Framing questions for a portable building.

[Fullblast]

Hello, I live in Houston and I’m preparing to build a 16x50 portable building/home. I don’t want it to have wheels.

I want to frame the walls 24” oc with 2x6s that way I can use R21 or R23 wall insulation for better energy efficiency and really to help soundproof it. I’m going to use double top plates also.

Is this advisable considering it’s a portable building and might be moved in the future, or should I stick with 2x4s on 16” oc. But if I do that I’ll lose my sound dampening and some r value.

I already have many 2x6s and 2x8s, enough to do the floor and the walls.

1) Will using 2x6 24 oc make it less structurally sound than 2x4s?

2) Would it make a big difference framing the floor out of 2x8s instead of the standard 2x6 floor?

3) Would there be an advantage of using 5/8 plywood on the walls vs 1/2”. I’m only going to use Cdx plywood, as I don’t like osb.

 

[ybnormal]

how many "hundreds of 2x6s and 2x8s" do you have? enough to finish the build?

 

[Fullblast]

Around 250 or so 2x6s, 2x8s, and 2x10s. Have a lot of 2x4s too

Ive got enough 2x6s to frame the floor and the walls for sure.

 

[ratflinger]

ICF is what you want (Insulated concrete forms).

Considering the price of wood, build a metal building with the thickest spray foam you can get. (ICF is still better)

 

[Fullblast]

Im going to definitely go with a metal roof. Metal is not very cheap either.

I would rather not use any spray foam, just batts or rock wool. I don’t want to breathe any potential gases or dust from spray foam.

I dont know how insulated concrete forms could be portable.

 

[ybnormal]

there are also special ICFs that can be lifted into place by 2 men; 10ft long and about 80lbs iirc. stack and mortar, cut your holes for windows, then pour concrete in the walls. you may also want to take a look at SIPs (Structural Insulated Panels). you can get them with pre-cut/formed channels for wiring etc

 

[Fullblast]

Yeah I’ve looked into the structurally integrated panels and thought about it. I saw one company that sells portable buildings with them.

I’m pretty much sold on wood framing because I have all of the lumber except for the trusses. I also have a disdain for osb, and sips are made from that.

My main concern now though is Will 2x6s on 24” centers affect anything structurally vs 2x4 on 16’’ centers if i go to move the building.

Lumber prices are not near as crazy as they were a year ago here. A 2x6 is 4.30, 2x4 is 3.09. 1/2“ Cdx is $24

 

[kbs2244]

16x50 sounds like 4 modules
each 8x25
to make it moveable

I have seen them going down the highway
so it is doable

 

[readhead]

My company builds up to 16x40 with four skids. The rigidity comes with the siding. Most shed builders use LP Smartside which comes in 3/8" and 7/16". We use 7/16" on all of our buildings. We frame everything 16" OC. If you go with 24" OC framing then a stiffer panel would be important. The walls need to be tied to the rim joist also. You are going to see a big jump in price to go to 5/8" siding.

 

[MerlinsBeard]

I'd always take 16" oc and live with the minor % insulation loss; the loss of utility for mounting things is too high. Use 2x6" studs if you can afford it. Prefer rockwool if you can afford it.

 

[readhead]

Have you considered insulating the floor? It takes some work but for that size I think it would be worth it.

 

[cannuck]

You might want to look at doing 2x6 plates with alternating 2x4 studs. Will give the thermal and sound break your want. Also another vote for doing the floor. A 2x8 floor and ceiling with fiber insulation both side could be well worthwhile even in TX heat. Note post #9 and think of using steel beams along each wall to move. 2x6 framing for windows and doors should be fine. The double top plates would be a huge thermal bridge in very cold places, but suspect won't be a big deal in TX.

 

[billconner]

I think the "portable" is key. I've noticed modular homes - not meant to be moved once in place - seem to be 2x6 often 16" on center and 2x8 or 2x10 floors. Very robust for that first and only highway trip. Heavier of course.

I do like 2x6 24" OC with 5/8 drywall and 3/4 sheathing, and as many windows as possible 22" rough opening. Keeps things simple.

