Portable garage, or small pole barn style building? It's Gramps Birthday.

[Piston]

My grandfather lives on a mountain in NH.  He is one of 4 houses on his mountain/road.  They get a decent amount of snow and he is still pretty active.  Unless the roads aren't plowed, he goes downtown every morning for his coffee, run errands, and to get his mail.  He doesn't have a garage so he has always had to clean his car off when covered in snow. 

About 5 years ago, we got him one of those portable garages (cheapo $300 dollar unit) to keep his car in over the winter.  Well, it lasted about 3 years until a good storm came and collapsed it. 

The following winter he bought another one, and we assembled it for him.  That one lasted 2 years before a good storm came and collapsed it. 

I was thinking of buying him another one for his 95th birthday, which is this coming month.  Instead of another cheap one that will fall down in a bad storm, I was going to get him a "snow rated" portable garage from Shelter Logic.  They are much more expensive at around $1400 for a 12x25.  Then I started thinking, that although this is "snow rated", I doubt it is "NH snow rated"  :D  I'd hate to spend all that money only to throw it away when a bad storm came along. 

Then I started thinking that maybe I'll just buy 6 or 8 pressure treated posts, bury them in the ground about 4' or so at even spacing, and put 2 large top plates on top of the posts, forming a "wall".  Then either buy, or build, some trusses and throw a roof on it.  It doesn't need to have sides as the main goal is to just keep the snow off the car.  I really don't want him out in his driveway clearing a foot of snow off his roof, or even worse, NOT clearing it off and having it slide off in front of someone else when he is driving down the road. 

The main issue here is TIME!  I will only have 3 days or so to put something up.  This is the main reason I was considering a portable garage, because I could put that up in less than a day, and then actually relax for a day or two.  Then I started thinking about the pole barn idea and how hard it wouldn't really be. 

Does anyone have any advice on which way I should go?  Should I just bite the bullet and buy a portable garage and hope that the "snow rated" one will last considerably longer?  Or would I be able to get a pole barn style building up in just a few days?  It would be fairly small, 12' or 14' wide, and 20'-24' long.  I was thinking of having the roof trusses made to save time, and I can easily dig the holes with the post hole digger on the tractor. 

Any thoughts?

[Al_Smith]

I'm looking into a portable type metal carport to keep an old relic of a Jeep in to protect it from the elements .Installed it's under 1000 dollars 15' by 19' and is considered personal property rather that real estate  improvement thus no property tax .Excessive property  taxes annoy me to no end .A subject I could pontificate on for hours but will forgo that conversation.

[pineywoods]

Single car, all metal portables go for $650 around here. I built a pole building like you describe for a mill shed. Took 2 days start to finish, including building the trusses. But I did have a helper, nail gun, and a tractor with forks.

[Al_Smith]

That price would be about right for a lighter build version with 5 foot side walls I suppose .The price I got was for 6 foot side walls ,heavier metal framework and 22 guage sheetmetal .There was only about 100 dollars diff over the lighter model .

As far as snow load I've never heard of even the light weights collapsing but this is Ohio not NH .

I've seen the canvas sheds and they are temporary at best .Fact just down the road a fellow had about 4 out of 6 of them get blown into the center of a 160 acre corn field the first big wind that blew up .

[Piston]

I didn't really think of a metal carport, that is another option I can look into. 

I built a pole building like you describe for a mill shed. Took 2 days start to finish, including building the trusses. But I did have a helper, nail gun, and a tractor with forks.

I'm not sure I'll have a helper, but I'll have the tractor/forks and nail gun.  Can you give me some details of the pole building?  What did you use, and how did you set the poles? 

How did you make your own trusses?  I was also thinking I could use 3 large tie beams and put a ridge beam down the middle, then just use rafters instead of trusses, but I would think the trusses would be quicker. 

How do I find out how much, or what type of trusses I would need or what they would cost?  Is this a lumber yard thing? 

