Ceiling in Shop

[Tommy Surrency]

I'm in the process of getting my shop ready for air conditioning. The shop is pole construction (24' x 48') that I have closed in over the last year. Over the last month I have been putting fiberglass (R-13) in the walls, with OSB painted with 2 coats of primer. I'm ready to start the ceiling (14' height) in one section and was planning on putting R-19 fiberglass in over a suspended ceiling. I was going to drop down about 1' below the bottom of the trusses to install the ceiling and then lay the insulation right on top of the tiles.

This weekend I found a deal on rigid insulation. I bought 75 sheets of 2 inch in 4' x 8' sheets for $150.00. I figured I could install in between the bottom run of the trusses, double it up (4") while off-setting the joints. This will give me a higher R-factor, and will be easier to install, at about 1/3 of the cost of fiberglass.

I still have to spend about $200 for the suspended ceiling (I have the tile and some of the cross tees).

My question is this. Could I cut the first layer of ridid installion between the trusses, and then install the second layer directly to the bottom of the trusses? My trusses are 3' OC, so I would have to install a support at the 8' mark for the joint. Do you think glueing it would be sufficient, or should I plan on screwing it, or install some kind of batten over each joint? Prior to installing I would paint it with 2 coats, and then touch-up after installing.

The reason I asking, is not saving the $200 as much as I think it could be done in 1/4 of the time. With the high ceiling I'm having to set-up scaffolding for each section. Everything is packed into two sections and I want to get completely through with one section (walls/ceiling) before I start the next one. I'm ready to get done with the shop and start some woodworking.

I would appreciated any help or suggestions.

Oh yea, I just thought of another question. Would it be OK to cut the rigid installation on my PM 66 tablesaw, or should I spend 1/2 day getting my old craftsman setup?

Thank you,
Tommy

[Jim Becker]

Installing the ridgid insulation as you state would actually reduce transference points since you'd be overlapping the joints of the first layer and also covering the joists/trusses at the same time. Tape the bottom seams with foil tape before installing your ceiling to reduce air infiltration in or out.

You can cut the ridgid insulation with your saw although be prepared to have a 'mess' floating about in the air!

[Steve Clardy]

Installing the ridgid insulation as you state would actually reduce transference points since you'd be overlapping the joints of the first layer and also covering the joists/trusses at the same time. Tape the bottom seams with foil tape before installing your ceiling to reduce air infiltration in or out.

You can cut the ridgid insulation with your saw although be prepared to have a 'mess' floating about in the air!

Yes on cutting the foam board with your table saw. Thats the way I cut mine.
And YES on the floating mess. Lol. It'll all be gone in a few moths of sweeping though.
Steve

[Tommy Surrency]

Jim/Steve,

Thanks for the reply and the heads up on sawing the rigid insulation. So you think the insulation will be OK as the finished ceiling?

Tommy

[Steve Clardy]

Sure. I know of a house that has it in the living room. Kind of unusual for a house, but whatever works.

[Lee DeRaud]

Two inch thick? How about using an electric carving knife?

[Tommy Surrency]

Lee,

Good idea, and I'll give it a try.

Tommy

[Rob Russell]

I would just get an 8' straightedge and cut the insulation outside with a circular saw. Given that you've got so much ceiling height, I wouldn't bother cutting the insulation into 3' sheets, but put both layers over the face of the trusses and just think of a good way to fasten it up. Perhaps screwing up the first layer with 3" sheetrock screws. Then spray adhesive on the first layer and glue up the second layer.

[Tommy Surrency]

Rob,

I haven't thought about spray adhesive, but I have liquid nails. Would that do the same thing. I like your idea of anchoring the first layer and then some kind of adhesive for anchoring the second layer.

Thanks,
Tommy

[Steve Stube]

Depending on the type foam it may not like some adheasives and melt on contact.

I am curious about the brand of foam and if it has an R rating. Cell size and blowing agent are factors to be considered too.

Code and Fire insurance may affect your decision to leave it exposed. Exposed in a living space, I expect is a No No.

[Dan Oelke]

If using Liquid Nails - make sure it's the stuff formulated for styrofoam. The solvents in the regular stuff can eat through styrofoam.

[Chris Padilla]

However you anchor it, you'll want large washers to spread the load of a screw or nail. I seem to recall nails with a squarish-type of washer.

[Jim Dannels]

Two inch thick? How about using an electric carving knife?

I have been using a electric Knife on foam for many years.
Foam cuts like butter with one and much less mess. If you want to do finer work get an electric Fillet Knife from the sporting Goods department The blades are pointed on the end.

[Dev Emch]

I have been fighting mouse house invasion with fibre glass insulation. I recently opened up a floor joist only to find that the mice had hauled every sunflower seed in the county into that space. They also did a nice job on the rock wool. How did they get into these spaces? And its not just one house... almost every structure we own have had this kind of invasion. The quick fix is to invite garfield and his buddies to come over and move in.

So for properties that are keepers, I am changing these areas over to rigid foam. There are some fire code issues to consider. For homes, you will need at least 1/2 inch of drywall or equivalent over rigid foam. I wanted to line one room with T&G blue stain ponderosa but found out that I first have to skin the room with 1/2 dry wall and then install the T&G. What ever makes these code monkies happy.

But I found the best way to cut rigid foam is with a hot wire. I jerry rigged a quick jig and strung a length of nichrome wire on a wood frame. Make sure to isolate the wire from the wood with nails pins and so forth. Then hook the wire up to a weller soldering gun or other low power power supply. IT cuts very fast, leaves a sealed smooth surface and does not make the horrid mess that normal cutting tools do when they cut foam. I picked this tip up from guys who make surf boards. Pretty trick idea from folks whose every other word is DUDE.

[Chris Padilla]

Google "hot wire cutter" and you will see how simple it is to make one of these...basically how Dev said it! :)

[Steve Stube]

Dev, the mice squirrels etc. will make a nest in Dow rigid foam too.

The only time I used hot wire cutting for rigid foam was when I wanted to cut 2" X 12" boards from 12" X 24" X 12' long billets and it wouldn't work on my table saw. I used a Variac (auto transformer) for the power supply.

I would cut anything I could handle sizewise on the table saw BUT will tell you that one of the most exciting times in my life was when I was left holding a small piece of 1" foam in my hands that just before the kick back and big boom had been a 4' X 8' sheet I was ripping (with the fence in place). It cuts so easy I was letting it fly thru the cuts - don't do that, cause foam can hurt you when it gets up to speed.