Hi All,
I have a quick question for you, I’m going to install drywall in my garage/trainroom soon, there is some insulation that is installed on the wall before you put up your drywall. Is it called vapor backing? or something like that? Thanks for the help
Trainsrme1[8D]
Is it the regualr pink, fiberglass insulation?
Yes it’s called a “Vapor Barrier” typically a heavy gauged plastic that comes in rolls and the seams are sealed with tape. if your garage is subject to moisture you may want to consider mold resistant sheet rock.
In our township its required my code for any new construction or up grade of anything below grade. It’s a little more pricey then standard rock but it’s well worth it if there is even the slightest hint of a moisture problem. Another thing a lot of guys around here use for insulation is believe it or not that pink extruded foam, yes it wasn’t really designed for model railroad scenery believe it or not also if your floor is not finished in the garage look into a sub floor system, they sell them in Lowes in 4x4 panels they have rubber backing on them and the top side isOSB. I am kicking myself for not doing it. We did my neighbors basement last year and you can not believe the difference, your feet will thank you.
The pink insulation foam (it can be beige, too) comes in paper-backed battens that are generally sliced to fit between the frame uprights. They are then covered with a poly sheeting of a certain weight (check your local codes). Over the plastic sheeting, which is your vapour barrier, you place the drywall sheets.
-Crandell
I would like to add to Crandell that all electrical junction boxes mounted on exterior walls are not allowed to break the vapour barrier, here in Ontario, check you building codes. In such a case specific plastic devices are made into which the boxes are installed. Consult your local building codes before installing the drywall. Also, to prevent surge currents designate receptacle circuits for your layout. If, for example the garage opener is on the same circuit as the layout power packs, voltage spikes can occur when the garage opener is activated. The garage opener, upon starting will draw a large current for a very short period of time which in turn creates a voltage spike which could damage voltage sensitive equipment.
Hope it helps,
Frank
Not to muddy the waters, but there’s been some controversy in the construction industry (I design buildings in order to support my train habit) about vapor barriers. In fact, we call them “vapor retarders” now. They’re effective so long as you don’t puncture them (like with those things you use to hold the drywall up, I think they’re called “screws”). Then also, the barrier is in contact with the drywall, so any water that does get between the two can’t evaporate off and you suddenly have an environment conducive for mold growth.
So find a local code official, or a builder, to find your wall construction requirements.
One of the posters to this topic stated that the fibreglass insulation is backed by paper and then a vapor barrier is then put up over this. That paper is “the vapor barrier” and it would be improper to add another vapor barrier over it.
If your town doesn’t have codes, check with a local contractor or building supply representative. Unless coded otherwize I would use the fiberglass insulation as it is cheaper than the foam type. It comes with two types of facing, brown paper and foil. In a garage, where you do not have a living space with cooking, showers, etc, the paper backing should do just fine.
Good luck,
There may be some conflicting information here. The basics are to put the insulation between the studs(with or without the kraft paper backing), and then do the entire wall with ‘poly’. Local codes may require you to purchase/install special seals around electrucal boxes). The kraft paper backing is not a complete seal for vapor protection. You can then hang your drywall. As mentioned, check with you local building inspector about wdhat is ‘code’ in your area. When I did my basement and garage, there was no ‘seal’ code with electrical boxes. I did seal them up with duck tape after cutting out the poly at the boxes before I hung the sheetrock.
As long as you are at it, make sure you insulate/sheetrock the ceiling as well(most of the ‘layout dust’ seems to come from that area. My layout is not in the garage, but I did a full insulate/sheetrock of my 2 car attached garage. I later added gas heat so I fhave a nice warm work area in the winter. In the basement, I used 3" foam between the studs and them applied the poly and sheetrock. Of course, I live in Minnesota…
Jim
Jim
The paper backing acts as a retentive spine for the batten. It does not constitute a vapour barrier because you have 1.75" of wood in the form of studs between each such batten. The wood is not vapour proof, as anyone who has had to deal with the changes in dimensional lumber on a layout knows. So, in Canada, at least, poly vapour barrier is very much required over any type of batten placed between the studs. Note that this is for living space, and may not be required by local codes for a garage or out-building in which animals or humans are not residing for part of the day.
-Crandell
If you can’t penetrate the vapor barrier with “screws” how do you attach the drywall to the studs??? is there some new method of applying drywall to studs now???
Contractors staple the edges of the fiberglass insulation to the studs, and then use drywall screws or nails to fasten the drywall; but I don’t think the edges of the battens are part of the vapor barrier.
