Grid Beam

[kyounge1956]

Yesterday I picked up a fascinating book at the library:
http://www.amazon.com/How-Build-Grid-Beam-Constructing/dp/0865716137

I have only skimmed it so far. Most of the text and photos relate
either to furniture or vehicles (including several solar-powered
ones) but there are also tantalizing mentions of small structures,
built with grid beam, using either the 2x2 steel sticks or user-
manufactured wooden ones made of 4x4. Some of these were temporary
(e.g. booths for trade shows) but at least one was lived in for a
number of years and another one inhabited during construction of
a larger permanent house.

To me, the idea of making a building frame this way has the same
confidence-inspiring "yeah, I could do that" feeling I get about
building with bales. I've always been fascinated by the plans for
panelized buildings like the "Bolt Together House" well know to
all members of this forum.

Unless you're making your own sticks, no power tools are needed,
which for me is another point in its favor. (The authors advise
against using a hand-held drill--it's too hard to get the holes
straight through, and if they aren't straight through you lose
the interchangability and reusablilty of the sticks which is one
of the chief advantages of grid-beam.

Has anyone here ever built anything with this stuff?

Karen

[n74tg]

Karen:
From the limited information available from the book ad, I think I have built a few things "this way".  Yes, there is a certain advantage to being able to dis-assemble your project and then re-use the materials later in a different project. 

For smaller building projects, like maybe a dog house, this method should be fine.  Even for something as large as a 8 x 12 backyard storage building, this method of construction might be okay because you wouldn't be occupying it (ie living in it).  For buildings you will occupy I might be worried that there isn't enough reinforcement to hold the building together in a storm with high winds. 

What type project or structure are you wanting to build using this method?     

[kyounge1956]

I am thinking of a small (well under 1000 square feet), but full-scale house, of non-load-bearing straw bale construction. I am wondering whether it would be possible to build the roof supports and the roof itself with grid beam and still use the bale infill for its insulating value (and good looks).

There are a couple of structures mentioned in the book which were occupied. One of these survived 80 mph winds and also a tree falling on it. The thing that appeals to me about the system is the simplicity of putting it together rather than the ability to take it apart and use for something else. My construction skills are really minimal. I can saw through a board, but usually I don't cut really straight. I can nail things together but I often bend the nails. I wonder how much the strength of a building's frame would be affected by that sort of accumulation of small imperfections at every point of attachment. Bolting pre-drilled sticks together, I know I could do.

Bracing would obviously be necessary, but it is possible to use the sticks diagonally for that purpose, or to use cables or metal strapping in addition to the sticks. Anchoring the structure to the ground would be necessary also. Some of the larger structures, such as trade show booths, were only intended to be temporary, and I don't know if they used any anchors at all. I think the ones intended for more extended use were held down with ground augers, but I don't see why a grid-beam building couldn't be attached to an ordinary concrete footing with bolts, just like the sill plate of standard framing is, or set vertically in concrete bases to make more of a pole-style frame.

I just wish there was more information in the book. There are books that give step-by-step instructions for building a deck or a garage or a log cabin. I wish there was one for how to build a house out of grid-beam, too.

Karen

Karen:
From the limited information available from the book ad, I think I have built a few things "this way".  Yes, there is a certain advantage to being able to dis-assemble your project and then re-use the materials later in a different project. 

For smaller building projects, like maybe a dog house, this method should be fine.  Even for something as large as a 8 x 12 backyard storage building, this method of construction might be okay because you wouldn't be occupying it (ie living in it).  For buildings you will occupy I might be worried that there isn't enough reinforcement to hold the building together in a storm with high winds. 

What type project or structure are you wanting to build using this method?     

[Don_P]

It could work, it'll probably cost more for what would likely be an inferior structure. Bolts are quite strong but they concentrate loads onto one small area. Wood is not particularly strong per unit area so typically we use larger dimensions and many smaller fasteners. This hopefully provides a good deal of redundancy and makes the building scream loudly and slowly deform long before it fails.

Using strawbale you are replacing the many redundant studs in the wall with fewer posts thereby concentrating the loads on fewer members. That makes each member and its connections more critical. In a studwall I can kick out every other stud under full design load and expect the building to stand. In a post and beam structure this is much less likely as each time a structural support fails it throws much more load on its neighbors. However there are usually more potential load paths then just the design one. I worked on one old cabin with a first floor door firmly stuck, I realized I didn't really want to open that door just then beacuse it had become a second floor support post. I've seen feed bunks and their stall walls become hayloft supports in barns when the floor beams have cracked. In your case the strawbales would become load bearing if the grid failed so a collapse of that section would probably not be likely. Free spanning members done this way might be a whole other matter if not thought through carefully.

