w*
Having enjoyed all the posts I follow over the last few years, I now find myself starting a post. Bear with me on this as I learn the process.
I have just started a 10' x10' office shed in a hidden corner of my backyard. I will take any and all recommendations on this project. i would like to build it well, as I hope to build a family cabin in the next 2 years after this project.
My little corner of the yard, hidden by back corner walls (painting them green in case you see the 2 colors.
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG00046.jpg)
another view
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG00047.jpg)
First supply run (MtnDon... The Cherokees keep going)
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_3832.jpg)
Cleared a patch down to the solid ground for work to start
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_3835.jpg)
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_3836.jpg)
Here is the hidden spot for my SHED... shhhh office.
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_3837.jpg)
Soomb, not only do we have the same taste in vehicles, except mine is dirtier and has scrapes and scratches that are too obvious, we both have shovels with blaze orange painted handles. :D Mine wander off and hide without orange painted handles. >:(
Nice private spot.
Concrete pads in. Pre-cast concrete in place and ready for PT lumber. My job foreman did a walk thru for me.
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_3838.jpg)
PT Beams in and I measured ahead and pre-nailed Simpson H1's into place. After reading the Floor Framing post, I took some of the good advice and square my PT beams prior to moving a step forward. I also took MtnDon's post advice to place the two outside joists first and make them square.
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_3932.jpg)
I set lines off of the squared joists using a 16d nail as my spacer.
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_3934.jpg)
Job Foreman showed up again to inspect my lines
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_3936.jpg)
side note: I filled all nail holes on Simpson ties and also toe nailed the joists. I also used a bead of liquid nails under each.
Quote from: MountainDon on May 11, 2010, 11:08:51 PM
Soomb, not only do we have the same taste in vehicles, except mine is dirtier and has scrapes and scratches that are too obvious, we both have shovels with blaze orange painted handles. :D Mine wander off and hide without orange painted handles. >:(
Nice private spot.
The camera is forgiving to my Jeep. I spray it off once every three months, whether it needs it or not ;D, But I would agree yours has seen more terrain than mine.
Today's progress. I have to take advantage of the cooler weather here in Phoenix.
(https://i177.photobucket.com/albums/w219/fleurdelv/IMG_3951.jpg)
corner to corner was dead on square.. THANK YOU to the forum folks who helped me get square!
(https://i177.photobucket.com/albums/w219/fleurdelv/IMG_3952.jpg)
Again, I used Liquid Nails on everything.
So my next step is blocking.. after that, I am thinking I should climb under and secure wire mesh (? Workman's Cloth?) so I can insulate the 2x6 floors from above. Thoughts?
I only have 10'x10' to subfloor, what would you choose? T&G or standard 4x8 sheet? Thickness? I plan on glueing and either nailing or screwing.
I'd do 3/4" T&G Plywood or OBS.
OSB if you will do a finish floor, or plywood so you can paint the subfloor and get many years of wear before you do the final flooring.
You have a good start on a picture tutorial.
We lived in Phoenix in the 70s around 42 Street . . . I thought that I recognized that block wall fence. Our house had the same windows.
Keep up the good work!
/
John, I think Plywood may win, as I like the idea of paint or stain it and use it now, and worry about final finish some other time.
Bayview, I am a little east of 42nd, just off Central. The windows are slowly being replace with industrial/commercial looking Low E windows.
That's looking great. T&G plywood will be a nice floor is stained or painted. Until such time that you might install a finish floor. And if you don't, well then it's finished anyhow.
(Eli here) I recently helped a buddy install 1 1/8 t and g ply, that is one stout floor. Any future floors, if I got the cash for it, that's what I am going with. As I've heard b4 on here "When in doubt, build it stout"
It's traditional here to do a victory dance on your new deck once you get it sheathed- and post a picture!
Quote from: MushCreek on May 12, 2010, 05:09:15 PM
It's traditional here to do a victory dance on your new deck once you get it sheathed- and post a picture!
I was hoping to have that picture tonight, but not sure if I will get time to get blocking and decking in place tonight. My next available work day will be Sunday, so the jig may have to wait. BUT I will post it.
