Sorry if this already been asked - searched the site and couldn't find a thread.

I'm in the Pacific NW and am about to install 3/4 thick solid maple (2 1/4) and have pulled out all the carpet and particle board. I've read it is recommended but not necessary to install plywood over the car decking subfloor. There is some deflection and slight cupping. My plan was to sand down the subfloor and install 30lb felt (edged to edge - not overlapped) to account for any variance. Then, lay a silicone paper over the felt and cleat directly over that (given this installation with no ply, would you cleat or staple?).

I read that some people don't put down plywood over the car decking - I'd prefer not to for all the obvious reasons. I'd like to know if back in the day (30-40 years ago) did installers install directly on top of car decking in the Pacific NW (or other areas of the country)?

Would I be looking at an installation failure or just some squeaky floors over time?

Thoughts/Opinions/Experience with this?

Thank you for taking the time to read/reply

The other day I watched a Don Bollinger video who lives in the Seattle area. Same situation. He preferred not to add extra plywood because of other rooms that had hardwood. This would have created the need for reducers which he didn't want. Like you, he sanded the subfloor flat and installed over it. More and more installers are going with cleats (3/4" hardwood) these days over staples...better expansion allowance.

Incidentally you can watch it here. Don't know how long it will last because it's a pirated video and I reported to Don.

http://www.youtube.com/watch?v=LnCg2GHRBn8

I think the most important aspect of cleats versus staples is moisture absorption over time. If you know your floor is going to suck up a lot of moisture, cleats might be a better idea. I generally prefer staples but cleats still have a place in this trade. I might recommend using some construction screws in any boards that aren't tight against your joists.

I still find lots of these sub floors here in Connecticut. We have lots of old homes and when a board is loose, a construction screw or ten will do the trick .

Thank you very much for the response and the link Ken - watched the video(s). I notice he didn't say whether or not his construction was decking over post and beam or decking over joists. There is some (minor) deflection when I walk across the deck now that the underlayment (particle board) has been removed. Do you know if back in the '70s it was standard to lay hardwood on decking on this type of construction and if it is just in the modern era that the NWFA decided decking on post and beam should have additional underlayment? Cause, if it is "old school", I'd feel more comfortable doing it than not laying underlayment if it wasn't considered necessary back in the day also.

Thanks for your input Paul - I'm assuming that when your talking about construction screws in boards, your talking about suring up the subfloor correct? I ask because I've recently seen videos or been reading about some people using headless screws on starter rows (pre-drilled at 45 degrees on the tongue) instead of blind nailing but to me that would seem to defeat the purpose or restrict the floor from expanding on the starter row end.

If you are talking subfloor, I know what you mean, I've found various places where they didn't nail boards or where they missed the beam completely (like around the fireplace they missed the entire 8 foot span of the end cut and that subfloor was spongy). I've gone into the crawlspace and added 2x4's across places like that to secure loose/floating end cut boards to adjoining boards and then sucked the boards tight from the top with deck screws. There is still some natural deflection when walking in some areas due to the 4' span - I'm hoping this wont effect the installation - or cause the installation to fail over time. My gut says once I nail her down, she'll be bomber without the additional underlayment?

I did mean the sub floor. You can use headless screws for first rows but you don't have to.

Seems to me they would not allow the floor to expand back and forth, but then some guys glue the first and last few rows, trying to avoid the nail holes. Me, I'd prefer to keep with old methods that are proven time and time again.

I don't know the answer to the post and beam. I don't think I've seen any reference to it in the NWFA manuals.

Expansion can be a problem. One builder I know likes to screw the first row with flush trim screws because he tends to work with wider plank and glue and staple. He opts for the screws so that his second,third,etc rows don't move his first row but it is just his preference.

I get the same result without the trim screws.

Just wondering what the beam span is under that 2x6 and how the 2x6 is run over it. Is it a Type I span or Type II or II or IV? Was checking my Western Woods Use Book, on page 164 of the design -Plank and laminated floors and roofs it has an illustration. Deflection is the main issue here I think.

I doubt there is any difference between going over a 1" plank and a 2" T&G as long as you know the moisture content, flatness, whats going on under it and which way you intend to run the hardwood.

As a DIY'er not sure the difference between types but my construction 4x6 beams set 48 on center with 1 1/2 x 5 T&G placed at 90 degrees. Let me know your thoughts on that.

I think I'd prefer to nail to allow for expansion as my total long run is like 40 feet - but this does raise a question for me:

I am actually planning to start in the middle of the floor, close to an island (center staircase) that I want to wrap around. I was going to run a control line off of the perpendicular outside wall close to the start of the island because it is the longest wall (27 some feet)/straightest. The parallel walls are offset and obscured by a fireplace with two sliders - not very straight/square with the house. After the control line, or mid room starting line, I plan to run a few rows in each direction blind nailing them to make sure the run isn't thrown off by the force of the power nailer. I'll try/hope to match the rows when I get around the island - backup plan is to put in a threshold or custom router a few boards when the two runs meet around the island.

What are your thoughts of using headless screws in the middle of the floor on the first row on both sides (after I add the spline). That makes me concerned about expansion also, but would make for a bomber mid room starting point for nailing against. oh, installing maple in case that matters. I've heard that maple can be squirrely as the seasons change so I'd like to let it go where it wants to.

Thanks!

Is the primary concern with deflection floor noise or that it will lead to flooring failure over time as fasteners work themselves loose and the floor expands and contracts?

http://www.architecture.uwaterloo.ca/fa ... struct.pdf

Pages 57 and 59, give examples, simple pattern, controlled random or 2 span continious? I would beware of the simple pattern.

You can use flush trim screws if you like. But another way to do it is to get some straight 2x4 or scrap wood to use as a nailing block. Face nail the wood to your sub floor directly behind your control / chalk line and then install your first row against it.Now work off of that and your first row wont go anywhere. When it is time to reverse direction, simply yank out the nailer row , install spline into the groove side of your first row and continue.

Thanks Paul. Great call! That's what I'll do. I've decided to place my cabinets on 3/4 ply instead of running the floor under them. I'll use those long straight scraps for nailing blocks.

After adding spine, should I also nail that starter board when I change directions? or just start nailing on the first row off of that?