Al and Robins 20x30 1 1/2 near Lake Eufaula, OK

[ajbremer]

Rim Joist and middle girder ready for floor joist. All is 2 x 12 treated.



And here's my sketch-up drawing:

[MountainDon]

I don't know if you want me to stop asking questions, but I have questions about those 2x12's?

Looking at the long side, 30 feet long, that means 7.5 feet between supports.

Table R502.5(1) in the IRC is a table for determining girder spans for exterior load bearing walls. These 2x12's will be under the long side walls, which with a standard gable roof makes the long sides load bearing, 25% of the weight of the structure and contents.

For a 20 foot wide building, with a ground snow load of 30 pounds, the minimum amount the charts begin with, the tables show that for a structure with the girders supporting a roof, a ceiling and one center bearing floor, TWO 2x12 would be required for an 8'1" span.

The same table for a structure with roof, ceiling and two center bearing floors indicates the same double 2x12 could span a maximum of 6'8".

It would seem that a single 2x12 on the sides would come up short on load carrying capacity. The table has data for 50 and 70 psf snow loads as well. If we extrapolate down to 10 psf that only gains 9 inches of extra span for the reduction in snow load.

Maybe I'm missing something here?

What else is planned to make this capable of carrying the load safely, especially considering your plans are for an extra half story, an extra floor?



Not to mention that I believe Don_P's comment regarding the welded steel supports would be a really good idea too.

G/L

[pmichelsen]

I would love to see some pieces of angle welded up under those 2x12's to help support them. Makes me nervous thinking about the amount of weight supported by screws and/or bolts.

However it is looking good and I'm sure you can't wait to start building and leave digging in the past.

[ajbremer]

Thursday - September 8th, 2011 @ 11:52am

Thank you Don and pmichelsen for those great comments! I do plan to put bolted or welded angle iron up to help support full weight on those outside rim-joist and I can also (at a later date) add bracing at anytime.

Be aware that those 2x12 rim-joist on the sides are not going to support the whole house weight. I'm putting 2x's down flat on the floor as a sub-floor and then sealing it for the weather for building and weather purposes. Then later I'll come in and put my permanent floor on.

All those tall metal piers will be cut off flush and that's what the sill and walls will sit on.

The weight of the sill plate and the walls will actually be on top of the metal piers. So most of the 'upper' house will actually be on top of the piers and not those 2x12 rim-joist.

Also, when I do the outside sheathing, it'll come down to the bottom of the rim-joist and the whole thing will be one unit. Those charts you refer to may not account for the way I'm doing this?

Does that sound sound? I can add another 2x12 to all inner sides also, that wouldn't be much trouble.

Any help would be appreciated from you guys.

[MountainDon]

I do plan to put bolted or welded angle iron up to help support full weight on those outside rim-joist and I can also (at a later date) add bracing at anytime.

In my opinion, and even more so from my personal experience, putting off something like welded in place support sections or bracing till later makes for a more difficult retrofit installation at the later date. I am in the process of planning a structural improvement retrofit right now. I'm not ready to go into that right now, but it is going to be more work than if it had been done in the first place, and it likely won't be as good as if it had been included in the initial design and build. But I know more now than I did three years ago, so I'll chalk that up as a learning experience.

And that doesn't even get into the area of "what if a problem develops because of the delayed installations?"

The idea behind the supports under the rim.girder is to remove the stress points created by the relatively thin screws through the wood. IMO, there should probably be more concern about the stress on the wood than on the screws. Wood is a wonderful, but imperfect, material. If the 2x12 was a steel component its nature would be homogenous throughout. A piece of wood may have no visible flaws but can develop flaws later after the structure has been in use for a time and the wood dries out.

IMO, welding is superior to bolting. Bolting creates another point load whereas welding spreads the load out. A bolt through a hollow tube may also deform the tube walls if the bolt/nut are tightened too much. At least it's something I'd be concerned about.