Next up: blocking and plywood, but first a question: When I go to framing walls, would you suggest 16" or 24" OC?
You save so little materials on a small building I'd go 16" Have to hit the hay, more tomorrow AM. Are you using 2x4 or 2x6?
My thoughts are 2x4 to save the floor space on the 10x10 outside footprint. In Phoenix my main concern will be cooling (Thru wall AC) and I love it cold so the winter months should be decent if I insulate well, as it will be me, 2 monitors tied to a CPU, at least 1 laptop, 2 printers ad a scanner running. I would even consider covering the external sheathing with a reflective barrier prior to tar paper.
If using 2x4 you must use 16" OC studs (code ).
There in Phoenix with no snow load (and being a single story, no loft, right?) you could probably get away with 24" OC 2x4. ??? I'm sure that's been done before.
There are advantages and disadvantages to 2x4 vs 2x6, but my head (Jaw) is throbbing this AM and I don't feel up to it. Maybe later if you want to start a theoretical/practical discussion on 16" vs 24" stud spacing. Could be interesting/informative.
I would use that foil backed foam on the outside. The foil will reflect heat back out, and the foam will provide a thermal break. Put furring strips to hold the foam in place, and to attach your siding to.
Don, I hope the jaw feels better.
Mush, so you are saying (from inside out) layers-Studs with insulation between, Sheathing, THEN foam, then tar paper, and lastly siding? Furring strips? On the foams exterior with long screws/nails to reach the studs?
Meant to say you are going to get arguments about the effectiveness of reflective films. They need an airspace to work. They only provide the ability to reflect radiant energy, no conduction insulation. If you peruse the Building Science website information on designs that range from very cold to very hot and hot and humid, I don;t think you will see any mention of using reflective 'insulations'.
It could be just me but I'm still on hold as to the effectiveness of reflectives. Data from some place other than a firm or individual with a connection to a foil manufacturer is what I'd like to see. Just take that as an opinion; don't take it to the bank. ;)
Don,
since I am not going with 2x6, what are your thoughts to the benefits to a foil foam layer on the exterior to make up for the insulation lost in skipping 2x6? Or is it all overkill?
Yeah- I'm not sure about the placement of the tar paper- I would think that would go on the sheathing, then foam, then furring, then siding, but I'm not 100%. There is a product (Can't remember the name) that plugs the gap between the siding at the bottom and the foam. Allows breathing, but keeps out bugs. Otherwise, that 3/4" gap makes a great habitat for creepy crawlies.
I believe the vent material is Core-a-vent or something like that.
You have the correct order of installation; sheathing, water resistant barrier, foam sheet insulation...
Thanks for the poke to my memory, Don. It is Cor A Vent. Here's link:
http://www.cor-a-vent.com/
As for foil covered- the jury is still out as to whether it helps or not, but a layer of foam will help. especially if you seal the seams and edges well.
Sheet foam is great stuff. BS has a very cold design (Alaska) that uses 4 layers of 2 inch foam, all applied to the exterior. No stud stuffing at all.
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Well it was 97 degrees out today and working in the dirt with long pants and long shirt made it slow going and I did not get as far as I would have liked, but I got blocking placed and the wire mesh mostly in.
Snapped a chalk line at the 5' mark and alternated the blocking down the chalk line. I was pleased that there was very little push/pull to get them in place. Only one blocking had a larger gap than I would like, but it may have been the accuracey of the cut, as I was still 10" on the chalk line after all blocks were placed.
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/OfficeSubfloor.jpg)
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/OfficeSubfloor2.jpg)
Once I have the 2 outside rafter sections meshed, I will install 6" bat insulation from above, then plywood T& G with Liquid Nails and either nails or screws. Thoughts on both? (nails & screws)
I used 1/2" staples to install the wire, placing a staple each 8-12", but I think I will take some scrap 1x2 and run strips on the underside of the rafters and screw that into place.
Quote from: soomb on May 16, 2010, 06:26:10 PM
Quote from: MountainDon on May 16, 2010, 05:50:51 PM
Sheet foam is great stuff. BS has a very cold design (Alaska) that uses 4 layers of 2 inch foam, all applied to the exterior. No stud stuffing at all.
