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$6000 House: Subfloor Repair

renosteinke's picture

My much-delayed project to remodel a house I bought last year is s l o w l y getting going. I know what I want to do, and have been replacing the utilities and doing the demolition in little steps.

Last weekend, I finally gutted the kitchen, right down to the studs. The old cabinets were a hazardous waste site in their own right, and (as expected) there were signs of considerable water damage over the years.

Indeed, under the cabinets the subfloor was destroyed. Between water, mold, and simple rot, there are major holes. Now, let's step back a moment ...

The counters were along the same wall that has the bathroom on the other side. The bathroom floor, in a similar manner, has severe water damage, and a replacement patch fit in around the toilet. So, we're talking about a significant bit of floor that needs complete replacement - perhaps a section 9-ft x 12-ft.

The original subfloor was made using 7/8" T&G planks, laid on a bias to the floor joists.

Here's my question: Would you repair by notching replacement planks, offsetting the joints - or would you make a square cut over the joists and just lay down some sheet goods?

Also: With the patch taking up half the kitchen floor space and 2/3 of the bath floor space .... would you just remove all of the flooring and do the complete rooms new?

a simple question b/4 you get started (post #207212, reply #1 of 10)

What's the finished floors going to be?

and what is the current joist spacing?


Another might be, any joist damage (water or plumber related)?

And of course, platform or balloon framed? as well as the partition wall between kitchen/ bath.

Crawl or basement and what plumbing / electrical / heating is going to be done?

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


I don't understand some of (post #207212, reply #2 of 10)

I don't understand some of your questions, but I will try to answer what I can.

House is 1957 typical ranch, balloon frame, over a crawl space. Floor joists are lumber, 2x8's, with a span of just over 8-ft. There's about 17" between the joists and the dirt, and joists are on 16" centers.

I have not probed the joists, or done any other testing. Other than water stains and perhaps surface mold, I'd be surprised if there is any damage. Nor are there any notches or holes in the joists. Floor is without noticeable 'bounce.' It appears that once the water got through the floor it was able to drain freely.

I can say this: with the removal of the old cabinets, damaged drywall, and fuzzy insulation, the kitchen no longer smells.

Existing wall between the bath and the kitchen will be removed. A new wall will be built about  30" away from the original location.

The wall on the opposite side of the bathroom will also be removed, and the bathroom expanded about 30" in that direction. Bathroom will 'grow,' while the kitchen and the other room will lose space.

Plumbing will be completely different from what now is in place. The sewer line might be the only thing that stays in place. The main might be replaced with a 1" main, water heater will be moved to inside the house (it was in the carport storage shed), and every plumbing fixture will be relocated, usually by about 2-ft. Additional fixtures will be installed, including a 'walk-in' soaking tub. Copper "tree" layout will be replaced by a PEX 'manifold" arrangement. New toilet will be wall mounted. I have two vent stacks to move.

New floors? Probably cork or rubber tiles in the kitchen and end room, while the bath will be a tile or terazzo method. Bath will likely have a heated floor as well, and the entire bath floor will be a 'shower pan.' (Hence the wall-mount toilet - one less place to leak).

I know not what is 'platform' framing. Floor is supported on piers over a crawl space. No termite issues.

A complete electrical re-wire is in the works; wires will be run in the walls.

Heating is central, with a registerin the ceiling. Air Conditioning is currently a window unit, but this will be changed. I'll either add central air to the heating system, or have a mini-split with the fan heads mounted outside the kitchen.

While the kitchen hood will exhaust out through the roof, I will probably bring in make-up air from below.

reno (post #207212, reply #3 of 10)

The reason for the questions, if you need to get into the crawl (and it's not spacious), then getting the subfloor out will perhaps benefit you down the road.

Platform framed-foundation, box and joists sit on that-floor is sheeted one end to the other.  Then 1st floor walls are framed on top of that sub floor. 

See what I'm getting at-gutted in balloon frame-no problem getting the sub floor out from "under" walls. 

Plan the job complete and see if you make it easier on yourself not having a subfloor in the way.

On ceramic and I would guess terrazo-the diag. subfloor is not as rigid as what plywood oriented properly would be.  With natural stone and perhaps terrazo, you'll need to keep deflection down to a minimum and if the joists are sound enough, it'd be a [CUTE LITTLE PUPPY] if cracks appeared because of the overspanned diagonal sheathing.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


Complete Floor Replacemnt? (post #207212, reply #4 of 10)

So ... you're advising not to 'patch' the damaged areas by any method, but to replace the entire subfloor, wall-to-wall, in the work area?

That can be done. Supports can be added where the edges would be unsupported. Where the saw won't reach the Multi-master will.

A complete new floor will give me a 'plane' that moves as one piece; less chance of the finished floor cracking where the seams are.

Here's what I'm suggesting. (post #207212, reply #5 of 10)

Figure your finish now.

Come up with what it'll take to get there with the same quality needed, but with the least amount of total real work.

Plan accordingly and proceed as you can.


You know, it's how us reno guys work.  End goal in mind, most reasonable way to get there w/o losing sight of a long lasting project.


