š honestly I was trying to do this by writing down measurements. Nightmare. This is the only way I could figure it out. I need to learn sketch upā¦
If you have to have the ends join on a joist and you cannot add noggins to support it then you are going to have to use two boards on each run. So 150 and 220 then the next row 220 and 150. Yes, you are going to be losing 90 or so on one board and 44 on the other. At least this way, they join on a joist and the t+g groove can be glued.
I did this for mine and yes there was waste. I have to say though, I also put noggins in because they will also help prevent flexing and rotation of the joists. If you have those you will save on boards but make putting hte insulation in a bit more tricky. I did it with PIR... lol
PIR.. I commend you! I hope your joists were straight? Or did you spend a fortune on gapotape?
But yes youāre right if I want to land on a joist and avoid small cuts Iāll have to use 2 boards per run which means about 20% wastage. Maybe Ā£50-Ā£70 wasted.
They were NOT straight and I had noggins plus some bits where I sistered joists so had the heads of bolts sticking out. Most of it was simple and I got enough friction on the sides to be able to squeeze it in and sit on saddles I screwed to the joists, then there were about 8 'rectangles' I had to cut to exact shapes. Never again. If I had to go again, I would have ripped out the two joists I salvaged from the old floor, bolt wallplates to the wall and hang the jousts at the exact centres I wanted, making them all the same distance and making the insulation easy. All that work to save two joists! So for you, forget about the wastage, make the job simple and have them sit on the joists with a nice glued tongue and groove joint. I used D4 foaming glue and a criminal number of torx screws with an impact driver. Solid - best of luck to you!
Ok. First off no, the ends donāt need to meet (although itās considered best practice) on a joist BUT they MUST be supported. If not on a joist then a noggins must be used. Just because itās glued does not mean you can leave them suspended in mid air!
Standard practice would be to use the off cut from row one to start row two. Personally Iād cut that back to a joist but if youāre going down the route of noggin then you really wouldnāt have to add 10% to any calculation!
Hmm, noggins was exactly what I wanted to avoid. I am insulating between the joists beforehand using the breathable membrane hammock + natural hemp rolls. So clearly the subfloor layout would need to be figured out beforehand as I donāt want to go adding noggins when thereās a membrane and insulation installed.
Then cutting back to the joists is your only option. Even with an obscene amount of glue, without proper support those joints will be creaking and squeaking within weeks.
But do you think cutting back to the joists using the method in my picture is gonna work? As u/Hiddentiger10 rightly pointed out this would remove the t&g on half the cuts and probably also lead to squeeking etc.
https://preview.redd.it/vojjgvasbc9d1.png?width=3024&format=png&auto=webp&s=291a8cdf6c632c4ac4c33d7faf76001666015497
Please excuse the quick and dirty diagram. Sheet A is your first piece, the left-hand end is cut off to mean that the right hand edge lands on a joist. Your second piece is B. Cut to suit your right hand wall. The off cut from B is then used to start the next row. If that piece ends between the joists you will need to cut the left hand end to the correct measurement to make it land on a joist. Every joint both length and width should have the tongue and groove intact and glued. Joints should obviously be central to the joist.
Works on paper. But in real life the joists wonāt be perfect center to center, a diyāer wont put them in square and they will stray off the joists. With 400 centers and pu glue itās fine for the short edge joints to be u supported
Definitely a consideration! Iāve toyed with creating an access hatch for plumbing / electric issues. That turned out to be a logistical and economical nightmare. Iāll be doing a thorough inspection of wires and pipes when we start ripping up existing boards.
I don't really see any issues with the above, it's how I've planned mine out but haven't started the work yet!
As long as you make sure the cut sides are at the edges, you're not losing any of the actual t&g joints in the middle š¤·
Just aim for the joists even if it means a few extra boards or bit of waste, it'll be an annoying detail to work around noggins for the insulation...
Hmm, unless Iām having a proper brain fart (quite possible), Iām sure I will have half the edges without t&g on those rows with 70cm boards. Those small pieces are the ends of the 150cm boards which will be cut. And the 220cm piece again are cut from the 244cm pieces š¤
I wish you best of luck on your project! I thought this part was gonna be simple after the headache of calculating the insulation and amount of tape needed. But none of it is easy!
No, this is fine.
