I am just about to start building a new workshop … about 3500 sq ft. Pad is in, waiting for the snow to melt to start building.
I thought a metal roof was out of my budget but then I found that some standing seam roofs can be used with purlins rather than fully sheeting the roof.
With the price of lumber so high, a standing seam roof built on purlins now becomes a viable alternative.
I want to stay with standing seam … I had a bad experience with an exposed fastener roof and both my neighbors have barns that now leak.
I am using purchased trusses … some parts of the roof are vaulted. The vaulted area of the truss is 24″ thick so even with 18″ of insulation, I should have about a 6″ air gap. Other parts have almost 6 ft of room between the ceiling and the roof.
One issue which I can’t find an answer on is condensation.
I live in Vermont.
I am not sure if it is just a matter of sealing the shop from the roof and having good ventilation or ???
Then “new” idea is to not put a vapor barrier but rather to let the interior wall sheathing be the barrier. In the house we built I did this, sealing with caulk every sheet of drywall to the studs and joists.
In the shop I plan on just having wood sheet cover the interior (OSB, thin plywood, … ).
I can do the same thing and seal this … or I can use a true vapor barrier (poly) or even use something like Tyvek (the same thing I will wrap the outside of the house in).
Even doing this, and with soffit/ridge venting, will I still get condensation or will this stop it.
I am 58 … I like the idea of a “forever” roof.
Any other recommendations?
Thanks …. Mike
Replies
You will get condensation whenever the dew point of the air that reaches the underside of the structural roofing panels is above the surface temperature of the panel. (which is why they will finish the inside as well as outside of the panels)
if you seal the interior surface of the enclosed space (especially the ceiling), with a vapor barrier, heated indoor air that contains moisture will not be added to the mix. This would include ground moisture that might come via the concrete pad.
Air coming in the roof venting system will still lead to some condensation, under some conditions, but it will evaporate when the conditions let it do so. (just like you can get some frost on the inside of your car windows sometimes)
With good air sealing and adequate roof ventilation, it should last a long time.
Tyvek is not a vapor barrier.
It would be interesting to hear if your price comparison makes sense after you price structural metal roofing, vs architectural roofing which needs a continuous deck under it.
Looks like a fine shop.
I know your looking to cut costs but the roof isnt the place to do it. If your pitch is over a 4/12 then use vented nail board. Yes its not the cheapest option but you won't have to worry about condensation. I have installed metal roofing for over 20 years and I've seen some crazy things happen. If you want to use purlins instead, you have to insulate between the purlins. Also I would use snap lock or batton lock panels. Standing seam (single lock or double lock) requires a machine to zip the seams together. You can rent them for about 4-6 hundred a week. Insulate and use the proper soffit and ridge vents, especially if your using dark colors. If you go to the manufacturers web site for the panels, they will have all the detail and ventilation requirements for your panels. Hope this helps some..
It's not a huge savings to put on a metal roof ... I was under the impression that a metal roof would last a lot longer and thus I would be getting more "bang for the buck".
I am looking at snap lock panels .... I didn't want to get into seaming and such.
It's a large roof so say $5K in sheathing .... $4K in shingles ... underlay .... ice shield .... so say $11 - $12K in materials.
For the roof system I was looking at ... about $6.5K in panels ... $2.5K in edging, clips, cap, ... $1k in purlins ..... so say $10 - $11K in materials.
If I need to sheet the roof first then I may as well go with a standard shingle roof.
I was planning on a black roof.
Since this is a shop, I am going to have no penetrations in the roof or walls. I will use conduit to do all the electrical work after the shop is up and has a finished interior.
I am hoping the shop will be relatively dry .... I put 2" of foam under the pad and also a vapor barrier (poly).
With luck this should not matter as I am thinking I will be able to do a good job sealing between the shop and ceiling and have a min of 12" ... probably 18" of insulation in it (there is 18" of blown insulation in the house ... R60 ... or at least that is what I asked and paid for).
So ... do I think with good sealing, good ventilation and insulation I will be OK with purlins or am I asking for trouble ....
Thanks .... Mike
Just FYI ... this shop has kind of gotten away from me. My wife (we met 12 years ago) was paralyzed from the shoulders down in a diving accident when she was 12. After 7 years of building, the house is "almost" done ... took me forever but I did do things like build and elevator out of an old forklift mast ($40k to buy .. $2K to build). I poured the pad when I build the house thinking I would build the shop almost at the same time. The shop should have been built three years ago but between health issues one summer, a job I took on the next summer (hard to turn down 6 months work when you work for yourself out of the house) and last year the pandemic, it has not gotten done. The snow is melting here in VT ....going to be 40 next week ... itching to get started. Thanks!
I think the metal on purlins will work out fine for you.
(with good vapor barrier, and good venting under the roof panels.)
What brand of roofing and model are you going for?
Are you going to build in the second floor access as shown in your original post?
I would not want a black roof, but it is your shop.
Just FYI ... got a price last year from two roofing contractors to put a standing seam on this building ... both came in at almost $40K !
Both said it would take less than a week.
I am sure I will need to hire a few guys to help but a $30K difference?
I also have a neighbor with a telehandler ... he owns me a few favors (older farmer who I have never charged to fix his equipment) ... should make getting things to the roof fairly easy.
My thinking is I will have the trusses come in three pieces .... the sides of the triangle will form the roof ... the shop ceiling ... and the walls of the attic.
I will cap a third truss.
I had them quote it this way ... even putting a 2 x 6 in the wall side so I can have a decent amount of insulation.
I will insulate and put a vapor barrier on the walls and the ceiling of the attic area.
Should be about 1000 sq ft of storage area.
The roofing I am looking at is from Best Buy Metals .. here is a link to it:
https://www.bestbuymetals.com/standing-seam-panels/vertical-seam/
As for color ... I was going for the red barn look ... but everyone has that here and I wanted something different.
I looked at an all black building ... board and batten .. but way too much money for the pre-finished board and batten and way to much work maintaining it if I go with real wood. Spent weeks looking at LP and Hardie.
So it's back to vinyl. I found a gold / yellow I liked. The back just happens to stand out nice (I think). My wife thinks it might end up looking like a bumble bee.
Here is a link to the siding I am thinking about (I kind of like the double 4" dutchlap).
https://www.abtco.com/products/siding/majestic/
Going off topic a bit ... one thing I need to decide on is the floor joist for the attic.
I know me ... probably will have a lot of heavy things stored up there.
I am looking at 16" wood I beams (every company calls it something different ...TJI, AJS, ...) .. about $150 each @16" centers.
I was thinking about 16" deep trusses ... I am having a bit of a problem finding them around here ... but I am guessing about the same cost.
I am even wondering if I can build my own trusses (no inspectors in our area ... no engineering drawings needed). Watched lots of videos. Even talked with the engineers at Titebond. Cost would only be about $50 in material each ... about a $4K savings on the project if I do them myself. Still just a bit concerned about building them .. plus it may take me forever even if I build a jig.
Thanks again ..... Mike
I thought about trying to build trusses once, went with an engineered product. then you only have to decide what to specify.
It looks sooooo easy watching videos but I like the idea of a truly "engineered" product.
Everything on the building is a trade off ... I am running all kinds on numbers with a spread sheet.
I would rather scrimp a bit somewhere else and buy the floor joist I think ... even it if only an attic area.
Thanks
Things that you can fall through or that can fall on you are good places to be conservative.
Did you end up getting the roof installed? I am looking at best buy metals as well and came across your post.