Best subfloor for bathrooms

Doozergirl

Gavin83 said:

Doozergirl said:

andyhop said:

grumbler said:

andyhop said:

For the last 15 plus years , I’ve stripped out every bathroom we do , back to brick and joists and every time replaced the floor with 25mm marine plywood .

Personally, I wouldn't tile plywood directly. That's what hardibacker exists for, but if you add it on the top of 25mm plywood, this will be thicker than the OP wants.

I never tried 'no more ply', but 22mm t&g looks perfect for the OP's requirements and can be tiled directly.

1000+ bathrooms without a failure , what do I know 

I don’t offer bathrooms with huge steps 

I don’t offer bathrooms with any PVC cladding 

I don’t offer value for money over a few years 

22mm T&G tiled directly to substrate 😂 

Hardibacker exists as people want quick fixes , as long as it lasts a few years , it’s good enough . It’s for the untrained , the unknowledgeable and those that want to to the minimal amount of prep for the most amount of money

If your floor flexes , adding endless amounts of overlay still isn’t going to solve the issue 

I don't see anyone else laughing?  

If you have superior knowledge, it's fine to share it without laughing or taking the proverbial.  People ask because they want to know what their options are, people answer because they think they might have something valuable to add.   Sometimes people say thank you and it feels great! 

I think the right answer is to suggest that people ensure that they have a stable base.    I've replaced floors with ply and put hardiebacker over it many times because adhesive keys better to the concrete and the concrete is moving even less than the boards.  Hell, I've even replaced joists, then ply, then hardiebacker. 

Every room is different, every person is different.   If I judge that someone doesn't have the budget for what I'd do, I just don't say anything at all because it isn't helpful.  

I’m certainly appreciative of any answers I get. I’ve been a member of these forums long enough to know how annoying it is when you give advice only for the OP to never return!

Doozergirl, what would you do in my position? While I wouldn’t go as far as to say my budget is limitless it certainly isn’t my primary concern here. I want it done properly.

It’s certainly a good job budget isn’t my primary concern, 25mm plywood sheets are far from cheap!

It’s also worth noting I’m making assumptions what the current subfloor is as I haven’t yet lifted the carpet in the bathrooms. However in several other rooms 18mm chipboard is used and I’ve no reason to assume they haven’t used the same. While I wouldn’t exactly describe the subfloor in the bathrooms as weak it’s certainly springy and creaky enough I wouldn’t feel comfortable tiling on it.

You really want to get it all up, look and check the joists too for any movement/rot.  

Then I think 18mm ply and 9mm hardiebacker.  We've not really used the 6mm, so I can't give an opinion on it, but your end build up versus neighbouring rooms is a consideration depending on the tiles you use, so might be an option.  

andyhop

Doozergirl said:

Gavin83 said:

Doozergirl said:

andyhop said:

grumbler said:

andyhop said:

For the last 15 plus years , I’ve stripped out every bathroom we do , back to brick and joists and every time replaced the floor with 25mm marine plywood .

Personally, I wouldn't tile plywood directly. That's what hardibacker exists for, but if you add it on the top of 25mm plywood, this will be thicker than the OP wants.

I never tried 'no more ply', but 22mm t&g looks perfect for the OP's requirements and can be tiled directly.

1000+ bathrooms without a failure , what do I know 

I don’t offer bathrooms with huge steps 

I don’t offer bathrooms with any PVC cladding 

I don’t offer value for money over a few years 

22mm T&G tiled directly to substrate 😂 

Hardibacker exists as people want quick fixes , as long as it lasts a few years , it’s good enough . It’s for the untrained , the unknowledgeable and those that want to to the minimal amount of prep for the most amount of money

If your floor flexes , adding endless amounts of overlay still isn’t going to solve the issue 

I don't see anyone else laughing?  