[beenthere]

This pole shed extension (24' x 24') that was only rim boards, and trusses covered with plywood and shingles, took 3 guys 4 full days (that was after the poles were in and set).
Just tossed in for some comparison.
Will take a good day just to set, brace, and nail in the trusses if working alone, IMO. 
Think I'd go with the cheap and hope it lasts at least two years again. Gpa may outlast it if all goes well.


 

[thecfarm]

2 feet deep would be plenty on the posts. that way you could buy 10 foot 4x4 pt and put them into the ground 2 feet. I did this with a horse run in,once every 4 feet years ago and it has done fine,so far.
Some of those metal carport has the steel roofing running the wrong way. the water runs off but the snow can not slide of from them. One of my friends has one and uses the snow rake to get the snow off

[SPIKER]

As someone mentioned the pole style would be property and subject to tax, maybe inspection? maybe permits?   The cheapo toss em up fabric structures are not as they last only a few years.   there also make aluminum car ports that are better cost more and last better with rounded top flat and rounded over side.

check for Farmtek they have several versions from cheap to very good ones and the fabric ones they have are top rated & warrantied for a long time.

Mark

[Piston]

I've made some phone calls and got some more information. 

I called a couple different lumber yards regarding trusses.  (Let me say, it absolutely kills me to buy lumber when I have a perfectly good mill out back! :D)
I gave them a quick sketch of the width/pitch I'd like for the building, for them to come up with a truss design/cost.  It will be 1-2 weeks before I hear back from them. 

I ended up going with a 16' width and a 24' length, figuring that the trusses will be 2' on center I'll have 12 trusses to put up.

Then I called my town building inspector and assessors office for some info.  The building inspector said that indeed I would need a permit, he told me to sketch up what I want to build and send it in, it would be a small fee for the permit of around $40 or $50 and would take 1-2 days, so that is fine.  The assessor gave me a "worst case scenario" of adding roughly $45 per year on the tax bill.  That is fine with me. 

I'm thinking I would use 6"x6"x12' pressure treated posts, 4 per side. 
Is it okay to dig a hole with the post hole digger, and place the posts directly in the hole, and backfill with tamped gravel?  Or, do I need to pour concrete around the post?  I plan to bury 4' of the post and leave 8' sticking up in the air. 

I'm still haven't decided which way to go yet, but I'm leaning towards the pole barn idea for now.  Once I figure out how much it will cost then I'll be able to decide. 

[Piston]

 Here is what I have so far.  Any advice for flooring materials?  I was thinking of putting some landscape fabric down, then crushed stone for drainage as the area get's puddled up and freezes in the winter, then more landscape fabric covered by gravel.  Does this sound like a good idea?  Should I use plastic somewhere as a vapor barrier?  I'll crown the middle for drainage. 


  

 

[scouter Joe]

Piston you need 13 trusses not 12 for a 24' building . You have it right in the sketch . scouter Joe

[Piston]

Piston you need 13 trusses not 12 for a 24' building . You have it right in the sketch . scouter Joe

Oh ya  :D

[Jim_Rogers]

The fence building book I read many years ago, said to back fill with crushed stone so that the water will drain and no wet dirt sits next to the wood. This is suppose to make the wood last longer.
The only place they said to but concrete would be at the surface as a collar around the post, if you wish.

That's what I did when I build one of my fences except I didn't use any concrete. Having a mill, I cut my own 4x4 fence posts and then painted the bottom 3 or 4' of the post with some wood preservative paint that I got from the hardware store. Back then it was Kuprinal (sp) #10 green, which I don't think you can buy any more.

Another customer of mine wanted to do a horse paddock fence and I milled 4x6 fence posts for her. She bought some fence post paint from Home depot that the paint department had to order in for her. It is for wood that is in direct contact with the soil. She painted the bottom 4' of her posts. The brand was Behr.

I would also suggest if you wanted to save money and you have the time to mill some posts for yourself for this project that you could do the short pole system.