BS?
BS ( as I used it) = Building Science.
I was feeling really lazy. I have a so far small infection in my face. >:( Talked to Dr. at noon and have anti-biotic already . I'll see him tomorrow. Crap!
once mesh is finished and floor is insulated, my question is: I plan on using 3/4" TG plywood and Liquid Nails, I am not sure of nails or screws and the fixation, thoughts?
For my money, nails only if they are spiral or ring shank (known as deformed shank), or hot dipped galvanized. (the rough zinc helps hold them in place), or deck screws.
Just for info, if there was any PT wood in contact with the fasteners, they must be suitable for PT wood.
Thanks Don, I think it may come down to screws or galvanized, as I have a decent supply of both already. Plus I hope that, if I keep an even pattern, it will look interesting once the plywood is finished as my interior floor.
Well, I will post the photo of me doing my jig in just a few minutes. But first, the update.
I fastened Workman's Cloth under the entire structure and then insulated from above, using faced 6" insulation. Once that was complete I set up guides to hold my 3/4" TG Plywood in place, since I am working alone (No pics, but vertical boards fastened to the outside of the joists/rim). I used Liquid Nails on every surface. I slide the TG into place and used 2" Galvanized deck screws. For the over kill I also used Galvanized ring shank nails in between the screws. A few mistakes/learning opportunities along the way. Mostly, I need to stop and think before just plowing along b/c the pace is going quickly. d* It is at the fast pace that I screw up.
My question for the next phase: Sheathing the walls... What to use? ???
I plan on doing the solid rear wall (low side of the shed) first. Walls will be 2x4 construction. I would like to have the sheathing overhang the bottom of the wall enough to fasten directly to the rim joist at the start, once tipped up.
As always, ANY and ALL input welcomed.
(https://i177.photobucket.com/albums/w219/fleurdelv/IMG_4053.jpg)
Nice work. :)
thanks Scott. I learned quite a bit from several posts, yours being one of them. Not sure I will get to rain screen this little office but I would like too
Quote from: soomb on May 23, 2010, 02:24:41 PM
(https://i177.photobucket.com/albums/w219/fleurdelv/IMG_4053.jpg)
[cool]
The obvious choice for sheathing on a building that small would be T1-11, unless you plan to sheath, vapor barrier, and put a siding on. In that case, OSB is (well, used to be) the cheapest way to go. That stuff went up almost 300% around here! I noticed today it went down.... a little. >:( Being as you want to use it as an office, it might be worth your while to use a full wall system, like a house. That mostly depends upon budget.
No pic yet (letting it dry/soak-in further), but I applied two coats of Behr Semi-Transparent stain to the plywood TG decking. The color choosen was "Coffee" apropos for an office. I am waiting to see how it dries, as the second coat got away from the semi-transparent and a bit more solid. I will post pics no matter what, just want to see if the wood grain shows thru.
[cool]
The obvious choice for sheathing on a building that small would be T1-11, unless you plan to sheath, vapor barrier, and put a siding on. In that case, OSB is (well, used to be) the cheapest way to go. That stuff went up almost 300% around here! I noticed today it went down.... a little. >:( Being as you want to use it as an office, it might be worth your while to use a full wall system, like a house. That mostly depends upon budget.
[/quote]
Jay, I think I will go with a full wall system. On this, my first small project, I want to have some of the experience for the eventual cabin build, so I think full wall will be the way to go. Don't quote me on that yet, but leaning that way. I want to experiment with siding as well, so not sure of rain screen, metal, board and batten, so need to do some head scratching.
C
My question for the next phase: Sheathing the walls... What to use? I think OSB, how thick? Anything I am missing?
I plan on doing the solid rear wall (low side of the shed) first. Walls will be 2x4 construction. I would like to have the sheathing overhang the bottom of the wall enough to fasten directly to the rim joist at the start, once tipped up.
As always, ANY and ALL input welcomed.
The Behr came out a little less transparent but here is the application pic..