This system seems to use the bolts as the bearing points connecting members. In construction we typically try to support the members and their loads on top of each other and use the connectors to simply hold alignment. Ideally wood is loaded along its axis when possible, a truss, it is used in bending where we must, a beam or joist, and it is not loaded in tension perpendicular to its grain if at all possible. There are certainly exceptions and more so recently with the frequent adoption of connectors like joist hangers. However those connectors typically spread the loads out rather than concentrating them. A bolted horizontal beam hanging on the bolt and then loaded is very likely to split at the bolt hole if not designed with care. In many situations this is a prohibited connection in wood.

It can work but... it depends. From what I've seen I don't think this book will get you into a safe permanent home, but without a doubt knowledge is a good thing.

[kyounge1956]

It could work, it'll probably cost more for what would likely be an inferior structure. Bolts are quite strong but they concentrate loads onto one small area. Wood is not particularly strong per unit area so typically we use larger dimensions and many smaller fasteners. This hopefully provides a good deal of redundancy and makes the building scream loudly and slowly deform long before it fails.

Using strawbale you are replacing the many redundant studs in the wall with fewer posts thereby concentrating the loads on fewer members. That makes each member and its connections more critical. In a studwall I can kick out every other stud under full design load and expect the building to stand. In a post and beam structure this is much less likely as each time a structural support fails it throws much more load on its neighbors. However there are usually more potential load paths then just the design one. I worked on one old cabin with a first floor door firmly stuck, I realized I didn't really want to open that door just then beacuse it had become a second floor support post. I've seen feed bunks and their stall walls become hayloft supports in barns when the floor beams have cracked. In your case the strawbales would become load bearing if the grid failed so a collapse of that section would probably not be likely. Free spanning members done this way might be a whole other matter if not thought through carefully.

This system seems to use the bolts as the bearing points connecting members. In construction we typically try to support the members and their loads on top of each other and use the connectors to simply hold alignment. Ideally wood is loaded along its axis when possible, a truss, it is used in bending where we must, a beam or joist, and it is not loaded in tension perpendicular to its grain if at all possible. There are certainly exceptions and more so recently with the frequent adoption of connectors like joist hangers. However those connectors typically spread the loads out rather than concentrating them. A bolted horizontal beam hanging on the bolt and then loaded is very likely to split at the bolt hole if not designed with care. In many situations this is a prohibited connection in wood.

It can work but... it depends. From what I've seen I don't think this book will get you into a safe permanent home, but without a doubt knowledge is a good thing.

I agree this book by itself won't get me into a safe home. There just isn't enough information in it. I am trying to find more online and via interlibrary loan but there doesn't seem to be much more out there. Next step may be to contact the authors at their website.

How would the considerations you've pointed out above apply to the metal sticks? Full-size wooden structures used grid-beam made of 4x4 stock, which I think is probably what would be used for the posts in an infill bale building of the size I have in mind. The 4x4 wooden sticks are not available ready-made, so if I attempted this at all it would probably be with 2"x2" steel grid-beam. The loads would still be concentrated on the bolts as you point out. I wouldn't think steel is likely to split as you describe for wood, but could it fail in some other way if used in that configuration? Or would it be the bolts that fail?

I haven't been able to find prices for the steel sticks anywhere online, so cost could turn out to make this a completely impracticable idea.

Karen

P.S. How seriously are the kind of multiple small flaws I described as likely to result from my low carpentry skill level likely to weaken the resulting structure?

[Don_P]

Steel has the same strength in all directions where wood is "anisotropic" it has different strength in different orientation according to grain direction so this method works better in steel. The bolts are in the neutral axis where a beam is neither in tension or compression when in bending so those are good things. Actually a 4x4 is a stock stick of wood actual dimension is 3-1/2"x 3-1/2" however in any material their dimensions mean absolutely nothing on your building, you or an engineer must determine the loads and provide materials and connections that can safely resist those loads. For instance a 4x4 spanning 1' with my weight on it is going to be plenty strong, if it is asked to span 16' with 16 of us on it, it will almost certainly hit the ground. This is just as true in steel. I can hang a certain amount of weight on a piece of steel of a given shape and length or on a certain size bolt and no more. Where you've seen me refer to the NDS when people get outside of the codebook here in wood construction, the AISC Manual of Steel Construction is the book you would need to get to know really well if you go this route in steel, you can get it through interlibrary loan, no it doesn't go into grid beam but the engineering you would need to understand to build grid beam in steel would be contained in there. It would also take an immense amount of study for you to understand it, it is an engineers book. and when you arrive at that understanding, you will choose another path.