FYI, the loads on the first pier at the end of each long wall girder is the lightest load in most pier and beam foundations. The second pier in from the ends is usually the highest loaded pier.

Be aware that those 2x12 rim-joist on the sides are not going to support the whole house weight.   ... All those tall metal piers will be cut off flush ....  

Those 2x12's will be supporting more weight than you may think. I'm not an engineer but here is what I see. (I assumed the posts would be trimmed off.)

#1; the floor joists are all connected to the sides of the 2x12's on the long sides. The floor weight will be directly transferred to those 2x12's. The center 2x12 will be supporting one half the floor load.
#2; the wall loads are spread out along the entire length of the wall. Engineering calculations assume evenly spread loads, unless point loads like heavy bookcases, gun safes and the like are specifically designed for. The wall and bottom plates is not perfectly rigid. While it is true that in the end the piers are supporting the entire load to the ground, there are loads being applied to the span of 2x12 between each pier. Coupled with the floor loads the loads from the roof down through the walls will be acting on the 2x12 rim in between piers as well as on the piers. That loading may exceed the safe load carrying ability of a single 2x12.

I can add another 2x12 to all inner sides also

That could help but does not improve the support for the floor joist ends. Those loads would still be on a single 2x12. That's getting into non prescriptive methods. I can't say for certain there is a problem there but I suspect there may be.

....when I do the outside sheathing, it'll come down to the bottom of the rim-joist and the whole thing will be one unit. Those charts you refer to may not account for the way I'm doing this?[/size

Having the structural sheathing extend from the top plate down covering over and attached to the rim is an excellent technique. That adds anti racking to the walls and makes the structure from the rim up stronger.

As for the tables I believe they have been developed with engineering science and may also draw upon what has been shown to work and not work in real world practice. If/when we move outside that information we may be treading new ground. That's why we will often find the cover your ass phrase, "according to accepted engineering practice" inserted into design discussions. and optional methods.

I'm putting 2x's down flat on the floor as a sub-floor....

I'm not sure I follow the reasoning behind that?  I believe sheet subfloor adds more strength to the floor diaphragm, makes the floor unit stiffer in the x - y plane (north-south, east-east). And costs considerably less. If weather is a potential issue Huber Advantec does have excellent weathering ability.  

[pmichelsen]

Honestly, had it been me I would have cut all of the posts level and then welded some type of saddle to the top that a double 2x12 would rest in and could be bolted to. That is how I plan on supporting my deck, unless I get really crazy and use I-Beams.

[Don_P]

I agree, and it should be redone that way. The pattern here is shown in several texts with a circle and diagonal slash through it. The girders need to be sized appropriately and supported rather than hanging. There should not be a row of screws widely spaced attaching the girders to the steel. The wood will split along the grain as the wood dries and shrinks and the screws and steel refuse to move.

Yes, assemblies are stronger than the sum of their parts. This is the realm of engineers. Prescriptively, and every engineer I've dealt with, you should be able to point to an element and show that it will safely carry the load. If there are other effects at work either calculate and show them capable of supporting the load or do it the simple way and consider any extra you can build in as gravy. If you try to get fancy you'll blow a detail and those increases are gone. Board sheathing is fine, it should be laid diagonally to triangularize the framing. I use Advantech and paint it with porch floor paint or similar, quicker, holds up well, usually cheaper and the floor diaphragm is stronger.

[ajbremer]

Wednesday - September 14th, 2011

Thanks to everyone who has concern about my build, you have made me rethink a few things and reassured me of what I was planning to do anyway.

The main concern that many have had about my build is that the rim-joist and middle girder was 'hanging from' and not 'sitting on' my metal posts, that they are just a single 2x12 and not doubled, and that they are 'just' screwed in. All rim-joist and middle girder will be doubled with 2 2x12's. Also, my metal post have now been cut off flush and I'm using the extra 4x4 galvanized angle-iron to make brackets that will be attached to the metal posts and these will be adding to the strength of the 'hanging from' and 'sitting on'.

