Horizonal load beams

I would most likely go with I beams. I have not run through the calculations to decide what size beams you would need for your application. (and am also reluctant to do so.)

I think you would be very wise to obtain the assistance of a qualified engineer to help with the proper planning of your structure.

Thanks for your reply. As always cost is also a factor which include materials available for use at a discounted price. When I talk to a quilified engineer I am sure he could list my alternate materials of usage. It is possible to buy "Z" beams at a discount which also changes the variable.

I'm a mechanical engineer used to calculate profiles and mechanical loads, that's why I'm writing something here although I'm not a civil engineer. Your structure seem to be simple, but I agree with the colleague that suggests you to talk to a qualified engineer in your place to do the work for you. Because we may make some "back-of-the-envelope" calculation and indicate a profile, but from here, we really dont know the foundation requirements for such structure in a flooding area just to start - this would be my main concern. As you stated yourself, you may loose a lot of material and work if someone make calculations and indicate a required profile and joints and all of those things including a generous safety factor - which is the way engineers do when they dont know exactly what to expect.

And, by the way, I beams are always the preferred choice for beams. For columns, H or two C profiles making a square would do great.

Do not forget to ask your engineer about the better alternative for joining the beams and columns, based on the material and building conditions you have.

Thanks for your reply. Now I do know for sure that "I" beams are 1st choice for horizonal loads, I was hoping that "Z" beams would be a good choice because of cost and availabity. For columns "H" beams sound great. Putting two "C"s together would involve a little more work but cost of material will also be considered. You have my interest peaked when you mention "the better alternative for joining beams and columns. Will you go into more detail? I will talk to an engineer and I am sure he will know what you are talking about.

Retain a structural engineer to work out the details, prepare drawings and take responsibility for his design. To act on advice received on a forum such as this would be absolute madness. Do the right thing!

As always things are not as simple as they seem. Thanks for the advice.

You really need a structural engineer to design this for you. Since this structure is in a flood plain, two additional factors must be considered. First, the load of the moving water on the structure. The load of the moving water is a lot more than that of wind. Second, the scour around the foundation from the moving water must be considered. This would probably take a bridge engineer to examine the scouring problem.

Or, as most people do where there isn't any code requirements, look around at similar structures and build yours likewise. Of course, when you are about to go to sleep in it, you might think of how much money you saved by not hiring an engineer.

Thanks for your reply. If/when the water gets this high it would be spread enough that there would not be much current, however any current would excert great load and will have to be considered. This building will not be on a river bank, just low lying area which is possible to be flooded based on history. Footers will be 36" below grade, 8" thick and 24" wide. Poured foundation will be a minimun of 3' high on the footer, and a minimum of 8" wide. Would not think scouring would be a problem but will bring these questions to the attention of an engineer.

First hire a Civil Engineer licensed to practice in your State who is familiar with structural design, regulations and locations you are considering. There is no need to go directly to a structural engineer, unless there are special considerations or code requirements in the local jurisdiction, or the Civil indicates you need a Structural Engineer. You can have the Civil retain the Geotech and Structural engineers as needed. A Structural Engineer may not be required at all, and a Geotech may be required because of the flood plain soils, foundation scour, Seismic zone, local codes, and other soils related factors. The Civil should know what will be required or be able to find out quickly.

have you think about bracing system.each squre A to be interconected. Do you have idea of that: such as cross (X) type or portal type. if you comment on above i wiil send you column,beam size

Yes each squared "A" will have to be interconnected. Depends on type of horizonal girts used as to how much bracing they will accomplish and what additional bracing will be required. Also the Structural insulated panels when properly attached will provide aditional diaganal bracing although I would want to rely on them for extra bracing as a additional safety factor not part of the required minimum bracing. Thanks for your reply. Additional questions for an engineer. Nothing is as simple as it seems.

Good morning Captain Skruffy. Some very good recommendations were provided, especially by bhrescobar and PAPADOC. You'd want to really have the foundation designed to meet any debilitating forces due to water soaked earth under or near it. It would be worth it to have a structural engineer registered in Ohio take a look at your intended designs. For anyone on a forum to make a design recommendation he would have to make so many assumptions that they would render the usefullness suspect.