If you have superior knowledge, it's fine to share it without laughing or taking the proverbial.  People ask because they want to know what their options are, people answer because they think they might have something valuable to add.   Sometimes people say thank you and it feels great! 

I think the right answer is to suggest that people ensure that they have a stable base.    I've replaced floors with ply and put hardiebacker over it many times because adhesive keys better to the concrete and the concrete is moving even less than the boards.  Hell, I've even replaced joists, then ply, then hardiebacker. 

Every room is different, every person is different.   If I judge that someone doesn't have the budget for what I'd do, I just don't say anything at all because it isn't helpful.  

I’m certainly appreciative of any answers I get. I’ve been a member of these forums long enough to know how annoying it is when you give advice only for the OP to never return!

Doozergirl, what would you do in my position? While I wouldn’t go as far as to say my budget is limitless it certainly isn’t my primary concern here. I want it done properly.

It’s certainly a good job budget isn’t my primary concern, 25mm plywood sheets are far from cheap!

It’s also worth noting I’m making assumptions what the current subfloor is as I haven’t yet lifted the carpet in the bathrooms. However in several other rooms 18mm chipboard is used and I’ve no reason to assume they haven’t used the same. While I wouldn’t exactly describe the subfloor in the bathrooms as weak it’s certainly springy and creaky enough I wouldn’t feel comfortable tiling on it.

You really want to get it all up, look and check the joists too for any movement/rot.  

Then I think 18mm ply and 9mm hardiebacker.  We've not really used the 6mm, so I can't give an opinion on it, but your end build up versus neighbouring rooms is a consideration depending on the tiles you use, so might be an option.  

You can’t buy 9mm Hardibacker . 6 or 12mm. 

Try bending a sheet of 18mm and then a sheet of 25mm . The difference is substantial . 

Maybe 3 extra cross layers depending on supplier

Your overlaying a product , with another product , with a layer of adhesive in between . More isn’t always better , it’s just something else to fail

£100 a sheet now for decent marine ply 

Doozergirl

andyhop said:

Doozergirl said:

Gavin83 said:

Doozergirl said:

andyhop said:

grumbler said:

andyhop said:

For the last 15 plus years , I’ve stripped out every bathroom we do , back to brick and joists and every time replaced the floor with 25mm marine plywood .

Personally, I wouldn't tile plywood directly. That's what hardibacker exists for, but if you add it on the top of 25mm plywood, this will be thicker than the OP wants.

I never tried 'no more ply', but 22mm t&g looks perfect for the OP's requirements and can be tiled directly.

1000+ bathrooms without a failure , what do I know 

I don’t offer bathrooms with huge steps 

I don’t offer bathrooms with any PVC cladding 

I don’t offer value for money over a few years 

22mm T&G tiled directly to substrate 😂 

Hardibacker exists as people want quick fixes , as long as it lasts a few years , it’s good enough . It’s for the untrained , the unknowledgeable and those that want to to the minimal amount of prep for the most amount of money

If your floor flexes , adding endless amounts of overlay still isn’t going to solve the issue 

I don't see anyone else laughing?  

If you have superior knowledge, it's fine to share it without laughing or taking the proverbial.  People ask because they want to know what their options are, people answer because they think they might have something valuable to add.   Sometimes people say thank you and it feels great! 

I think the right answer is to suggest that people ensure that they have a stable base.    I've replaced floors with ply and put hardiebacker over it many times because adhesive keys better to the concrete and the concrete is moving even less than the boards.  Hell, I've even replaced joists, then ply, then hardiebacker. 

Every room is different, every person is different.   If I judge that someone doesn't have the budget for what I'd do, I just don't say anything at all because it isn't helpful.  

I’m certainly appreciative of any answers I get. I’ve been a member of these forums long enough to know how annoying it is when you give advice only for the OP to never return!

Doozergirl, what would you do in my position? While I wouldn’t go as far as to say my budget is limitless it certainly isn’t my primary concern here. I want it done properly.