 

[Joemctag]

My company builds up to 16x40 with four skids. The rigidity comes with the siding. Most shed builders use LP Smartside which comes in 3/8" and 7/16". We use 7/16" on all of our buildings. We frame everything 16" OC. If you go with 24" OC framing then a stiffer panel would be important. The walls need to be tied to the rim joist also. You are going to see a big jump in price to go to 5/8" siding.

16 x 40 moved as a whole building? Are mobile-home movers who does this. OP could build in way that makes moving it later easier. The 16’ wide ones have 4 lengthwise beams/girders?

 

[PoorUB]

Hello, I live in Houston and I’m preparing to build a 16x50 portable building/home. I don’t want it to have wheels.

How you intend on moving it may have some bearing on how you build it. Are you going to crane it on a semi trailer? Hire a house mover? Slide it onto a semi trailer?

 

[theoldwizard1]

Hello, I live in Houston and I’m preparing to build a 16x50 portable building/home. I don’t want it to have wheels.

The big question is, what are you going to use for skids under each footer ? I would use triple 2x8 or 2x10.

1) Will using 2x6 24 oc make it less structurally sound than 2x4s?

2) Would it make a big difference framing the floor out of 2x8s instead of the standard 2x6 floor?

3) Would there be an advantage of using 5/8 plywood on the walls vs 1/2”. I’m only going to use Cdx plywood, as I don’t like osb.

1) Yes. How tall are the walls ?

2) Floor joist depends on spacing and on what you plan on using for the sub-floor. If you are going 24" O.C. and 3/4 T&G plywood. you should probably use 2x10. These joist need to be ABOVE the top of the skids. You need blocking down the center where the sub-floor meets.

3) Are going to have plywood interior wall sheathing ? When you are dragging this thing around, the wall will be moving. I would use 5/8" on the inside and out side.

 

[nadogail]

Rather than ask a bunch of wannabees for free advice, why not pay a professional whose license and reputation depend on your getting the information you are seeking?

Free opinions are rarely worth what they cost you, I guarentee that any advice you get from me will be worth exactly what the check you write me for it is worth.

I am a fan of wide top and bottom plates and studs spaced on the edges; that way sound vibrations on one wall are not mechanically coupled to the other wall on the same plate in addition to fiberglass, sound board can be woven through the space between the studs.

 

[readhead]

Relax everyone. 16x50 is a very common size in southern states. The skids are laminated 2x6's and usually a double lam under each side wall and a quad lam for the two center skids at 5' OC. They are made up with ground contact PT.

The shed industry has dedicated shed hauling trailers to haul these buildings that are pretty magical. The trailers extend to whatever length you need to haul one or more buildings. They can move sideways, they tilt to unload, they have a winch system to help load and even a spinning base to turn small sheds if they need to face a different way coming off the trailer.

What the OP wants to do is not strange or unusual at all. If anyone wants to see how these buildings are transported there a lot of shed videos on Youtube.

 

[alinc100]

Why not frame with 2x6 at 16" centers. this would require more 2x6's but gives you the most R-value. Also the suggestion of 2x s staggered for sound is great suggestion.

 

[Fullblast]

Thank you Redhead, I’m glad you know exactly what I’m talking about.

I can custom build one with cdx plywood, flooring, drywall, insulated and a Mini split ac for cheaper than the price for a pre built. I already have a lot of wood anyway. Pre built 16x50s are in the 25-27k range.


I know most of them use Lp smart siding panels, but I had planned to use Hardie planks. Would it be more rigid with 7/16 smart panels?

I would think with 5/8 cdx plywood sheathing, that should make it pretty structurally sound.

You might want to look at doing 2x6 plates with alternating 2x4 studs. Will give the thermal and sound break your want. Also another vote for doing the floor. A 2x8 floor and ceiling with fiber insulation both side could be well worthwhile even in TX heat. Note post #9 and think of using steel beams along each wall to move. 2x6 framing for windows and doors should be fine. The double top plates would be a huge thermal bridge in very cold places, but suspect won't be a big deal in

My company builds up to 16x40 with four skids. The rigidity comes with the siding. Most shed builders use LP Smartside which comes in 3/8" and 7/16". We use 7/16" on all of our buildings. We frame everything 16" OC. If you go with 24" OC framing then a stiffer panel would be important. The walls need to be tied to the rim joist also. You are going to see a big jump in price to go to 5/8" siding.

