This Monday the Pole Barn Guru takes reader questions about spray foam in an attic space, cutting “rat guard” trim, and ceiling joists for a 9′ span between trusses.
DEAR POLE BARN GURU: I am in the process of completing my Hansen building and decided to spray foam the roof and gable ends above the walls. When they came in to do the work I found they had foamed over the ridge vent closing it off. When I questioned this they said that is what you do when foaming the roof and the attic becomes a conditioned space. R14 on the roof does not sound sufficient. My floor is wood 4 feet off the ground. Is this right? Where should I go from here? Thanks ED in MYRTLE BEACH
DEAR ED: Provided you are including your building’s attic area in your conditioned space (not insulating directly above ceiling) then closing off your vented ridge would be correct. I have not been able to find anything printed to verify adequacy of R-14 for roof insulation with closed cell spray foam in Climate Zone 3 (South Carolina), indeed 2009’s IECC (International Energy Conservation Code) used by South Carolina would seem to lead one to believe ceilings require a minimum of R-30 (Please see Table 402.1.1 https://codes.iccsafe.org/content/IECC2009PDF/chapter-4-residential-energy-efficiency).
When you have an opportunity, please send back photos of your building, they would be greatly appreciated.
DEAR POLE BARN GURU: Hello there, for the life of me I cannot figure out how to cut the “Rat Guard trim” at the outside corner! At a 45 degree angle!!!! Please help!!!!! DANIEL in VANDERGRIFT
DEAR DANIEL: In my humble opinion, base trim should be mandatory for steel sided building panels. It keeps creepy, crawly critters from entering your building via open steel panel high ribs.
Direct from Hansen Pole Buildings’ Construction Manual, here are your instructions: https://www.hansenpolebuildings.com/2016/12/cut-install-base-trim-corner/
DEAR POLE BARN GURU: I have a 9 foot span between my trusses on my pole building and want to install steel on my ceiling. Do I need to install 2×4 braces between the trusses for additional support? I am planning on blowing in some insulation once the ceiling is installed. JASON in ROCKFORD
DEAR JASON: While I have heard of builders installing ceiling steel liner panels on trusses spaced even 12 feet apart without any additional support, my personal comfort zone is five feet – meaning, in your case, I would be adding 2×4 ceiling joists between my trusses. Make sure your trusses are designed for at least a three psf (pounds per square foot) ceiling load (truss drawings will show this as BCDL – bottom chord dead load) otherwise they will not be adequate to support weight of a steel ceiling.
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/