However, I understand your intentions are to have vertical members from each end of the roof members, so a cross-section would still maintain a 20' x 20' box, with the angled outriggers set ~7' from the base. I assume you do not want any intermediate columns under the roof or floor. I assume you mean to have the floor and roof extend out over the boat storage a cantilevered distance of 10', making the total length 80'; and that there will be no outriggers on either cantilever. I assume your snow load would equate to ~30#/sf, and that since the roof is flat, an additional snow drift snow load of 15#/sf would not be unreasonable. I assume that you will leave summer's ice boxes, shades, book cases, etc., for an additional 10#/sf. This gives a design Live Load of 55#/sf.

I assume you will want your roof rafters/floor joists to be 16" OC, running perpendicular to the steel beams. Since the beams could be as far apart as 10', this will be the tributary distance used to approximate the beam. I assume the Dead Load of the roof will be 20#/sf or less. I assume the ends of the beam will be fixed, so as to bear some degree of moment.

Based on the above, for the roof beam, I get a reaction at the end of each beam of 7810#, and a moment of 24,900ft#. This demands a Section Modulus of at least 9 in^3, which would lead a person to specify a W10x11.5 steel I-beam, with 50ksi, which has an S of 10.5 in^3. If the IBC is used to determine maximum deflection, L/360 should be used for the LL, and L/240 for the TL. Using these figures, a A992-50 W8x31 would be your choice.

This is only examining one member. You can see the numerous assumptions and details that're involved. And you've still got the wind loads, columns, outriggers, cantilevers, foundations, and connection details to look at. If you could find an experienced engineer to help you look at some of these items it would be worth it in the long run.

Thank you for your reply. I was not planning on outriggers but things are not as simple as they appear. Outriggers may figure in as a must in this structure. Yes you are correct that the total length will be 80' long. Additional snow drift load on a flat roof will have to be taken into consideration. As to the plans of rafters/floor joists, was going to use the Structural Insulated Panels run lengthwise with the structure for the floor as well as the roof, which would be attached directly to the horizonal support beams for the floor and roof. More questions to ask an engineer.

Good morning Captain Skruffy. In your original note, when you described your frame assembly as resembling a truncated "A", I took this to mean you were planning on having outer columns installed at an angle. I called these "outriggers". In your note above, you say "I was not planning on outriggers". This is confusing. Is it going to be a truncated A or not?

The plan was to have the supporting frame when viewed lengthwise would look like a squared capital letter A. What I was trying to describe was vertical posts with the floor and roof supporting beams at 90 degrees to the straight vertical.

Since talking to an engineer he has suggested the I rotate the supporting frame 90 degrees and span 60' as the width and 20' as the length. Which would be off the shelf plans for a building with a 60' span and length in increments of 20'.

This method would have a break in the middle of the roof which it would have had anyway, 60' long building, 40' long panels X 2= 80' roof panels will cover the building with 10' cantilivered overhang on each end. With 1/2 12 roof pitch the center would raise 15" from the end walls. The overhang would lower by 5" on the 10'. Which will be acceptable. Sorry for the confusion. Thanks for the reply. Stay in touch, Karl

You must be planning on hanging this building from a sky hook, as I don't see much information about the foundation, "you know", you know the place where all building construction begins.

Before you determine what the structual portion of a building will be constructed of (material) you must know just what you expect to support it with. You mentioned putting this building on the edge of a river and in a flood plain.

I am a retired general contractor. I read between the lines of your post, and this is what I see.

Flood Plain, an area where there has likely been flooding and a blend of organic materials not suitable for foundations for building construction may be underground.

Rivers edge, high water table, maybe muck and other spongy soil conditions exist below ground.

Water, Many moving bodies of water are where they are because the surrounding area is rocky, and consealed by sediments containing both organic matter and sand.

Post and Beam Construction, Does not matter whether you are building with steel, wood or concrete posts, they will all need to be placed deeply enough into the ground to support the structure, and that can be really difficult to accomplish if you find rock, or non bearing soil conditions below the surface.

Before you go any further with your dream vacation home you need to have test borings made where you think you are going to place such posts, no matter what they consist of.

TMF

Well as they say, don't assume anything. I did not mention foundation as I assumed everyone would know it was approprate for the structure. Ground has been farm land for years with enough slope that drainage is not a problem. Wooden fence posts have been set in concrete and soil is solid. Bottom of footer will be 36" below grade, 8" thick and 24" wide witha poured wall a minimum of 3' high and 8" thick/wide.

There was a house on this property years ago with only the foundation and concrete walks remaining after house was consumed by fire.

Thanks for your reply. More questions for an engineer.

