I’m looking to add on a 30×30 addition to my house with a full basement. All I will have in the basement will be a utility room and bathroom. Outside of those rooms I’d like to not have any support beams to allow me to have an open basement. What do you recommend to accomplish this without having any floor bounce on the main level floor above it? The basement walls will be 8″ poured concrete and only the main level above the basement.
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Put the bathroom in the middle
What do your plans show?
This is not something that should be constructed without permits, a hired professional, plans and code official oversight.
The arrangement of your ultility room will be essential to breaking the span your engineered beam so that you can maximize the open space.
You're going to need trusses or steel beams. Requires actual design.
My plan was to have the stairs, bathroom and utility room on one wall which will leave me with an open area for our family to watch tv, play pool, etc.
I'm working with a contractor that I'm not familiar who will do the work. I just wanted to check with others to see their recommendations to verify my guy has a plan that will work and is safe. BTW I live in a rural area out in the country where we do not have permits for remodels/additions.
What area do you live and what is your guy's plan?
Southern Iowa. He is bringing the plans over next week to discuss.
Here's betting that the plans will include some posts.
So, are you saying that your southern Iowa town or county doesn't require building permits for structural work or that you just haven't chosen to obtain one for your project? Also, it seems a little premature (not to mention odd) to verify plans with complete strangers when you have yet to discuss them with your own builder. There's nothing yet to verify.
Span
If you can live with a span less than 23' you should be able to do it conventionally with sawn lumber. You can get that with 2x12s at 12 oc.
Physical Laws Don't Need Inspectors to be Enforced
SO WHAT if there are no permits or inspections required? The job won't perform unless it's done right, no matter. It's just that you don't have a bureaucrat to ask, who might catch an error. Sounds like you lose there.
Once spans get over 20 ft, simple boards won't do. Nor should they - just try finding a perfect board that long! No, you're in the area of other solutions. TJI's (wood 'I-Beams"), steel, etc. Most common will be an arrangement that uses three steel beams - one for each side, and one down the middle. The house will be built atop these, using conventional lumber to span the 15-ft. between the main beams.
No matter what you do -even if you pour concrete atop solid rock - there is some 'floor bounce.' What uoi mean is you want very little noticeable bounce. That's what the various span tables are for - they, and the codes, have agreed on how much bounce is acceptable.
Don't worry too much about how "thick" the floor will be. The only practical result is that the basement will have to be dug deeper. You'll want the 'extra' joist space anyway, for running your pipes and ducts.
bounce this
renosteinke wrote:
What uoi mean is you want very little noticeable bounce. That's what the various span tables are for - they, and the codes, have agreed on how much bounce is acceptable.
Actually, span tables and building codes address acceptable deflection. "Bounce" is a nebulous term as applied to building structure and I have yet to find it mentioned in the code book.
Deflection in long spans is always a big issue.
Deflection (bounce) is limited by code for each span to a formula where overall deflection in a span cannot exceed L/360 where L is the length of the span in inches. Say you had three spans of 10' (120"). By code, each span could deflect as much as 120/360 or .333". Say you had one span of 30' (360"). By code, this span could have a maximum deflection of 360/360, or 1". Even though the same criteria is used for both spans, the longer span will "feel bouncier" because the floor is allowed to move more.
This is why trusjoist and many of the "i" type joist manufacturers increase their deflection criteria to L/480 to help limit deflection.
After 40 years as an architect, I would advise you to install open web wood floor joists and get permission from your contractor to speak directly with the truss manufacturer about your concerns. They will help to explain what I described above. The trusses will be taller (18" plus), but will deflect less; will allow for better access to all the other trades (electrical, plumbing, hvac), they will be true, light weight for the span and quick to install. I would definitely not use standard lumber (i.e. 2x12's) on long spans- I guarantee you will not be happy the results. Just my opinion.
may want to revisit your logic
Deflection ,wmheinz, does not have a symbiotic relationship to the term "bounce". "Bounce" is a term that infers a notion of "rebound" and is not limited by code. If you think it is, then I challenge you to prove it. In fact, I'd say it confuses the unique nature of each term to use them interchangabley and shows a certain level of structural ignorance. Bounce is precisely why engineered joists regularly address deflection beyond code dictates. Actually, you fail to recognize the significance of these two terms being non-interchangable within your own example.