(https://i177.photobucket.com/albums/w219/fleurdelv/IMG_4072.jpg)
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/1stwall.jpg)
I prepped the 1st wall (rear wall, lower side of the slight shed roof) on the deck of the office. I used true stud cut 2x4 from HD. Everything is glued and screwed to the sole and top plate. After a quick check of a few post here, I tipped it up. Maybe it is me, but an 8' wall seems VERY tall, but I think that is the height from the ground and perspective. My wife assures me, going with a lower rear ceiling height will only make me (6'5") feel like I am in a Hobit office.
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/1stwallup.jpg)
I had attached guides to the rim and floor joists, as well snapped a chalk line on the deck at 3 1/2". I did not put sheathing on prior to tipping up because I did not know what to expect, so I went light. The sole plate was prepped with Liquid Nails, and screws we pre-started in each wall bay. Once I tipped the wall up, I hustled to both sides to attach the braces to the joists. I then took each and went for level (clamped the level to the studs to free hands). Once secured, I went back and added nails to each bay to penetrate the plate, 3/4" TG, and into the rim. I hope I did it right, or at least over did it.
Be sure to rack the wall plumb and brace or sheath it before moving too far along. How are you joining your corners? I see no 2nd stud at the corner.
You might want to review this short video. It explains about corners and a good way to frame them and why - just a suggestion and a style I like.
http://www.hgtvpro.com/hpro/pac_ctnt/text/0,2595,HPRO_20196_55073,00.html?c=481&videoid=66884
Quote from: ScottA on May 26, 2010, 06:58:11 PM
Be sure to rack the wall plumb and brace or sheath it before moving too far along. How are you joining your corners? I see no 2nd stud at the corner.
Scott, Thanks I will rack the wall plumb and then plan on 1/2 OSB sheathing. I did not know how to join my corners until today, was doing some reading as I went along, so I have extra studs ready to go in to make a 3 stud corner.
Thanks for pointing that out.
Quote from: rick91351 on May 26, 2010, 07:27:21 PM
You might want to review this short video. It explains about corners and a good way to frame them and why - just a suggestion and a style I like.
http://www.hgtvpro.com/hpro/pac_ctnt/text/0,2595,HPRO_20196_55073,00.html?c=481&videoid=66884
Rick,
Thanks! the 3 stud corner it will be. It pays to go slow and ask a lot of questions ;D
Looking great soomb.
I am in the Valley as well and dreaming of something up North...
Looking forward to watching your progress.
Looks great so far.
I don't know if this is too late, but sheathing can be had in 4 x 9 foot sheets if you look in the right places; real lumber yards. Using that you can have the sheathing overlap the joists/rims.
My plan was OSB laid horizontal and having the 8" mark fall OC of a stud. I have not looked into going vertical with OSB, but I have not committed to more than a few sheets at this time. Is there any appreciable difference to strength on vertical vs. horizontal?
Front wall up today, side walls later this week. (pics coming)
The only "problem" a person might run into with horizontal sheathing is that code may specify that all edges of a panel must be nailed. If the the sheets are horizontal that means blocking may have to be installed to nail to.
I like the idea of the vertical sheets lapping over the joists/rim joists, but that may be just me.
Quote from: MountainDon on May 31, 2010, 08:19:43 PM
The only "problem" a person might run into with horizontal sheathing is that code may specify that all edges of a panel must be nailed. If the the sheets are horizontal that means blocking may have to be installed to nail to.
I like the idea of the vertical sheets lapping over the joists/rim joists, but that may be just me.
I may still go with horizontal, but I will have the sheets start at the bottom of the rim/joist to tie it all in. My thoughts were to have full boards top and bottom and rip boards to fill the middle.
Front wall up. 3 stud corner. Used 96" studs to create a higher front to have a slight shed slope. There will be 1 LH in-swing door and 1 36x24 window at a height just above my monitors. This will hopefully cut glare some, and allow my seated view to be more of the sky and trees than the close by pool house.
(https://i177.photobucket.com/albums/w219/fleurdelv/image001.jpg)
Wall #3 up, with another 36x24 window at the same height and distance from the corner as the front wall window. I have racked the front and rear walls plumb and made sure they are vertical. I braced them and started with full sheets of 4x8 OSB to anchor things together. I allowed the OSB to go to even with the bottom of the rim joists to tie the structure together. SURPRISE! everything was glues and screwed.
