Solving Sagging OSB Floor: Find Expert Solutions in Technical Electronics Forum

Hello,

I have a problem with sagging OSB floor in the room. I made the floor myself. Originally, these were boards (a tenement house from the 1950s) that creaked terribly while walking. After breaking the boards, it turned out that underneath them there are ... also boards, only placed crosswise with spaces - serving as joists. These boards lay loosely where they could - clinics, pieces of rubble, etc. I decided to use them as supports for the new floor. I leveled them and made them stiff. On it I put a 22 mm OSB board. For this, in turn, the underlay and floor panels. Satisfied with the effect, I put up two partitions and furnished the room densely. Unfortunately - after some time the floor started to sag in some places when walking, so you can clearly feel the bend under the foot and the furniture tilts around. It seems that the greatest deflections are in the places where the OSB boards meet.
Therefore, I am looking for a patent to stiffen the floor pointwise (even at the cost of destroying a few panels). Disassembling it and adding, for example, another layer of OSB board is not an option. There are already partitions, besides, there is a lot of furniture and, in addition, it is a studio where I live, so I would not even have anywhere to take them out in time to make the floor (not to mention that now I will not even find time for such operations). I was thinking about re-drilling the floor in places (in places of deflection) and applying a lot of mounting foam to the holes. However, I don't know if that would make anything stiff. The second idea is to cut a larger hole in the floor (in an invisible place, e.g. under a wardrobe) and insert bricks, for example, under the bends. But it would be difficult to do with feel. So I am looking for some clever patent for this problem. I know that there are a lot of people here who cut their teeth on the construction site and will advise something. Any ideas, gentlemen?

The foam method should be effective, but check the strength of the foam you intend to use, choose something with high strength (probably more strength means less foam volume for the same weight). The question is why the floor began to sag after some time - the OSB board became less stiff, did some of the supports stop supporting it?

The plates have buckled because they are bending where the two plates meet frontally.

Better than the mounting foam will be glue in the foam for plasterboard. The price is higher, but it holds much better. It sticks to everything with everything, I recommend it because I used it. It is very low-pressure and cannot be moved when it solidifies. After some time, the foam will work and it oxidizes quite quickly.
The necessary condition is to spray water into the holes, even a lot. Apply the foam even when wet, it bonds with the substrate stronger and faster.

Sorry, but both methods will only have a short-term effect. It was not the board that lost its stiffness, but the crossbars. Pressing the foam or other substances will not do anything. You have two exits, take everything apart, make new rigid frames, or remove only the parquet and lay the second layer of the board so that the joints do not come out in one line.

These are not the bars. The records are made. They only bend where they touch and have no support. I put the boards overlapped, but I think I made too long gaps between the "joists". Already figured out a patent on how to deal with it:

I found such spring anchors, the so-called "umbrellas" for the M10 thread. And a piece of a rod can be screwed into it. So the plan is as follows - in the places where the OSB plates are bent, I drill holes, then in the same places I drill a little into the floor (so that the pin stays firmly in the ground). The anchors will go into the holes in the OSB board, and the M10 pins will go into the anchors for holes in the floor. Twist tightly and cut the pins from the top. In addition to these fasteners, I will drill smaller holes and apply mounting foam to stiffen the supports. Must hold.

Added after 4 [minutes]:

nieistotny wrote:

Better than the mounting foam will be glue in the foam for plasterboard. The price is higher, but it holds much better. It sticks to everything with everything, I recommend it because I used it. It is very low-pressure and cannot be moved when it solidifies. After some time, the foam will work and it oxidizes quite quickly.
The necessary condition is to spray water into the holes, even a lot. Apply the foam even when wet, it bonds with the substrate stronger and faster.

I will examine this glue carefully.

And I have one more idea: drill a few holes, make a plaster mortar, pour as much as you can - when it hardens, it will stick. Only the plaster needs to be worked in such a way that it can be pushed under the board through small holes. Or maybe pour dry plaster and then put water on it? Or combine: when the mortar hardens and dries, add dry and water ...