This is you buy pressure treated stock and only use that below ground. Above ground you use your stock. You stand one over the other and sister some 2by stock (PT most likely) onto the sides at the vertical joint.
Like this:



 

Years from now if the below grade post rots out then you would just hold up the roof with a temporary support and dig out the rotten bottom post and replace it. No need to replace the entire post.

Just some ideas to pass along to you.

Jim Rogers

[Piston]

Jim,
When you built your fence, and painted the bottoms of the posts, did you use the timbers green, or let them dry a while? 

If I could get away with using green timbers by painting them, I could use my own logs/mill which would be nice.  I could also mill them larger than the 6x6 dimensions I can get from the lumber yard. 

I do have a white oak that came down in a storm last winter and could use that for posts instead of pine. 

[Hilltop366]

Piston I would be tempted to use logs you have and later if required convert over to Jim's setup by cutting the post off and replacing the bottom.

For the roof framing with a short span like that some old stick frame style rafter framing with ridge board would be easy and faster than getting trusses unless you can find some trusses already made.

I was wondering if a few braces would be required in your drawing?

Your Gramps is lucky to have a you as a grandson! Happy birthday!

[Jim_Rogers]

Jim,
When you built your fence, and painted the bottoms of the posts, did you use the timbers green, or let them dry a while? 

It was a very long time ago, I don't honestly remember but I would say most likely green.

If I could get away with using green timbers by painting them, I could use my own logs/mill which would be nice.  I could also mill them larger than the 6x6 dimensions I can get from the lumber yard. 

I do have a white oak that came down in a storm last winter and could use that for posts instead of pine.

Use what you got, white oak is very rot resistant and you may need some bracing and some proper hold downs so that the wind doesn't blow the roof away like a kite or sail.

Jim Rogers

[Piston]

Piston I would be tempted to use logs you have and later if required convert over to Jim's setup by cutting the post off and replacing the bottom.

For the roof framing with a short span like that some old stick frame style rafter framing with ridge board would be easy and faster than getting trusses unless you can find some trusses already made.

I was wondering if a few braces would be required in your drawing?

Your Gramps is lucky to have a you as a grandson! Happy birthday!

Hilltop,
I was wondering the same thing about braces.  I'm sure they wouldn't hurt.  I was wondering that if they're buried 4' down into the ground, will that be sufficient strength and rigidity against wind side loads?  I suppose there won't be much side load with only the roof exposed to the wind?

Regarding using rafters and a ridge beam, I don't know how to size the rafters properly for the snow load, span, or pitch of the roof, which is the main reason I am avoiding using my own materials.  If I used something like 2x10's for rafters and a 2x12 for a ridge beam, would that be sufficient? 

I'm not "against" using rafters over trusses if it isn't going to take me too much longer to do it that way.  I'd be milling the lumber at home anyways, so that isn't included in my "time constraint" of a few days. 
I should mention too, that I'm fully aware there is a good chance this wouldn't be finished right away.  The most important part is that I get the posts in the ground and set by the time the ground freezes.  I could always come back the following month to finish the roof, I'd just prefer to start and finish it and be done with it. 
(Some day I'd like to just go up there and relax you know ;D)

[thecfarm]

I only used a one inch board for my ridge beam.

[Jim_Rogers]

In order to correctly size and space the rafter stock we'd need to know what the actual snow load is for his location. Your building inspector could tell you that.

And we'd need to know what type of wood you'd want to use. Then we can use the online red toolbox calculator here on the forum to figure out the size and spacing of the rafters.

Also, if you are going to talk to the building inspector to get the snow load, you could mention that you may want to do it with your own stock and see what he says. Hopefully he won't ask you to have it graded.

Jim Rogers

[beenthere]

Piston
The first thing I'd suggest, is drop the expectation that this will just be "a few days". ;)

That will help keep your sanity and you will not be disappointed.