 

[Fullblast]

You might want to look at doing 2x6 plates with alternating 2x4 studs. Will give the thermal and sound break your want. Also another

vote for doing the floor. A 2x8 floor and ceiling with fiber insulation both side could be well worthwhile even in TX heat. Note post #9 and think of using steel beams along each wall to move. 2x6 framing for windows and doors should be fine. The double top plates would be a huge thermal bridge in very cold places, but suspect won't be a big deal in TX.

Im liking the idea of staggered walls, 2x6 plates with alternating 2x4s as a decoupler. I know it eliminates thermal bridging, but will you be able to put more insulation In it than a 2x6 24 oc wall?

I had planned on installing R23 rockwool in the walls with Hat or R channel, then using 5/8 drywall.

I planned on Doing R38 insulation in the attic, along with polyiso under the roof sheathing.

Also I planned on insulating the floor with R19

Will 2x6 joists on 20” oc with 3/4” cdx not be enough?

The building will be elevated off the ground about 20 inches on a bunch of telephone poles I have. It needs to be that high because we get serious floods.

I’m very concerned with efficiency because it’s going to be ran completely off grid with solar.

 

[cannuck]

Im liking the idea of staggered walls, 2x6 plates with alternating 2x4s as a decoupler. I know it eliminates thermal bridging, but will you be able to put more insulation In it than a 2x6 24 oc wall?
I’m very concerned with efficiency because it’s going to be ran completely off grid with solar.

Same amount. Simply use 6" batts and split them in half. The thermal and sound break will easily give you $R19 over the whole wall, not with a bunch of cold spots at each stud.
for reference, here are the recommended R values for roof, floor & walls (note in cold areas they suggest insulated sheathing to get a thermal brake for studs, foot and top plates. https://www.waldeneffect.org/blog/Insulation_R-values_and_cavity_depths/ If you are going off grid, suggest you insulate one class colder than your geographic location.
I made an omission on floor - meant 8" of insulation but not realistic to have 8" floor joists spanning 16'.
Now, back to the table and your status off grid: Note the top end of roof insulation is R60 - where you need to be. Plan on R19 batts between rafters on ceiling, but need 2 more layers runnng 90 degrees (rolls) to make that value. You need to design diffent from most to get that. Also think about dropping the eaves to cover top plates

 

[Fullblast]

So are you saying that just by having a staggered wall, it’s automatically R-19 without insulation?

What would a staggered stud wall be with R23 rockwool?

I’m really starting to dig this double staggered wall idea. It looks like it will solve my problems, add more mounting options and will only be a few hundred bucks extra.

It does add some additional weight, but I’m going all cdx plywood and metal roof so it should balance out.

So I see the point of 2x6 trusses is to use R19 insulation directly under the roof sheathing.

Most of these buildings are built with 2x4 trusses though. Its not going to hold any snow or anything, so I don’t see any other reason to go 2x6.

Yes theres going to be about a 4 to 6” overhang and going to go with vented soffit there.




Here are a few pics of portable buildings inside and out and how they are loaded up on a trailer.

 

[Firebrick43]

Thank you Redhead, I’m glad you know exactly what I’m talking about.

I can custom build one with cdx plywood, flooring, drywall, insulated and a Mini split ac for cheaper than the price for a pre built. I already have a lot of wood anyway. Pre built 16x50s are in the 25-27k range.


I know most of them use Lp smart siding panels, but I had planned to use Hardie planks. Would it be more rigid with 7/16 smart panels?

I would think with 5/8 cdx plywood sheathing, that should make it pretty structurally sound.

You do not want to use hardi planks and then move it.

 

[billconner]

Instinctively, the staggered stud wall can't be as strong. A stud wall with sheathing - ply and gyp - attached to both sides is stiffer than sheathing one side only. Stronger still if skins are glued to studs. I dont know whether a staggered stud wall is strong enough to be portable.