It’s certainly a good job budget isn’t my primary concern, 25mm plywood sheets are far from cheap!

It’s also worth noting I’m making assumptions what the current subfloor is as I haven’t yet lifted the carpet in the bathrooms. However in several other rooms 18mm chipboard is used and I’ve no reason to assume they haven’t used the same. While I wouldn’t exactly describe the subfloor in the bathrooms as weak it’s certainly springy and creaky enough I wouldn’t feel comfortable tiling on it.

You really want to get it all up, look and check the joists too for any movement/rot.  

Then I think 18mm ply and 9mm hardiebacker.  We've not really used the 6mm, so I can't give an opinion on it, but your end build up versus neighbouring rooms is a consideration depending on the tiles you use, so might be an option.  

You can’t buy 9mm Hardibacker . 6 or 12mm. 

Try bending a sheet of 18mm and then a sheet of 25mm . The difference is substantial . 

Maybe 3 extra cross layers depending on supplier

Your overlaying a product , with another product , with a layer of adhesive in between . More isn’t always better , it’s just something else to fail

£100 a sheet now for decent marine ply 

There's more than one way of doing things. 

It doesn't matter whether 18mm bends or not when it's not part of another structure, it's about the solidity and span of what is underneath that too.   

Our whole house is built from a foam sandwich of 11mm OSB and it's stronger than masonry when built.  

We've never glued Hardiebacker to anything, so that's an assumption.  Yes, it might be folly to use it without dealing with any problems underneath, but it is a perfect product for tiling to and it does have rigidity.  

andyhop

Doozergirl said:

andyhop said:

Doozergirl said:

Gavin83 said:

Doozergirl said:

andyhop said:

grumbler said:

andyhop said:

For the last 15 plus years , I’ve stripped out every bathroom we do , back to brick and joists and every time replaced the floor with 25mm marine plywood .

Personally, I wouldn't tile plywood directly. That's what hardibacker exists for, but if you add it on the top of 25mm plywood, this will be thicker than the OP wants.

I never tried 'no more ply', but 22mm t&g looks perfect for the OP's requirements and can be tiled directly.

1000+ bathrooms without a failure , what do I know 

I don’t offer bathrooms with huge steps 

I don’t offer bathrooms with any PVC cladding 

I don’t offer value for money over a few years 

22mm T&G tiled directly to substrate 😂 

Hardibacker exists as people want quick fixes , as long as it lasts a few years , it’s good enough . It’s for the untrained , the unknowledgeable and those that want to to the minimal amount of prep for the most amount of money

If your floor flexes , adding endless amounts of overlay still isn’t going to solve the issue 

I don't see anyone else laughing?  

If you have superior knowledge, it's fine to share it without laughing or taking the proverbial.  People ask because they want to know what their options are, people answer because they think they might have something valuable to add.   Sometimes people say thank you and it feels great! 

I think the right answer is to suggest that people ensure that they have a stable base.    I've replaced floors with ply and put hardiebacker over it many times because adhesive keys better to the concrete and the concrete is moving even less than the boards.  Hell, I've even replaced joists, then ply, then hardiebacker. 

Every room is different, every person is different.   If I judge that someone doesn't have the budget for what I'd do, I just don't say anything at all because it isn't helpful.  

I’m certainly appreciative of any answers I get. I’ve been a member of these forums long enough to know how annoying it is when you give advice only for the OP to never return!

Doozergirl, what would you do in my position? While I wouldn’t go as far as to say my budget is limitless it certainly isn’t my primary concern here. I want it done properly.

It’s certainly a good job budget isn’t my primary concern, 25mm plywood sheets are far from cheap!

It’s also worth noting I’m making assumptions what the current subfloor is as I haven’t yet lifted the carpet in the bathrooms. However in several other rooms 18mm chipboard is used and I’ve no reason to assume they haven’t used the same. While I wouldn’t exactly describe the subfloor in the bathrooms as weak it’s certainly springy and creaky enough I wouldn’t feel comfortable tiling on it.

