How to create a curbless walk-in shower - best subfloor set up?

[squeakysim]

Hi all,

I'm in the throes of dismantling my bathroom as part of a renovation on my newly purchased first home, originally built in the 70s. I'm going to reconfigure the layout, and plan to install a walk-in shower across the window using a preformed shower tray. The subfloor is constructed of bearers, joists and hardwood floorboards. Joists spacing is 450mm at most. The hallway/doorway is going to be sanded at the existing floor level, so this is a big part of the consideration. As I don't want a big lip in the doorway! I am at the point where I have pulled up the existing tiles and underlay and am now left with the exposed boards and am trying to decide which way is the best to proceed tyring to get a balance of cost effectiveness, time to build, and finished appearance. Each option I have come up with has a compromise in at least one of these areas.

Here are the options I have come up with:

1. Take up floorboards in the area of the shower in order to drop the floor and install noggins to accomodate shower tray, and lay 6mm Hardie backer board across the whole floor, before water proofing and laying tiles.

Pros - Most cost effective and least time to complete.

Cons - Likely to have a step of at least 17mm to the hallway floor and consequential frequently stubbed toes!

2. Take up all floor boards and lay 19mm Scyon board across the room, except for shower are, drop floor and installing noggins for the shower tray. Waterproof and lay tiles.

Pros - Straightforward to lay once floor is taken up, and saves 6mm in height at doorway due to not needing tile backer.

Cons - Most expensive option (over $500 more than Opt 1), still have a lip of around 10mm at door.

3. Remove all floor boards, install noggins on every joist, install 19mm ply (or reuse cut floorboards) on noggins between joists so the whole floor sits at the joist height,  in shower area add noggins and take off 19mm off joists to accommodate the tray. Install 6mm Hardie tile backer across main floor and waterproof and tile. 

Pros - Best overall finish as the tiled floor will be almost flush with the hallway. If floorboards are reused, should only cost $150 more than option one.

Cons - Most time consuming (especially if reusing floor boards!), but if using ply, the cost is nearly same option 2.

In your opinions are these all viable options?

I would like to go with Opt 3 and reuse the floor boards, but interested to know what you think about doing this. The reason for wanting to reuse the floorboards is not just financial, I also want to avoid as much waste as I can.

The noggins I planned to use will be 70x35 fixed to either side of joist, but I will also be able to rest on the existing bearers if I use some a 1mm packer. Floor boards are 19mm. One of my concerns with this is some of the joists have twisted a bit at the ends some may make getting the floor level more difficult.

Thanks in advance!

[JacobZ]

Hi @squeakysim,

A warm welcome to the Bunnings Workshop community, it is fantastic to have you join us.

You've clearly put some thought into the process, and it's great to see things have already started to progress. 

It should be noted that removing material from joists will lessen their load-bearing capacity, so it is worth having them checked by a suitably licensed professional, such as an engineer, to ensure this won't weaken the floor beyond a reasonable level.

As noggins are not technically structural members, I would not consider 3 a viable option, as you are relying on non-structural elements to support the weight of the floor. To make the noggins structural, you need to add joist hangers with suitable fixings to the end of each noggin, which would blow out the budget quite fast.

My suggestion would be to go with a modified version of option 2, where you still add noggins for strengthening, but you use an electric planer to remove 10mm from the top of the joists and the Scyon is laid on top of the joists. Check out How To Level a Subfloor for an example of what I mean. 

This approach would give you a nice flat surface where the weight is transferred into the joists, the flooring is immediately ready for waterproofing, and you don't have too many steps in the bathroom.

It would be a fair bit of work, but I can't see a better option.

Allow me to tag @Nailbag and @Dave-1 for their thoughts.

Jacob

[Dave-1]

Good Afternoon @squeakysim 

I have around a 20mm step from my floorboards into the tiled bathroom (think it has two layers of tiles ) and I havnt stubbed my toes as yet

I am not particulary keen in removing any of the timber joist/beam material as I figure its doing the job of supporting not only the room but where the joists stretch to.

Being a 1970's house you should make sure that there is no abspestos within the area. As a first step (and yeah I know you have started already but it would be lax for me not to mention the possibility)

I would probarly remove the floorboards and then install new particleboard on the existing beams to get the floor as close to the floor level itself. that way only the mud and the height of the tiles you wil have as height of the room. You will potentially want some kind of fall in the room so I cant really imagine another way of creating a fall.