You have a number of things to figure out, but if on a short leash then setting the posts, setting in the rim boards (leveling and notching into the posts, or bolting them on?), setting up the trusses with help from some 16' bracing boards or 2x, adding additional bracing to keep everything level and then whatever you decide on roofing (I missed if going to be shingles over plywood sheathing or if stripping the trusses and putting up metal roofing) will take a fair amount of time.

Wish you well on the planning and gathering of materials.

[Piston]

Beenthere,
I have accepted the fact that this will be a longer project that I was originally planning  :D

Jim,
I called the building inspector, he said that I could use my own ungraded lumber as long as it was not going to be an occupied residence, so anything from garage/barn/outbuilding and so on.

The snow load is 90 lbs/sq foot. 

I'd more than likely be using EWP. 

[Jim_Rogers]

Can you either post the plan here or in the plans section and I can download it and look at the roof area?

Jim Rogers

[Piston]

Jim,
I'm not at the computer with the file stored on it but I'll do so tonight. Actually, the file is pretty basic, I just threw that quick sketch together to satisfy the lumber yards needs. I haven't actually made a real model yet, I wanted to wait and see what the prices were going to look like before spending much time on it.

The roof is a 6/12 pitch and 24' long. Not sure if that is enough info or not?  I did go on the toolbox and messed around a bit but couldn't figure out how to get the dimension needed.



I did look on craigslist real quick and didn't see anything that matches up to what I'd like to do, but there is a garage truss package in there for a 20'x24' gambrel building including floor trusses for a bonus room up top.
I'm sure it isn't rated for a 90lb snow load though.

[Stephen1]

I am going to throw my comment in. Gramps is 95, I would think one of these would out last him. I picked up a shelter logic, 2 years ago, and it has held up quite well to our snow load here. I mounted it on 8x8 pine beams. We are at 60lbs snow load. It is enclosed on the sides and the ends if you want. I picked up from Habitat for Humanity reuse store, for 250$ , 10x12x20. I see we have the same on on sale at the Canadian Tire for 275$ . I use the one I have now for a quick storage of my table slabs I needed to protect.
A permanent structure you never regret though.
All the best on on what you decide

[Hilltop366]

Piston I would be tempted to use logs you have and later if required convert over to Jim's setup by cutting the post off and replacing the bottom.

For the roof framing with a short span like that some old stick frame style rafter framing with ridge board would be easy and faster than getting trusses unless you can find some trusses already made.

I was wondering if a few braces would be required in your drawing?

Your Gramps is lucky to have a you as a grandson! Happy birthday!

Hilltop,
I was wondering the same thing about braces.  I'm sure they wouldn't hurt.  I was wondering that if they're buried 4' down into the ground, will that be sufficient strength and rigidity against wind side loads?  I suppose there won't be much side load with only the roof exposed to the wind?

Regarding using rafters and a ridge beam, I don't know how to size the rafters properly for the snow load, span, or pitch of the roof, which is the main reason I am avoiding using my own materials.  If I used something like 2x10's for rafters and a 2x12 for a ridge beam, would that be sufficient? 

I'm not "against" using rafters over trusses if it isn't going to take me too much longer to do it that way.  I'd be milling the lumber at home anyways, so that isn't included in my "time constraint" of a few days. 
I should mention too, that I'm fully aware there is a good chance this wouldn't be finished right away.  The most important part is that I get the posts in the ground and set by the time the ground freezes.  I could always come back the following month to finish the roof, I'd just prefer to start and finish it and be done with it. 
(Some day I'd like to just go up there and relax you know ;D)

Cutting out rafters is not hard to do once you have one just copy an cut it goes pretty quick, if you take the time  to get your top plates even and straight you could pre-cut the rafters and have them ready to go it should not take much longer than putting up trusses and will be easier to handle,  not sure on the lumber size but would guess a 2x6 24" oc  would be a place to start to check.

A ridge board (goes in between the rafter tops) can be a 1x but I find a 2x easier to toe nail the rafter to.