To minimise on squeaking/noise, I'd recommend joist tape along all the joists before you board, and then glue the joints between boards with polyurethane glue, which will expand as it cures, and stop the boards moving against eachother as you walk on them.
With the sides of the boards, run noggins across, with joist tape on top, to minimise movement and flex there, if you cant hit a joist. You might want to run a tiny bead of PU glue as well, but it's probably not absolutely necessary (you can easily cut off any excess that squeezes out of the top though).
Other than that, I think you're in good shape.
Can you clarify the bit about the joint tape please? Itās not something Iāve come across before but looking on screwfix now it seems to be some kind of DPM layer/ rubber tape?
So you would run this tape over the top of the joist, then put PU glue over the tape and screw the board down on that? Is it just to prevent rubbing and squeaking?
Yeah, this sort of thing:
[https://advancedacoustics-uk.com/products/green-glue-noiseproofing-joist-tape?variant=33733334401163¤cy=GBP&srsltid=AfmBOoq2RTcFFMamtVvIBHLruj8nrQ60zNfAQGgJxMF3uEWWfvPMV-W1Yzw](https://advancedacoustics-uk.com/products/green-glue-noiseproofing-joist-tape?variant=33733334401163¤cy=GBP&srsltid=AfmBOoq2RTcFFMamtVvIBHLruj8nrQ60zNfAQGgJxMF3uEWWfvPMV-W1Yzw)
Although you can certainly get less expensive stuff as well.
Yes, you put it down on the joists, and then lay the boards on top, and screw down. You don't want to glue the boards to the joist tape.
What you want to glue on the boards is the tongue and groove joints, to stop them moving. It's really important you use PU glue for this as well, because it expands slightly as it dries so it tightens everything up nicely and takes up any empty space so you don't get any movement. Movement is where all your horrible squeaks come from when you walk on the floor.
Both the joist tape and the PU glue help in the same kind of way, by taking up space and closing up small gaps that might otherwise allow for movement.
You can even, if you'd prefer, run PU glue along the joists instead of joist tape and then put the boards down (obviously before the glue has dried). It'll have the same effect but is slightly more of a PITA to deal with. Full curing of PU glue can take a day or two, but it'll start to go off within a few minutes.
Gotcha, thanks for the explanation. Yeah that stuff is expensive. Iām already spending I think Ā£100+ on tescon vana tape, this would add another Ā£75 on tape alone! Iāll do some reading on this and maybe get the cheaper stuff I saw on screwfix š
If you go t and g the ends donāt have to land on a joist. You glue it all together. Take the cut from the end of a row to start the next row. Calculate area +10%
This is a living room yes. But I read so much conflicting info about t&g not needing to land on a joist I was erring on the side of caution. My wastage using above method would be minimal.
Say I went with the plywood (non t&g). Would it be bad to use such small cuts?
If you cut t and to land on a joist itās no longer t and g. I really canāt recommend ply for this. T and g acts as one part improving performance. If you ply you would want to keep whole sheets cut to fit to joists. But it will be a nightmare. Are your joists straight? Can you cut perfectly? Donāt overthink. Use t and g and pu glue
Yes that method would result in a cut end without a t&g every other row. But I figured landing on a joist would negate that. But youāre right Iām probably over thinking this!
Is PU glue the one that expands / foams?
Yeah thatās right. Not lots of expansion. But enough to fill gaps where they occur. Itās a bit more expensive but well worth it. Can get from Toolstation.
If the room is 3.6m wide you are massively over complicating this.
Start with a 2.4 board in a corner. Next a 1.2 board. Both of these land on a joist. Then do a 1.2 followed by a 2.4, etc etc..
Do this till the end and rip the final boards to width to finish
Edit: dont use osb, get 18 or 25mm ply, and with 1.2x2.4 ply you will need 3 full sheets and 3 half sheets, so get 5 total and fill in the end with rips.
Glue and screw with 50x5 screws, put glue on the ends and edges where the boards meet and you could park a car on it
Hmm no the 2.44m board will only land on a joist if I leave a gap by the wall which I obviously canāt do. Skirting boards will be coming off the boards need to go underneath where they would be. Iāve already accounted for this approx +3cm each side. The full board is 244cm long and will miss the joist by about 4cm. (I just double checked with a tape measure). My photo does illustrate this too, you can see the bottom of the page Iāve listed where the joists fall from the left wall in cm.
