Steel I Beam instead of wood

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Old 04-27-06, 09:04 AM
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Steel I Beam instead of wood

I posted this in the decks section, but haven't got any bites, so I thought I'd repost in a different section to see if I can get any information...

Hello All:

I have deck plans that call for 2 2x8's for the beams. In order to lower the overall height of the deck (I would like to keep its finished height as close to ground level as possible), I'd like to use steel I beams in place of the 2x8's. What size steel I beam would I need to use in order to maintain the same structural integrity? Pier spacing (which the 2 2x8's beam would rest on) is 6.5 feet and joists are 2x6 12"O.C. in case this info is needed. Thanks for your input.
 
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Old 04-27-06, 06:15 PM
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How close to the ground are we talking?

The reason I ask is you make it sound like the closer the better. Well, if that is the case, you will be needing joists of probably no less than 5 1/2 inch thickness and possibly 7 1/4 inch thick. Are you planning to excavate out any ground to accommodate the joists? If so...what 's the difference then if you excavate out for the carrying beam? Or, how about having no carrying beam at all? Why not use the box sill method instead and have all joists just sit on compacted ground? (Treated lumber of course).

Or, you could consider forgetting the deck entirely and pour concrete or use pavers in some pattern of your choice, like herringbone or something. That way you could grill on it without worry of fire.
 
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Old 04-28-06, 09:52 AM
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The way the plans are drawn, the 2x8 beam plus the 2x6 joists plus the surface material has a total height of 14.25 inches. If I can use a lower profile beam (i.e. 3 inch steel I beam) in place of the 2x8, I would end up with a lower overall height of around 9.75 inches. This height will allow installation without having to do any excavation and maintain the deck surface 2.5 inch below the door threshold. The deck is approximately 600 sq. ft. which would make for a lot of digging.

Concrete is not cost effective (this was my original plan) because of the size of the poured surface and the inaccessability of the work area would mean all concrete would have to be brought in by wheel barrow; too much labor. I'm not familiar with the term box sill, however, my understanding is that even treated lumber when in contact with the ground will decay quicker over time that treated lumber not in contact with the ground. Also, the property has a slight slope to it so there would still have to be digging in order to create a level surface.

I also already have a small patio for my smoker/grill away from the house, so that really isn't a concern either.

I do appreciate your reply, as I haven't been able to get anyone in the least to post to my thread(s). Any input you or anyone else has will be most appreciated.
 
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Old 04-28-06, 01:21 PM
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dont know

can you not hang the 2x6 off the 2x8 rather than setting it on top? it would mean a bit more expense...but it seems like that would work. and, if me math is correct, 14.25-5.5=8.75...which is lower than your 9.75.
off hand...i would say asking for a 3" steel I is going to be rather pricey. also...i am thinking it wouldnt really work. 3" isnt much...and itd have to be some pretty hefty steel (i think...but i dont really have a LOT of experience with the matter).
anyhow...ye gots another reply (even if it wasnt any help).
 
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Old 04-28-06, 02:37 PM
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Jake,

It sounds like you have the plan and it probably should work just fine.

But what is the dimensions of the deck? 20 x 30? 12 x 50? I'm trying to figure out how you can get by with just one of these cross beams? Or, are you going to have two; one crossing the middle of the deck, and one out near the edge of the deck (but perhaps in some for that cantelever effect)?

And how are you going to secure the joists to the metal?
 
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Old 04-29-06, 04:48 AM
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Jake:

Give me the dimensions of your deck, and if you are planning or not on having it attached to your house. You can attach them or have them free standing. I will tell you how to build it.
 
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Old 05-01-06, 07:33 AM
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Dimensions are 48 X 12, with the 48 being along the back edge of the house. It will be attached to the foundation using a ledger board. Plans call for two rows of beams, one at 5.5 ft from house and one at 11 ft. from house with one foot of overhang. Beams are on concrete piers 6.5 feet apart with joists 12" o.c. This was designed for the possibility of adding a solid surface to it (i.e. tile, etc.) in the future.

Thanks for your input.
 
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Old 05-01-06, 02:57 PM
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Oh, BTW Warren Piece 14.25-7.5=6.75, 6.75+3.0=9.75
 
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Old 05-01-06, 05:14 PM
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Steel I Beam instead of wood

From a practical standpoint, you are dreaming if you think you can find a 3" deep steel beam to replace the double 2x8s.

