Replies

1. Expert Member
   Dana Dorsett | Apr 01, 2019 04:28pm | #1

   ocSPF and ccSPF are standard terms , though sometimes the vendor-specific product name would be used.

   Often it will be quoted in board-feet rather than nominal inches, sometimes by nominal R value.

2. GBA Editor
   Martin Holladay | Apr 01, 2019 04:31pm | #2

   Russell,
   The word "nominal" is used when the actual measurement differs from the designation.

   A nominal 2x4 measures 1.5 inch by 3.5 inches.

   My interpretation of "2.5 inch nominal" is "we call it 2.5 inches, but in reality it might measure less."

1. Expert Member
   Dana Dorsett | Apr 01, 2019 04:59pm | #3

   That might be a bit too cynical.

   I'd take it to mean "we call it 2.5 inches, but in reality that would be the average depth, not the minimum or maximum."

   With a some pre-installed depth gauges it wouldn't be hard to keep it pretty near the nominal depth.

2. Expert Member
   BILL WICHERS | Apr 01, 2019 05:07pm | #4

   I agree with Dana here. “Nominal” in this case would be the average depth of spray foam in a given area. I’d take this to mean that some areas will be a bit higher or a bit lower, and areas against framing members might rise up in an arc. “Nominal” in engineering terms is usually an average with a specified tolerance so something like “2.5 inch +/- 0.25 inch”. “Nominal” in lumber terms is more of a “back in the day we cut it 2x4 inches, but now we kiln dry it and surface it so it’s 1.5x3.5, but we still call it a nominal 2x4 inches for old times sake”. Different uses for the same term.

   I’d change this spec to “2.5 inch minimum” though. You’re more concerned with voids than thicker bumps. Thin spots can be a problem with larger spray foam installs.

   Bill

1. 
   RussMill | Apr 01, 2019 08:50pm | #6

   This is a 25k bd ft job. IF i were to go full bore as planned. I've backed off that though. Not the cost, its that no one wants to do a full fill and scrub on this much volume.

3. 
   RussMill | Apr 01, 2019 08:47pm | #5

   I understand nominal in lumber terms. Yes, we will be verifying thickness. It just concerned me. This one was MUCH MORE honest and a pleasure to talk to. I will request a change to the contract.

   Oh cellulose is so much easier... if i just had a person to install it. I cannot justify the blower cost, at least not a dense pack capable machine. We have a regular blower.

4. 
   RussMill | Apr 01, 2019 08:52pm | #7

   Also, i requested 2 inches so, i assume its to have his installer bump it up a notch so i get my 2"