 

[readhead]

The staggered stud design is great for decoupling one side from the other for sound. It is used for party walls in townhouses and hotels but it has its own set of problems. You will use twice as much material. Material equals weight which will make it difficult to impossible to move. Batt insulation is difficult to install. For this build maintaining the 16” spacing and being precise about installing the shear assembly is going to be very important. I have seen video of long buildings like this failing because the siding wasn’t installed correctly. By the way if you ever think you will move this building then Hardie is out. You need to think light for everything you do.

I think a better and easier way to deal with the sound issues would be horizontal metal hat channels or wood strapping to mostly decouple the inside from the outside.

 

[Fullblast]

The staggered stud design is great for decoupling one side from the other for sound. It is used for party walls in townhouses and hotels but it has its own set of problems. You will use twice as much material. Material equals weight which will make it difficult to impossible to move. Batt insulation is difficult to install. For this build maintaining the 16” spacing and being precise about installing the shear assembly is going to be very important. I have seen video of long buildings like this failing because the siding wasn’t installed correctly. By the way if you ever think you will move this building then Hardie is out. You need to think light for everything you do.

I think a better and easier way to deal with the sound issues would be horizontal metal hat channels or wood strapping to mostly decouple the inside from the outside.

So the real question here is what is the maximum amount that a shed hauler can move.

My plans now are a building with standard 16 oc framing with 5/8 drywall and hat channels, completely insulated, 6 foot deck on front, Smart siding panels, laminate flooring, a framed bedroom, a small room, a bathroom. Kitchen, washer dryer, mini splits ac, Wood stove and solar panels mounted to the roof.

Basically an 800 square foot off grid house.

All my batteries are mounted to a separate solar trailer.

Or would I need a
lowboy and a semi to haul this or hire a moving company? I would rather stay away from an expensive moving company.

I have a friend with a semi and 53' lowboy and I have a big forklift too.

I'm pretty sure that lowboy trailer would haul it, and I could also make it 3 feet longer.

 

[readhead]

A forklift would concentrate to much load in a very narrow space. It would have to be a crane. I know that Dirksen moves buildings that large but they are usually new and empty. There are trailers that can haul more weight but you would have to find one near you. Call some dealers around you and tell them what you want moved and they can probably point you in the right direction. Keep in mind that when you get wider than twelve feet you will have the expense of pilot cars.

 

[Fullblast]

Thanks, I'm going to plan just with the basics now and I'll figure the rest out as I go. I really just want a building for now.

Could you tell me the basic framing specs for one of these buildings?

I know the floor is 2x6 but what is the spacing.

The rafters are 2x4 but what spacing?

I definitely want to add solar panels so I need the build the roof at a 7/12 pitch for a 30 degree angle.

I'm going to go ahead a frame 2x4 16 oc but I see they put a double 2x4 every 4 ft. What's the reason for the double 2x4?

Also use 1/2" drywall on hat channels and fiberglass batts throughout instead of Rockwool because of the weight.

 

[readhead]

Floor is 2x6@16” oc
Walls are 2x4@16” oc
Trusses are 2x4@24”oc

The reason for the double stud every four feet is because the guys installing the siding can’t seem to get the laps to line up on the studs. My guys don’t seem to have that problem. What will really piss you off with the double stud is that only one bay every four feet will take a full batt. You have to rip an 1 1/2” off all the others.

 

[Fullblast]

Floor is 2x6@16” oc
Walls are 2x4@16” oc
Trusses are 2x4@24”oc

The reason for the double stud every four feet is because the guys installing the siding can’t seem to get the laps to line up on the studs. My guys don’t seem to have that problem. What will really piss you off with the double stud is that only one bay every four feet will take a full batt. You have to rip an 1 1/2” off all the others.

Thank you Readhead,I appreciate it.

Do y'all use 16' 2x6 joists?

I have a bunch of 2x6x8s and a bunch of 2x6x10s and 12s.

Can I scab the 2x6x8s onto the 2x6x10s for the joists?