Keep in mind that the screws that I used to 'hang' the 2x12 rim-joist and middle girder to the posts are TEKS Wood to Metal Fasteners. The particular ones that I've used are the 1/4-20 x 3" #3 Phillips head. These screws are made to go through 2x's into steel framing. I used 5 evenly spaced screws where every 2x met a steel post. These screws have a pull-out value of 1,803 lbs and a shear value of more than 2,820 lbs. Those screws are not going anywhere! If anything moved it would be the 2x12's. As far as my 2x12's, I got this wood from a house builder friend and it has been sitting and has done most of its moving and bowing. I used the best boards for the rims and middle girder.

After I completed the single 2x12 rim-joist around the outside and ran a single girder down the middle, I nailed another 2x12 onto the middle girder to strengthen it. There are 3 post sticking up in the middle so I used 3 single - 2x12x20's running across each post. I used the screws to attach them to the metal and also nailed the ends of them as usual. The rest of my floor joists are not single 20 footers but lapped 12 footers. They are on 16" centers but the lapped joist are offset the width of a 2x. I'm using joist hangers and nailing the floor joist through the single rim-joist. When I'm done with all of the floor joists I will then nail another 2x12 all around the rim in order to double their strength. After that, I will cut and grind sections of those angle-irons and screw them into the post underneath each rim post for more support.

I have had a building inspector and a home builder come out and they both like the way it's being done and totally believe that there will be no problem with the strength of using this method.

Please continue the comments and suggestions, I would like to always post here about what I'm doing because you guys have 'been there/done that' and this is my first build.

Here are some pictures:





Here I'm experimenting and trying to jack out a bow condition. It worked a little bit but I've learned that it's a lot easier if you just use a straight piece of wood in the first place.

[Don_P]

Thanks to everyone who has concern about my build, you have made me rethink a few things and reassured me of what I was planning to do anyway.

The main concern that many have had about my build is that the rim-joist and middle girder was 'hanging from' and not 'sitting on' my metal posts, that they are just a single 2x12 and not doubled, and that they are 'just' screwed in. All rim-joist and middle girder will be doubled with 2 2x12's. Also, my metal post have now been cut off flush and I'm using the extra 4x4 galvanized angle-iron to make brackets that will be attached to the metal posts and these will be adding to the strength of the 'hanging from' and 'sitting on'.

Keep in mind that the screws that I used to 'hang' the 2x12 rim-joist and middle girder to the posts are TEKS Wood to Metal Fasteners. The particular ones that I've used are the 1/4-20 x 3" #3 Phillips head. These screws are made to go through 2x's into steel framing. I used 5 evenly spaced screws where every 2x met a steel post. These screws have a pull-out value of 1,803 lbs and a shear value of more than 2,820 lbs. Those screws are not going anywhere! If anything moved it would be the 2x12's. As far as my 2x12's, I got this wood from a house builder friend and it has been sitting and has done most of its moving and bowing. I used the best boards for the rims and middle girder.

Some form of bracket will improve things. I'm going to dissect this a little not to be mean but in the hopes that anyone considering this will have more to think about.

A 1/4" 4x4" steel tube 5' long used as a column has an allowable load capacity of 86,000 lbs if the load is placed "concentrically", squarely on top of the post. If the floor system were sitting on the posts we would be simply talking about the bearing strength of the wood.

Hardened structural screws are good things, the manufacturer is giving a shear value of ~2800 lbs/ screw, but, as you recognize, the wood is probably the weak link here. At 1/4" diameter in southern pine, perpendicular to grain, not even 200 lbs/ screw allowable shear. You have 5 in a row, it doesn't work this way, you're violating other rules, but call it 1,000 lbs allowable capacity.

