More than a few owners of old homes have called me concerned about the floors in their old house. They’re shocked to discover that their house doesn’t have a subfloor. They’re thinking someone remuddled the place and somehow removed the subfloor or maybe termites ate the whole thing clear away.
I’ve gotten the question so often that I felt it was high time I wrote a post about it to explain this phenomenon to folks to assuage their fears that their house is about to fall apart.
Subfloor Design
Prior to WWII most homes were built with a crawlspace or basement foundation. The technique of a monolithic concrete foundation was still a few years away from catching on during the post war building boom.
In these days of pier and beam or stem wall foundations the common technique was to build floor joists from rough lumber supported by a series of masonry piers. Then over top of those floors joists 1×4 to 1×8 sized subfloor was installed (usually diagonally to provide additional racking support). These boards served as the subfloor prior to the integration of the plywood we use today.
These same 1×4, 1×6, 1×8 boards were also commonly used on the exterior walls as sheathing to strengthen and protect the frame. Though depending on your region this step was often skipped completely with the wood siding being installed directly onto the wall framing.
Builders have always been looking for ways to build faster and cheaper, and the old days were no exception. Skipping the wall sheathing created a big savings with only the small downside of a slightly less well insulated and minimally less sturdy structure. At the time the solid wood siding being installed was much stronger than the options we use today and that strengthened the structure sufficiently.
This same mentality was transposed to the subfloor in homes where historic builders would install the finish floor directly onto the floor joists. Then the walls of the home were built and installed on top of that finish floor.
You may think this is shoddy craftsmanship, but in the days of solid 1″ thick tongue and groove heart-pine flooring it was hardly thought to be a problem. The tongue and groove design made the missing subfloor design doable since it effectively blocked air and bugs from entering the home and provided enough strength to support the rest of the structure.
How to Tell If You Have No Subfloor
There are some sure fire signs that your house was built with no subfloor. There are regional differences, but down here in the south I find that homes without subfloors are most commonly smaller homes in historically working-class neighborhoods where budget was a large concern for the structure of the home.
For us in the south that means heart-pine floors rather than the more expensive red or white oak floors found in more affluent homes. The big giveaway is the joint pattern on the floor. If you see long floor boards with joints between boards that often line up in the same plane then you likely have a home with no subfloor. That indicates that the floor boards were nailed onto the floor joists rather than in a house where a subfloor exists which allowed the flooring installer to start and end boards anywhere they chose. Subfloor homes have a more random pattern to the joints placement of floor boards.
What to Do About a Missing Subfloor
First, let me encourage you to not freak out that your subfloor is missing. In a 100-year-old house this is not uncommon and shouldn’t be something you’re concerned about. There are a few things that you may want to thinking about differently if this is the case with your house.
Insulation
Without a subfloor your floor is going to feel a lot colder in winter. In a crawlspace designed house, that’s not too difficult to fix. Grab some of your preferred insulation (I prefer mineral wool for subfloors) and install it below your floors in between the floor joists. You can use strapping or netting to hold it in place underneath the house.
Do not install spray foam insulation! For new construction I’m a fan of foam insulation, but to retrofit it into old houses it can cause a lot of problems, especially when you have what are likely loose tongue and groove joints on your flooring. You’re likely to get foam squeezing up and into your floors that will make a real mess of your finished floor.
Flooring Repairs
If you need to replace damaged floor boards on a house with no subfloor the work is a bit more difficult. You’ll have to make sure that the boards being replaced are cut to a precise size so that they end on a joist. Also, any boards that run underneath a wall will be almost impossible to fully remove, so you’ll have to make cuts at the wall to get them out leaving a small chunk remaining underneath the wall to support it.
Other than these two small things, an old house with no subfloor should not be a problem for you. Don’t be concerned, don’t run for the hills and skip buying that dream bungalow if you find this to be the case. Just realize that you’re buying a unique style of historic house that comes from a different time before building codes mandated the design of our homes. The fact that it has lasted 100 or more years already means that it has stood the test of time and will continue to stand for decades more in all likelihood.
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I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.
While replacing floor board to tongue and groove red oak(no sub-flooring) noticed the 1×6 beams ( 6 together) had some spacing at the end of the staggered beams-( house was built in 1929) do I need to concern myself?
