Tiling on plywood - do i need noggins?
- Thread starter richardadc
- Start date
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Standard NMP is only 6mm thick & as you’re over boarding just a 16mm thick T&G timber floor (they may have been power sanded at some time), I would be concerned about providing enough rigidity. NMP also comes in 9mm I believe which would be better but, personally, I’d go for 12mm Hardiebacker or, as your floorboards are only 16mm thick, 15mm WBP.
The BS & adhesive manufacturers’ minimum spec for over boarding existing floors (usually 18mm) is 15mm but it’s generally recognised that 12mm is sufficient in most cases. For tiling over new suspended floors, 25mm WBP is specified but, again, you can get away with as little as 18mm in low use/load areas but it depends on the floor structure. What size/pitch/span are your floor joists?
The BS & adhesive manufacturers’ minimum spec for over boarding existing floors (usually 18mm) is 15mm but it’s generally recognised that 12mm is sufficient in most cases. For tiling over new suspended floors, 25mm WBP is specified but, again, you can get away with as little as 18mm in low use/load areas but it depends on the floor structure. What size/pitch/span are your floor joists?
It's about 8cm from the bedroom joist to that side of the partition so about 13cm away to be level with the wall in the bathroom.
The joist seem to be 8.5 x1.5 with a 40cm gap. I'm not sure on the span.
If i did go for 15mm ply would that help if the floor boards were a bit on the loose side? Also, should i be screwing the ply into the floor board and/or the joists and is there any need to use grip adhesive?
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The depth is OK but 1½” is a bit slim, they are usually 2”; it’s just as important to know the joist span between supports.
You must ensure the original boards are not loose, fix with additional screws as necessary. Screw through into the joists not just into the top of the original floorboards; no need to use grip adhesive.
Glue and Screw Aquapanel to your existing floor.
Use a rapidset flexy adhesive for gluing, 6mm trowel.
Use the Glass fibre tape on joints, apply with more RS flexy.
This will give the same rigidity as 18mm ply overlay.
Knauf Aquapanel can be bought in Wickes.
I have done a lot of these floors over the years, in particular natural Stone, never a failure.
Use a rapidset flexy adhesive for gluing, 6mm trowel.
Use the Glass fibre tape on joints, apply with more RS flexy.
This will give the same rigidity as 18mm ply overlay.
Knauf Aquapanel can be bought in Wickes.
I have done a lot of these floors over the years, in particular natural Stone, never a failure.
I seem to be finding it quite hard to get hold on 15mm plywood - it all seems to be either 12mm or 18mm.
If i can't get hold of it would the 12mm Hardiebacker or 12mm ply be the best choice? I have noticed that NMP comes in 12mm now as well if that makes any difference.
ok, thanks for your advice but it would seem i'm going to have to remove the floor boards anyway. After some more investigation to cure some of the squeaking in the floor boards it turns out there are a few boards that have been cut in half that's not resting on a joist - it's just the T&G that's holding it in place. 
Going back to my original problem, if i was to lay noggins going under the wall to the other floor what size would i need to be able to cut two 1 inch notches out of them (for the two 22mm pipes)?
I then intend to cut another 1x1 inch notch out on the side of the noggin that's in the other room to fit a piece of wood 1x1 going 90 degrees to the noggin so that the bedroom floor boards can then lay on this. Please let me know if this sounds ok?
Going back to my original problem, if i was to lay noggins going under the wall to the other floor what size would i need to be able to cut two 1 inch notches out of them (for the two 22mm pipes)?
I then intend to cut another 1x1 inch notch out on the side of the noggin that's in the other room to fit a piece of wood 1x1 going 90 degrees to the noggin so that the bedroom floor boards can then lay on this. Please let me know if this sounds ok?
Please see the image attached for clarification.
Red indicated the current joists.
Blue indicates the noggins i intend to put in place
Grey indicated the pipes
Orange indicates the 1x1 piece of wood for the floor boards to lay on
Red indicated the current joists.
Blue indicates the noggins i intend to put in place
Grey indicated the pipes
Orange indicates the 1x1 piece of wood for the floor boards to lay on
How are the joists supported either side of the room? Why cant you just stick in another full with joist supported on joist hangers instead of all the noggins & 1 x 1 bearer which won’t offer much support anyway. As it’s so close to the wall, it will only be lightly loaded unless it’s where one of the bath feet ends up so doesn’t necessarily have to be the same size as the rest of the joists.
On the left side of the picture there is a wooden support going down the length of wall that supports the joists. I'm not sure where the other support is - it's not in the room. The room however is only 1.7 x 2.1 so i imagine the other support would be a distance from this room.
As for why i can't put a joist in, it mainly down to the joist would have to go where the pipes are currently running and also i'm not sure where the other support is. I don't want to have to pull up the landing to find it.
As for the 1x1 bit of wood not offering much support - there will be a joist 5cm away from it so i imagine that will offer most of the support. The 1x1 was just intended to nail the end of bedroom floor board in to.
Please let me know what you think.
You could fit a noggin between the joists at the unsupported end to take a joist hanger, fit a joist hanger to the support on the left hand side of the room & fit a new joist.
I know it’s an inconvenience but sometimes you have to undertake additional work to get the right solution. Lift floorboards to gain access if you have to, move a pipe if it’s in the way; you can’t make an omelet without breaking a few eggs.
Don’t use nails for the floorboards or over boarding, use screws.
I know it’s an inconvenience but sometimes you have to undertake additional work to get the right solution. Lift floorboards to gain access if you have to, move a pipe if it’s in the way; you can’t make an omelet without breaking a few eggs.
Don’t use nails for the floorboards or over boarding, use screws.
You could fit a noggin between the joists at the unsupported end to take a joist hanger, fit a joist hanger to the support on the left hand side of the room & fit a new joist.
I know it’s an inconvenience but sometimes you have to undertake additional work to get the right solution. Lift floorboards to gain access if you have to, move a pipe if it’s in the way; you can’t make an omelet without breaking a few eggs.
Don’t use nails for the floorboards or over boarding, use screws.
Once again thanks for your reply. Can i just check though if the idea that i came up with is not an acceptable/safe way to do this or if improvements can be made to it to make it suitable e.g. if 1x1 bit of wood isn't ok, to use further noggins going along the length instead?
Your idea does certainly sound like the best way of doing it if i had the budget but i haven't got the budget to get the pros in to move pipe work etc. I'm also not sure how the wall would be supported while this work is being done as i'm going to have to remove all the floorboards at once rather than just doing sections if i was to use noggins. I'd also have an issue (that i missed on my diagram) in that the soil stack is in the way of the support on the left so i'd have to implement another set of noggins there.
Please note that i will be using 25mm ply if the noggin method is acceptable.
I'm also not trying to get out of doing the job properly - it's more a case of deciding if i can go ahead with the project or not.
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