square tube steel instead of wood in pier and beam?

mikkelibob · March 29, 2008, 11:07:33 PM

I'm working through various options at our small ranch property here in central Texas. Its looking like pier and beam foundation will be the best method to go with our dream of a 16x20 cabin. I'm very concerned about termites and rot, so am willing to pay extra bucks to go with something highly resistant. Would 4"x4" nominal (3.5x3.5 actual) square steel tube be a strong enough base to build on? For a 16x20, it would be 6 16' lengths, so about 96 ft. of steel. Expensive, but doable. I figure I could drill and screw the steel tube into regular 4x4 post bases. I could also get nominal 2x4 (1.5x3.5) rectangular steel running between beams, hung with standard joist hangers. For decking I'd try to find a cement board product.

Or am I just crazy and treated lumber is good enough (especially if its already 24" off the ground)?

MountainDon · March 29, 2008, 11:28:12 PM

mikkelibob

Steel! I don't have a clue on how to go about sizing that.

Interesting thought, though. Do you know any engineers? Something like that would have to be run past an engineer and his stamp if there's any building departments to deal with.

I would think that concrete piers with the appropriate termite shields under the wood might be easier.

We'll see what others think, I'm sure.

glenn kangiser · March 29, 2008, 11:50:35 PM

Unless you are used to working steel -- besides the above -- everything you do would turn into another chore and problem. Then the transition to wood would bring more problems and as mentioned, since unconventional, all would require an engineered design.

It would turn into a giant snowball.

Redoverfarm · March 30, 2008, 08:06:15 AM

I would have to agree with the majority of the comments. If you used a good termite proof base then use what is easiest to work with. That is unless you work with steel and have it readily available and want to do the project as a challange for which it will be.

March 30, 2008, 04:30:37 PM

Well, I'm in rural texas, so as long as its not a well or septic, there aren't much in the way of building standards. In theory there are state building codes, but they are pretty limited. I think the only thing the county would be mad at is if they didn't get to tax whatever I build. And I don't blame them, the roads here need some TLC!

Part of my inspiration was the box steel and angle iron trailers. They seem to frequently be on 4 or 8 ft centers, and carry a lot of weight. I figure if the trailer can carry all my building materials, then a house built of those materials should be strong enough. But I did find an equation (http://www.woodworkforums.com/showthread.php?t=43292), but I don't think those calcs indicate it would have the strength I need. I could live with the cost; 3 20' beams would be something like $700, which isn't terrible. The box steel would have been cool simply because it would be able to use the same simpson hardware as lumber. Pipe or i-beams would probably work, but its just not as plun-n-play as the 4x4 nominal square steel. I'm curious why PT lumber would be more durable than the steel. There's a got to be a reason why the ranch fences around here use steel and not treated posts. Anyway, back to the drawing board.

What about products like TradeReady and i-span? Around here metal joists and beams have become pretty common., even for starter homes. Clearly i-beams can be found strong and cheap enough, but that would require a bigger MIG than I have handy, and I can't seem to find any pre-made simpson type brackets that would do what I need (basically I'd need a saddle for the piers to hold the i-beams, and some non-welding way to bolt on joist hangers). Is there a way to use these in the ground foor of a pier and beam structure? I think new mobile homes are all built with steel framing, including the floor.

For my walls I'm going to use a product that is steel framing c-channels with extruded sytrofoam (ultraframe is the trade name I think), and do external cladding with hardipanel. Roof will be metal, on steel trusses If I can find a supplier. It would be a shame if I build something virtually maintenance free, only to have problem with the lumber beams 20 years hence.

MountainDon · March 30, 2008, 07:48:13 PM

One of the drawbacks I see about using steel is the fastening of one thing to another; steel to steel, steel to wood. Seems to me there'd be a lot of hole drilling and using special self tapping screws for the smallest of things. I don't mean to totally discourage you, but here's some questions that pop into my mind.

Let's say you use three steel beams as the basis.

What are you going to use for floor joists and subflooring?
How to fasten them to the steel beams?
If wood joists, how to secure to the steel?
If steel joists, how to fasten the subflooring (OSB or plywood) to the steel joists?

You mentioned Hardipanel and C-channels with extruded styrofoam. Hardipanel I know. Is the "ultraframe" you referred to a SIP; Structural Insulated Panel? Usually come in 4 ft wide sizes? They usually are constructed with an inner and outer skin of OSB or similar panel. You're not getting away from wood altogether. If so it seems to me that for a small sized cabin, unless you've already worked with SIP's, they will be more trouble and certainly more expensive than they will be worth in the end. Just my opinion, understand.

Is using something like that going to require special doors and windows or can conventional ones be used?