If you build a typical stick frame house following the prescriptions given in the codebook you stand a much better chance of having a safe and successful build than if you try to invent something new. It is commented on pretty often by professionals that DIY'ers seem to be the ones who go for alternative means and are probably the least equipped to be doing so, there is no grounding knowledge or experience to let you know when you are getting into trouble structurally. I can push the edges of the typical envelope from knowledge and experience gained from decades of doing this, I also have no problem calling in an engineer when neccessary to help guide me. I talked with one for several hours yesterday, he cleared some fog pretty quickly. DIY'ers rarely do so, or know when to do so. The methods in the codebook have worked successfully on quite literally millions of homes. Conventional construction is generally pretty tolerant of amatuer efforts. Much more so than the direction you seem to be heading. A chop saw can make perfect cuts, which aren't really neccessary, a nail gun doesn't bend nails, so to some extent we have many tools now that make up for lack of expertise. Their mention of a hand drill not being accurate enough means you would need a drill press to fabricate the connections for grid beam. Cutting and machining steel accurately is not fast or particularly fun. It's pretty often laughingly said that its a poor piece of wood that can't be pounded into place an extra 1/16", you often can't move a piece of steel into place if its off by a few thousandths.

I'm not wanting to blast this method or anything but I do think you'll find it harder and more expensive to arrive at a satisfactory house going this route.

[kyounge1956]

Steel has the same strength in all directions where wood is "anisotropic" it has different strength in different orientation according to grain direction so this method works better in steel. The bolts are in the neutral axis where a beam is neither in tension or compression when in bending so those are good things. Actually a 4x4 is a stock stick of wood actual dimension is 3-1/2"x 3-1/2" however in any material their dimensions mean absolutely nothing on your building, you or an engineer must determine the loads and provide materials and connections that can safely resist those loads. For instance a 4x4 spanning 1' with my weight on it is going to be plenty strong, if it is asked to span 16' with 16 of us on it, it will almost certainly hit the ground. This is just as true in steel. I can hang a certain amount of weight on a piece of steel of a given shape and length or on a certain size bolt and no more. Where you've seen me refer to the NDS when people get outside of the codebook here in wood construction, the AISC Manual of Steel Construction is the book you would need to get to know really well if you go this route in steel, you can get it through interlibrary loan, no it doesn't go into grid beam but the engineering you would need to understand to build grid beam in steel would be contained in there. It would also take an immense amount of study for you to understand it, it is an engineers book. and when you arrive at that understanding, you will choose another path.

So there aren't tables (like rafter or joist tables) where you can look up the safe span for a given roof load and size of steel?

If you build a typical stick frame house following the prescriptions given in the codebook you stand a much better chance of having a safe and successful build than if you try to invent something new. It is commented on pretty often by professionals that DIY'ers seem to be the ones who go for alternative means and are probably the least equipped to be doing so, there is no grounding knowledge or experience to let you know when you are getting into trouble structurally. I can push the edges of the typical envelope from knowledge and experience gained from decades of doing this, I also have no problem calling in an engineer when neccessary to help guide me. I talked with one for several hours yesterday, he cleared some fog pretty quickly. DIY'ers rarely do so, or know when to do so.

With straw bale it wouldn't be typical (2x4 @ 16" oc) framing anyway. I will need to have an engineer or architect check the plans whatever method I end up using. Are types of framing with fewer more widely spaced members as forgiving as ordinary stud-frame? From your description it sounded like the reason the latter is so forgiving is redundancy...loads are spread out over lots of different members and lots of fasteners etc. Is that correct?

The methods in the codebook have worked successfully on quite literally millions of homes. Conventional construction is generally pretty tolerant of amatuer efforts. Much more so than the direction you seem to be heading. A chop saw can make perfect cuts, which aren't really neccessary, a nail gun doesn't bend nails, so to some extent we have many tools now that make up for lack of expertise. Their mention of a hand drill not being accurate enough means you would need a drill press to fabricate the connections for grid beam. Cutting and machining steel accurately is not fast or particularly fun. It's pretty often laughingly said that its a poor piece of wood that can't be pounded into place an extra 1/16", you often can't move a piece of steel into place if its off by a few thousandths.

I'm not wanting to blast this method or anything but I do think you'll find it harder and more expensive to arrive at a satisfactory house going this route.

I wouldn't give it a second look if I had to drill the steel myself (or drill wooden sticks myself for that matter) or make my own connectors. The steel comes pre-drilled and is available in various pre-cut lengths, and for most sorts of joints the connectors are purchased bolts--no fabrication necessary.

I have never used power tools other than a drill, and once an electric reciprocating saw under the parental eye. Building the house, I will in all likelihood be working alone most of the time, and I'm extremely nervous about using power tools in those circumstances. That is why the ability to assemble grid beam with hand tools only is so appealing to me.

I don't think my state has adopted a code yet for straw bale construction, although there are other states that have. There may be one for post & beam or pole construction, and if so, I suppose that is what would apply to the kind of building I have in mind. The straw is just "non-structural baled cellulosic insulation".

Karen

[Don_P]

There are span tables for steel studs and joists in the codebook, the steel manual has safe load tables for structural shapes like I beams and C channel. The shapes you are describing aren't going to have tables as they are not normally considered structural steel.

The type of framing you propose is less forgiving than typical stick frame construction. There is no prescriptive code for strawbale that I'm aware of so yes it falls under "engineer required" if the inspector wishes.

You can either cut the steel or pay someone to cut it, that is typically the case when buying steel precut.

If you wish to go this route I think I've played devil's advocate enough to let you do your homework now. The next step might be a general inquiry of a structural engineer for feasability.

[firefox]

I would like to suggest that you start practising with some power tools. Maybe a friend that can come over and give you some safety pointers until you get comfortable with it.
I think that once you get over the confidence curve you will have a whole new future open up for you.
I was once where you are now and thanks to a wonderful person who recognized my potential and taught me to get over the humps without hurting myself, I now feel confident to build just about anything.
Bruce

[kyounge1956]

There are span tables for steel studs and joists in the codebook, the steel manual has safe load tables for structural shapes like I beams and C channel. The shapes you are describing aren't going to have tables as they are not normally considered structural steel.

Aha, that explains it.

The type of framing you propose is less forgiving than typical stick frame construction. There is no prescriptive code for strawbale that I'm aware of so yes it falls under "engineer required" if the inspector wishes.

That's what I figure, unless they let me use some other state's code on the assumption that if it won't fall down in California it won't fall down in Washington either.

You can either cut the steel or pay someone to cut it, that is typically the case when buying steel precut.

It's always either the one or the other...ya pays yer money and takes yer choice.

If you wish to go this route I think I've played devil's advocate enough to let you do your homework now. The next step might be a general inquiry of a structural engineer for feasability.

Fortunately I know just the fellow. I'll have to take the book to church next Sunday and run it past him.  Now if only I knew how to get hold of a classroom full of engineering students in search of a senior project....

[kyounge1956]

I would like to suggest that you start practising with some power tools. Maybe a friend that can come over and give you some safety pointers until you get comfortable with it.
I think that once you get over the confidence curve you will have a whole new future open up for you.
I was once where you are now and thanks to a wonderful person who recognized my potential and taught me to get over the humps without hurting myself, I now feel confident to build just about anything.
Bruce

Thanks, but no thanks. The possibilities for a major injury from just one slip-up are too high for me. I suppose it's possible, but I've never heard of anyone severing part of their own body or bleeding to death as a result of an injury with hand tools. The more I think about it, the less inclined I am to go that way.

Anyway, I don't know if there will be power available at the site, because I haven't bought it yet.

[considerations]

"I have never used power tools other than a drill, and once an electric reciprocating saw under the parental eye. Building the house, I will in all likelihood be working alone most of the time, and I'm extremely nervous about using power tools in those circumstances. That is why the ability to assemble grid beam with hand tools only is so appealing to me."

I was the same way, but not anymore.  I'm humble about using a power tool, but I do use them.  I don't just automatically line up and start cutting.  I do each preparatory step with a mental checklist...where is the cord, where are my hands, where is the cut off piece going to go, etc...  I'm slow, but not nearly as slow, tired and sore as I was just using a hand saw, hammer, and screw driver...  I don't think the cabin would be this far along if I hadn't transitioned to using power tools.