Installing over old finish floor

ardrysdaMay 11, 2014

I am looking to install flooring in our 1928 Bungalow that was built without a subfloor, the finish floor is 3/4 inch, T&G, narrow plank, close grained wood of unknown species (I cannot access the house right now to say exactly what the floor is). The old finish floor is installed as a subfloor in that it was laid before the interior walls were framed and the planks are continuous under the baseboards and walls, the floor is laid perpendicular to the joists.

At some point in the past, carpet was laid down over the floor and the doors were cut at the bottom (poorly, I might add) to accept the height of the pad and the carpet. All carpet is being removed and the old flooring is in rough enough shape (wear, gaps between planks, etc...) that I would like to lay a new floor down. The floors in the house are largely, but not exactly level with very minimal bounce.

Although I know it wouldn't be quite standard, is there any reason that I cannot lay 3/4 solid flooring perpendicular to the old floor (it would be parallel to the joists) using the old narrow plank finish floor as a subfloor. Adding a plywood or other subfloor over the prior finish floor would take up too much height and require adjusting exterior doors and thresholds, and ripping out the old finish floor to lay a proper subfloor is not an option.

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Sophie Wheeler

Your ''not an option'' is the only correct way to do it. Remove the existing floors, assess the joists, and then install a proper dimensionally stable plywood subfloor suitable to doing a naildown wood. And plan on using yourAC in the summer and a humidifier in winter if you don't want the same edge crush gaps to develop between the new floors.

Learn the lesson now of doing things the harder more difficult way rather than the cheap and easy way. Then you only have to spend money once on the project rather than having to remove your mistake and replace it for more money than doing it right in the first place.

    Bookmark   May 11, 2014 at 11:24PM
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What hollysprings said: YES!

    Bookmark   May 11, 2014 at 11:30PM
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If your existing finish floor is stiff and shows no sign of having sagged between the joists (in other words it is flat) then that becomes the subfloor for your new flooring. There would be no reason on earth to rip it out and install something different. In fact, you would be creating lots of problems attempting to do that. The existing flooring IS your subfloor! Make sure that it is firmly attached to the joists, that any weak spots are addressed and then install how you would any new floor over a firmly attached 3\4" subfloor.

    Bookmark   May 12, 2014 at 7:54AM
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Re: Hollysprings- I do know that this isn't standard for today's building specs, on the other hand just a finish floor over joists like I currently have isn't to spec either. As a point of information, the estimate to do what "isn't an option" comes in at over a 1/4 of the value of the entire house- in this market with what we already owe on the house (which I have owned for 9 years), I cannot put that kind of investment into the house without any hope of return in the next 5-10 years (welcome to the real estate market in Michigan).
I have certainly learned the lesson of 'doing it right' is the only way mindset as an engineer- but currently I am a veterinarian and many times the right way in not affordable to my clients and they have to elect for a not quite as good, but good enough option- kind of like this situation.

If the floor will fail in 30-40 years verses the normal 100-200 year lifespan of a hardwood floor, I can live with that. I need to do something that isn't carpet due to allergy issues in the family and this is an affordable option- but I am open to other options if I can afford it.

    Bookmark   May 12, 2014 at 10:31AM
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Glennsfc is on the button here. As long as the exsisting floor isnt sagging and its not too thin in some spots then yes absolutely go a head.

I would take some time to refasten the old planks to the joists but otherwise you should be good to go.

    Bookmark   May 12, 2014 at 8:43PM
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I agree. If it's structurally sound, then why fix it? I'm Mr. Overkill, and I would side with Glennsfc and gregmills.

    Bookmark   May 13, 2014 at 11:28AM
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Should the new floor be perpendicular with the old floor which is perpendicular with the joists?

    Bookmark   May 13, 2014 at 11:35AM
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You're gonna get a LOT more movement with that new floor over a plank subfloor than you would over ply. The plank subfloor will move around, and so will the flooring above. If you're OK with your new floor potentially having those issues (squeaks and gaps, etc.) then proceed. If not, it really isn't that hard to DIY take a multi tool and remove the old subfloor and install plywood over it. Installing the wood on top of new smooth plywood would be a piece of cake even for someone without a lot of DIY experience.

    Bookmark   May 13, 2014 at 2:15PM
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Those of you advocating removing the plank subfloor are forgetting the difficulty in the details. If you slice out around the walls, you'll no longer have support under much of them (small slices of what used to be longer planks, supported by joists further away). If a wall is parallel to the joists, it will have no support at all! You'd need to slide the new plywood underneath the walls, while having temporary supports...not quite the "simple DIY job" some are suggesting.

We did such a thing with just one bathroom wall, because we had to replace floor, subfloor, and joists due to water damage. Not rocket science, but I wouldn't recommend that route for an entire house without very good reason.

I vote for either keep what you've got and accept the charachter or lay something new over top of it.

    Bookmark   May 13, 2014 at 10:30PM
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Weedyacres has accurately described the problems you will encounter when attempting to remove flooring that walls are built on. Good job! I didn't have the time to get into that topic...but good advice. Avoid unnecessary problems...leave the flooring down! As I said before...the existing flooring is the subfloor for whatever you lay over it.

    Bookmark   May 13, 2014 at 11:14PM
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Thanks for all the replies everyone. I do have another flooring guy coming in to look at refinishing the original floors- the first guy wouldn't say it couldn't be done, only that he couldn't do it and recommended someone with a lot more experience than he had to make that judgment. If not, I'm still not sure of the final plan yet.

    Bookmark   May 15, 2014 at 10:03AM
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Almost any wood floor can be refinished. We even finish subfloors for customers when that is what they want.

    Bookmark   May 16, 2014 at 1:13PM
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Pulling up this old thread - hope you don't mind but my searches did not answer my question. I am sure you in the know may think it is an obvious one but I need advise for replacing carpet with hardwood.

Tore up the old 40 yr old carpet (yuck) padding and the particle board underlayment. What is left is a 1/4" plywood running perpendicular to the joists. It is "spongy" in spots - most of them are the areas that are well traveled i.e. front of kitchen/bath/landing of stairs etc. Would it make sense to lay another layer of plywood - 1/4" or 1/2", offset by still perpendicular to the joists. I will have 1/2 to 3/4" oak 2 1/2" hardwood and I just want to make sure it does not start getting spongy again. TYIA for your help.

    Bookmark   October 20, 2014 at 12:00AM
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1/4" plywood is what is left? A typo perhaps?

    Bookmark   October 20, 2014 at 8:33AM
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Yikes glenn, that sounds "scary"! That is it! 1/4" plywood. My gut was that it would not be enough - the only thing that seemed okay to me was that at least the plywood was perpendicular to the joists. My "guess" FWIW, was I would need at least 1/2" - correct me if I am wrong. I am guessing by your response that it will need to be thicker, which leads me to the question as to whether I should just add an additional layer, as I said, offset to the existing plywood but still perpendicular to the joists, or does it make sense to just tear the damn thing up and start new? Thanks for your quick response by the way.

    Bookmark   October 21, 2014 at 1:07AM
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Glenn - based upon your response, I had Son #2 measure this time. It is definitely 1/2". He measured and then I verified it. Sorry for the confusion.

    Bookmark   October 21, 2014 at 10:31AM
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3/4" solid T&G hardwood anything creates a very solid and stable construction when all mated together and properly fastened. You do have to pay attention to moisture content levels of the subfloor and the finish flooring prior to installing and maintain an acceptable relative humidity below and above the floor for it to remain stable.

The spongy areas indicate that the plywood has lost integrity in those locations due to fiber fatigue and/or breakage. You might also see delamination of the plywood in those instances. If most of the plywood is still intact and stiff, then just replacing those weak sections may be all you need to do. However, if you can afford the additional height, adding a layer of 1/2 " plywood properly staggered and secured down would be the other way to go.

The better the subfloor is secured, the better the finish flooring will perform. Remove loose fasteners and use acceptable construction screws or hardened spiral flooring nails to fasten the plywood. Kill all squeaks.

Hope this helps.

    Bookmark   October 21, 2014 at 6:55PM
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Glennsfc, this is great info! We are in the middle of a addition/remodel that has gone horribly over budget. Of course I ignored everyone's warning, telling myself I was going to keep to my numbers. Of course, as I am sure you are well aware, you start with the question "wouldn't it be nice if we did this?" and it goes downhill from there. I am at the point that I must finish the remodel and I am (with husband and 3 reluctant older children) trying to do as much as we can on our own to save money. I am thinking after reading your response that it might be the time to call my carpenter in. We can handle the hardwood install - did it in the three addition rooms, but as you warned, I do not want to spend all that money and effort if the floor is falling apart in a few years.

I really appreciate your help.

    Bookmark   October 22, 2014 at 1:19AM
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