You have to consider two different criteria: strength and deflection. even if you find a can find a steel beam strong enough, it probably would have too much deflection for your requirements.

From a elevation standpoint, you have a system of stacking materials (beams, joists and flooring). It is cheap but does not work everywhere.

Two routes to explore are:

1. Consider cutting spans so you can decrease the depth of beams and joists - Three beams instead of two - not cheap, but it can help.

2. Consider using hardware and hanging the joists or some other approach more creative to fit your pre-conceived ideas and required structure thickness. It will not be a conventional, cheap method but it can be done if you do not want to use concrete or excavate and provide ventilation to extend the life of the wood.

Dick
 
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Old 05-02-06, 07:38 AM
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Thanks everyone for taking the time to contribute your 2 cents to my dilema.

But I'm afraid that I've either not been very clear or you have missed the point. Most of you seem to be concentrating on a 3 inch steel I beam. I don't necessarily want to use a "3 inch" steel I beam. My question is: What other approach can I take to replace a double 2x8 wood beam? I used a 3 inch steel I beam as an example to illustrate my train of thought, but am not suggesting that this is what I want to use.

Posed another way: What size structural steel member would I need to replace a double 2X8 wood beam and maintain the same integrity? If I need to double the number of support beams to get the lowest possible profile height, then that would be an option if one suggests that.

Thanks again for your time and energy.
 
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Old 05-02-06, 03:18 PM
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Steel I Beam instead of wood

As I suggested earlier, you can increase the number of beams to cut the span and decrease the thickness.

Unfortunately, as long as you are going to stack decking on top of joists, that are stacked on beams, that are sitting on piers there is little you can do to drastically decrease the depth as much as it seems you would like. Just going to a different material will help, but you could still have a deflection or "springy" problem even if the deck is strong enough.

Add more supports to cut spans is a definite step in the right direction. Go to a different structural system such as a box-type system that hangs joists from beams. There are many methods to decrease the depth slightly, but they are more costly. You may want to get a to professional design for your unique situation.

Any wood deck that is close to the soil will have a limited lift and it appears you may have a site where you cannot avoid this.

It may be better to rent a concrete pump or put in a paver patio that will last much longer.

The other choice is to dig out a lot of dirt and hope water does not accumulate under your wood deck.

Dick
 
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Old 05-02-06, 03:29 PM
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Thanks for your reply. I hadn't thought about the "box" design. that actually may work quite nicely in my situation.

I'd still like to hear what other have to say...

I really appreciate everyone's time and enjoy this forum.
 
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Old 05-02-06, 06:36 PM
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You could nail 2 inch wide x 9 1/4 inches long, treated spacer blocks on your house, if you have house down low to nail to. Nail one of these verticaly every 16 inches. The top of these spacer blocks will be at 4 inches down from your exit door so that when the 1 1/2 inch deck boards are screwed ontop, your finish height will be your desired 2 1/2 inches down.

Nail across these blocks a 2 x 10 (9 1/4 inch actual width). (The spacer blocks merely hold out the 2 x 10 to prevent rotting of your house siding/sill, from having a 2 x 10 pinned up against it.)

Nail on 2 x 10-sized joist hangers on this 2 x 10 every 8 feet The first one will be at the start of the one end of the 48 foot run of deck. You will nail on 7 of these 2 x 10 beam-joists. (Just not quite yet...but that is the plan)The last one will be out at your 48 foot mark.

Now you square-off from your house, ...perpendicular outward, from each beam-joist joist hanger. Measure outward from your siding of your house 10' 6 ''. Make a straight stringline at this distance of 10' 6 '' for the entire 48 feet. (The finished deck will extend outward past the posts, obviously, another 16 inches. So, each of the 2 x 10 beam-joists will be cantelevered past the posts by 14 1/2 inches...16 inches after the band joist is nailed on) This will be where you will either sink a 4 x 4 or 4x6 post in cement, at each of these 7 locations. (The one on the far left will be so that the left side of the post will be 1 1/2 inches to the right of your from your 0 mark (start of the deck on the left)...and the far right post...post #7 will be so that the right side of the post will be 1 1/2 inches to the left of the 48 foot mark.) [Very critical if you choose to sink and concrete them in, that they are placed at exact locations and in a straight line!] These posts are what you will bolt each of the 7 2 x 10 beam-joists to. Therefore, the posts will come up to the top height of the beam-joist height which is what the height is you nailed (or better yet) galv. or stainless screwed that 2 x 10 to the house spacer blocks.