Because of connection design that bearing point has dropped from 43 tons capacity to less than a half ton, that is one heck of a hit. Generally it is easy to design the members, it is the connections that require the most thought.

As you go from "hanging on" to "sitting on" the wood is still going to be most tightly fastened in the hanging on position. It isn't going to know it's sitting on until it slips down enough to fully bear on whatetever bracket you fabricate. Watch for splitting around the screws as you load up and if you see any pull the offending screws and let it sit down on the new seat before reattaching to the post. Figure up the loads and make sure the new seat has the capacity to bear all loads from above. The post is now loaded eccentrically, on one side, rather than concentrically. This reduces capacity, the further you step out from the post the greater the strength reduction.

The concept of using steel here has great potential, this is just food for thought for others considering this method.

[texasgun]

Al I  have done several metal buildings and have thought about using pipe or tubing just like you did and still think it looks like a great option if you noticed my location it is West Texas and in my area we just dont use wood to ground contact anything(I know some people still use cedar posts for thier fence but with pipe so cheap I dont know why) it looks to me your possible problem of the screw to wood conection could be greatly inproved by the wood sitting on something. At the point you are at you could just go buy some metal either heavy angle,square,or chanel and run it full length under the 2xs and weld it to your posts. If you dont weld call someone that puts up buildings and has a mobile rig it will be reasonable and also see if they have any leftover metal alot of time they do and those guys are use to making deals and are very familar with metal fabrication. If you did this all the way around your building I think it would be very stout and would brace all your posts and make them all act as 1 structure. Heck if it was me I would do it under the 2xs and the again a couple of inches off the ground and use colored metal to close in under your building that would match my roof. I might be completly out of line offering anyone advise since I am not anykind of enginer I just build everythind I do extra stout so problems dont happen down the road. I used those screws on my last project and have put lots of trailer bottoms in with them but for your metal connection under your 2xs I would weld it will be lots stronger. ::)After building a couple of large buildings and a house I have found there is lots of places to save money doing it yourself but the foundation is not 1 of them over build and you will never be sorry

[ajbremer]

Saturday Afternoon - September 17th, 2011 @ 12:19pm Oklahoma, USA

Here is a pic of some bracing that I've made out of the cut off galvanized pieces that were left over. There will be at least 2 braces at every post.

[ajbremer]

Sunday Morning - September 18th, 2011

Basically got the floor joists done. Now I'm going to band around the outside with another layer of 2x12's treated in order to make them 'double-girder' - just like I have the middle girder. I guess in my case, the rim-joists are also the girders.

Then, after that, I'll do middle bridging with straight pieces of 2x12's and then the cross bridging. When that's done I will add the angle iron brackets at all post locations like you see in the pic above.

Then, I'll lay down 2x12's on the floor. Apparently nobody does it that way because at that point they usually put down 4x8 sheets of something as a sub-floor and then later put something on that.

I'm laying 2x12's on the joists because:
#1) I've got the wood and am saving money because I don't have to buy any 4x8 sheets
#2) It'll make a stronger floor system because of the thickness
#3) They will lay on top of the posts at 15 locations so that the rest of the weight of the building will not be totally on the floor system but on top of the posts.
#4) It's pressure treated and I'm also going to coat it with a sealant so that the weather won't hurt it if the build takes its time.

Question: Some people have told me that when they build the walls, they don't cut out the window and door spots till after they have it all up because it's easier. Is that a waste of wood, is it easier, what would be the best way for me since I'm doing it by myself?

Any comments and/or suggestions is always welcomed. Here's the floor joists pic:

[RIjake]

Al, your build certainly is coming along!  Please don't take this the wrong way but I just reread your thread and I'm trying to figure out why you went with the steel instead of wood. 

[dug]

Question: Some people have told me that when they build the walls, they don't cut out the window and door spots till after they have it all up because it's easier. Is that a waste of wood, is it easier, what would be the best way for me since I'm doing it by myself?

