This Wednesday the Pole Barn Guru answers reader questions about insulating a metal post frame garage in Florida with vented soffits and peak, replacing nails with EPDM gasketed screws on an existing structure, and ideas to replace rusted steel on the lower 3′ of a structure.
DEAR POLE BARN GURU: I have a metal post frame garage in south central Pa. I want to insulate this building. It is metal siding screwed to 2×4 wood purlins. It has vented soffits and is vented at the peak of the roof. How would I go about insulating this building? My hope is to use Polyiso foam board and insulate the slope of the roof, not the flat ceiling. Please give some advice for air gaps and vapor barriers for the roof and methods for insulating the walls. JASON in MANHEIM
DEAR JASON: Unless you are willing to use closed cell spray foam applied directly to underside of your roof steel, sealing off soffit and ridge vents, you are stuck without being able to insulate with slope of roof.
Why? Air impermeable insulation must be installed either directly above or below your roof deck – your roof purlins negate ability to consistently do this. Otherwise, an inch or more of unobstructed airflow must be provided directly below roof deck from eave-to-ridge (again, purlins are obstructing). Insulting at ceiling level is indeed your best bet. Install a ceiling and blow in granulated Rockwool (best) or fiberglass. Walls – completely fill insulation cavity with Rockwool batts, use a well-sealed interior vapor barrier (6mil or thicker clear visqueen).
DEAR POLE BARN GURU: I have a 1000sf metal building with Galvalume roof (on 2×10 purlins, no deck) built in 1999 with gasketed nails. I’m experiencing some small leaks from some of the nails. The metal is still good. Do you know someone that can replace the nails with screws, approximately 800. MIKE in CINCINNATI
DEAR MIKE: I would recommend posting on your local craigslist under “gigs” for a project such as yours. Nails should be replaced by #14 diameter screws, ideally with at least a 1/2″ greater penetration into wood than your nails. Look for screws with EPDM rather than neoprene rubber gaskets.
DEAR POLE BARN GURU: The bottom 3′ of our metal sided maintenance shop has been rusted out by salt. Do you know of an organization that could replace the bottom sections? MARK in ROCHESTER
DEAR MARK: For local projects, such as yours, I normally recommend posting in your nearby Craigslist under “Gigs”. You will usually get a fair number of responses. You may want to consider replacing this lower portion with material other than metal – something resistant to ravages of deterioration due to chemical reaction of salt with metal
You should replace all nails with screws of a larger diameter than nails and 1/2″ greater in length. Look for screws with EPDM washers (not neoprene rubber). If you find a location where water leaks have caused wood deterioration and screws are not “biting” place a wood ‘filler’ in hole – we’ve heard of people using wooden match sticks for this purpose, however would recommend ripping some small squares (roughly 1/8″ square) out of Douglas Fir using a Table Saw.
DEAR CRAIG: While it might be possible to raise a portion of the roof, it should only be done with involvement of a Registered Professional Engineer who can make a determination of adequacy of what you have, and what would need to be done to insure structural adequacy. Chances are good columns in area to be taller will need to be larger in dimension to properly withstand wind loads.