How is the electrical and plumbing run through the walls? Do the runs have to be fully planned and the SIP's configured when they are built, or how? I don't know, that's why I ask.

As for longevity of the structure you could build a conventional wooden structure and by doing it right have it last longer than the rest of your life. You could also build a steel structure and have errors slip by that allow water infiltration and have major problems sooner than later. Wood, steel, brick; water is the enemy and water will always win. The devil is in the details no matter what the material is. There's nothing really wrong with time proven wood construction when combined with modern treated wood where necessary.

On the other hand if we always stuck with the time proven we wouldn't have a lot of the things we have, use and are thankful for these days. It's just that when you use unconventional means you usually run into unconventional methods and costs.

This is just to say that you need to plan out the entire process, and cost it out, before beginning.

John_C · March 30, 2008, 08:09:25 PM

Steel is used quite often in commercial buildings. In areas where wood beams would be too large and expensive due to a long span; and to meet various fire code regulations. If it was better than wood at anything close to competitive costs you would see more steel residential houses. All the ones I know of are manufactured housing, engineered and built under controlled conditions. I just don't see it as practical for a small owner built house. I doubt the Simpson connectors would work well. They are designed around the structural properties of wood. Steel is usually joined either by welding or with much thicker plates than a Simpson bracket and larger bolts than one could accommodate.

How many 50 yr. old houses do you see? A lot. How many 50 yr old cars? Not that many. Bridges last a long time but the maintenance schedule is daunting. In Europe there are many house that are hundreds of years old; built of wood and stone.

mikkelibob · March 30, 2008, 09:22:35 PM

I can be convinced wood is the way to go, I'm just stubborn. I'm pretty wary of Texas Termites and quick moving grass fires. But if theres no other reasonable way to do the beams, then I guess I'll be headed to the lumber yard. The original plan was going to drystack cmu, but the ground would require too much leveling, a pier&beam makes adding utilities easier, the soil has too much expansive clay, and the hot summers mean we need r-value, not thermal mass.

As far as the walls, we'll probably be going with:
http://www.transconsteel.com/products/ultraframe/
Its galvenized metal studs with a styrofoam core. Its not the osb-foam-osb that a lot of SIPs are made from. Installation is pretty much just laying down the channel, then panels (labels a1, a2, b1, b2, etc), and then header. For doors and windows you order the panels with the apprioriate frame outs. The fact that the studs comromise some of the r-value is a hinderance, but I like the fact that they build a lot like sticks, and can pretty much just plug in into existing plans. It should go up fast, has decent r-value, and is fairly reasonable in cost. My estimate is that panel, tyvek, and hardipanel should run about $6 per sq ft of wall. There will be a lot of 3-day weekends involved, so the ability to bring in pre-made panels and get them up quickly will help a lot.

I was under the impression the new formulation of PT lumber might be more eco-friendly, but not necessarily as durable. Is there a way to be extra sure the PT lumber will last? An extra coating of thompsons weather sealer? Varnish? Latex paint? Fiberglass em? (okay, that would be too much work)

Redoverfarm · March 30, 2008, 10:24:48 PM

If you are going with PT then I would suggest the highest rated saturation(probably below grade type) rather than above grade. There is definitely a difference in the grades. They might be a little heavier but for a foundation I would think that would be a plus factor.

i wish we were up north · March 30, 2008, 10:28:18 PM

Hi, I'm new to the forum (well, ok, I've been lurking for ages - just not ready to commit yet!). Anyway, this post caught my eye so I thought I would share this product with you for protecting wood posts underground. Made for the post-frame industry I guess but it looks pretty good to me.

http://www.plasti-sleeve.com/plastisleeve.html

Redoverfarm · March 30, 2008, 10:39:40 PM

i wish we were up north

Intresting product. I am sure that the members here would find them useful. Myself I try to use mason products on foundations. Your name indicates that you are at least below the north someplace.

i wish we were up north · March 30, 2008, 10:50:16 PM

Just in SW Wisconsin (near Iowa). We'd prefer to be near Lake Superior but have some acreage in the central part of the state so probably end up there in a year or two.

March 30, 2008, 11:31:19 PM

I've seen you lurking for a while. Glad to have you speak up.

The only thing you'd have to be very certain about is keeping water out of the sleeve. Careful installation and careful packing the earth back in the holes. Then sealing that top joint where the sleeve stops. That would have to be done with the utmost care and attention to detail. Otherwise you'd be incubating rot.

But it looks like it could work. I wonder what they cost?

Garrett In Tahoe · March 31, 2008, 02:05:42 PM

Mikkelibob,

I have to agree with most of the other posts regarding your hybrid approch to buiding with steel and some wood to discourage termites and fire. It may become quite costly and your going to find yourself re-inventing the wheel so to say.