This is a very innovative structure you are specifying.

You also state that you are deliberately ignoring the advice of the professional designers and contractors for this type of building, specifically regarding the use of the roof type and beams they recommend.

Additionally, you are specifying SIPS which have wonderful properties, except when wet.

Go with the pitched roof. Go with the tapered beams. If you want to use the SIPS for the upper story, living area, go ahead. For the shed do not use anything stronger than sheet metal panels. These will somewhat withstand the wet and or flooding and fail if truly inundated which is desirable as the upper story MAY thus be preserved on pilings as it were.

In the lower level some non-panel structural diagonal cross bracing will be necessary or at least highly recommended.

It is clear from what you state that you have consulted several professionals and ignored their advice. Now you come to this forum for professional advice from perfect strangers on technical matters that could involve us in a legal liability for a structural collapse with attendant fatalities.

Why not put up a shed which is both legal and sensible and drive a camper or two in for the summers which is also legal and sensible. What you are planning to do is not recommended by FEMA, the local contractors, nor anyone in this forum for very good reason. It is an almost unbelievably bad plan. But, as you say there are no building codes available to actually STOP you.

VERY sincerely,

Mr. Gee

Mr. Gee,

Thanks for your comments on the very inovative structure.

I am not deliberately ignoring the advice of professional desiginers. They design and build from their style of most common plans which do not include a flat roof. Could relate this to going to a car dealer to buy an industrial fork lift. Just because they don't sell it does not mean that is does not exist. There are quite a few flat roof building which are built from lumber, properly desigined steel should/could be stronger.

The steel building contractors which I have talked to are building buildings greater than four times the size of my plans. Mostly they do not want to mess with one odd building that is too small for them to make any money. Again compare to a truck company and asking them for an economy car, it doesn't fit into their plans.

The SIP's are to be of closed cell design, but you did bring up a great idea that as this is basicaly a house on stilts that it would be a good idea to have a weak point such as the sheetmetal panels over the lower garage area providing a breakaway for safety in the event of floodwaters.

Yes, diagonal cross bracing will be a required must which was not mentioned in my original question.

As they say in life "you get what you pay for". As things are never as simple as they seem, many additional questions have been brought to my attention in this forum making my list of questions for a paid engineer even greater.

Yes I have consulted with several professionals, I would not say I have ignored there advice. They deal with off the shelf buildings and do not want to bother with this onetime odd job. If everyone in history listened to what they were told we still would not have the lightbulb, airplane and spacetravel to name a few.

I am sure if there is a will there is a way, cost may be MUCH greater than what I am willing to pay, but will discuss this with a paid professional engineer of the metal structure building field.

Do not want to build anything which is unsafe or will wash away in flood waters.

Property has been surveyed for FEMA with the basic flood elevation survey. FEMA has never said it is not recommended. They say to have living quarters in this spot on my land the floor of the living area will have to be 12' above the ground either on posts of steel or concrete.

No contractor or anyone on this forum has seen the land, river, or even asked for the "lay of the land." Just because there are not building codes doesn't make building of any unsuitable dwelling proper. If I didn't care as to safety I would have just build something and seen what happened. Ask questions first, build later. As this building will be insured I am sure at some point in time the insurance company will require the approval of a professional design. Things are never as simple as they seem. Many additional questions have been raised in this forum, which is a good thing. I am not sure that I would even want to go with the ideas of just one paid engineer with a design of this type in this area.

OK, it is clear you did listen to my comments and those of the other members. I like to innovate myself so I have a natural affinity for those who also like to do this.

Flat roofs are almost always used in conjunction with cement walls in industrial buildings.

In this situation they work fairly well because of the nature of the walls they are mated with.

Pitched roofs are preferred for structural member buildings because they shed the moisture of rain and snow better and the diagonal trusses stabilize the entire structure. The rafters in tension prevent the walls from spreading apart and the roof from bowing down.

A flat roof in an unheated structural member building would create point load bearing point problems in the supporting walls.

If over time there is bowing of the roof, settling of the building, or erosion of the sealing materials the possibility of leaking is significant. The unheated factor means that various points in the roof will likely be subjected to repeated freeze thaw conditions to which they would not normally be subjected.

On the other hand pitched roofs have been known to leak too.

Do you perceive the metal trusses of the flat roof as the benefit to your preferred approach or is there some other appeal?

