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How to retrofit a metal skin pole building?

Kelsey Thomas | Posted in General Questions on

I am up in Seabeck/Silverdale WA State (4c zone) area and have inherited a pole
building work shop.

It was not used for a long time and mice had gotten into the insulation and destroyed it.

We plan on fixing up the building to use as a computer shop / art studio, so need to insulate it and put Sheetrock up and control the moisture in the finished area. I am trying my best to avoid taking the metal siding off (way beyond me) and have also ripped out as much of the white vinyl insulation/vapor barrier out as I can since the mice destroyed it. I don’t plan on using and air conditioner just heater.

Some back information: The shop is not vented however it does not have closure strips between the metal and the framing that allows for some air movement and also mice. I plan on blocking all of these off at ground level from the inside to stop the mice. it was built back around 1996 As a rough idea. Currently there is minor condensation problems during certain times of the year with just the standard vinyl backed insulation not horrible. The floors seems to sealed concrete that’s good and the area we are finishing has a wood stove.

I am currently cleaning the room that’s to be finished and blocking off mice entry ways.

My big question is: What are my options in WA ST climate (4c) to insulate / stop condensation in the
building?
I have gotten a few different and conflicting ideas on how to do this:
1. Spray foam, however, its pretty spendy and I have heard it can make the metal buckle not sure though if thats unusual. Also was thinking of doing 2″ CC SPF then putting up insulation bats and sheet rocking but I don’t know if that would cause a moisture problem in the wall…. would I want to use poly as well?

2. Also had it suggested by an insulation guy to PACK FULL the walls with fiberglass un-faced bats, make sure its touching the metal and fit as much in as we can then poly and sheetrock.

3. Use fiberglass bats and make sure its not touching the metal so it can wick condensation and use poly.

I am also wondering how much of a vapor barrier the metal siding is I know it’s not air tight but it also doesn’t breath a bunch.

Really looking for some good information here on what to do next have heard and read so many ideas that I am not sure what will really work and still work 10 yrs down the road. THANKS

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Kelsey,
    The best way (in my view) is rather wasteful of interior space. I would advise installing plywood on the interior side of existing wall framing, and abandon any idea of installing insulation within the framing cavities. Tape the plywood seams for airtightness. Then install a couple of layers of rigid foam -- as thick as you can afford -- with staggered seams. On top of that, install your preferred wall finish material, screwed through the foam to the plywood.

    It would basically be a site-built SIP.

  2. Kelsey Thomas | | #2

    Not a bad Idea Martin, However, The placement of the door is Such that I cant ad but more then 1/2 in top to the framing on the wall and still open the door that goes into the shop. Unless I tore down the block framing that was installed but man that block framing is SOLID!

  3. Expert Member
    Dana Dorsett | | #3

    Metal siding is highly vapor retardent, but not air tight, so as long as there is at least SOME cavity between the metal and the rest of the assembly, the assembly will be able to dry toward the exterior.

    The coefficient of expansion of metal siding and polyurethane differs by quite a bit, and yes, spraying closed cell directly onto the siding WOULD create warpage that shifts with season & sun.

    Packing fiberglass batts directly against the metal is guaranteed to end up with wet spots in the insulation- bad idea, which can only made worse by putting poly on the interior. If you're going to put insulation directly against the metal, use rigid EPS, and don't glue it to the metal- support it by other means. Open cell foam might get you there too, and has more flex than closed cell, but would be somewhat susceptible to moisture from rain at the seams (not that it ever rains in Kitsap County :-) ).

  4. Mike Momb | | #4

    You are experiencing a problem which could have been solved very inexpensively at the time of construction – making the building walls “rodent tight”.

    An adult mouse can crawl through a hole the size of a dime, so the solution is – eliminate the dime holes.

    One place builders and building owners save money, or miss just by not knowing better, is failing to purchase and install base trim (aka “mouse guard”) between the bottom of the pole building wall steel and the pressure treated skirt board).

    If you building has a concrete floor and overhead sectional doors (as opposed to sliding doors), you have a good starting point. Sliding doors will not keep rodents and small cats out and should be replaced before moving forward.

    New insulation blanket is not the answer. Here is how to do the job right.

    Step #1 Remove all wall steel. Discard any existing wall insulation (wear appropriate gloves, masks and eye protection as rodents carry diseases.

    Step #2 Add framing to the walls to create “commercial” or “bookshelf” style wall girts. Basically you want to have horizontal framing every two feet between the wall columns, flush to the inside of the posts.

    Step #3 Look for any open spaces, cracks or knots in the treated splash plank around the bottom of the building – especially at all four corners. If necessary remove and replace and bad skirt boards, or fill voids with pressure treated wood (keep the dime in mind).

    Step #4 Take the distance around the perimeter, subtract the width of any doors and divide by three. Order this many “inside closure” strips to conform with the ribs of the steel siding. These will be placed under the bottom edge of the steel siding to fill any gaps.

    Step #5 Install base trim/mouse guard around the entire building other than at doors. You will need to order from someone who can provide good instructions on how to place around corners to avoid sharp edges, or gaps.

    Step #6 Place a quality housewrap on the outside of all exterior walls.

    Step #7 Reinstall wall steel (use new screws of a larger diameter than what was originally on the building).

    Step #8 Ideally use BIBS insulation in walls, but if not available rock wool batts.

    Step #9 Drywall.

    If you are going to do it, you might as well do it right.

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