What is the reason for having the siding start 4" I believe above the rim joist? Is that to get a shed forklift under there without breaking the siding?

 

[readhead]

Joists need to be continuous because when it is on the trailer only the two center skids are supported.
The wall height is based on a 8’ sheet so most builders start 1” above the bottom of the rim and go to the top of the top plate to get maximum shear value. That space can vary. My builder starts the sheet at the bottom of the rim which looks best to my eye.

 

[Fullblast]

1 inch would sure look better than 3 or 4" like I'm seeing around here.

Do you use pressure treated 2x6s for the joists?

How about the rim joist, what lengths do you y'all use to make 40 footers?

Are the skids continuous also?

I have over 200 feet of old true 3x5 cedar boards I wanted to use for skids. Would that work?






Heres a pic of a shed I took yesterday with at least 3" of rim joist showing.

 

[readhead]

We don’t use PT for joists because it is very dry here but it is used in other parts of the country.

The rim is made up with whatever lengths the builder wants to use. The rim is supported by a skid attached directly below it.

We use laminated skids over 16’. Side skids are two wide PT 2x6 and the two center skids are four wide PT 2x6.

Cedar is not very structural but it would probably work on a small building, maybe 12’ long. If you don’t plan on moving it, maybe longer.

 

[Joemctag]

1 inch would sure look better than 3 or 4" like I'm seeing around here.

Do you use pressure treated 2x6s for the joists?

How about the rim joist, what lengths do you y'all use to make 40 footers?

Are the skids continuous also?

I have over 200 feet of old true 3x5 cedar boards I wanted to use for skids. Would that work?






Heres a pic of a shed I took yesterday with at least 3" of rim joist showing.

We did a lot of design work for a portable building that we never built and the max height above the road was a consideration.
I’d bring that up with the hauling guy before I got the roof built and everything.
I think it’s more than just “ keep it under 13’-6”. You can maybe be higher, just not go through a very few places.
With your 7:12 roof,skids, hauling vehicle itself, it adds up.
I admire you goal of having an off-grid home that you can move. Wish you the best!

 

[Fullblast]

We don’t use PT for joists because it is very dry here but it is used in other parts of the country.

The rim is made up with whatever lengths the builder wants to use. The rim is supported by a skid attached directly below it.

We use laminated skids over 16’. Side skids are two wide PT 2x6 and the two center skids are four wide PT 2x6.

Cedar is not very structural but it would probably work on a small building, maybe 12’ long. If you don’t plan on moving it, maybe longer.

Man that sounds like some pretty heavy duty skids! I was really hoping to use those cedar 3x5 for something.

Also, my building will never ever be directly on the ground because of floods.
I have a bunch of telephone poles I’ll cut about 20 inches high and set the building directly on those Instead of cinder blocks.

I planned on staining the entire underneath and the skids as well. I still may go with PT skids though.

Theres a shed upgrade center called Enterprise and they are building custom fully finished cabins for $110k to 150k That’s drywall, real windows, 2 bedrooms 2 baths, triple transom, lofts, cabinets, central air…..the whole 9 yards. Going to call them monday and see how they move these once they are completed.

 

[Fullblast]

We did a lot of design work for a portable building that we never built and the max height above the road was a consideration.
I’d bring that up with the hauling guy before I got the roof built and everything.
I think it’s more than just “ keep it under 13’-6”. You can maybe be higher, just not go through a very few places.
With your 7:12 roof,skids, hauling vehicle itself, it adds up.
I admire you goal of having an off-grid home that you can move. Wish you the best.

Thank you for the encouragement. I planned on building the roof for the max allowable height while being towed give or take A few inches. I do plan on making the eaves over hang about 6 inches so I can put vented soffit on there for better ventilation in this brutal heat.

I may never even move this thing, but I want peace of mind knowing that I can take it anywhere and can survive. All I need is to drill another well or catch rainwater wherever I go.

 

[readhead]

I wouldn’t worry to much about height. In Colorado it is 16’ without a special permit. It may be similar where you are. At 16’ wide you will have to have a pilot car, maybe two. They will run the route before hand with a pole and change the route if necessary.