As a final caution I would comment that building of the type you propose is not normally permitted in permit only areas due to the fire hazard concerns, so please spend a little extra time planning how each sleeping area or general area of the living space could be evacuated in the event of a fire.

Steel structural members are generally stronger than comparable wooden ones but are known to fail much faster than wood in a fire. The closed cell foam in the SIPS has a strong tendency to convert back into petroleum during a fire and burns as a hot, toxic sticky, flaming liquid which could make evacuation difficult or impossible. If the SIP can be constructed with a wood footing that may slow or prevent fire from entering the panels I would consider that a good thing.

In my area there are fairly large tracts of unzoned construction and several families live full time in above the shop structures of the type you are contemplating. Adding the flood plain consideration to your situation only slightly alters the equation. These individuals have saved some money and have a great deal of convenience in their living arrangements. Generally, they are quite happy and pooh pooh the critics. They are probably right. I am rather sorry I put myself in the critic camp. I hope you complete your project and enjoy the time you get to spend there.

Sincerely,

Mr. Gee

Mr. Gee,

You have given great thought about my project, I wish to thank you sincerely for this. Yes I did sort of take it that you wanted to pooh pooh my project from your wording in your first responce. So many people do not or can not think a project through from thoughts, to paper, to finished project because of engineering details. I have had quite a few projects with satisfactory results such as designing and building an engine driven hydraulic log splitter, which appears much more simple than it is . But I will admit that my merry-go-round project was a failure. Worked great when my daughter was quite young but as she got older (heavier) the spindle was from a small car and didn't have the strengh it needed without flexing. One example that using materials at hand (free) is not always the best choice. Didn't give it much thought about flat roof homes being of cement or block but the flat roof homes I have seen were indeed of block construction. I have given thought as to the weight of snow/ice/rain on th flat roof. My concern was as you stated, weight will cause saging, holding more water, saging further until breaking point such as rain on a tent roof, holding more and more until colapse. You raise another concern which I have considered, fire escape. I did not give it much thought about the closed cell foam being a concern as to toxic fumes during a fire. With a steel structure and steel on both sides of the foam the fire hazard should be somewhat less that wood construction, however anytime vehicles with batteries and gasoline are stored in a garage the potential for fire hazard is present. As to fire escape, the plan is to have an outside door about the middle of the structure with stairs to the ground and a sliding glass patio door on each end, one end would be a family/ living room and the other would be a bedroom. For a one time (hopefully never) a rope securely attached to an anchor point and thrown over the cantilever balcony from either end could be used as a means of escape. A fire ladder which is required on most three story buildings having no fire escape ladder may be a better choice. Not fire escape stairs but a rope or chain ladder securely attached is thrown over and climbed down. Both of these would require having the escape device ready to use much as having a fire extinguisher in a visible spot, ready for imediate use.

A major concern which I did not think about is that any current from the river would create such force as to destroy this project. Thought has now been given as to making the bottom 12' of this with panels of breakaway construction, sacrificing the walls to save the home.

I did talk to a civil engineer today and was told something else I did not consider. Rotate the structure of the building 90 degrees. Span the 60' as width and have the 20' as the length. Result would be the first 20' of a much larger building with a span of 60' resulting with an off the shelf building design. Would be going to a sloped roof with a pitch of 1/12 or 1/2 /12. Would acomplish having a cantilever roof, that would not look as if it were crooked (leaning), covering the cantilever balcony . Roof panels would have had a break in the middle anyway, now the break will be 15' or 30' high midspan depending on roof pitch. Gutters would only be needed on the two 20' ends not the entire parameter. Strength would be much greater with tapered structural beams. Floor joists would in a sense be supported by tensile from overhead load bearing tapered beams resulting in a fairly open (60') span which would make it easier to design the garage walls with the breakaway feature. He did explain that this construction would possibly need his help as to design the footers with anchor points which is a little more complicated than just vertical load bearing posts stuck into the ground. With this off the shelf building the strengh is also derived from the foundation holding the supporting structure so it will not spread. Concrete has great compressive strength but not tensile strengh, which everyone reading this already knows. The 60' span supporting beams will have to be anchored together with cable to keep them from spreading. I am sure the building manufacture will address this.

I will keep everyone posted as to the progress. To everyone who has taken the time to read and then respond I wish to thank you so very much. I am sure there will be additional comments with concerns which I may have overlooked, which would be very much appreciated. Thanks again for everyones support. Karl

Make a tree house! all the kids in the neighborhood will be full of envy