What kind of screws? Some screws, like the common yellow zinc plated deck screws, are quite brittle and will shear off if stressed enough. Appropriately sized nails are what the building codes spec for anything structural. Mails will deform, bend, well before they will shear off. Others have used screws on small projects with apparently safe results though.
I will get the box, but these were 2 1/2 inch gray/silver galvanized screws. I also used nails as part of the over kill. The OSB was held by screws in several spots, but then I also nailed the edges and field with nails (I will get the box, but 1 1/2 nails I think) Every contact point (sole plate, studs, jacks, cripples, rim, joist, etc) was also hit with construction adhesive as well prior to nails and screws being applied.
I will get the box labels and transcribe or photo.
My own test is to screw the screw into a 4x4 2/3 to 3/4 the screw length. Then whack it sideways with a hammer. Usually they break off, whereas a nail will bend.
6D (2") deformed shank (ringed or spiral) or 8D (2.5") common is the nail for wood sheathing, 3/4" thick or less.
{table R602.3(1) in the IRC.} http://countryplans.com/smf/index.php?topic=6224.0
Don,
I hope I am in the ball park here....if not, I am not sure what to do.
I have used:
8D 2 1/2" Bright Ring Shank Common - Framing
2 1/2" Primeguard Ten Exterior Screw - Framing & anchoring OSB
6D 2" Exterior Galvanized Box - Nailing the fields of OSB
Liquid Nails on all contact surfaces- Shear Strength: 7+ days of >425PSI
I have a feeling I may be going back and adding more nails if my sizing was not proper for this 10 x 10.. It is a learning experience, and I would rather leap before I look, and learn hard lessons in preparation for doing in spot-on right when it counts.
Your thoughts?
Quote from: soomb on June 07, 2010, 09:34:38 PM
Your thoughts?
For the sheathing since you used construction adhesive and not in an earthquake zone, you'll likely be ok, although adding some 6D deformed shank (I like ring shank) nails would be insurance.
As for framing with 2x members, considering you used ring shank 8D and some screws that could be okay too. IRC calls for 16D common when end nailing studs to top or sole plates. 8D when toe nailing stud to sole plate.
This page https://www2.iccsafe.org/states/Virginia/Residential/Res-Frameset.html (https://www2.iccsafe.org/states/Virginia/Residential/Res-Frameset.html) has the IRC for the State of Virginia, 2006. Most of what is in it is applicable to other states. Chapter 6, Wall Construction, has the nailing table. Well worth a look. Page 6-2. Everything you could possibly nail together in a building is listed. They are protected files but if you use Firefox, get the DownThemAll add-on and it should be able to download the whole set to your own computer. About 15 MB in total. That's what I have done with several versions of the IRC.
You should also be able to find whatever code is applicable to your area in AZ at a public library in the reference section; about 690.8 in the Dewey Decimal System. :D
We're heading back to the cooler ;D mountains for a few days tomorrow so I won't be around till Friday or so.
All four walls up. Thanks to suggestions here I have my 3 stud corners and have switched to 8d ring shank nails. I do have another question: ??? I have gone horizontal with the OSB sheathing, and I was wondering whether to use full sheets at the top and bottom and rip OSB to fill the middle or just full sheet on full sheet and rip the boards in at the top plate?
I don'y know if there is a 'right' way but I think if it was me I'd put the full sheet at the top. My reasoning being that provides more bracing for the wall than a narrow strip would. On the other hand you are not exactly in earthquake or hurricane/tornado country so it might not make any noticeable difference. ???
Mtn. Don-
Thanks for the link to the Virginia Code - we do not have any inspection or permitting process in our MO county, but nonetheless are trying to build as close to code as we can. (As we can figure out what code is anyway)
The span and header tables in this doc are way more detailed than what we have been able to find in framing books.