You really want to get it all up, look and check the joists too for any movement/rot.  

Then I think 18mm ply and 9mm hardiebacker.  We've not really used the 6mm, so I can't give an opinion on it, but your end build up versus neighbouring rooms is a consideration depending on the tiles you use, so might be an option.  

You can’t buy 9mm Hardibacker . 6 or 12mm. 

Try bending a sheet of 18mm and then a sheet of 25mm . The difference is substantial . 

Maybe 3 extra cross layers depending on supplier

Your overlaying a product , with another product , with a layer of adhesive in between . More isn’t always better , it’s just something else to fail

£100 a sheet now for decent marine ply 

There's more than one way of doing things. 

It doesn't matter whether 18mm bends or not when it's not part of another structure, it's about the solidity and span of what is underneath that too.   

Our whole house is built from a foam sandwich of 11mm OSB and it's stronger than masonry when built.  

We've never glued Hardiebacker to anything, so that's an assumption.  Yes, it might be folly to use it without dealing with any problems underneath, but it is a perfect product for tiling to and it does have rigidity.  

 Not an assumption . It’s the way it should be laid . 

https://www.jameshardiepros.com/getattachment/98adb0c7-1bd1-49e7-a9d4-a8275d29ae4a/hardiebacker-installation-guide-english-spanish-hb1710.pdf

Doozergirl

andyhop said:

Doozergirl said:

andyhop said:

Doozergirl said:

Gavin83 said:

Doozergirl said:

andyhop said:

grumbler said:

andyhop said:

For the last 15 plus years , I’ve stripped out every bathroom we do , back to brick and joists and every time replaced the floor with 25mm marine plywood .

Personally, I wouldn't tile plywood directly. That's what hardibacker exists for, but if you add it on the top of 25mm plywood, this will be thicker than the OP wants.

I never tried 'no more ply', but 22mm t&g looks perfect for the OP's requirements and can be tiled directly.

1000+ bathrooms without a failure , what do I know 

I don’t offer bathrooms with huge steps 

I don’t offer bathrooms with any PVC cladding 

I don’t offer value for money over a few years 

22mm T&G tiled directly to substrate 😂 

Hardibacker exists as people want quick fixes , as long as it lasts a few years , it’s good enough . It’s for the untrained , the unknowledgeable and those that want to to the minimal amount of prep for the most amount of money

If your floor flexes , adding endless amounts of overlay still isn’t going to solve the issue 

I don't see anyone else laughing?  

If you have superior knowledge, it's fine to share it without laughing or taking the proverbial.  People ask because they want to know what their options are, people answer because they think they might have something valuable to add.   Sometimes people say thank you and it feels great! 

I think the right answer is to suggest that people ensure that they have a stable base.    I've replaced floors with ply and put hardiebacker over it many times because adhesive keys better to the concrete and the concrete is moving even less than the boards.  Hell, I've even replaced joists, then ply, then hardiebacker. 

Every room is different, every person is different.   If I judge that someone doesn't have the budget for what I'd do, I just don't say anything at all because it isn't helpful.  

I’m certainly appreciative of any answers I get. I’ve been a member of these forums long enough to know how annoying it is when you give advice only for the OP to never return!

Doozergirl, what would you do in my position? While I wouldn’t go as far as to say my budget is limitless it certainly isn’t my primary concern here. I want it done properly.

It’s certainly a good job budget isn’t my primary concern, 25mm plywood sheets are far from cheap!

It’s also worth noting I’m making assumptions what the current subfloor is as I haven’t yet lifted the carpet in the bathrooms. However in several other rooms 18mm chipboard is used and I’ve no reason to assume they haven’t used the same. While I wouldn’t exactly describe the subfloor in the bathrooms as weak it’s certainly springy and creaky enough I wouldn’t feel comfortable tiling on it.

You really want to get it all up, look and check the joists too for any movement/rot.  

Then I think 18mm ply and 9mm hardiebacker.  We've not really used the 6mm, so I can't give an opinion on it, but your end build up versus neighbouring rooms is a consideration depending on the tiles you use, so might be an option.  

You can’t buy 9mm Hardibacker . 6 or 12mm. 

Try bending a sheet of 18mm and then a sheet of 25mm . The difference is substantial . 

Maybe 3 extra cross layers depending on supplier

Your overlaying a product , with another product , with a layer of adhesive in between . More isn’t always better , it’s just something else to fail

£100 a sheet now for decent marine ply 

There's more than one way of doing things. 

It doesn't matter whether 18mm bends or not when it's not part of another structure, it's about the solidity and span of what is underneath that too.   

Our whole house is built from a foam sandwich of 11mm OSB and it's stronger than masonry when built.  

We've never glued Hardiebacker to anything, so that's an assumption.  Yes, it might be folly to use it without dealing with any problems underneath, but it is a perfect product for tiling to and it does have rigidity.  

 Not an assumption . It’s the way it should be laid . 

https://www.jameshardiepros.com/getattachment/98adb0c7-1bd1-49e7-a9d4-a8275d29ae4a/hardiebacker-installation-guide-english-spanish-hb1710.pdf

We do it as per walls.  The best way to stop any floor from moving and preventing flex is to screw it down to the joists.  

danrv

Gavin83 said:

I’m intending on tiling. 

I missed this on the first read. I guess you’d want a floor with the least amount on joins or sections.
I went with T&G chipboard from Wickes as it’s a lot cheaper than marine ply.
Certainly sturdy enough for the flooring I’m using. 
Any thicker than 18mm boards would have raised the level too much.

A couple of the joists were heavily notched for waste pipes but have now been strengthened with sister joists.
I did have a suggestion to use a single sheet of plywood but that might be a bit awkward to get through the door.

plumb1_2

18 or 25mm plywood every time for me, and no cement board on top. 

andyhop

Doozergirl said:

andyhop said:

Doozergirl said:

andyhop said:

Doozergirl said:

Gavin83 said:

Doozergirl said:

andyhop said:

grumbler said:

andyhop said:

For the last 15 plus years , I’ve stripped out every bathroom we do , back to brick and joists and every time replaced the floor with 25mm marine plywood .

Personally, I wouldn't tile plywood directly. That's what hardibacker exists for, but if you add it on the top of 25mm plywood, this will be thicker than the OP wants.

I never tried 'no more ply', but 22mm t&g looks perfect for the OP's requirements and can be tiled directly.

1000+ bathrooms without a failure , what do I know 

I don’t offer bathrooms with huge steps 

I don’t offer bathrooms with any PVC cladding 

I don’t offer value for money over a few years 

22mm T&G tiled directly to substrate 😂 

Hardibacker exists as people want quick fixes , as long as it lasts a few years , it’s good enough . It’s for the untrained , the unknowledgeable and those that want to to the minimal amount of prep for the most amount of money

If your floor flexes , adding endless amounts of overlay still isn’t going to solve the issue 

I don't see anyone else laughing?  

If you have superior knowledge, it's fine to share it without laughing or taking the proverbial.  People ask because they want to know what their options are, people answer because they think they might have something valuable to add.   Sometimes people say thank you and it feels great! 

I think the right answer is to suggest that people ensure that they have a stable base.    I've replaced floors with ply and put hardiebacker over it many times because adhesive keys better to the concrete and the concrete is moving even less than the boards.  Hell, I've even replaced joists, then ply, then hardiebacker. 

Every room is different, every person is different.   If I judge that someone doesn't have the budget for what I'd do, I just don't say anything at all because it isn't helpful.  

I’m certainly appreciative of any answers I get. I’ve been a member of these forums long enough to know how annoying it is when you give advice only for the OP to never return!

Doozergirl, what would you do in my position? While I wouldn’t go as far as to say my budget is limitless it certainly isn’t my primary concern here. I want it done properly.

It’s certainly a good job budget isn’t my primary concern, 25mm plywood sheets are far from cheap!

It’s also worth noting I’m making assumptions what the current subfloor is as I haven’t yet lifted the carpet in the bathrooms. However in several other rooms 18mm chipboard is used and I’ve no reason to assume they haven’t used the same. While I wouldn’t exactly describe the subfloor in the bathrooms as weak it’s certainly springy and creaky enough I wouldn’t feel comfortable tiling on it.

You really want to get it all up, look and check the joists too for any movement/rot.  

Then I think 18mm ply and 9mm hardiebacker.  We've not really used the 6mm, so I can't give an opinion on it, but your end build up versus neighbouring rooms is a consideration depending on the tiles you use, so might be an option.  

You can’t buy 9mm Hardibacker . 6 or 12mm. 

Try bending a sheet of 18mm and then a sheet of 25mm . The difference is substantial . 

Maybe 3 extra cross layers depending on supplier

Your overlaying a product , with another product , with a layer of adhesive in between . More isn’t always better , it’s just something else to fail

£100 a sheet now for decent marine ply 

There's more than one way of doing things. 

It doesn't matter whether 18mm bends or not when it's not part of another structure, it's about the solidity and span of what is underneath that too.   

Our whole house is built from a foam sandwich of 11mm OSB and it's stronger than masonry when built.  

We've never glued Hardiebacker to anything, so that's an assumption.  Yes, it might be folly to use it without dealing with any problems underneath, but it is a perfect product for tiling to and it does have rigidity.  

 Not an assumption . It’s the way it should be laid . 

https://www.jameshardiepros.com/getattachment/98adb0c7-1bd1-49e7-a9d4-a8275d29ae4a/hardiebacker-installation-guide-english-spanish-hb1710.pdf

We do it as per walls.  The best way to stop any floor from moving and preventing flex is to screw it down to the joists.  

So you manage your installs to the complete opposite to what the manufacturer dictates . Sounds sensible 

Flex can only be prevented by going back to traditional methods, proper herringboned joists not just a couple of extra dwangs with multiple overlays and bang in a few extra screws 

We keep moving towards speed and cost, gone are the days of quality and durability. Now we churn out crap with a that’ll do attitude , Bricks and mortar will last hundreds of years !  OSB…. 60years max they says and that’s it it remains dry 

Everything that is wrong with the industry can be seen in a new build . Chipboard, stud walls, lightweight structures. Removing the skill. Removing the quality . 

danrv

andyhop said:

Doozergirl said:

andyhop said:

Doozergirl said:

andyhop said:

Doozergirl said:

Gavin83 said:

Doozergirl said:

andyhop said:

grumbler said:

andyhop said:

For the last 15 plus years , I’ve stripped out every bathroom we do , back to brick and joists and every time replaced the floor with 25mm marine plywood .

Personally, I wouldn't tile plywood directly. That's what hardibacker exists for, but if you add it on the top of 25mm plywood, this will be thicker than the OP wants.

I never tried 'no more ply', but 22mm t&g looks perfect for the OP's requirements and can be tiled directly.

1000+ bathrooms without a failure , what do I know 

I don’t offer bathrooms with huge steps 

I don’t offer bathrooms with any PVC cladding 

I don’t offer value for money over a few years 

22mm T&G tiled directly to substrate 😂 

Hardibacker exists as people want quick fixes , as long as it lasts a few years , it’s good enough . It’s for the untrained , the unknowledgeable and those that want to to the minimal amount of prep for the most amount of money

If your floor flexes , adding endless amounts of overlay still isn’t going to solve the issue 

I don't see anyone else laughing?  

