I would like to manage with a 28-mm total height on top of wood joists, which seems difficult unless you install a load-bearing floor, such as plank flooring. In my case, there will be 14.7 mm of floating click flooring on top. The practice for 60c/c is at least 22 mm chipboard. I thought that if you reduce to 30c/c and screw-glue (tongue, groove, and to the joists) 12 mm chipboard it should hold. But then I talked to the supplier and he said that it's not something they recommend but "it works" until the wrong situation arises and you get an unusually strong point load. Then there's a risk it will break through. Does anyone here have any experience? Could another solution be used? Would raw boards be stronger?
I would absolutely avoid 12mm chipboard as a supporting base for an engineered wood floor. You would essentially have a stronger parquet that you have to rely on to distribute the pressure, with all guarantees against creaking going out the window as soon as it's laid. If your wooden joist structure is reasonably straight, you can recess chipboards between your floor joists, but even that requires a fair bit of tinkering and wood blocking as you won't be able to take advantage of a larger continuous board.
If I were forced to do it myself, I would add wood blocking quite liberally between the joists and then find the stiffest plywood possible, around 15mm. Significantly stronger than a 12mm fiber-based board even with the same underlying framework, and you avoid the risk of breakthrough. However, there's probably a similar risk of deformation if you have large point loads.
If I were forced to do it myself, I would add wood blocking quite liberally between the joists and then find the stiffest plywood possible, around 15mm. Significantly stronger than a 12mm fiber-based board even with the same underlying framework, and you avoid the risk of breakthrough. However, there's probably a similar risk of deformation if you have large point loads.
Exactly, I am currently looking into the possibilities of installing a board between the floor joists. Afterward, I could lay 12mm chipboard on top of that. It should work, although it makes the underfloor heating ambition more complicated. Ideally, the recessed board would also be grooved for the heating. Of course, this reduces the strength of the board, but if you glue the recessed board together with the board on top, it should be strong enough.
Note that a tracked chipboard is hopelessly weak along the loops so you have virtually no strength if you lower one. You only have 3-4mm of thickness under the loops to the bottom edge of the board. Similarly, you must have heat distribution plates that prevent you from having adhesion to any board above.
If you want to install underfloor heating in this construction, it becomes even more complex. My thought spontaneously goes to decking with a sparse panel or ready-made cassettes with built-in heat distribution plates and a screwed and glued 15mm plywood above, but again, that's out on very creative and thin ice. The ready-made cassettes do, unfortunately, have the disadvantage that you cannot really use them for load-bearing purposes. If you use a sparse panel to lay the loops, they help with load-bearing.
Even if it hurts, is there any chance to just arrange a new subfloor so you can do it according to a normal construction?
If you want to install underfloor heating in this construction, it becomes even more complex. My thought spontaneously goes to decking with a sparse panel or ready-made cassettes with built-in heat distribution plates and a screwed and glued 15mm plywood above, but again, that's out on very creative and thin ice. The ready-made cassettes do, unfortunately, have the disadvantage that you cannot really use them for load-bearing purposes. If you use a sparse panel to lay the loops, they help with load-bearing.
Even if it hurts, is there any chance to just arrange a new subfloor so you can do it according to a normal construction?
Mmm glanced at the sparse panel variant. There are a few who have done this here on the forum. It's clear, if you overdo it with support and set 28mm spacing AND frame at 30c/c, a screw-glued 12mm particleboard has a lot of support. The underfloor heating plate adds 1mm so the spacing must be 1mm below the top of the floor joists. Then you would need to check if you can glue the plate on both sides, against the spacing and the particleboard.
I have also considered removing material from existing beams in the floor joist system and supplementing with beams to get down to 30c/c. The existing ones are 3"/8" so there is material. This also means that at 30c/c, the span between beams is less than with 30c/c built with 45mm beams. Then I could lay a 22mm particleboard. However, none of the options have felt quite right. It ends up being a mess of compromises.
I have also considered removing material from existing beams in the floor joist system and supplementing with beams to get down to 30c/c. The existing ones are 3"/8" so there is material. This also means that at 30c/c, the span between beams is less than with 30c/c built with 45mm beams. Then I could lay a 22mm particleboard. However, none of the options have felt quite right. It ends up being a mess of compromises.
I have done some more research. Byggelit, which supplies chipboard to companies like Uponor, passes all tests and is approved as a load-bearing floor directly on framed beams 60c/c. It is therefore 22mm floor chipboard with a routed groove for a 17mm pipe. The groove itself is 18.7mm(+-0.1mm) wide and 18.2mm(+-0.2mm) deep. Not much material left at the bottom of the groove and a proper fracture line. The board is approved for continuous installation with free jointing. Various tricks and secrets have been implemented to achieve sufficient strength in the board, despite the thin material thickness. Tricks that are not used in the renovation board at 12mm. If the board quality had been identical between the boards, 12mm should hold better than a 22mm with a deep groove in the middle, but that is not the case. You learn something new every dayM myrstack said:
Hmm, there is nothing magical about 22mm slotted chipboard flooring. It's like any other chipboard flooring. However, its load-bearing capacity relies on it being laid across the joists, meaning you mostly have 22mm chipboard where you need load-bearing capacity. If it were laid along the joists, a child would step through it. The few millimeters under the loop are completely normal. On a 12mm board, you naturally have 12mm everywhere.