A brace from the top of first and last rafter down to bottom cross tie will keep the whole roof from moving end to end. As Jim mentioned some hurricane ties would be a good plan too.

[Piston]

I am going to throw my comment in. Gramps is 95, I would think one of these would out last him.

You'd be surprised.   ;D  I don't see the portable garage outlasting him.  He still mows his 1.5 acres of lawn, shovels his walk way, climbs ladders to shovel the snow off his roof, and is planning on scraping and painting his entire house in the spring.  Although he works slow, he hasn't slowed down.   :D

I should mention something, my grandfather isn't really 95.  He's actually 65.  When he reached his 80th birthday, he decided that instead of getting a year older every year, he is going to go the other way, and get a year younger  ;D  So ever since he turned 80, we've been counting backwards.  In fact, now that I think about it, I believe it's time for him to come out of retirement and get back to work.   :D  He says once he turns 100, he'll be able to get his face printed on a Smuckers jar  ;D  Apparently they do that.   

Really though, the main reason I'm hesitant to go with the portable garage, is because one bad storm will take it down.  He's gone through 2 of them in the last 5 years or so, the last one only lasted 2 winters, and really not even that long, since it collapsed during the second winter. 

What is your snow load up there?  I wouldn't be surprised if it's less than we have down here. 

Even if the shelter would outlast him, it doesn't mean I only want it to last that long.  I am hoping that his house and land stay in the family for my grandkids to enjoy, and I can only dream of being the "mountain man" as he is referred to, and sitting there on the porch drinking a warm glass of scotch while my grandson builds me a dang car port.   :D :D

[sap retreiver]

I'll agree with watching my grandsons do some building! On the topic of post in the ground, I say no concrete, even as a cap. Thats the first place it'll rot. The newer pt will take it pretty good but if your gonna waste time you mine as well waste it the right way.The oak will last 20 maybe 30 if treated right, pt longer. Not a fan of straight stone either some good crushed gravel that drains would be ideal (just remember it needs to drain out of the hole you dug also), it would also be good for your base for the driveway then you could leave it as is or put stone over it to look pretty and get thrown on the lawn with the snow. The fabric or plastic just stops weeds for the first couple years. Once you have a roof over it and pitch it no more puddles and gramp is happy happy happy!
oh ya, my vote is for the American made pole barn. Good luck!

[thecfarm]

I would use the ground fabric. It's not really used to keep the weeds down. The real reason is to keep it from mixing and sinking into what is already there. Than you have mud again.My Father and me did the woods road with gravel.We did not know about that stuff. The gravel is just about gone into the ground.My 500 foot driveway was done with ground fabric. It's still there,even after 2 times of logging trucks.The woods road,not so good.

[Stephen1]

Well if he is only 65  8) then by all means build the  good shelter.

[beenthere]

Piston
Took a pic of the laminated post cut-offs that I used (concrete pad at the bottom of the hole and tamped gravel around the posts). Also a pic of the top of the posts showing the two 2x10 rims bolted onto the posts (outside lams cut off for a step rest easily done after the posts were set and could get the height of the rims). The tops of these lam posts are not glued so easily sawn and prepped).

The lam cutoff




And the rim connection with trusses on them
(boxed in so birds couldn't nest on the rims)

[rmack]

as far as the posts go, I saw a new product in home depot last week, it's an epoxy polymer foam that is supposed to be able to take the place of concrete. you mix it and pour it in a sono tube around/under the post like you would concrete. it does dry very hard.

it was very pricey but I believe it claims to get around the moisture issues related to concrete.

[beenthere]

But it seems it wouldn't get around the negative trapping of moisture around the post, which is the biggest problem with encasing them in concrete.. as I've grown to understand.

[Piston]

I received 2 quotes for the materials needed to build the carport, with premade trusses to make it easier/quicker to build.  I was on the fence with the cost of materials but figured it would be better to bite the bullet and build the real deal rather than a fabric garage.  I verified with the tax assessor that his taxes wouldn't go up very much (less than $40 per year worst case) and made the final call to my grandfather to let him know when I'd be coming.  Up to that point, he had no idea I had been planning this (in fact, he still doesn't know), well I told him I wanted to buy him a portable garage for his birthday, and was just about to explain my 'change of plans' to a more permanent structure, when he interrupted me and told me he "beat me to it".   ??? ??? 
I was unaware that earlier this spring, he found a sale on Shelterlogic portable garages and purchased a 12'X20' model for the winter time.  He said he was going to ask me to put it up when I came up.   :

Well, there that plan went  :D  No real carport this year!  Oh well, it made it easier for me and he seemed to be real happy about the 'deal' he got on it, win win I suppose. 

I told him that instead of just throwing this one up and placing it on the lawn like the last ones (that didn't last) we were going to make a proper base/foundation for it.  Also, he had a drainage issue where he would get standing water as the snow melted, then it would freeze solid when it cooled off, so I told him we'd take care of that as well.

He got his first "garage" back in 2008.  He wanted to put it in a spot that was right under a large pine tree that my father planted when he was a little boy.  He wanted that tree taken down and put the tent garage there.  No problem grandpa...

(Fall of '08)


  

 

He actually wanted the portable garage right where the tree was, but since I didn't have my handy dandy stumpgrinder (or tractor) at the time, we worked around it.  (I'm going to refer to the portable garage as "garage" from now on, despite the fact that I hate calling these things garages and have an awkwardly strong "aversion" to these fabric "garages")
Since then, he's gone through 2 of these garages, and we'll see how long this one lasts.  This WILL be the last one.   ;D


Here is my little update on how it went: 
First thing I had to do, was finally take care of that (now 5 year old) stump.  It wasn't so much that the stump was the problem, but the large shallow roots spread out quite a ways from the stump, so I had to "chase" them to get rid of it all.... a lot of re positioning chasing roots 



  

  

  

   

  

 

Sometimes, I get take a little bit too big of a bite... It's surprising how "solid" the stump can be once you get a few inches below ground, into the "heart" of the stump.  I always thought Pine rotted quickly.  ???
 

 



Because of the drainage issue, I was going to add quite a bit of crushed stone, enough to bring the base up about 10" or so.  My grandfather also suggested we put some drainage pipe in, the only problem was I'd have to remove part of the 5' retaining wall on the other side to get the pitch correct on the pipe.  So that is what we (I) did. 
 

  

 


Next step was to measure and mark the hole locations for the Sonotubes.  Rather than measuring them out, I thought it would be more "idiot proof" to set up the frame (since I had to do that anyways) and square if off in place, then just mark the 4 corners, move the frame out of the way, and drill all the holes with the post hole digger.
 

  

 


Time to drill some holes  ;D....
 

 
 

    




Then I had a truckload of stone delivered.  I thought I'd only need about 8 yards but since the truck was going to cost me the same for delivery whether it was an 8 yard load, or a full 12 yard load, I figured I'd spend a few extra dollars on stone and get the 12 yards.  I thought I would have plenty left over to use in other areas, but it turned out to be the perfect amount, and I wouldn't have wanted any less.
 

 

Then put the bucket on the tractor to spread the stone.  It worked okay, but I kept wishing I had my 8' rear blade to level the stone.  It was a bit of a pain leveling the stone from left to right.  The right side was a bit lower than the left, so I had to scoop a bit of stone from the left, dump it on the right, then backblade it a bit to level, and keep doing that.  I even had to get off the tractor and actually use physical labor a couple times     You know, like with a real shovel  ;D 
You'll see something that you'll rarely EVER see in my pictures, in some of the next ones.  Notice that instead of the grapple on the front end loader, there is a bucket.  That is a very rare thing for me to have on my tractor  ;D
 

 


Then I attached the pressure treated sill over the concrete piers, using anchor bolts that I set when I poured the concrete.
 