If you have superior knowledge, it's fine to share it without laughing or taking the proverbial.  People ask because they want to know what their options are, people answer because they think they might have something valuable to add.   Sometimes people say thank you and it feels great! 

I think the right answer is to suggest that people ensure that they have a stable base.    I've replaced floors with ply and put hardiebacker over it many times because adhesive keys better to the concrete and the concrete is moving even less than the boards.  Hell, I've even replaced joists, then ply, then hardiebacker. 

Every room is different, every person is different.   If I judge that someone doesn't have the budget for what I'd do, I just don't say anything at all because it isn't helpful.  

I’m certainly appreciative of any answers I get. I’ve been a member of these forums long enough to know how annoying it is when you give advice only for the OP to never return!

Doozergirl, what would you do in my position? While I wouldn’t go as far as to say my budget is limitless it certainly isn’t my primary concern here. I want it done properly.

It’s certainly a good job budget isn’t my primary concern, 25mm plywood sheets are far from cheap!

It’s also worth noting I’m making assumptions what the current subfloor is as I haven’t yet lifted the carpet in the bathrooms. However in several other rooms 18mm chipboard is used and I’ve no reason to assume they haven’t used the same. While I wouldn’t exactly describe the subfloor in the bathrooms as weak it’s certainly springy and creaky enough I wouldn’t feel comfortable tiling on it.

You really want to get it all up, look and check the joists too for any movement/rot.  

Then I think 18mm ply and 9mm hardiebacker.  We've not really used the 6mm, so I can't give an opinion on it, but your end build up versus neighbouring rooms is a consideration depending on the tiles you use, so might be an option.  

You can’t buy 9mm Hardibacker . 6 or 12mm. 

Try bending a sheet of 18mm and then a sheet of 25mm . The difference is substantial . 

Maybe 3 extra cross layers depending on supplier

Your overlaying a product , with another product , with a layer of adhesive in between . More isn’t always better , it’s just something else to fail

£100 a sheet now for decent marine ply 

There's more than one way of doing things. 

It doesn't matter whether 18mm bends or not when it's not part of another structure, it's about the solidity and span of what is underneath that too.   

Our whole house is built from a foam sandwich of 11mm OSB and it's stronger than masonry when built.  

We've never glued Hardiebacker to anything, so that's an assumption.  Yes, it might be folly to use it without dealing with any problems underneath, but it is a perfect product for tiling to and it does have rigidity.  

 Not an assumption . It’s the way it should be laid . 

https://www.jameshardiepros.com/getattachment/98adb0c7-1bd1-49e7-a9d4-a8275d29ae4a/hardiebacker-installation-guide-english-spanish-hb1710.pdf

We do it as per walls.  The best way to stop any floor from moving and preventing flex is to screw it down to the joists.  

60years max they says and that’s it it remains dry 

I’d be happy with that for my chipboard subfloor. It’s screwed down to the joists and doesn’t move. 

Doozergirl

andyhop said:

Doozergirl said:

andyhop said:

Doozergirl said:

andyhop said:

Doozergirl said:

Gavin83 said:

Doozergirl said:

andyhop said:

grumbler said:

andyhop said:

For the last 15 plus years , I’ve stripped out every bathroom we do , back to brick and joists and every time replaced the floor with 25mm marine plywood .

Personally, I wouldn't tile plywood directly. That's what hardibacker exists for, but if you add it on the top of 25mm plywood, this will be thicker than the OP wants.

I never tried 'no more ply', but 22mm t&g looks perfect for the OP's requirements and can be tiled directly.

1000+ bathrooms without a failure , what do I know 

I don’t offer bathrooms with huge steps 

I don’t offer bathrooms with any PVC cladding 

I don’t offer value for money over a few years 

22mm T&G tiled directly to substrate 😂 

Hardibacker exists as people want quick fixes , as long as it lasts a few years , it’s good enough . It’s for the untrained , the unknowledgeable and those that want to to the minimal amount of prep for the most amount of money

If your floor flexes , adding endless amounts of overlay still isn’t going to solve the issue 

I don't see anyone else laughing?  

