Presently working with an architect for plans to add a complete 2nd floor to my 1927 Bungalow home (25′ x 40′).
He’s introduced many good ideas, but I have some concern about “I” Joists spanning the entire width of my home (25′) and how much work has to be done to improve header strength above present windows and doors. It was my hope I could get away with minimal damage to the current living space (aside from droping a new stairwell and installing new windows and doors). Can the Rim Joist be used as a Header?
I’ve also expressed my desire to expand current living space, down the road, and if there was a way of designing in – additional bracing etc… to allow for removal of present carrying wall – without adding another exposed beam (and support columns). His initial answer was that the new “I” Joists may be able to support the present ceiling joists, using metal brackets or straps. I’ve done a little research and found I would need a 16″ “I” joist (16″ OC) which would have the maximum span of 26.’ I’m concerned how much more can be asked of these “I” joists in supporting the weight of the first floor ceilings when the carrying wall is eliminated.
Any suggestions or comments are appreciated. Merry Christmas.
Replies
I'm just a builder, not an engineer, but can you afford to set 3 1/2" glulams or other engineered headers/beams on top of the existing walls?
This would support the new floor joist over any openings you put in in the future.
You can look at this Floor Vibration thread to get ideas about stiffening those long joists.
SamT
WMA,
As SamT mentioned you can put 3-1/2 x whatever size I-joist your using gluelam or engineered lumber above the existing headers, we do it all the time. There flush headers. This eliminates ripping out the existing headers on the first floor which is a lot of work and a waste of time. You will then hand the I-joists with top mount hangers This is good on the exterior walls.
Presently working with an architect for plans to add a complete 2nd floor to my 1927 Bungalow home (25' x 40').
I've also expressed my desire to expand current living space, down the road, and if there was a way of designing in - additional bracing etc... to allow for removal of present carrying wall - without adding another exposed beam (and support columns).
I've done a little research and found I would need a 16" "I" joist (16" OC) which would have the maximum span of 26.'
Your Architect should be the one to tell you what size I-joist you should be using and when he comes up with the size then it doesn't matter what wall you take down underneath because these I-joists can clear span 25". I framed a garage last year with 25' clear span with finish rooms above and the I-joists were 3-1/2"x 14" @ 12" o.c.
Now you have another issue that you mentioned as to nailing the old ceiling joists to the new I-joists and then removing walls underneath later. Now do you screw and glue them with straps, do they add any extra weight to the new I-joists, this is something that has to be figured in from your Architect or Engineer.
As far as stiffening I-joists I've never seen it done before nor have I ever done it before or heard of it done before until it was brought up here. If these I-joists are calculated to clear span x amount of feet and had to be stiffened some how then all the Architects, Engineers and I-joist manufactures would put them on every blueprint.
Joe Carola
In support of what Sam said, you can use LVLs or similar engineered lumber as headers by placing them inside the rim board that will be the edge of your 2nd story floor system.
Re your 3rd paragraph, I'm not entirely sure of what you are getting at, but will say, when you are looking at span charts, don't plan on approaching the maximum rated span for a particular size member. Others here may be more qualified to give you exact numbers, but for a acceptably performing floor, it may be better to stay around 75% or 80% of the max span. I think you will find that I-joists with wider flanges will be able to comfortably span the distance you are talking about.
I like I joists and yes, they can be engineered by your archy to handle it all. I like an LVL rim joist for spreading that load.
You might also aask himn to look into open web floor joists. They might be less expensive and span it with a better load rating. They have the advantage also, of making it easier to run electrical and mechanicals
Excellence is its own reward!
No way would I go for 16" deep I-joists spanning that far, if it was up to me.
I'm the one who wrote the Floor vibration thread that SamT referred you to. Based on the experiences I relate in that thread, I'm VERY conservative on floor design. Once you put up those I-joists, it's extraordinarilly difficult to stiffen them up any. It's a whole lot easier to do it right the first time.
I'd suggest a minimum of 18" deep for your floor system regardless of the spacing. Going with 20" deep would probably result in a better floor.
Once you get into stuff that deep, the cost difference between wood webbed floor trusses and I-joists narrows quite a bit. But pricing also varies a lot by region. It might be worth checking around and seeing how the prices run in your area.
Sometimes I wish life had subtitles.
The gents have made good points. I don't like the span and Boss' post answers the why and what fer. Ask your architect to show you a finished space with that joist size, spacing, and span and go for a walk on it. Don't be shy next to the curio cabinet/china hutch. It's only "charm" in an old house and even then it's not.
...that's not a mistake, it's rustic