Dougpete
Four walls up. 2x6 rafters 90% up. Will start sheathing roof in the next few days. The very tops of the walls are still open b/c I am full solo on this job and have had to rig ropes to move materials up top. I built the overhang shown on the ground and worked it into place and secured it. Being solo makes you stop and think often, and I need that or I charge headlong into something I have to pull apart once I have an "ah ha!.....oh sh!t" moment.
Western wall with thru-the wall 5500 BTU a/c opening
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_4754.jpg)
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_4751.jpg)
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_4767.jpg)
OK.. I am not fully solo on the job site.
(https://i177.photobucket.com/albums/w219/fleurdelv/Shed%20-%20Office/IMG_4770.jpg)
Ok, I am fully closed in and roof mostly on. I have roof sheathing on. I had exterior paint laying around and used it to create multiple coats of paint on the roof. I covered that with a gallon of elastomeric roof paint in white for the sealing value and the white reflective properties for the AZ sun. I have now covered the roof in two layers of 30# roof felt and I would like to put off the shelf roofing (corrugated) on. Any thoughts on furring strips and the like.. or just screw right to the roof?
My roof is a shed roof with a very low pitch. I have the vertical furring (left over 2x4x10') ready to go, but I do not know if I can place horizontal strips between them, or if I need to have the horizontal strips attached to the vertical base layer in order to leave room for moisture, should it get under, to exit? I will be placing flashing to cover the high side from water as well as the side.
Thoughts?
I dont have a solid answer to your question, but I am approaching putting roofing on my place soon and just opened a thread in the "general forum" section about roofing that you might find useful in your project. good luck!
My personal opinion is that furring strips just add complication to a metal roof. The only roofs I see being installed with furring strips here in the desert are tile and fake tile roofs. All the metal around me is metal screwed down directly over felt or synthetic underlayment. I'm also of the belief that installing metal roofing on furring strips can provide the pathway for water to condense on the underside of the metal, whereas if the roofing is installed flat on the underlay, there is no space for this condensation to occur. OK, the underside of the metal ribbing could have some condensation occur, but the ribs also provide a clear path for any moisture to run down.
My opinion.
Quote from: MountainDon on October 18, 2010, 08:04:24 PM
My personal opinion is that furring strips just add complication to a metal roof. The only roofs I see being installed with furring strips here in the desert are tile and fake tile roofs. All the metal around me is metal screwed down directly over felt or synthetic underlayment. I'm also of the belief that installing metal roofing on furring strips can provide the pathway for water to condense on the underside of the metal, whereas if the roofing is installed flat on the underlay, there is no space for this condensation to occur. OK, the underside of the metal ribbing could have some condensation occur, but the ribs also provide a clear path for any moisture to run down.
My opinion.
I have 2 layers of 30# down with 2x4's as vertical holders to avoid losing the tar paper in a wind or rain (twice before I placed them). I am at that stage where I either add to it with more furring or pull it and start with just 30# tar paper and get metal or fiberglass roofing from Lowe's. this is just a 10x10 office and I think I am way over doing it. Over thinking a small building.
Quote from: soomb on October 18, 2010, 08:26:48 PMthis is just a 10x10 office and I think I am way over doing it. Over thinking a small building.
I thought the same when reading about the paint and the elastomeric.... ;)
How long has the felt been down? Is it still in good shape, not brittle, torn, loose.... ?
Now that I think back, I did have a few strips of 1x2 material holding the edges in a few spots. I used screws to secure them so removal was easy.
Another thought on metal roofing and furring strips.... Much of the material I have seen at HD is 29 gauge metal. That might be a tad on the thin side for use on furring strips. ??? Easier to have bending/denting issues; walking on it, hail....
I think you can tell I don't think much of metal on furring strips... ;D
HOWEVER, in hot climates there may be an advantage to building a roof system with a ventilation space provided between the hard deck and weather resistant barrier and the finish metal roofing. Placing vertical battens/furring/purlins... first and then placing horizontal battens/furring/purlins...across them can provide this. You need to have easy entry and exit for the air movement. This may provide significant energy savings on the A/C power bill. It's the same principle that was used years ago by Land Rover.
(http://www.eastcoastrover.com/Info.%20Scans/88sales4.jpg)