You cut each beam joist 12 feet long...LESS 4 1/2 inches! (3 inches at the house and 1 1/2 inches out where the outer band joist will go. That way your deck boards will be actually 12 feet! (But me.....when I do this, I go undersize even more so that I have some wood to cut off from the board for cutting out cracks and squaring. So...that said, you may want to lop about 6 or 6 1/2 inches off the length of the 12 foot 2 x 10 beam joists, so that the needed 7 wil be about 11 foot 6 inches.

Now with these cut, you rest each one in the pocket of your 2 x10 joist hangers, then hold up the dangling end and temporarily tack these to each of your 7 sunk posts that are out in your yard, 10 feet 6 inches out. Now you drill and bolt these.

Now you nail on your outer 2 x 10 band joists (naturally these will be 2 x 10's and go the length of the 48 foot deck.)

Now you need many 2 x 8's. (You will need 8 of these 2 x 8 cross joists per each section of 2 x 10 beam joists.) The 2 x 8's will be your actual joists that will go inbetween the 2 x 10 beam joists. These will be all nailed parallel to the house and outer band joist, every approx. 16 inches. You can use 2 x 8 joist hangers. Mark off 16 inches or thereabouts so that an equal number of the cross-joists divide out equally between the 2 x 10 up against the house blocks and the outer band joist. (And I have already figured out that it indeed will be very close to 16 inches, requiring 8 such cross-joists)

Now your framing is done. (I hope you are following this.)

Now you can deck this out with that rounded edge 5/4 boards (1 1/4 inches thick), or full 1 1/2 inch...treated lumber. If yo use treated lumber, you can space each board using a nail as a spacer as you go. But you don't HAVE to. Many people do not realixze this, but treated wood will shrink and automatically open up a gap of an 1/8 inch or more after the juice dries out of the wood.

Note that your lumber on top your deck will be 12 feet long and be perpendicular to your house. You will have no joints. You only need to use, say, 2 x 6 treated lumber or the 5/4boards as I stated.

There!!! You now have a solid deck slab that is 9 1/4 inches total thickness. If you followed this, you will note that this box-style framing does not rely on the joists to have to SIT ON any crossing beams underneath!

............................................

I used to do building, and my own design work... and this plan, albeit just one design you are seeking, will work, with minimal deflection. *IF* you want to absolutely kill any deflection you can simply use ALL 2 x 10's for everything.

Railing designs are the limit and you could copy rails you have seen that interest you.

I used to do building as a living and made quite a few decks and engineered all of my own work.
 

Last edited by DaVeBoy; 05-02-06 at 07:05 PM.
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Old 05-03-06, 08:44 AM
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I took a great deal of time posting that post above, and I thought about the design and posted it, on the spot last night, without even having to think about it, as I have that much experience in this field. For those that have a hard time following detail, I am going to condense it to the basics so you can visualize this deck and its skeletal support system:

You have 2 x 10's running along the house, down about 4 inches from the bottom of the door.

Attached to this, coming out from the house, you have 7 evenly spaced 2 x 10's. The first one is at the far left and the right one is 48 feet away from the first one.

You have 48 feet of 2 x 10's nailed onto the end of those.

Each of the 7 2 x 10's coming away from the house is supported by a post, that is set in from the outside of the deck, about 16 inches. This maximizes the strength of the support system and cuts down on deflection or bowing of the 2 x 10's, as sort of a counterbalance.

Between each of the 2 x 10's that comes out from the house are 2 x 8's nailed in between. (I said in my earlier post that one might chose to use 2 x 10's, but upon further thought and review of homes, 2 x 8's are very ample for an only 8 foot span!) There will be 8 per 2 x10 section, or 48 are needed in all. After this framing is complete, it will apear there are 10 (rather than 8) crossing joists after you count the 2 x 10 up against the house and the outer 2x 10 that is like a box joist out farthest from the house.

