace 7 años
      Última modificación: hace 7 años

      Its not usually necessary to use long span joists or floor trusses over a crawlspace since intermediate supports can be installed and ducts can be below the joists. For a basement the spans would depend on how you planned to use the space. There are too many possibilities to cover in one response.

      The requirement for fire protection under first floor joists is intended to provide greater safety for firefighters; you and your family should be out of your house long before the first floor collapses. There are also exceptions to the I-Joist protection rule although they vary by jurisdiction. Some common exceptions are homes with an automatic sprinkler system or floors over a crawl
      space not intended for storage or fuel-fired
      appliances. I would never use a crawl space for either of those purposes. I-Joists can also be protected in the factory with an intumescent coating instead of a field installed layer of drywall.

      Pinebaron agradeció a User
    • BT
      hace 7 años

      My jurisdiction allow mixing, you can have floor trusses in the bathroom and I joist or dimensional lumber in the adjacent bedroom.


      To be perfectly honest, it is a pretty difficult decision, dimensional lumber 2x12x16 Grade I machine sorted ~$20. 2x10x16 much less. I do not know personally if I would put 10k or more into premium joists - or invest into 2+ family vacations and use dimensional and ensure that subfloors properly attached. Full foam on exterior will be a fraction of premium over these trusses.



      Pinebaron agradeció a BT
    • Pinebaron
      Autor original
      hace 7 años
      Última modificación: hace 7 años

      JDS, joist spans will be 15' over 4x10 beams, which is perfect for 2x12 I-joists since these can span almost 20' however be extremely sturdy at 15'. Also confirmed today that we won't need additional fire protection due to automatic sprinkler system, one less thing to worry


      about.

    • Pinebaron
      Autor original
      hace 7 años
      Última modificación: hace 7 años

      Brian, I like how you think but here in PNW with high moisture, the thought of dealing with lumber swelling, especially in a huge unconditioned crawl space is scary. Also discovered all homes in our small development use I-joists.

    • worthy
      hace 7 años
      Última modificación: hace 7 años

      For now, I'm sticking to dimensional lumber with the occasional speced Parallam beam.

      As noted above, over a basement or crawl why bother? Besides, with a little planning at the design stage, in every finished basement I've built, the steel posts have been hidden in closets and walls.

      Nailing, gluing and screwing subfloors to joists takes care of the squeaking problem. But with true carpenters checking for crowns becoming scarcer, manufactured joists can save the day.

    • BT
      hace 7 años

      >Brian, I like how you think but here in PNW with high moisture

      Not sure, in the high moisture - I would most likely to select PT JOISTS.

    • Pinebaron
      Autor original
      hace 7 años

      Only plates in contact with piers will be PT.

    • mushcreek
      hace 7 años

      One of the reasons I went with I-joists was due to the poor quality of framing lumber available. When I built my barn, it was a real battle trying to build a straight wall or ceiling. That's why I used manufactured floor joists, and steel framing for interior walls.

    • User
      hace 7 años

      Do you mean a 2 1/16 x 11 7/8 I-joist? 2x12 S-P-F #2 lumber would also be "very sturdy" for a 15' span.

      I couldn't understand your foundation plan; what are all those little squares?

      Are you designing the structure yourself? It sounds like you may be over structuring it.

      The crawl space should be conditioned.

    • Pinebaron
      Autor original
      hace 7 años

      Yes 2 1/2 x 11 7/8 I-Joists. The little squares are concrete piers spaced 6' apart across and 15' apart down, lots of squares but it's a large footprint. 4x10 beams will span left to right whilst 30' I-Joists will span top to bottom. I entirely architected the home myself whilst engineering was done by a local firm. Here it is rare though not unusual to see conditioned crawl spaces. I may consider a rat slab in which case it could easily be converted to a conditioned crawl space.

    • User
      hace 7 años
      Última modificación: hace 7 años

      Why would the I-joists need to be continuous over two spans? Why would you need a 4x10 beam for a 6 ft span? Your framing looks like something I would expect to see in a factory or warehouse. What loading would require such a floor structure?

    • bry911
      hace 7 años

      Fixed - Now you have have 12' spans - use whatever you want.

    • Pinebaron
      Autor original
      hace 7 años
      Última modificación: hace 7 años

      Hi JDS, Foundation is a Post & Pier foundation is for the home raised at least 4' or more off grade, built on sandy soil and then some clay. In addition the decent crawl space will permit easy maintenance of plumbing, ducts, underfloor insulation etc. Though I don't intend to use the space for storage, building a wine cellar below kitchen with a trap door access, did cross my mind. My intial goal was to build a walkout basement on grade, however backed away from the idea due to a high water table, height and other code and engineering considerations. The foundation plan is what has been approved on my building permit.

      Post and Beam detail below; it's not just 4x10's rather a combination of 4x6 and another 4x10 above. 6' spacing, though may seem extreme, is not unusual for large crawl space raised structure and also 6' spacing will eliminate sagging effects and ensure integrity of foundation floors; the foundation area (not including garage slabs etc.) is 85'x62'.