 

All the hard work was done at that point, then it was just a matter of screwing the garage frame down to the sill with lag screws, and fitting the canvas over it. 
 

  

 

I put his Explorer in the new garage.  He was very happy about how it turned out.  It was good timing as well, the next morning he woke up to snow on the ground, even though it was just a dusting he was happy to have his car nice and clean. 

And that's that, one more project out of the way...we'll see what he has for me next time I go up there  :D

[thecfarm]

A nice story and nice job.That will make Gramps happy. It's nice you have all that stuff to play with.  ;D   He won't be in the mud and water this spring. I don't like them "garages" either. But saying that I have seen some that last for years, and some not much more than 2.
I do alot of clearing behind the house. I want to get it back again as a field,like it was when I was growing up. Those white pine stumps will stay there for years. And be nice and solid inside. Almost look like I just cut it. I dig them out with the tractor after 5-6-7 years. I have a few that I can try this summer to get out. Most times they come out all in one piece too. A white maple, if I keep the suckers off it,is just about gone in the same time frame. The stump is all rotten.

[Stephen1]

Grandpa is Happy, and when that shelter dies you have a base for a real structure.

[Hilltop366]

What is this shovel thing you speak of?

Well done!

[Thehardway]

Hope you don't mind me hijacking the post since your project is kinda done.  I have been toying with the same general idea, only in my case it will be a tractor/ machine shed instead of a carport.

Lately they have been doing a lot of utility work around here and replacing all the power poles.  Many of the rural landowners keep the poles for fenceposts etc. but in the more dense neighborhoods they have no use for them and end up back at the power company.  I have lined up several for my project.  I can cut them or use them whole.

So my big question is this, if time is of the essence, would it not be easier to lay down two long poles or timbers as sill plates and build up from them rather than burying multiple poles?  If you bevel the ends of the sill plates to form skids, and brace it well, the whole structure can be relocated using a tractor or 4WD truck to drag it.  Since I am always changing my mind about where to put stuff, this seems a desireable thing.  No holes to dig, no concrete to pour.  2- 30' sills made from a treated power pole and each put on a shallow gravel trench each side of the building about 16-20' apart, some home milled EWP or SWP posts to support the lightweight trusses or rafter and tie system.  Some 1/2" rebar driven through the poles into the ground could be used to hold it in place if you were concerned about wind or uplift.   I think this could be done in 2 days time with a helper.

Only downside I see to this is that side entry is obstructed by the sills.

Any opinions?

[Rockn H]

Hardway, something you may want to check on to help make up your mind is taxes.  Here, as soon as you put a hole in the ground for footings or to anchor your "portable" carport it goes on your property taxes.  Anything on blocks or skids does not go on your taxes. ;)

[Piston]

Hardway,
I would think something like that would work.  It sounds like you basically want to build a more traditional style foundation with full length sills?  It would obviously need very sturdy bracing and you'd need to make sure your cross sills were at least a bit higher than the long sills (so when you "tow" it around it doesn't dig in).  I'm not sure how easy or effective it would be to tow it, but theres only one way to find out  ;D

Essentially, if I had put beefier sills in place of the 2x6's that I used, say 6x8s or bigger, I could tow it around just fine.  Are you planning on using a portable garage like I did, or building a real structure? 

[Holmes]

Nicely done Piston. 

[Thehardway]

I would plan on building a "real" structure.  It would basically be about 4 or 5 bents morticed or bolted into an uninterrupted sill with braced girts and top plate supporting some lightweight trusses and a tin roof.  No holes or permanent foundation to maintain the "portable" status and keep it off the tax records.  Just some gravel or rubble to give the sills drainage.  Hopefully I'll get to it this spring.  Picked up 30- 15' poles yesterday plus some stubs I can use as fenceposts.  I'll post a sketch when I get a few extra minutes