Tag Archives: 5/8″ Type X drywall

Zero Lot Line Post Frame Construction

There are occasions where the best location to place a building just happens to be right up to a lot line. Let’s face realities – if your site’s required setbacks without fire resistive construction are five feet, what is going to accumulate in this area? Most often it is either “stuff” or weeds, neither of these being aesthetically pleasing.

Reader CLINT in SPOKANE, is faced with this and writes:

“I have a unique question regarding a firewall.  In Spokane County you are allowed to build up to the property line of your neighbor given that you have a 1hr rated fire wall from both sides on the property line.  (2hrs total).  I’ll attach a copy to the code requirements.  To meet code apparently you have to use “type x” drywall on both the interior and exterior of the wall.  I understand the install and have even read up on your reference to a 3hr firewall from some time ago.  My question is, how do you weather-proof the exterior drywall? It seems that putting metal siding directly over-top the drywall could lead to moisture damage.  I’m guessing that even if it is OK for most of the wall what about the lower ground level part?  Do you need a vapor barrier or special trim/flashing to prevent splash damage from ground level. Or maybe even humidity alone could be bad?  I’ve seen what drywall does with water so that is my concern with it being only a metal layer away from the elements. Thanks for your help!”

Mike the Pole Barn Guru advises:

While your copy of Spokane County’s requirements did not make it, I am fairly familiar with them as I was once their most prolific post frame building contractor (built over 200 buildings in Spokane County in a single year).

To reach two hours, you should have two layers of 5/8″ Type X on each side of your framed wall. You also need to insure any rain or snow coming off your roof does not land in your neighbor’s yard. This will entail a slight setback to allow for gutters and you will need a snow retention system on this side of your roof (this is assuming we are discussing an eave side and not an endwall).

Start with investing in “green board” 5/8″ Type X drywall. While not waterproof, it is moisture-resistant. It is available from providers such as GTS Interior Supply in Spokane. You should use a Weather Resistant Barrier (WRB) on your exterior between drywall and steel siding. Screws for steel should be three inches in length for this wall, in order to get adequate penetration into wall girts. Base trim (aka rat guard) can be special ordered with a longer flat leg to seal off water splash up from ground. Mineral (rock) wool insulation should be used in this wall, as it is not affected by moisture.

Extended reading about NFBA’s three hour firewall testing can be found at https://www.hansenpolebuildings.com/2012/03/firewall/

Fire Separation Requirements for Barndominiums

Fire Separation Requirements for Barndominiums and Shouses

Loyal reader CHUCK in MERINO timed asking this question perfectly, as fire separation requirements for barndominiums, shouses and post frame houses had just made it to my list of subjects to research and comment upon.

Chuck writes:

“I was wondering if you could pen your interpretation of the construction details pertaining to the separation wall and/or sheetrock detail of each side of a shop and house all being under one roof?

I live in rural Logan County Colorado with no official construction inspection required (other than state electrical and plumbing). This is from the county website:

“Logan County has adopted the 2006 IBC building code and the 2006 Energy Conservation Code.  All new structures must be compliant with these codes. No building shall be erected, occupied, moved or structurally altered until a permit therefore has been issued by the Building Department.  Building Permits are required for roof repair or replacement”

Thank you Guru, you are the best!”

Good question, glad you asked and thank you for your kind words! I also appreciate clients who want to do things right, even when plan reviews do not exist and there are no inspections. Meeting Code requirements is a fire, life and safety issue.

I was always brought up believing it took 1/2″ drywall on the house side of a wall between garage and house and 5/8″ Type X on the garage side. If the garage side did not have a ceiling then drywall had to run up to the roof line. Even when I worked for a sheetrocker as a teen, this is how he did everything. All made sense to me.

Well Building Codes have their own ideas. If your shop (aka garage) is 1000 square feet or less, then it is classified as a “U” occupancy and these are requirements:

Garage to residence or attic – 1/2″ gypsum board on garage side

Gambrel HomeIf there is a habitable room above garage – 5/8″ Type X gypsum board on ceiling
Doors between garage and residence shall be 1-3/8″ minimum thick solid wood, solid or honeycomb-core steel doors not less than 1-3/8″ thick, or 20-minute fire-rated doors, equipped with a self-closing or automatic-closing device.

If your shop/garage is over 1000 square feet, is becomes an S-2 occupancy and fire separation requirements get tougher:

If equipped with an automatic sprinkler system one hour fire separation is required, if no sprinklers two hours. If the area (shop/garage) is used only for private or pleasure vehicles, then it can be reduced to one hour. 

I have run into this two-hour rating requirement before with a gambrel style barndominium, where our client was living upstairs and parking below. Because it “looked” like a barn, our client’s Building Official required two-hour separation. Walls and columns supporting this second floor also were required to meet two-hour requirements! No amount of debate was going to change this Building Officials’ mind either.

To achieve a one-hour rating would take a layer of 5/8″ Type X gypsum wallboard on each side of a wall, or two layers on a ceiling. A two-hour rating would double these requirements.

I personally like 5/8″ Type X and use it on walls and ceiling everywhere in our shouse. It lies much smoother than 1/2″, does not dent as easily, plus it affords added fire protections, with minimal added investment.