I've built with lots of structural steel in previous jobs, so it's not necessarily new, but normally is used to increase spans and provide more shear value where a design calls for a lot of glass in a wall, especially in seismic regions and commercial buildings. I don't think though that is your concern here.

First off the use of simspon type hangers are simply not designed for steel, some are but welding is required for those applications.

If your convinced this is the way you want to go then here are a few suggestions.

If your using square tube steel posts then you need to have base plates welded to the bottoms w/2-4 holes and then they are bolted down to anchor bolts matching that pattern set at each pier.

2X4 rails (beams) sound inadequate, normally a wide flage beam (I Beam) is used as floor beams. These beams are normally attached to the posts where a plate w/2 holes is welded vertically to the post. The plate insets against the web of the beam which has two matching holes, and the beam bolts to that plate and the post continues up. If the beam rests on top of the post then a cap plate is welded to the top of the post and the beam is bolted to the cap plate.

Normally threaded studs (nelson studs) are welded to the posts or beams where you need to clad wood to it for attachment. Holes can also be punched in the flanges of the beams for bolting.

Corrigated steel decking can also be used for your floor. You would need to add a few additional floor girders though. The corrigated decking is welded to the steel girders and a slab floor is poured on top. You would need to sleeve for future plmg & elec penetrations. It sounds pretty heavy duty but you have small spans, so your beams can be pretty small.

It gets a little confusing, especially when trying to explain it, so the previous recommendations of getting an engineer involved is a sound one.

Most commercial steel fabricators have what is know as "Steel Detailers". They produce the drawings for fabrication. The steel is then fabricated in a shop and erected in the field. I would suggest you start by contacting a Steel Detailer and talk with them regarding your ideas. They can probably be most helpful (and cheaper than an engineer) and should know the appropriate sizes of steel, bolts, decking, connections, etc, and the best way to fabricate steel for this type of project. Once fabricated though a crew could easily erect it all and put the decking down in a day.

Good Luck!

Okie_Bob · March 31, 2008, 04:34:28 PM

I actually strongly considered steel tubing for my house on Cedar Creek Lake about 60 miles SE of Dallas. I had the same fear of the Tx Termites as you have an still do. I went with pier and beam also and so far am very happy with it. The exterior of my
foundation is concrete block (hydite as some call them) sitting on a good footing with lots of steel. Then I bolted a 2X6 flat on top of the concrete blocks. The 2X was pressure treated. In the interior of the foundation I have 5 piers in strategic places and that is what holds it all up.
My eventual decision is based on the idea that the concrete blocks are at least two courses high at the lowest point so I can readily see if termites try to build a tunnel up the sides of the blocks. Of course they can't get up into the wood if they can't tunnel up as they would die in transit! So far so good and I know for a fact that a piece of wook left on the ground anywhere on my lot will have termites within a week or two. Living next to the lake there is just no way to kill them all or stop them from returning if you try. I also used Hardi board for the exterior so they won't eat that either.
But, the steel tubing is still a good idea and one I might be persuaded to go with if I were to do it again.
Okie Bob

mikkelibob · March 31, 2008, 06:42:24 PM

Thanks Okie Bob for understanding my irrational fear!

I saw this mentioned elsewhere here: http://www.plasti-sleeve.com/

I wouldn't want to cover up a beam entirely if it would create some condensation problems and rot from the inside. But that seems a potentially useful (and maybe cheap) solution to my problem.

glenn kangiser · March 31, 2008, 09:58:12 PM

Do your termites in Texas build the little mud tube tunnels up the side of the concrete blocks so they can get to the wood as they do in some places?

Redoverfarm · March 31, 2008, 10:10:15 PM

Doesn't anyone use a termite shield anymore. I mean like flashing with a 30 deg angle which the experts say they cannot manuver. I realize that flashing with PT wood is a no no but there is a way around that with builders felt between the wood and the aluminum or if you want to go high end you could use copper flashing which is compatable.

April 01, 2008, 05:14:41 AM

Glenn, that is exactly the type we have here. Just a little mud tube they crawl up to keep them out of the light.
Makes it easy to see where they are if you have a masonry wall they have to climb to get to the wood.

Never thought about the condensation possibility from the steel tube since it is enclosed basically on all sides. Humm. Could be.

glenn kangiser · April 01, 2008, 08:49:35 AM

Sneaky little tubular critters.

I this case I don't really expect there to be enough space for condensation between steel and wood and if some on the outside due to a quick air change the moisture would be quickly gobbled up by the termites waiting at the bottom and be no problem.

Great to see you in class two days in a row, BoB.

square tube steel instead of wood in pier and beam?

John_C

John_C

John_C