The room will have to be waterproofed so maybe have a chat with what they would recommend and have seen in practice? 

Dave

[squeakysim]

Thanks for your response!

I think I may have misinterpreted what a noggin was...! I now realise it's the bracing element between studs or joists...! Whoops!

For option 3, I meant the noggin was the 70x35 timber to be fixed to the side of the joist like in the image here. Except in my bathroom the bearer is the crude sketch I've made in blue. Because the joist is only 90x45, the blocking timber (really not sure what else to call it!) will not only be fixed to the side of the joist, it will also be resting on the bearer. Thereby maintaining the weight bearing properties of the joist and bearer and not compromising structural integrity, or not?

[squeakysim]

Thanks @Dave-1 

Firstly, you are right there was asbetos, but it has already been dealt with and removed responsibly.

I'm curious as to your suggestion of use particleboard onto the joists. I didn't think this was a recommended material for use in bathrooms? Don't I still need to use cement sheet over the top before tiling? In which case, I may as well leave the floor boards as they are and go with Option 1, saving the cost of new boards. Or have I totally misunderstood your suggestion...?!

Thanks

[Dave-1]

Afternoon @squeakysim 

Its a waterproof styled particle boartd that I cant remember the name for May have uit wrong but I have seen them laid in bathrooms tho they may not have been particle board. The whole idea was to get a uniform solid base to start with. I would wait for clarification from @EricL , @MitchellMc or @JacobZ 

I dont like the idea of recessing the floorboards with the attached timber strips on the side of the beams, mostly as I dont see it being anywhere near as strong or level compared to a set floor height.

I have not tiled over floor boards But figure a smooth solid surface would be best to start with. Floor boards and then cement sheet on top (I am unsure of the ruling for that) would give a smooth surface but you were trying to go for as close to level as possible. (6mm for the cement sheet, mud plus tile) I did have a look for the type of board used in bathrooms/wet areas but didnt see anything easily.

Dave

[Nailbag]

Hi @squeakysim 

Personally I would do what ever it takes to ensure there is little to know step. So, I'm with @JacobZ in considering Option 2 which is one I have done myself in both an ensuite and master bath. I pulled up all the floorboards, then hired an industrial electric planer that was similar to this one that I could crank the depth right down as it had the power to take 2mm off per pass. But as @JacobZ highlighted, this reduces the structural strength of the joists. So I laminated 70mm x 45mm structural pine to each one and packed them where required to the bearers. This was pre-approved by the building inspector.

For the shower recess joists I made a couple hundred cross cuts at the right depth with my circular saw. It didn't take as long as it sounds. Then it was a quick knock out of the sections with a hammer and wide chisel. I never knew about  products like Sycon (possibly wasn't around). I laid down 2nd hand yellow-tongue which I think I got for free. These were supported by additional noggins and joists on all joins.

Then tile underlay was placed on top and the room waterproofed. I think I about 2-3mm out on the finished level to the WIR carpet which was never noticed.

Regards Nailbag

[squeakysim]

Thanks for that @Nailbag !

What size were your joists and how much did you end up taking off them? 

Also, can you explain what you mean by laminating the timber to the joists?

[Nailbag]

Hi @squeakysim 

Refer to images below. Measurements are best guess from memory as it was several years ago

Nailbag

[squeakysim]

Thanks so much @Nailbag !

Your joists are a fair bit deeper than mine! So I imagine it may not be an option for me...! My joists are only 90x45, and I think the bearers are 90x90. This structure appears to be purely to support the floor as the walls are all brick and go down to the foundations and the bearers do not pass through.

The current joists are quite warped in places, therefore I imagine will make trying to get things level quite challenging! Not to mention all the broken nails in the joists have now rendered the idea of planing them, completely out of the question! Therefore, I'm thinking of going one step further after I had a suggest from a plumber of laying new LVL joists. Obviously I still need to drop the floor by around 15mm, so I started wondering if I could take a  6-7mm notch out of the bearer and joist where they meet? This would allow enough for the scyon, tile and adhesive to sit on top and maybe a variance of 2-3mm of lip at the doorway. I could potentially lay the joists closer and/or add in noggins to give extra strength?

My reason for th above suggestion is that I am only reduce the height of the joist/bearer a given point, rather than taking off 10-15mm of the whole joist. One would assume the former is stronger than the latter...?

Thanks for your help so far everyone