If you have superior knowledge, it's fine to share it without laughing or taking the proverbial.  People ask because they want to know what their options are, people answer because they think they might have something valuable to add.   Sometimes people say thank you and it feels great! 

I think the right answer is to suggest that people ensure that they have a stable base.    I've replaced floors with ply and put hardiebacker over it many times because adhesive keys better to the concrete and the concrete is moving even less than the boards.  Hell, I've even replaced joists, then ply, then hardiebacker. 

Every room is different, every person is different.   If I judge that someone doesn't have the budget for what I'd do, I just don't say anything at all because it isn't helpful.  

I’m certainly appreciative of any answers I get. I’ve been a member of these forums long enough to know how annoying it is when you give advice only for the OP to never return!

Doozergirl, what would you do in my position? While I wouldn’t go as far as to say my budget is limitless it certainly isn’t my primary concern here. I want it done properly.

It’s certainly a good job budget isn’t my primary concern, 25mm plywood sheets are far from cheap!

It’s also worth noting I’m making assumptions what the current subfloor is as I haven’t yet lifted the carpet in the bathrooms. However in several other rooms 18mm chipboard is used and I’ve no reason to assume they haven’t used the same. While I wouldn’t exactly describe the subfloor in the bathrooms as weak it’s certainly springy and creaky enough I wouldn’t feel comfortable tiling on it.

You really want to get it all up, look and check the joists too for any movement/rot.  

Then I think 18mm ply and 9mm hardiebacker.  We've not really used the 6mm, so I can't give an opinion on it, but your end build up versus neighbouring rooms is a consideration depending on the tiles you use, so might be an option.  

You can’t buy 9mm Hardibacker . 6 or 12mm. 

Try bending a sheet of 18mm and then a sheet of 25mm . The difference is substantial . 

Maybe 3 extra cross layers depending on supplier

Your overlaying a product , with another product , with a layer of adhesive in between . More isn’t always better , it’s just something else to fail

£100 a sheet now for decent marine ply 

There's more than one way of doing things. 

It doesn't matter whether 18mm bends or not when it's not part of another structure, it's about the solidity and span of what is underneath that too.   

Our whole house is built from a foam sandwich of 11mm OSB and it's stronger than masonry when built.  

We've never glued Hardiebacker to anything, so that's an assumption.  Yes, it might be folly to use it without dealing with any problems underneath, but it is a perfect product for tiling to and it does have rigidity.  

 Not an assumption . It’s the way it should be laid . 

https://www.jameshardiepros.com/getattachment/98adb0c7-1bd1-49e7-a9d4-a8275d29ae4a/hardiebacker-installation-guide-english-spanish-hb1710.pdf

We do it as per walls.  The best way to stop any floor from moving and preventing flex is to screw it down to the joists.  

So you manage your installs to the complete opposite to what the manufacturer dictates . Sounds sensible 

Flex can only be prevented by going back to traditional methods, proper herringboned joists not just a couple of extra dwangs with multiple overlays and bang in a few extra screws 

We keep moving towards speed and cost, gone are the days of quality and durability. Now we churn out crap with a that’ll do attitude , Bricks and mortar will last hundreds of years !  OSB…. 60years max they says and that’s it it remains dry 

Everything that is wrong with the industry can be seen in a new build . Chipboard, stud walls, lightweight structures. Removing the skill. Removing the quality . 

There's nothing 'that'll do' about anything we do, nor speedy, nor cheap.   Quite the opposite and you're the first to say that, so I'll ignore your rudeness.  

It's quite a romantic view that there's only one way to do things, almost anything it seems, when it comes to building houses, but we're off topic and I'm tired of being lectured.  If I'm "that'll do" then you are going to have a big job on your hands sorting out our country's housing stock by yourself.