You have the choice of sheathing the walls either before or after you stand them up. There are pros and cons to both methods, one being easier to raise the lighter unsheathed wall and the other is much easier to apply the sheathing while the wall is on its side. Either way I believe the sheathing is best applied continuously and openings cut out later. I think it makes for a stronger wall and the waste is not much in the grand scheme of things, usually you can find homes for the the scraps in other areas.

[RIjake]

You have the choice of sheathing the walls either before or after you stand them up. There are pros and cons to both methods, one being easier to raise the lighter unsheathed wall and the other is much easier to apply the sheathing while the wall is on its side. Either way I believe the sheathing is best applied continuously and openings cut out later. I think it makes for a stronger wall and the waste is not much in the grand scheme of things, usually you can find homes for the the scraps in other areas.

Plus, by applying the sheathing while it is laying down you can square up the walls and the plywood will keep it square and rigid! 
Dug's right about the scraps.  Who doesn't need a few pieces of plywood lying around just in case?

[Don_P]

Do remember when using boards for floor or wall sheathing that they should be put down diagonally to triangularize the flat plane they are on. That same type of triangularizing, bracing, needs to happen between the posts and your floor system to provide racking resistance.

I really like texasgun's idea for anyone considering this. If it were designed with C channel rims and girder they have load and span charts that are easy to use and welding those to the posts would provide plenty of rack resistance. Joist hangers can be top hung over a wood plate and face welded to the C channel and then the floor could be done conventionally from there.

[ajbremer]

Sunday Morning - September 18th, 2011

Thank you all for your great information.

The reason I went with metal piers and am doing my build high like this is because I liked the idea of no rotting and no insects in the metal. As far as rust is concerned, the metal I've used is galvanized or primed and I also sprayed Permatex Rubberized Undercoating to the bottoms of each post so the concrete wouldn't be able to mess with the metal. The main reasoning behind the floor being so high is so that I can have some storage room underneath and also to make it very easy to build with plenty of room underneath for plumbing and other things.

As far as my question about the walls, what I actually wanted to know was if it is ok to nail all the wall joist to the top and bottom plate and then when all walls have been raised, then cut out the locations where windows and doors will be, then do cripple studs, king and jack studs, etc.. I wasn't thinking about the sheathing in my question but I'm glad it's been mentioned. That way the walls would go up faster and after seeing the view, I could then decide or change my mind about where exactly I wanted a window or door to be.

I'm thankful for Don_P about reminding me of the 45 degree angle of the sub-floor boards on the joists. I saw this real good Navy video over at youtube about doing exactly what I'm doing now. It shows floor joists going in and then the bridging, sub-floor, walls, etc.

Here is that Navy build video link:

I'm confident that my rim-joist will have no problem holding up my build with 2 angle-iron brackets screwed in 5 spots each at the 15 post locations like you see above. I agree that welding angle-iron under each post running the whole length of all the rim-joist would be great, overbuilding, and take more load but I just don't think I have to go that far. Remember that my 20x30 countryplans don't even show a middle girder on page 1 of my foundation plan. I've already overbuilt by putting a middle doubled 2x12 girder attached to metal piers...haven't I?

I'm thankful for all of your patients with me here, I am a beginning builder. I'm telling the truth when I say this, 4 months or so ago I wasn't exactly sure what the difference was between a joist and a stud...no lie! I'm totally consumed with this build. I don't do any of the things I used to do in life - in my 'pre-countryplan' days. All day long I read about how to do stuff, ask everybody all kinds of questions at work, and I'm all over youtube watching build videos. I will tell anybody, countryplans.com is the best place to be to build your house - hands down!

One of my problems is that I'm a machinist with an eye for .001 of an inch. I've been out there building with my digital calipers! Oh ya, by the way, I've measured the thickness of many 2x12's and none of them are 1.5", they range from 1.330 to about 1.44. Also their height differs quit a bit here and there 11 1/4, 11 1/8, 11 3/8, etc.