_jta_ wrote:

And I have one more idea: drill a few holes, make a plaster mortar, pour as much as you can - when it hardens, it will stick. Only the plaster needs to be worked in such a way that it can be pushed under the board through small holes. Or maybe pour dry plaster and then put water on it? Or combine: when the mortar hardens and dries, add dry and water ...

As far as I know, plaster must be mixed with water, it is not enough to pour it over. I was thinking about something similar, only to pour something harder - concrete instead of plaster. The problem is that I have a good 5 cm under the tiles, and maybe more to the floor. In addition, the room is 20 square meters, so in order for such mortar to come under the slab, I would have to pour half of the concrete mixer.

Are you sure that you have a concrete floor in this "tenement house from the 1950s"? Back then, the methods of building tenement houses were different and there does not need to be concrete there, because concrete was expensive. I suggest you make 200% sure first, before using this invasive method with anchors.
For me, all of this is in the short term. The mistake was made in the beginning and will now take revenge. Place real joists and OSB board (preferably tongue and groove) with a thickness corresponding to the expected loads plus a "safety factor" (minimum expected load x 1, 3). Joists can be replaced with polystyrene. Anyway, if it is to be good and for a long time, there will be no demolition. But that is my opinion.

krau wrote:

Are you sure that you have a concrete floor in this "tenement house from the 1950s"? Back then, the methods of building tenement houses were different and there does not have to be concrete there, because concrete was expensive. I suggest you make 200% sure first before using this invasive method with anchors.
For me, all of this is in the short term. The mistake was made in the beginning and will now take revenge. Place real joists and OSB board (preferably tongue and groove) with a thickness corresponding to the expected loads plus a "safety factor" (minimum expected load x 1, 3). Joists can be replaced with polystyrene. Anyway, if it is going to be good and for a long time, there will be no demolition. But that is my opinion.

They glued the bricks to the sand, but for the concrete floors or whatever they had poured out there, all luck was enough. I was already drilling into this floor when I was installing boards that served as joists. And even hard it was, very hard, hard with the stroke. I know that I made a mistake at the beginning - that I decided on the crossbars and plates at all - I had to make a spout. Well, a few people said that the OSB 22 boards will definitely not bend. I gave the crossbars every 80 cm. And now I have - sagging plates at the joints and rumbling when walking. But as I wrote - rough demolition is not an option, I would have to take all the furniture and things out of the room somewhere, and I do not have time for such maneuvers at the moment.

The question is, what hole must be made in order to insert a foil bag through it (this is to limit the range, so as not to spread / spill over the entire floor), then pour (with light tamping) gypsum (you can mix it with sand to make gypsum less cost) and finally pour the water to make the plaster harden and form a support? And how many such supports do you need (how much plaster would you need to use for them) to achieve sufficient floor stability?

What are you gentlemen with that plaster? After all, it is not suitable because it is too fragile.
From bida one could rather think of a self-leveling screed. For it to make sense, the pouring holes should be at least 20mm.
But just like the plaster as well as the screed, it will dry a little while drying and a little slack is enough and after some time it will start to crumble.
Anyway .. how much will be cooled without air access? Week?

Gypsum, if you add water in the right proportion, does not need to dry! School chemistry knowledge bows. And if I remember, it swells up rather than shrinks.

Virtually nothing is known from the author's description.
Many tenement houses from the so-called the 1950s are much older tenement houses, renovated and remodeled after the war.
It is very likely that there is a ceiling on wooden beams with the so-called a sub-floor on which rubble was once poured as a soundproofing and insulation, and poured with mortar on top.

It would be best if the author described what he saw under the floor a little more, to even guess what the ceiling was.
Adding plaster or other materials under the floor may end up with holes in the whole thing like Swiss cheese, and the floor will still sag, if not in one place, then in another.

The surest thing to do would be to break what is there, to check the ceiling properly, to stiffen the joist boards and to correctly install the boards and panels.

And what is the thickness of the underlay under the panels, what is the thickness of the OSB board and what is the spacing of these boards-joists?