Go Back  DoItYourself.com Community Forums > Interior Improvement Center > Insulation, Radiant and Vapor Barriers
Reload this Page >

"Squeegee" spray-foam on top of roof deck? (to save $?)

"Squeegee" spray-foam on top of roof deck? (to save $?)


  #1  
Old 06-06-13, 03:00 PM
L
Member
Thread Starter
Join Date: Jun 2013
Location: USA
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
Question "Squeegee" spray-foam on top of roof deck? (to save $?)

I'm gutting and rehabbing my small 1950s house on a shoe-string, in the rainy Pacific Northwest. I'm doing most of the work myself, learning as I go. (I have no cash; it's either do it on the cheap to rent for 5 years, until prices go up, or tear it down now. Whoever buys it will definitely tear it down, it's not a fancy house, only 1,400 sq ft interior main house. It is not currently liveable due to water-damage/mold, but it's in a nice location.)

It has a concrete slab foundation with radiant-floor gas heating, single-story (no basement), and a flat roof (no attic) that has leaked on and off for years. (1:16 pitch, too flat). So I need to tear off layers of old build-up (hot-tar) roofing, and repair parts of the deck, and fix some joists/rafters that are rotted for 3'. (I'll "sister in" parallel joists and cut out the rotted old tails.) I'll probably pay for torch-down roofing membrane, possibly even DIY PVC membrane if I could get some cheap off CraigsList -- the roof is key. I am gutting all the drywall, as there was extensive mold and water-damage, especially along the longest wall. I'll spray bleach on the wood to kill mold. There is currently no added insulation anywhere in the house! Neither ceiling nor walls. The roof deck is tongue-and-groove boards, about 5" wide. (I'll replace the lowest 4' edge with marine OSB/plywood.)

Question: to help seal the roof for insulation purposes, would it save money (if not exactly kosher) to spread DIY spray foam on top of the bare roof deck, having one person spray and the other person use a big home-made wooden "squeegee" to spread the foam around and work it into the cracks? I've never used SPF, so I've no idea how it handles -- I read it sets in 2 minutes, so it would have to be a 2-man operation. I can imagine various problems -- not being able to get a smooth enough surface for the top roof-membrane, foam clinging to the squeegee and having to replace the wood 'blade' often, not saving much money because it will bubble up rather than working into cracks, etc. But if it worked, it would help seal for insulation (and maybe for mold), and I could try it on the walls as well.

Another option would be to get lots of Dow Great-Stuff spray foam, and laboriously go along the all the 5" deck boards and seal all 2200 sq ft of roof, either on top or from below. Yet another labor-intensive option is to rip off all the roof deck and put down OSB sheets everywhere. Of course another option (and maybe the best!) is to forget sealing the air leaks, just use fiberglass batting, and make sure the tenant pays for heating. (It needs plenty of other things worked on.)

It needs a lot of other work (new boiler & pump for heat, new water-heater, exterior staining of cedar-panels and interior painting, some structural work, possibly put down inexpensive laminate flooring on the polished-concrete floor, I'm leaving in place the large single-pane windows, etc.), and I wish (!) I had the money to "do it right" (or even half-way right!). But I don't. So I'm really cutting corners, on materials and labor costs.

I'd really welcome any helpful suggestions, on the insulation and other issues. Thank you!
 
  #2  
Old 06-06-13, 03:13 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 36,607
Upvotes: 0
Received 10 Upvotes on 9 Posts
Welcome to the forums! You'll go broke on the spray foam, and no you don't spread it, it spreads itself as it expands. 2200sf will cost a bundle and the energy savings will be minimal, IMO. I think insulation on such a roof would be low on the priority list. You got bigger fish to fry.....roof, mold, sheetrock, plumbing, electrical.
 
  #3  
Old 06-06-13, 06:13 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
Received 39 Upvotes on 31 Posts
Is the radiant heat still usable? Most of those slabs with the radiant in this area were built using regular black steel pipe and have long since rotted out.

And, I agree completely with Chandler. You not only don't, but can't squeegee the foam. If you use the slow expanding (and setting) one-part foam it is incredibly sticky and absolutely won't go where you want but it will gunk up your tools almost immediately. The two-part foam expands and sets way too fast to even think about tooling it into place.

One more thing, 1400 square feet is not something to sneeze at, my first home, in Mountlake Terrace, was around 850 before I added the inside access utility room. My current home (Bothell) is 1540 square feet.
 
  #4  
Old 06-06-13, 10:12 PM
L
Member
Thread Starter
Join Date: Jun 2013
Location: USA
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks for the prompt replies! I'll take your words of advice about the foam/insulation, thank you!!

Yes, fortunately the radiant heat uses copper pipes (not iron) in the floor; I had it air pressure tested, and no leaks. But I'd need to learn a boatload about plumbing (and gas) before I felt comfortable hooking up a replacement gas-boiler/pump/expansion tank (all of which are rotted out and need replacing). For now, I'm waiting to see if the right handyman offers a used boiler (or an on-demand unit that is approved for continual boiler use) for sale and will install it as part of the deal. Ditto on the water-heater -- I've read all the raging debates about tanks vs tankless (w/ or w/o a 6-gal mini-tank to avoid cold-water gaps), and I'm basically waiting for the right deal, whichever comes my way first. It'd be nice to have extra closet space inside the house.

The house has only one bathroom, which is a drawback for renting. Putting in a second bathroom on the concrete slab (avoiding radiant pipes) is beyond my budget and experience. There's a back room that may be off the slab (it has an electric baseboard heater, not radiant heat), so it's possible I could add a bathroom there -- but again the cost ($5k min?). I've even thought of putting in a high-end composting toilet in a garden-shed out back, and maybe an on-demand shower there, for emergencies. No money = time for creative thinking! :-) )

And yes, electrical. It's all 1950s 2-wire (not grounded), still a fuse-box not a circuit-breaker. The wiring in two rooms where the roof leaked definitely needs replacing. I've met a guy who claims to be licensed and bonded and will replace the fuse-box for $600, which might be worth it (so I don't get zapped or spend a lot of time). I'm debating whether it's worth replacing all the wiring, while the sheetrock and ceiling are down. I might also just replace most of the 2-prong outlets with 3-prong GFCI's and label them "ungrounded".

As Chandler very helpfully prioritized: roof, mold, sheetrock, plumbing, electrical...

Thank you again, very much!
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: