# Old house, no subfloor; how to reinforce?



## twsager (Dec 22, 2015)

We have an 100 year old home. The main level floor has no sub-floor. It is in good shape and stable, but there are a couple slightly flexible areas, and a gap or 2 in the boards. I have pretty good access to the underside from the basement. Any suggestions on how to reinforce this floor from below? Also thinking of insulating, so ideas also welcomed for that. Thanks!


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## Ron6519 (Mar 28, 2007)

You want to determine what caused the issue. Access to the underside should give it to you.


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## twsager (Dec 22, 2015)

Thanks! I should have been clearer. The joists are in excellent shape - the originals have been reinforced with new (daughter?) joists bolted alongside by the prior owner, so the structure is strong. However, a few of the floorboards edges have split off, leading to some slits of daylight, and a slight "give" in a couple of floor sections. It's the old floorboards themselves that have the slight flex. I was thinking of cutting strips of plywood to fit from underneath those sections for support, mounted with a cleat on each joist. There's a full basement below, with an open but low ceiling, maybe 6 1/2 feet, so plenty of room to work.


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## SeniorSitizen (Sep 10, 2012)

For the floor to "give" on strong joist the flooring lumber evidently isn't touching the joist. From below shim those areas with cedar shingle material as you would a door jamb during installation.


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## Ron6519 (Mar 28, 2007)

If the floor boards are not connected to the joists, re-connect them. If the edges are split, add a 2x4 nailer under the floor attached to the joist. Drill pilot holes in the board ends and finish nail then the added lumber.


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## joecaption (Nov 30, 2011)

How about a picture so we can see what your seeing?
So far we have no idea what's there?
Hardwood, 1 X 6's ?
What's the plan for the finished flooring?
Going over the whole floor with 1/2" sub flooring rated plywood will cover all those air gaps and strengthen the whole floor.


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## rjniles (Feb 5, 2007)

Take up the flooring, install subfloor and relay flooring.


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## ddawg16 (Aug 15, 2011)

rjniles said:


> Take up the flooring, install subfloor and relay flooring.


I'm in the process of putting back down some oak flooring that originally came with the house.

Originally the oak was nailed to 1x6 planks (sub floor)



In those places where I am putting it back down, I put 3/4" T&G plywood down on top of the existing sub floor...and then the oak.




No squeaks...nice and solid....quieter (you don't hear the thumping as you walk). 

Overkill? Maybe...but I'm happy


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## Nestor_Kelebay (Jun 17, 2008)

If you don't have a subfloor, then I expect the walls in your house were installed directly over top of floor boards. That pretty much rules out the possibility of removing the existing boards and relaying them over plywood. That's because there are likely to be nails under the walls holding your floor boards down to your joists. How you can remove those boards under those conditions without dismantling your walls is something I don't know.


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## rjniles (Feb 5, 2007)

Nestor_Kelebay said:


> If you don't have a subfloor, then I expect the walls in your house were installed directly over top of floor boards. That pretty much rules out the possibility of removing the existing boards and relaying them over plywood. That's because there are likely to be nails under the walls holding your floor boards down to your joists. How you can remove those boards under those conditions without dismantling your walls is something I don't know.


Pretty easy. Cut the boards along the wall with a toe kick saw.


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## Nestor_Kelebay (Jun 17, 2008)

rjniles said:


> Pretty easy. Cut the boards along the wall with a toe kick saw.


Fine, but then what do you nail your plywood and wood flooring down to along those walls when it comes time to put everything back together?


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## rjniles (Feb 5, 2007)

Nestor_Kelebay said:


> Fine, but then what do you nail your plywood and wood flooring down to along those walls when it comes time to put everything back together?


Depending on the construction, you sister a 2x to the existing joist or install blocking every 16 inches.


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## gregzoll (Dec 25, 2006)

The 1x6's are the Subfloor. No need to remove it, unless rotted in places. If squeeking, use deck screws to secure to the joists.


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## rjniles (Feb 5, 2007)

gregzoll said:


> The 1x6's are the Subfloor. No need to remove it, unless rotted in places. If squeeking, use deck screws to secure to the joists.


I read the poster as saying the boards are the finish flooring.


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## gregzoll (Dec 25, 2006)

rjniles said:


> I read the poster as saying the boards are the finish flooring.


Some of the older homes had the finished floor as the only thing across the joists. It was cheaper and a lot of the homes were built with "Barge board". They basically took the barges and dismantled them when they arrived somewhere, then used the lumber to build homes and buildings.

In the OP case, they would have to treat that old floor as a Sub Floor, if they wish to make it not having to deal with using rope for closing the joints.

There are some that love the old floors and the look that they give. But if you have a crawl space or earth directly beneath, you know that you are best to use Tar Paper or plywood to help place the new flooring over. You would still have to seal the gaps before placing the new sub-floor material over the old flooring.


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## Bondo (Dec 8, 2007)

> There are some that love the old floors and the look that they give.


Ayuh,.... My rental house is a 100 year old cottage,....

I ripped up all the junk floorin', 'n refinished the sub-floor boards as the new floor,....
Been 10 years now, still lookin' Good,...









twsager could do as I've done,....

Go below, 'n find the reason ya got a soft spot, if the board is missin' the joist, block it up with whatever ya got,...

I spent a couple of weeks cleanin' the cracks, seams, 'n knotholes, fillin' 'em all with black caulkin',...
4 cases I think,...
Then I rented a floor sander, 'n sanded it out, followed that with a few coats of floor poly,....
It's been hand sanded, cleaned, 'n re-varnished once in 10 years,...

'bout 5 or 6 years ago, I did staple up hydronic radiant heat under it,...

Because of the in-floor heat, it needs re-caulkin' again, 'n of course resandin', 'n varnishin',....
A small price to pay for the joy of in-floor hydronic heat,...
Nice heat transfer too,....

Thinkin' 'bout tryin' a clear epoxy, rather than poly,......
just scared of what long term sunlight is gonna do to it,...


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