Then the 12 foot long deckboards will be perpendicular to the house and therefore require no butt joints. If 2 x 6's are used, there would need to be 104 2 x 6 x 12's! (At least it's not coming out of MY walet! )

.............................

So, just to frame and deck out the surface, not counting the stairs or rail system....

You would need say...6 2x10 x 16 footers for what nails along the house and what nails out at the outer band joist = 96 feet worth.

You wil need 7 2 x 10 x 12 footers for those perpendicular support joists I refered to as beam-joists.

You will need 48 2 x 8 x 8 footers as cross joists.

You will need 104 2 x 6 x 12's (or 5/4 boards) for decking.

You will need, depending on what part of the country you are in, for frost depth...but approximately 7 posts dug into the ground, bell bottom dug, with at least concrete poured in the bell bottom or encapsulated up to the surface. You could buy 4 8 or 10 footers of 4 x 4's or 4 x 6's and cut them in half to use as 4 or 5 foot long posts with about 3 feet in the ground.

There.

.....................

Anyone else?
 
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Old 05-03-06, 09:59 AM
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DaVeBoy, you're the man! I understand your plans completely, or at least I think I do. Basically, there is a series of boxes made from 2 x 10's supported at the house and then at the corners posts/piers. Then 2 x 8's as joists in each box running parallel to the house. Then decking on top if this...

Makes good sense!

My only question is: I've been told that you should never embed wood posts in concrete. I realize nothing lasts for ever, but would it be better to put the posts on top of the concrete? I don't have near the experience that you have, but I am very capable to follow plans and build just about anything (within reason of course); setting posts in concrete and cutting them off level is much easier than pouring a series of level piers.

Thanks again!
 
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Old 05-03-06, 05:57 PM
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The posts would be treated. Supposedly, in theory, it is supposed to last for many years. It's up to you if you want to rest them on pads, or use that anchor plate where you fill dug holes with cement up to the level ground, and then you imbed these plates in the concrete. These plates then accept 4 x 4 posts into them. If you don't know what I mean, or have never heard of or seen such metal hardware before, let me know. Since the deck will only be up in the air less than 16 inches off the ground and you will have the posts secured to almost 10 inches of joist material, the lost lateral stability by such a method, as just resting the posts on pads, or secured in those plates, will not really compromise the lateral stability very much.

Here is something else: You may want to double up the 2 x 10 x 12's, that come away from the house, for the 5 that are at the 8,16,24,32,and 40 foot marks. The ones at the far left and far right are okay to leave singular. But if you do decide to double these up...screw them to each other. Do not screw one to one side of the post and the other to the other side of the post. Even though the installation is nifty this way, what happens is you can cause a problem: If one of the joists bows in relation to the other, it will twist the deck boards at these locations! Also, you will have the work of cutting 3 1/2 inch cross-blocks every 16-24" to fit between the two.

You said about understandsing my plan, but then you said about the posts out at the corners. No post will be out at a corner. Well... the 1st and 7th one will be at the 1 1/2 inch mark and 47' 10 1/2" mark along the 0-48 foot run of deck. BUT...coming out from the house, they will NOT be out at the outer band joist, 12 feet out from the house. They will be in toward the house about 16 inches.
 
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Old 05-04-06, 07:36 AM
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Yes I understand, I was merely indicating that there are a series of boxes being supported by the house on one end and two posts on the other (not literally at the corners). One question (since you made a slight change to your original plan): Would putting a second row of support posts, i.e. 5 ft. from house [roughly half way from house and outer row of posts] eliminate the need to double up the 2x10's or would doubled 2x10's still be better?

Also, I am familiar with the post anchor plates, while I was drawing this out last night, I included this in the plans.

Thanks again for your efforts.
 
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Old 05-04-06, 08:38 AM
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jake,

I have been dealing in car/truck, lawnmower and housing issues for 35 years now and having to deal with Murphy's Law, the entire time, and have taken my lumps, and witnessed how others have been bitten .........

Regarding deck building...there are a couple key things besides leveling it that need great attention to detail: That is... how you secure it to your house. The other is in the squaring of the framed skeleton of the deck.