I have a 100 year old same situation no subfloor under 5 inch oak. The issue is that they are over an 12 inch dirt crawl space. I’m concerned with dirt and moisture coming up into the house. It is too small to and varied to entirely encapsulate or insulate. Any suggestions ? Thanks
So my 1930’s Nashville TN home has a 1″ x 6″ subfloor as mentioned in the article over a full size basement. My issue is I use this basement for laundry and a small shop for motorcycles etc. To say the original flooring has loose tongue and groove is an understatement…I can see pin holes of light if I left the lights on in the basement at night through the floors. My issue is the dust and anything liquid spilled upstairs goes straight into the basement and constantly covers everything I keep down there. Between that and the obvious HUGE loss of efficiency in conditioning my living space I want to seal this floor up but have no idea how to best do this. I like the original flooring so I’ve considered putting up some insulating board to the ceiling of the basement. Maybe spacing it a few inches from the subfloor to allow some air movement to allow drying when things get spilled upstairs but this gap I’d leave will fill constantly with dust and whatever we spill, so this space could get really nasty fast…any ideas on how to resolve this?
I’ve got the exact same issue. No subfloor in one room, can see light coming up from the basement at night. It actually is kind of pretty and looks like stars but I agree with you that is a pain in terms of energy efficiency and the consequences of spilling something are bad. Did you ever hear back about this? Curious to know what you ended up doing? I am thinking about maybe trying to cut rigid foam board and put it underneath from the basement, then adding Insulation.
I’m also suffering (or challenged) by this in a reno house we just bought. I’m going to try the rigid foam insulation with insulation; that sounds great! Thoughts?
I have a lot of repairs needed to my floor that has no underlying subfloor.
There are spots where obviously something too heavy was placed on the areas that were not supported at all, and have cracked straight through. I can cut the broken pieces out, but I’m not sure how to attach new ones that won’t have the same issue. There are plenty of creaking areas where I can tell the same thing will happen if too much weight is applied and I’d like to reinforce those areas all over the house. As well, I’m not sure what wood to use to replace them.
Also, there are areas that used to have asbestos tile (which has since been removed) that appear to have been patched with different wood that looks terrible.
https://imgur.com/a/AzpO3Xo
Any help would be appreciated.
I recently bought a streamline moderne house in Los Angeles and the original windows have been replaced. Is there a company that makes the old style steel windows? Any thoughts on the window manufacturer that William Kesling used? Thank you.
T&G hardwood flooring with no subfloor can be a definate problem. It is about specifics.
My house in SW Pennsylvania, built in 1929 with full basement has first floor T&G red oak nailed direct to floor joist on 16 inch centers. End joints are ramdom. That is to say some end joints ar on the joist and many are not. There are several cases where a concentrated load has “popped” a board end where the end joint is midway between joists. The bottom side groove edges are splintered out. These become springy soft spots. In 1979 the soft spots were reinforced from below. There are now a few added soft spots. In preperation for refinishing the top surface, the old supports will be removed and new more robust under-support will be installed. The question: Is plaster better than construction adheasive for “mudding” betwen the flooring and the under-support?
I am so happy you tackled this — I literally just posted the link on Reddit because folks over there were incredulous when I mentioned having no subfloor. My home has 3/4″ T&G old-growth oak floors, with nothing but joist under them.
Our Dallas home is 80 years old. The piers are a mere three feet on center, so I imagine the rest of it was well built, despite some of the updates that occurred before we acquired in 12 years ago. Upon movie in, we found a rodent issue, so had to get under there right away. An architect friend pointed out to us that our subfloor might seem “shoddy” because there are so many small spaces between the boards, but that this was intentional. He said the (original, but no more) shake over board sub roof would have had spaces as well, and that these spaces (along with our mystery attic window) would have moved warm air through the house in an upward drift, to cool it, and would have swollen shut in cooler weather to keep it warm. We also have an enormous fireplace in 12×12 living room.
I’m thinking about installing vinyl plank tongue & groove or 12mm glue down vinyl plank flooring over my 3/4″ red oak wood floors. I have 2 concens with my small 800 Sq Ft 100 yr old house, the 2 1/4″ boards are separating & sqeak terribly and with 4 different floor finishes exposed to each other house looks even smaller! There is 1″x 8″x 3/4″diag sub floor under wood.
What are your thoughts on this resurfacing project? Can anything be done about squeaks besides putting screws up thru 1 x 8’s before installing vinyl? Sure need some suggestions.
Thanks,
Sher, again…