Thanks again for your comments, all help is always appreciated.

[MountainDon]

As far as my question about the walls, what I actually wanted to know was if it is ok to nail all the wall joist to the top and bottom plate and then when all walls have been raised, then cut out the locations where windows and doors will be, then do cripple studs, king and jack studs, etc..

The openings should be planned out ahead of building. Once you have the subfloor in place you can walk around and decide where to place windows. Then draw it out and build in all the studs in all their flavors, all the headers, etc. Squaring and sheathing flat of the deck is nice but does make a heavier wall to raise. It could be done in sections; just plan it out beforehand.

[texasgun]

Al when people talk about cutting the windows and doors out after they stand the walls the openings are usually framed out completly on the deck and sheathed over and cut after they are stood up. This allows the wall to be stiffer and allows you to be "dried in" quicker openings can be cut later in the build when you are ready to install the window or door. The reason I sugested running metal all the way around under your 2 x 12s is it would better tie the structure, give something to rest on and would provide bracing that you are going to need when you install the large wind sail (house)on top of your tall posts.I feel the cost of metal to wrap around your foundation and tie it together will be a small cost compared to the overall cost of your build. Most mistakes can be repaired in a build but foundation problems effect everything and are often very expensive or impossible to repair once a house is sitting on top of it. I still thing with these fixes your foundation will be very stout.

[ajbremer]

Thanks for your feed back texasgun and MountainDon.

Yes, I talked with a guy tonight and I lined up getting 130 feet of 3" angle-iron to have welded all around under the rim-joist. Thanks guys!

[MountainDon]

Hopefully he is aware of the hazards the welder and bystanders can be exposed to from the zinc galvaizing at high welding temperatures. Best to grind it away first I think.

[Don_P]

While he is there, I've drawn in red on your pic where it would be good to have bracing from the posts to rim or post to joists to help triangularize and brace the posts.



In brown I drew in the direction sheathing boards should be laid, notice again how it triangularizes the floor system. Triangles are locked, they cannot change shape unless the members fail where shapes with 4 or more sides can change shape if the connections act as pins, even a simply pinned triangle is stable.

The green arrow points to joists lapped over the center girder, that lap means the girder is supporting half the floor's width plus any other loads from above. I don't know that 2- 2x12's is sufficient for the girder... what is the span between posts in the center row and are their any loads from above also landing on that center girder?

[ajbremer]

Monday Morning - September 19th, 2011

Thanks Don_P for your advice. Getting the bracing done while the welder is out here is a great idea, I will do it.

My middle girder with the doubled 2x12's supported by the angle-iron and bracing should be sufficient. The 20x30 plans that I purchased from countryplans don't even show to use middle piers and a girder.

I do plan on laying my 2x12 boards down at 45 degrees to the joists.

By the way, did you build your place using countryplans plans? I looked here in the 'Owner-Builder Projects' and couldn't find ya. I just wanted to see how you built your place.

Ok, now it's time for the bridging.

[Don_P]

You've made a change to the floor system that required the center girder, it is now a load bearing element. Think of it this way, remove it and the floor will collapse. In John's plan if the girder was not there the floor would not collapse. You've broken and lapped the joists over that center girder. There is nothing wrong with the girder, it actually makes for a stronger floor if sized correctly... but it is not an unneeded extra with the modifications that have been done. Be careful that you understand what you are doing as you modify plan.

My house predates Al Gore. It is a design I started in high school arch drafting class. Dad was a builder and later became a building official. I grew up in the trades and am a licensed residential contractor. My house is a solar tempered design quite similar to John's home. It is built on a crawlspace and raised radiant slab foundation.

[NM_Shooter]

In some of the pictures, the wood appears to be pressure treated.  Can you please clarify if that is the case?  Modern PT wood will require hot dip or stainless metal fasteners.  Any PT wood to non-hot dip / stainless material should have a barrier of some sort.