Rememeber how I said you should space blocks of some sort along the house every 16 inches...perhaps every foot, so that you just don't nail or screw the 2 x 10 flat up against the house? I have had to replace rotted out deck structures because of people who screwed a big deck support board up against the house and it trapped water and rotted out both the board and the siding and the band joist (box sill) of the house's framing! So it is very important NOT to just take the easy way out and screw or nail the 2 x 10's along the side of the house.

The other issue is in the squaring up of the decks skeletal framing before you start nailing on the deck boards.VEEEERY important! If you go with the method of simply buying those big square concrete pads you can buy, and just setting the support posts on them...this is the only way you will be able to have the opportunity to rack the deck square, after you frame it. If you imbed the posts or anchor plates in concrete, there is no chance to rack the deck square afterwards! You have to have the layout perfectly square in this case, TO BEGIN WITH. And to make sure the cement holes, then the posts and/or anchors are in the EXACT spots, you have to have established a perfectly square layout using what they call batterboards with stringlines attached. (I can explain all this in another post or in a PM if you need to know)


But if you choose to just have the posts sit on concrete pads, here is how you can actually rack the deck square, after all the framing is done:

You use a squaring method called the 3,4,5-method (in cae you haven't heard of this before). Only, because your deck is as big as it is, you can use the same method extrapalated to being the 9,12,15 (foot)-method. What you do is make a mark on the top outside edge of the first left 2 x 10 beam-joist that is on the left side of the deck, out 9 feet from the house. Then you make another mark on the top outside edge of the outer band joist (that stretches 48 feet worth) from left to right, at a point 12 feet out from the left corner. Then you measure between these 2 marks, on that diagonal, and see if it is exactly 15 feet. If it is under 15 feet you would have to grab the front of the deck and slide it ("rack" it) to your right. And if it is over 15 feet you wold grab the deck and rack it to your left. If you wanted you could do the same test over on the right side of the deck framing to confirm this works over there as well. (It should if your 2 x 10's are straight and all cuts equal each other.)

Now with the deck racked square to that 15-foot measurement , you can start screwing down deck boards. If you did not have the deck framing racked square before hand?...you would see crooked cuts up against the house and also your final 2 x 6 deck board would have to be cut triangular shape!

Lots of people now like using those square-bit screws, rather than phillips, as there is no reaming out of the head like you can
have with phillips head screws. But it is up to you. Having 2 drills set up...one for drilling holes first, and one that contains the screw bit is the fastest method.
 
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Old 05-04-06, 08:58 AM
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Originally Posted by jake452
Yes I understand, I was merely indicating that there are a series of boxes being supported by the house on one end and two posts on the other (not literally at the corners). One question (since you made a slight change to your original plan): Would putting a second row of support posts, i.e. 5 ft. from house [roughly half way from house and outer row of posts] eliminate the need to double up the 2x10's or would doubled 2x10's still be better?

Also, I am familiar with the post anchor plates, while I was drawing this out last night, I included this in the plans.

Thanks again for your efforts.
You could do it your way only if you simply rested the posts on those concrete pads, because otherwise you would have a framing/squaring-up nightmare by having that many concrete imbedded posts. (*I* could do it. But even for me, it be tedious and requrire a lot of stringlining and careful placement)

I think my doubled-up 2 x 10's shoud be strong enough as the cantelevering will help, and the span from the 2 x 10 at the house and the securing point of the 2 x 10's coming out from the house, at the support post will be under 10' 6"...about 10' 3" that is unsupported.

But you COULD easily first frame it my way...doubled up 2 x 10's. Then AFTER this was done and the deck was racked square, you could easily slip down through the joist openings the additional posts and pads, eliminating you from trying to align all this in advance!

Would just one 2 x 10 be okay then? Perhaps. But even then I still might go with 2. No danger of breakage with one. It is simply a deflection issue. There would be little deflection if you jumped around, but could be some, especially with a group of people. And if you havd a big party out there with lots of people on the deck..therefore err on the side of overbuilding. It won't cost THAT much more money.

If you go the route of the two rows of posts, then you can move out the farthest post to wherever you wanted them...like to 11 feet or more, let's say. OR... if you wanted to use the posts incorporated into your handrail, you could have them out to the 11' 10 1/2 inch mark out from the house, and use longer posts that would run up beyond the top of the deck by 3 feet to carry the handrail!
 
 

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