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Temporary subfloor for 2nd floor in 1.5 story platform frame farmhouse

navi_jen's picture


I have a c1928 1.5 story farmhouse, approx 950 sq feet in total. Platform framed, Joists are 2x10, 16" on center.  Original subfloor is/was spaced wood planks 0.5x6" run perpendicular to the joists. It's only me in the house. Layout is LR/DR/KT down, 1 BA + 2 BDs up. House is in a very desireable neighborhood, last house on a dead end street and abuts a 60 acre, wooded, town park.

The previous owner had a plethora of pets (including many cats), and getting rid of the smell and allergens have been challenging to say the least. The animal residue was so bad that the HWF T&G was rotting and the subfloor (not just the HWF, but the subfloor) is stained both black and white due to the ammonia in the cat pee. It's bad.

I have ripped up the first floor (and the 2nd floor bathroom) HWF and subfloor and replaced with Avantek w glue and screw (which I hate, too squishy underfoot, but that's another story). My allergies are still going wild, and the remainder of the 2nd floor still needs to be done. My plan is to replace the 2nd floor subfloor (and the bottom 18" of plaster), wait a few months to literally have the dust settle and see if my allergic reactions subside. Then, either 1 of 2 things will happen:

1.  If my allergies go away, I want to finalize the architectural design plans for the renovation (which may move a few walls upstairs and down) and rebuild both subfloors with period appropriate dimensional lumber (I know, I'm crazy like that).  Then, finish the renovations.

2. If my allergies don't go away, I will need sell the house as is, as a tear down/contractor special.

During the 6 months of the 'dust settle period' the only thing that I plan to have in the 2 upstairs bedrooms are a queen sized bed and 2 dressers. Nothing super heavy (as most of my stuff is still in storage).

So, my actual question is:  Given the short duration of the interim period, the small amount of load, the potential that the house will be a teardown (and/or redesign of the floorplan), I would prefer to remove the 2nd floor subfloor and simply tack the new subfloor into place (avoid all the extra work of blocking and glue and screw). Am I risking permanent damage to the structure?

Please know that should I decide to stay in the house, I do want to do it right in the long run....I just don't know if it's worth it now, because I have not finalized the final building plan and I don't want to put in more subfloor patches should I decide to move walls. Or, waste time/money if the house really is a teardown.



Without going into other (post #216318, reply #1 of 6)

Without going into other issues I would use 3/4" CDX or, if you can find it, 3/4" OSB. If you screw it down you'll be able to take it up and reuse it somewhere else.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Thanks. Absolutely going to (post #216318, reply #2 of 6)

Thanks. Absolutely going to use 3/4" plywood..I don't like Advantek or OSB.


And if I didn't have the allergy component, I would have already completed the design with my architect and done it right the first time. I'm just trying to find an interim solution while my respiratory system decides whether this is the long term house for me.


Protip to myself for any future RE buys: Stay away from any house that has an abundance of cats.

I  didn't consider your (post #216318, reply #3 of 6)

I  didn't consider your allergy issues. Maybe you should bring a piece in the house and see how you react. Playwood is full of some nasty glues.  If you have a reaction you'd have to use sort of boards which would take a lot and a lot of time to install.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Aside form your structural (post #216318, reply #4 of 6)

Aside form your structural questions have you considered coating every surface witha shellac primer such as BIN or Kilz? The shellac seals in any and all odors. I would rent an airless spray gun and coat every available surface including floor joists, stud bays  plywood, plaster,ceilings, walls, floors etc

Hi Steve...I actually not (post #216318, reply #5 of 6)

Hi Steve...I actually not only considered, but have already gone the shellac route. Even after Boston's best mold remediation company de-molded the house and angle ground the joists in the basement (to get rid of of the stalagmites of white ammonia crystalas), I could still see faint ammonia rings on the joists, where they ammonia had soaked into the grain. So ever single joist that holds up the first floor is covered with 2 or 3 layers of shellac (I forget how many). I assume I will have do to the same for the 2nd floor joists when I renovate.

I thought about shellac for the 2nd floor least as a temporary measure. There are quite a few boards are split/cracked due to my home's age and the moisture.....and in the long run, I wanted to make sure the house is 300% allergy free. So, long term strategy is to just rip and replace (wiith either period appropriate dimensional or marine grade 1")  in the long run. If I were to shellac, it would take a couple of tries, as it would be hard to empty both bedrooms in such a tiny house. But maybe I should try it as a first resort.


Sounds like you are on the (post #216318, reply #6 of 6)

Sounds like you are on the right track. It must truely be aweful if the remediation hasnt helped. Shellac first. Rip and replace next! 

Good luck