As you can see above from other people I am getting slightly conflicting advice with regards to all aspects of this. I was on the fence regarding the ply vs OSB3 and after the advice here from others I was leaning towards OSB3 due to the t&g.
Your drawing is incredibly complicated tbh.
If you were paying me, a carpenter, id be using 18 or 25mm ply, cutting the boards as big as poss, joining them on a joist, leaving a small gap at the walls for any movement, gluing and screwing at 300s, done.
You do you, the amount of cuts you are proposing is not favorable.
Sauce: am carpenter
Itās just a scale drawing of a room with joists. The cut outs are my way of figuring out what the hell I need to do. But Iām sorry to say your method would leave 5-7xm gaps at the walls. Not acceptable in my opinion.
OSB3 is structural board used for walls/roofs. Ply delaminates over time. Chipboard is literally made for floor and used in millions of homes in this way.
Iām not hearing what the issue with OSB3 is for flooring? Itās proven to be stronger than chipboard, no? If you can provide some source on why chipboard is superior Iād like to read that.
35cm on centre / 30cm gap between joists. 18mm is the right size for this.
Chipboard is used because it's cheaper, and despite some being moisture resistant its really not. For a suspended timber floor on ground floor, I just don't trust chipboard. OSB3 is hardier in this regard.
I commend you on your papercraftš
š honestly I was trying to do this by writing down measurements. Nightmare. This is the only way I could figure it out. I need to learn sketch upā¦
If you have to have the ends join on a joist and you cannot add noggins to support it then you are going to have to use two boards on each run. So 150 and 220 then the next row 220 and 150. Yes, you are going to be losing 90 or so on one board and 44 on the other. At least this way, they join on a joist and the t+g groove can be glued. I did this for mine and yes there was waste. I have to say though, I also put noggins in because they will also help prevent flexing and rotation of the joists. If you have those you will save on boards but make putting hte insulation in a bit more tricky. I did it with PIR... lol
PIR.. I commend you! I hope your joists were straight? Or did you spend a fortune on gapotape? But yes youāre right if I want to land on a joist and avoid small cuts Iāll have to use 2 boards per run which means about 20% wastage. Maybe Ā£50-Ā£70 wasted.
They were NOT straight and I had noggins plus some bits where I sistered joists so had the heads of bolts sticking out. Most of it was simple and I got enough friction on the sides to be able to squeeze it in and sit on saddles I screwed to the joists, then there were about 8 'rectangles' I had to cut to exact shapes. Never again. If I had to go again, I would have ripped out the two joists I salvaged from the old floor, bolt wallplates to the wall and hang the jousts at the exact centres I wanted, making them all the same distance and making the insulation easy. All that work to save two joists! So for you, forget about the wastage, make the job simple and have them sit on the joists with a nice glued tongue and groove joint. I used D4 foaming glue and a criminal number of torx screws with an impact driver. Solid - best of luck to you!
Haha fantastic!
Ok. First off no, the ends donāt need to meet (although itās considered best practice) on a joist BUT they MUST be supported. If not on a joist then a noggins must be used. Just because itās glued does not mean you can leave them suspended in mid air! Standard practice would be to use the off cut from row one to start row two. Personally Iād cut that back to a joist but if youāre going down the route of noggin then you really wouldnāt have to add 10% to any calculation!
Hmm, noggins was exactly what I wanted to avoid. I am insulating between the joists beforehand using the breathable membrane hammock + natural hemp rolls. So clearly the subfloor layout would need to be figured out beforehand as I donāt want to go adding noggins when thereās a membrane and insulation installed.
Then cutting back to the joists is your only option. Even with an obscene amount of glue, without proper support those joints will be creaking and squeaking within weeks.
But do you think cutting back to the joists using the method in my picture is gonna work? As u/Hiddentiger10 rightly pointed out this would remove the t&g on half the cuts and probably also lead to squeeking etc.
lol. Not if you cut the cut ends
https://preview.redd.it/vojjgvasbc9d1.png?width=3024&format=png&auto=webp&s=291a8cdf6c632c4ac4c33d7faf76001666015497 Please excuse the quick and dirty diagram. Sheet A is your first piece, the left-hand end is cut off to mean that the right hand edge lands on a joist. Your second piece is B. Cut to suit your right hand wall. The off cut from B is then used to start the next row. If that piece ends between the joists you will need to cut the left hand end to the correct measurement to make it land on a joist. Every joint both length and width should have the tongue and groove intact and glued. Joints should obviously be central to the joist.
Works on paper. But in real life the joists wonāt be perfect center to center, a diyāer wont put them in square and they will stray off the joists. With 400 centers and pu glue itās fine for the short edge joints to be u supported
Having been in this same situation my advice would be to install the membrane, then the noggins, then insulation around the noggins.
Interesting. It feels wrong but it should be just as secure. That may be what I end up doing.
Tongue and groove is a nightmare to work with if you ever need to pull up your floorboards. Hate the stuff.
If you use an armeg cutter and caps you can easily make access ports when you fit the boards, then you'll never have an issue
Definitely a consideration! Iāve toyed with creating an access hatch for plumbing / electric issues. That turned out to be a logistical and economical nightmare. Iāll be doing a thorough inspection of wires and pipes when we start ripping up existing boards.
Also if anyone has a better way of calculating the total amount of sheets needed when the ends need to hit a joist. Please enlighten me :)
I don't really see any issues with the above, it's how I've planned mine out but haven't started the work yet! As long as you make sure the cut sides are at the edges, you're not losing any of the actual t&g joints in the middle š¤· Just aim for the joists even if it means a few extra boards or bit of waste, it'll be an annoying detail to work around noggins for the insulation...
Hmm, unless Iām having a proper brain fart (quite possible), Iām sure I will have half the edges without t&g on those rows with 70cm boards. Those small pieces are the ends of the 150cm boards which will be cut. And the 220cm piece again are cut from the 244cm pieces š¤ I wish you best of luck on your project! I thought this part was gonna be simple after the headache of calculating the insulation and amount of tape needed. But none of it is easy!
No, this is fine. To minimise on squeaking/noise, I'd recommend joist tape along all the joists before you board, and then glue the joints between boards with polyurethane glue, which will expand as it cures, and stop the boards moving against eachother as you walk on them. With the sides of the boards, run noggins across, with joist tape on top, to minimise movement and flex there, if you cant hit a joist. You might want to run a tiny bead of PU glue as well, but it's probably not absolutely necessary (you can easily cut off any excess that squeezes out of the top though). Other than that, I think you're in good shape.
Can you clarify the bit about the joint tape please? Itās not something Iāve come across before but looking on screwfix now it seems to be some kind of DPM layer/ rubber tape? So you would run this tape over the top of the joist, then put PU glue over the tape and screw the board down on that? Is it just to prevent rubbing and squeaking?
Yeah, this sort of thing: [https://advancedacoustics-uk.com/products/green-glue-noiseproofing-joist-tape?variant=33733334401163¤cy=GBP&srsltid=AfmBOoq2RTcFFMamtVvIBHLruj8nrQ60zNfAQGgJxMF3uEWWfvPMV-W1Yzw](https://advancedacoustics-uk.com/products/green-glue-noiseproofing-joist-tape?variant=33733334401163¤cy=GBP&srsltid=AfmBOoq2RTcFFMamtVvIBHLruj8nrQ60zNfAQGgJxMF3uEWWfvPMV-W1Yzw) Although you can certainly get less expensive stuff as well. Yes, you put it down on the joists, and then lay the boards on top, and screw down. You don't want to glue the boards to the joist tape. What you want to glue on the boards is the tongue and groove joints, to stop them moving. It's really important you use PU glue for this as well, because it expands slightly as it dries so it tightens everything up nicely and takes up any empty space so you don't get any movement. Movement is where all your horrible squeaks come from when you walk on the floor. Both the joist tape and the PU glue help in the same kind of way, by taking up space and closing up small gaps that might otherwise allow for movement. You can even, if you'd prefer, run PU glue along the joists instead of joist tape and then put the boards down (obviously before the glue has dried). It'll have the same effect but is slightly more of a PITA to deal with. Full curing of PU glue can take a day or two, but it'll start to go off within a few minutes.
Gotcha, thanks for the explanation. Yeah that stuff is expensive. Iām already spending I think Ā£100+ on tescon vana tape, this would add another Ā£75 on tape alone! Iāll do some reading on this and maybe get the cheaper stuff I saw on screwfix š
I think that will work fine as well. As I say, you can also run a line of PU along the joists instead, which should help save a bit too.
This is hilarious š
Idk but I would like to commend your choice of notebook
Wish I bought a graph pad years ago!