I'm not there so am a little limited in what the exact plan should be.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


Reno,  just a few (post #207212, reply #7 of 10)


 just a few comments.... 50's era house is most likely  "platform framing"......balloon framing would have the studs sitting on a plate that sits on the foundation , the joists would then be installed on the same plate next to the studs......when the joists sit on the foundation plate and thenhave subfloor installed and then  a separate plate that the walls sit on, you have platform framing........Balloon framing was abandoned roughly after the 30's, but that will vary by location.......but by the 50's, and for single story buildings,  platform framing was pretty much the prefered method.....but nothing is absolute in construction.....where your cutting the old subfloor out just cut parallel to the wall plate, being careful not to cut too deeply when cutting perpendicular to the joists below, there's no need to add support between the joists where the ply runs perpendicular to the joists...only where the ply runs parallel at the to your ' plane' for the tile movement, I would suggest you look into Schluter- Ditra as a tile underlay and isolation membrane.. in areas that get wet and will have tile installed in them,like entry-ways, bathrooms, mudrooms , excellent product IMHO...
  Good luck with the "reno" vation   :)


Guess What I'm Doing Christmas? (post #207212, reply #6 of 10)

I have ordered the subfloor material; I asked for delivery next Friday. Six sheets of 1-1/8 plywood T&G subfloor grade material.

(This town lacks a lumberyard. The guy at the Box shook his head and mutterd about never having hear of such a thing in all his 15 years in the business - only to nearly drop the phone in surprise when his supplier knew exactly what I was asking for. OK, I got charged a premium, but doo doo happens).

This means I have until then to complete the demolition work in my house. Oh Joy. Mainly, this will mean taking out two walls (non bearing), and stripping te remaining walls to the studs. It means more temporary fiberglass insulation and temporary cardboard wall coverings.

Temps will be mild for December, reaching the 50's during the day. Still, I'll be giving the furnace a workout while the floor is open. For that reason, I'll probably do the floor in sections, one sheet at a time. I expect I will really like my Multi-master by the time I'm done; with the change in floor thicknesses, I will have to make my seams right at the wall line.

I've cut through the floor before, when I installed an access hatch for the crawl space. The task - subfloor covered by 1" oak flooring - really made me appreciate the added power and stability of my Makita "hypoid" saw.

Eat your heart out.......... (post #207212, reply #8 of 10)

We'll be off to Nashville for a family visit-

ha ha ha.

With all the presents we'll be hauling, no room for tools.

I won't be doing a damn thing but playing with the grandkids.


Best of luck and Merry Christmas!



By the way, I have had a MM for years and rely on it often.  You've heard me rave on it's uses.


I think I'd rely on my sawzall (with maybe fine tuning by the MM) on most of the hard to get to or close work demo.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


Platform? Balloon? Well... (post #207212, reply #9 of 10)

Platform? Balloon? Well - my lack of vocabulary aside ... does it matter?

The original question assumed I'd match the original thickness, and I asked: piece in new boards on a bias, or just cur a square for a bit of sheet goods? A question artfully dodged, and rendered irrellevant as the plan was refined.

I'm simply not worried, in the least, about the specific floor finish to be used. I figure a good, solid subfloor can have any top layer you might want. With this remodel, the finish flooring won't be done for a year or two; I might lay a sheet of vinyl as a temporary measure. Most of the house has the floors covered by sheets of cardboard right now.

Sawzall my patootie. I expect my primary tool for cutting the old floor out will be a Makita hypoid saw. The depth control for that saw is awesome. Multi-master will be reserved for those few areas where I'll really need to cut flush to the existing framing.

My whole plan / rythm took a hit at the very start, in the wee hours this morning. A rather modest winter storm killed my power for eight hours - hard to do much without lights, power, or heat. When inside temps dropped to 48 I bit the bullet and visited the all-night Wall-mart for a kerosene space heater and some candles. The space heater got one room up to 60. (Outside temps were near 30).

One thing nice about leaky old construction: you can use a space heater. That can quickly become a problem in 'airtight' construction. In Nevada a few years back, a construction worker died from carbon monoxide poisoning as he used a gas-powered saw in a properly 'tented' area. The same plastic that kept the dust 'in' also kept the fresh air 'out.'

FWIW, the power was restored in fits and starts, with low voltages and an intermittent leg. This was followed by two more hours of no power. Moral of the story? Well, it really stresses the need for a quality transfer switch if you have a generator, a switch that won't switch back to 'grid' power until the grid has full voltage.

Ion-type smoke detectors, btw, are extremely good at telling you when you have lit a candle.

Anyway, the plan is Demo walls - demo floor - new subfloor - make my final layout - frame new walls - get the plumber in. Might even have a water heater by summer

I suspect the same storm that cut my power will push the materiel delivery to next Monday, even Wednesday. We'll see.

Last Sunday I finally dropped the roof of the old laundry addition. Paul Bunyan could not have dropped that roof more precisely; I got lucky.  With the final cut, it swung away from the house, flipped, and laid itself flat on the lawn.  It remains for me to demolish the "foundation" of this addition. This will clear that area for placing a slab for the air conditioning equipment.

Hey Reno (post #207212, reply #10 of 10)

If you don't want answers, don't ask.

Subfloor/joists?   any subfloor can support a finished floor?   Say you use large profile stone?


I know, it's a shack-you ain't putting stone in.

Then fine.

Scab in whatever  you feel like. 



Maybe now you know the difference?   or who cares?  Either way, it could have made a difference on the advice you would be given regarding the demo of all/part/none..........of the subfloor.

And I'll defer on your tool choice, you're there-we aren't.  But how dumb do you take us for?  of course you'd use a circular saw for all but the inaccessible cuts.  Who wouldn't?

Nice listening to you.

Best of luck on the project.


A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.