      I-Joist size: I believe he may be using 30' but its up to the builder; I'm waiting to hear from the builder.

      bry211: Beam direction will be across and joist structure will be down permitting easier plumbing, ducting and other utilities etc. hence I-Joists will have 15' longitudinal spans.

    • PRO
      Virgil Carter Fine Art
      hace 7 años

      I know this is pointing out the obvious, but you'd save money with an engineered slab on grade. I always hated putting money into things which never show! :-)

      PS: Yes, of course this requires a somewhat different strategy for utilities and HVAC, but money back in your pocket is always a good thing.

    • Pinebaron
      Autor original
      hace 7 años

      Virgil, I doubt it. A slab will not work for my project in damp PNW. As stated previously, it would have been different if I was building a basement, my original desire. A 5300 sq ft floating slab elevated to four or five feet and not including 3000 sq ft of attached garages and shop on slab makes no sense and will not save me money. A high/raised crawl space is the next best thing to a basement. Great insulation, easy access to HVAC, utilities, plumbing etc.

      Because floors are off the ground, routing wiring for electrical,
      telephone, television and Internet service is easy and inexpensive. Air conditioning ducts will be installed under the floor, directing air more efficiently
      throughout the living area. Even if we change our mind, as can happen
      during construction, we decide to move the kitchen sink or alter the
      size or plumbing of any of 8 bathrooms, it's a piece of cake. Try that with a slab!


    • PRO
      Virgil Carter Fine Art
      hace 7 años
      Última modificación: hace 7 años

      You seem very convinced of and committed to a crawl space foundation. "A high/raised crawl space is the next best thing to a basement". Some folks will certainly agree with you, but many will strongly disagree.

      Of course, the controversy between slab on grade and crawl space construction is one of long standing.

      More recent research, however, points to many pros and cons between sealed crawl space construction and vented/open crawl space construction. Hope you have the data for both types of crawl space well in mind and know which approach you will take.

      If you are building in the Pacific Northwest and are in regional location, chances are you are in an active seismic zone. If so, and with a structure the size of yours it's likely you will need both perimeter and interior engineered reinforced concrete footings and stem walls sufficient to receive and resist the various lateral loads which the structure will endure during a seismic event. Shear walls with proper tie downs to the concrete stem walls will be required throughout and the entire roof will likely need to be designed as a diaphragm and tied into the shear walls.

      And if you decide "to move the kitchen sink or alter the size or plumbing of any of 8 bathrooms" during or after completion of construction you aren't saving money, you are spending more money.

      The time for all of these decisions is before bidding and start of construction! :-)

    • PRO
      Baratto Brothers Construction
      hace 7 años

      I would highly recommend open web floor trusses, and we space all of ours at 20". All ductwork, electrical, gas lines, etc can run through them so you do not have to frame soffits in on the lower level. We also use 3/4" tongue and groove plywood for our subfloors. The plywood is BOTH glued and screwed to prevent and squeaks.

      Pinebaron agradeció a Baratto Brothers Construction
    • Pinebaron
      Autor original
      hace 7 años

      Virgil, Yes for the reasons I mentioned. We have permits. We are in an active seismic zone and engineering already took that into account else we would not have received a permit. There is nothing outstanding and we are ready to commence construction. And if I decide t change something, it is easier and possible as opposed to fixing something embedded in solid concrete which would be a nightmare.

      Baratto, It would still be a pier and post crawl space. I'd love nothing more than use open web floor trusses.




    • User
      hace 7 años
      Última modificación: hace 7 años

      Over engineered structures can still get permits too. But they might as well be using dollar bills as dimensional lumber. This is why so many self designed projects come in grossly over budget. Too many amateurs think that if a little is good, more must be better.

      You would do far better to consult a professional and put the money that you save into open web trusses. Or a slab. Nothing at all wrong with a slab. You'd have lots of $$ left over too.

    • Pinebaron
      Autor original
      hace 7 años

      I used a professional for engineering. Out of the question; I would never build a home on a slab for all the reasons stated in previous posts, my only regret is not having a full basement foundation which I was initially prepared to build on grade but the final structure would not pass maximum height code.

    • PRO
      Virgil Carter Fine Art
      hace 7 años
      Última modificación: hace 7 años

      I know it's pointless to continue this conversation, but since you can't build the basement you wanted, you're going to go ahead and frame the first floor as if there was a basement, and just call it a crawl space? A slab on grade would save a substantial amount of money, and there are many other proven ways to deal with all of the other issues (which is one of the reasons slab on grade construction is as popular as it is).

      Good luck going your way!

    • Pinebaron
      Autor original
      hace 7 años
      Última modificación: hace 7 años

      It is absolutely pointless and your assumptions of what I was thinking are baseless as to why I chose to go for crawl space when basement was not an option, because a crawl space offers everything a basement offers but no additional space. I made space by extending the garages and shop to 3000sq ft, though a basement would have offered more than double that, so that is taken care of. I don't need to explain any more to slab lovers, it is not happening.