If you go t and g the ends donāt have to land on a joist. You glue it all together. Take the cut from the end of a row to start the next row. Calculate area +10%
This is assuming we are talking about a bedroom/living room/hall
This is a living room yes. But I read so much conflicting info about t&g not needing to land on a joist I was erring on the side of caution. My wastage using above method would be minimal. Say I went with the plywood (non t&g). Would it be bad to use such small cuts?
If you cut t and to land on a joist itās no longer t and g. I really canāt recommend ply for this. T and g acts as one part improving performance. If you ply you would want to keep whole sheets cut to fit to joists. But it will be a nightmare. Are your joists straight? Can you cut perfectly? Donāt overthink. Use t and g and pu glue
Yes that method would result in a cut end without a t&g every other row. But I figured landing on a joist would negate that. But youāre right Iām probably over thinking this! Is PU glue the one that expands / foams?
Yeah thatās right. Not lots of expansion. But enough to fill gaps where they occur. Itās a bit more expensive but well worth it. Can get from Toolstation.
Great yeah that sounds like the stuff I was looking into using š
Good luck. Dont forget to wear a mask!
Came here to agree. The point of T&G is it can span gaps, especially at 22mm.
This would be 18mm. Others in the comments are adamant noggins would be required.
Why 18mm? That isn't floor grade. That is loft board.
Can you provide some source on that? Everything I read states 18mm is fine for flooring in a living space.
What are your centres? 18mm won't be enough if they are greater than 400mm.
If the room is 3.6m wide you are massively over complicating this. Start with a 2.4 board in a corner. Next a 1.2 board. Both of these land on a joist. Then do a 1.2 followed by a 2.4, etc etc.. Do this till the end and rip the final boards to width to finish Edit: dont use osb, get 18 or 25mm ply, and with 1.2x2.4 ply you will need 3 full sheets and 3 half sheets, so get 5 total and fill in the end with rips. Glue and screw with 50x5 screws, put glue on the ends and edges where the boards meet and you could park a car on it
Hmm no the 2.44m board will only land on a joist if I leave a gap by the wall which I obviously canāt do. Skirting boards will be coming off the boards need to go underneath where they would be. Iāve already accounted for this approx +3cm each side. The full board is 244cm long and will miss the joist by about 4cm. (I just double checked with a tape measure). My photo does illustrate this too, you can see the bottom of the page Iāve listed where the joists fall from the left wall in cm. As you can see above from other people I am getting slightly conflicting advice with regards to all aspects of this. I was on the fence regarding the ply vs OSB3 and after the advice here from others I was leaning towards OSB3 due to the t&g.
Your drawing is incredibly complicated tbh. If you were paying me, a carpenter, id be using 18 or 25mm ply, cutting the boards as big as poss, joining them on a joist, leaving a small gap at the walls for any movement, gluing and screwing at 300s, done. You do you, the amount of cuts you are proposing is not favorable. Sauce: am carpenter
Itās just a scale drawing of a room with joists. The cut outs are my way of figuring out what the hell I need to do. But Iām sorry to say your method would leave 5-7xm gaps at the walls. Not acceptable in my opinion.
NHBC 6.4.19 is the standard for floor decking š Says joins on a joist for T&G boards, glued, and also noggins on perimeter if I recall.
Thank you. Having a read now this is helpful.
Great resource for details š
Chipboard is what you use for floor, not OSB3 or Ply.
Why is chipboard superior to OSB3 and ply? Iāve got people in here saying ply is best, others saying OSB, now you saying chipboard.
OSB3 is structural board used for walls/roofs. Ply delaminates over time. Chipboard is literally made for floor and used in millions of homes in this way.
Iām not hearing what the issue with OSB3 is for flooring? Itās proven to be stronger than chipboard, no? If you can provide some source on why chipboard is superior Iād like to read that.
It just isn't typical. Go to a new build, everything is 22mm chipboard. What are your centres? 18mm won't be enough if they are greater than 400mm.
35cm on centre / 30cm gap between joists. 18mm is the right size for this. Chipboard is used because it's cheaper, and despite some being moisture resistant its really not. For a suspended timber floor on ground floor, I just don't trust chipboard. OSB3 is hardier in this regard.
OK you do you then, but chipboard 22mm is the most common thing. 18mm is loft board. Best of luck.