Structurally speaking, you can't have bounce without deflection. Yet you can have deflection without bounce; particularly in the case of excessive and persistant dead loads. To prove this point, one can simply imagine a a floor system loaded beyond its code dictated level of acceptable deflection and quantifiably measuring it against a lenght of jet line. One can easily measure this deflection while not detecting the least bit of bounce.
I'm so glad you were available to help the OP with his issue. I'm sure he was totally confused at my explanation. Of course you are right ( that's what you want to hear, right?) - I don't know what we would do without your contribution.
doncha goes atellen' him dat 'e iz rite when 'e aint !
ya knows ya gonna gives him a big hed ?
an here ah wnet and agreed wit him dat udder day! mahbe ah wu;z drahk ?
...deflection without bounce... false for most building materials, true only if E = 0
bounce -- aka rebound per fist dictionary definition
so, yer statemeant : False... perchance what you are thinking is that the "bounce' when the damping factor is over 1.0 the displacemtnt value of 'bounce' only has a positive value, no negative value. Anytine a load is added, then reduced, the deflection 'bounces' back, if one wants to use the work 'bounce'.
If ya wants ta get technical, use all the right terminology, e.g deflection, 'response' or 'rebound' vs. 'bounce', etc...
Imma guessing yas might understands the process <G> is that if one considers a lump of soft clay that has a modulus of eleasticity of zero, there is only deflection and no bounce - drop a lump of clay on the floor and it jes' goes splat, no return of the deflection at all ?
ah knews weda be gettag back ta disagrein' <G>
Dead loads.
Since a dead load is by definition the weight of the materials in a building, excessive dead loads would imply that the building won't support its own weight. That dead loads are persistent goes with out saying since the building must always carry its own weight.
Actually, in a morgue dead loads can come and go.
In a mogue.....
dead bodies are a live load. Zombies?
Excessive dead loads can also imply that material deflect beyond acceptable limits. That doesn't always mean failure.
Possible examples of excessive dead loads:
1. Kitchen remodels with newly installed large, granite topped island features that exceed original floor dead load design specification. Most of the time this results in excessive deflection, but not failure. And folks wonder why their grout and ceramic tile starts working it's way loose.
2. Hot tubs on decks that exceed original dead load (and LL) design specifications. Dry, they weigh very little. However, load it up with water (LL) and you change the ball game. Usually that ball game is played out steadily over a series of months, if not years. I'd call that a LL morphing into a persistent (and many times excessive) dead load. This condition is so common that many plan reviewers now use a rubber stamp prohibiting the use of hot tubs if not designed into the deck structure at the time of permit.
3. Retrofit bookcases that exceed original LL desing specifications. Books are generally not considered part of the structure, yet can remain in place for long periods of time (persistent) and essentially constituting a dead load that may exceed original dead load design specification.
You can clear span 30' with wood webbed floor trusses 24" deep. Just make sure you put strongbacks on per the recommendations of the manufacturer.
Span issue
If budget allows, Spancrete.
Spend a couple hundred bucks and get an engineer to design and stamp a plan for you. Then you will know it is done right and you won't have problems down the road.
Huh?
gfretwell wrote:
Spend a couple hundred bucks and get an engineer to design and stamp a plan for you. Then you will know it is done right and you won't have problems down the road.
Apparently said by a man who has never seen Engineering Disasters Vol 1-????. An engineer, no matter how much some people want to claim to the contrary, is no assurance that anything will be right or good. They are a CYA for a builder and person to sue when something does go wrong however.
Its better advice than you offer.