I don’t know much about Canadian building codes, except for what I see on Holmes on Homes, but here in NY the Kraft paper or foil on the insulation “is the vapor barrier” and is overlapped and stapled to the face of the studs. No other vapor barrier is needed. If you use unfaced fibreglass insulation then a 4 or 6 mil polyethylene shield is stapled to the studs before sheetrocking.
A lot of folks use the ‘tabs’ on the kraft faced insulation stapled to the studs as the vapor barrier. The problem is that not every cavity will be 16" OC. From my construction experience, just buy the cheaper 16" un-faced battens, and use poly - You know you have a good vapor barrier then. Or watch ‘Holmes on Homes’ on TV - He finds these ‘el cheapo’ solutions and show the problems that result from this type of construction. Having to tear out a wall in a room is bad enough. Having to remove the layout because of a bad construction decision is even worse!
Jim
As said elsewhere the problem with plastic (well poly) is that it is not a perfect barier either as the screws and such cut into it and thus vapor and get past it. The other real big issue, that a lot of folks in the industry are beginning to worry about is that any vapor that gets past the gyp bd will sit on the poly and may lead to mold on the back of the gyp bd paper. So thier are currently plusses and minuses to the whole converstation. I did not need a poly barrier in my state when I built a few years ago and I choose not to due to the mold issue, so to each thier own depending on what the local codes allow.
Doug M
Doug is right on spot. Codes vary acording to climate and needs. There is no one right answer or best answer without knowing more
To all our dear friends in Canada, the US is made of 50 states, with local county and city governments who regulate these issues as is best for their area, again, there is no one answer.
Building too tighly IS THE CAUSE of toxic mold problems and is being reconsidered by many in the building industry. Including the use of vapor barriers beyond the craft paper on fiberglass insulation.
In any case, the best drywall is the new paperless kind. In place of paper it is coated with a fiberglass cloth set in an elastomeric coating on both sides. This coating IS a vapor barrier and is present on the living space side where it is more effective.
For decades old house restoration professionals and DIY’s have used a product called Nu-Wal to repair and resurface plaster walls. It is an elastomeric paint which is used to adhere a 4 mil fiberglass cloth to the finish side of a plaster or drywall wall. It strenghtens the wall and creates a vapor barrier on the living space side where that concept works the best. Learn more at www.nu-wal.com
My 1901 Que
Not to muddy the waters further, but when I was doing architectural drafting work in SE Pa. in the 80s and 90s, garages were required to be drywalled with firecode X gypsum board.
At first it was just the ceilings, then all walls
It wouldn’t matter to you, a train layout’s not likely to burst into flames (with one noteable exception), but the next owner of the house might want to put a car in the garage
Again, check your local building codes to see what’s required
Eric
Again, codes vary. The current IRC (International Residential Code), used by many jurisdictions, requires attached garages to have 5/8" fire rated drywall on the ceiling only if there is living space above the garage. Side walls and common attic spaces require only 1/2" drywall. Walls not ajoining the dwelling may or may not covered.
Many local codes do have additonal requirements above this.
Sheldon
A little more info. The current IBC call for vapor barriers in only about 1/2 of the US. The Southeast and lower Southwest have no vapor barrier requirment. And even here in Maryland, we are in one of the zones exempted from the vapor barrier requirement.
And, careful note is made about proper venting and construction to prevent mold or moisture deterioration from building too tightly.
Sheldon
Useful information from the government on insulation and moisture control: (Who would have thought the government would actually be useful?) 
http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11220
When I did my basement, I sealed the walls with drylok. I then sealed any cracks in the basement floor, and covered it with epoxy based paint (garage floor paint). I then covered the cinderblock walls with 2" pink Owens-Corning insulation board (Available at home depot.) It’s about half the price blue extruded foam board. I then sealed the seams with house wrap tape. And sealed the bottom with a vapor barrier + house wrap tape. (To keep moisture from escaping out the bottom) I then put up 2x4 walls with pressure treated lumber for a footer and a 1/2" gap between the foamboard and wall. I then covered the 2x4 walls with moisture resistant gypsum board.
Foamboard is a lot more expensive than fiberglass. However it does not support mold growth. And it’s R value does not change if it gets wet. And if it does get wet, it doesn’t hold water well. So it doesn’t have to be ripped out like fiberglass would.
Please note that national building code requires that blue foamboard be isolated with 1 hour rated firewall because the fumes are toxic when it burns!
Over all it took about about 6 1/2" from each wall. But it will be dry and mold free for a long time to come.
Total cost for a 32x32 basement using foamboard will be roughly $2500->$3000 (including exterior 2x4 walls) if you do it yourself.
If you want to use fiber glass + a vapor barri