      I did not ask if I should choose between a slab or other foundation but asked for readers (assuming they built something that used them) choice of floor joists/material/type and reasoning for your decision, not choice of foundation. So let's stick to answering that question and not sell me a solution I did not ask for; in fact my question has been eloquently answered by a few on this thread and I have thanked them. Number one choice is obviously open web floor trusses followed by I-Joists followed by nothing and yes use 3/4 tongue and groove plywood and I've planned for that already.

      Thank You All

    • PRO
      Springtime Builders
      hace 7 años
      Última modificación: hace 7 años

      I agree! All commercial construction uses slabs, changing waste plumbing or other mechanicals is not a big deal for professionals. Same for earthwork of well planned foundations based on site conditions. Vented crawlspaces are on their way out for residential construction, make cost comparisons to unvented crawl.

      It's a free advice forum and you get what you pay for, which has been very valuable from everyone so far. Other readers are influenced by discussion here and future buyers of your home may prefer the advice some are trying to share.

      Pinebaron agradeció a Springtime Builders
    • Pinebaron
      Autor original
      hace 7 años
      Última modificación: hace 7 años

      Andy and Springtime Builders: You are both absolutely right and thanks for reminding me; I don't often choose most economical solutions, but ones that best serve my needs. Thank You.

    • worthy
      hace 7 años
      Última modificación: hace 7 años

      my only regret is not having a full basement foundation which I was initially prepared to build on grade

      Just curious, if a "full basement foundation" is built on grade, how is it a foundation rather than a first floor/ground floor?

      Number one choice is obviously open web floor trusses followed by I-Joists followed by nothing

      As the spokesman for "nothing", I'm sticking to what the overwhelming number of builders in my benighted backwater use: dimensional lumber with I-Beams limited to exceptionally long spans.

      But in an unconditioned crawl in a damp climate, engineered lumber, which resists twisting from dampness better than dimensional, may be the more appropriate choice for any span.

      Incidentally, Building America remains strong on conditioned crawls everywhere while some experts insist the Pacific Northwest is different: http://www.energy.wsu.edu/documents/AHT_Conditioned%20crawl%20spaces%5B1%5D.pdf

    • Pinebaron
      Autor original
      hace 7 años

      " Just curious, if a "full basement foundation" is built on grade, how is it a foundation rather than a first floor/ground floor?"

      If you can dream it, it can done. My intention was to artificially raise grade, by grading up to the 13' higher second floor, making the second floor appear as a first floor, which would no doubt require thousands of yard of dirt but I had access to free dirt; the size of the lot made it feasible. Visually it would appear as a raised home or on a hill, with a driveway leading up; not an uncommon sight when I lived in NJ. I was keen on a full basement to accommodate a couple of bowling lanes, something I may vaguely consider building as a separate inconspicuous structure somewhere on the lot, however there are other important things at hand now, like completing interior design and renderings; these are close to getting finished, just need to complete designing builtins around the fireplace then the walkin pantry to DW's specific requirements.

    • Andy
      hace 7 años
      Última modificación: hace 7 años

      I propose the following addition to the unofficial etiquette of this forum:

      If you are able to afford a bowling alley in your basement, and are seriously considering one, that needs to be mentioned in any and all questions for help. It will make a huge difference to the experts...once they understand that money and efficiency isn't a concern, there's a much higher probability they will take your questions at face value. Why try to convince somebody what the most efficient way to do something is, when they have bowling alley money/mentality?

      You seem like a cool guy PineBaron, I read your other post on redundant mechanical/electrical systems. So don't take this as a passive aggressive knock, it's not. If I had money for a bowling alley I'd be doing all sorts of suboptimal things just because that's what I want, also.

    • worthy
      hace 7 años
      Última modificación: hace 7 años

      A home one-laner runs as low as $81,900.

      Couldn't be worse than the in-ground pool I built at one house to quell our kids' whining; they used it for two weeks, then back to the electronics. For other families, the pool becomes the centre of summer living.

    • Pinebaron
      Autor original
      hace 7 años

      Andy, I still try and take smart decisions though somewhere between practicality and excess, just how much I can get away with between what is a need or a want and how to convince my DW who can easily put her foot down, then it's not happening; the art is catching her at her most vulnerable moments.


    • Pinebaron
      Autor original
      hace 7 años

      worthy: Sounds crazy but I usually play 40-60 games non-stop Fridays and yes my shoulder is still attached; I use 15lb bowling balls

    • Ron Natalie
      hace 7 años

      It seems to be a regional thing. Up where I used to be (DC Area), I-joists are common. Down here in NC it seems to be trusses. I'm not convinced either is superior. We've got the trusses and it seems easier to run stuff through (no cutting of the webbing).

      As for bowling, we poured gypcrete subfloors (they hold the radiant heat tubing).


    • Pinebaron
      Autor original
      hace 7 años

      Ron, Though all joists will be along length of the house, there is bound to be plumbing/drains that will go across and will need to ride just below the joists in 10" space between beams making it a somewhat an easier install using the beam sides for support clamps.

      If using radiant heat tubing I prefer warmboard, ecowarm or similar.

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