Shower Repair

[burger]

Hi,

I need to repair the floor in my upstairs shower with the usual waterproofing and retiling. I will get the waterproofing done by a professional however I need to prepare the cubicle floor properly before doing this.
On removing the existing shower base the particle board underneath is damp and rotted. The flooring looks like it is yellowtongue (I think that is the name from what I can see from other posts on the forum) as it has a yellow plastic strip in the joints between the boards which run through the middle of the shower cubicle.
From what I can see the only option is to cut out the existing board and replace it with either 19mm or 6.5mm cement sheeting. I have a few questions that I need some help with:

Given that this is the floor of the shower would it be best to go with the thicker sheets to provide more support?

Is it also an option to let the particle board dry out and then fix a sheet of 6.5mm villaboard to the top of it as a base for the mortar bed?

Do I need to cut the board out to the base of the framing or should I just cut out what is rotten?

I have attached a pic of the current state of the shower. Any help or suggestions for this would be very much appreciated. My approval for future projects by the better half sits on the success of this job

Cheers,

Mark

[journeyman Mick]

Mark,
usual way is either 19mm CFC or the thinner stuff on top of yellow tongue, ply or T&G. You may get away with just replacing directly under the base, provided the bottom plate of the walls isn't affected (or the bottom of the studs as well) or if the water damage doesn't extend out under the rest of the flooring.
At a minimum you will need to replace the whole base section, however when you remove it you may find you need to fit more support around the perimiter (blocking).

If the sheeting is water damaged it will have swollen, once this has occured it must be replaced as it is weakened and it definitely won't shrink back.

Number one priority is assessing the extent of any water damage/rot etc and removing/replacing it. Cut out the existing sheeting under the base and post some pics if you want.

Mick

[burger]

Mick,

I removed the rotten board and fortunately it does not look like there is any damage to the stud or bottom plate. The rot seems mostly to have been around the waste. The top of the joists have a little bit of rot on them but it is not too extensive. I was planning on cutting a 5mm rebate into the joists and repacking with a ripped piece of 100x25 to give me a nice flat surface to place the floor on to once I decide on what material to use. I am probably leaning to the 19mm CFC at the moment. The joists run nicely along the edge of the shower walls providing plenty of support for the floor. At the moment it does not look like I will have to do any additional blocking for support but I will find out tonight. Is the rebating and repack an acceptable way to fix the rot? It certainly does not warrant any major work but I want to make sure I have cut it all out.

Thanks for the tips. Its been a few years since I have had to get my hands dirty doing this sort of thing!

Mark

[rat52]

Hardies put out a 'SCYON" wet area floor sheet 19 mm

Whatever you replace it with make sure you silicon seal all joints.

Also the floor outlet should be a special type that drains any moisture that gets under the tiles. (the name escapes me at the moment but I'll look it up later)

A caution after waterproofing (which is not too diffacult to do). Don't let anything sharp come in contact with the floor. Especially tile chips.

[burger]

here are some pics with the rotten floor removed. By the looks of things I am going to have to place some blocking under the back of the wall and also along the right hand side to give it some more support.

[journeyman Mick]

Mark,
looks pretty good from what I can see in the pics. Does it need blocking? as l;ong as there's about 30mm or so of joist to sit on it should be fine.

Mick

[burger]

Mick,

when I first looked at it I thought not but I have had more of a look at it and whilst the joists running through the middle and on the left hand side will provide enough support there is nothing supporting the corners on the right hand side. I am worried that if I put the floor down it could flex and move a bit in those corners and possibly cause issues with the waterproofing membrane over time. I am thinking 75x25 should do the job adequately or maybe 100x50 framing timber would be better. Do you think the 19mm CFC is overkill for this and it would be easier to lay 19mm water resistant chip board and a 6mm sheet of CFC over top? The top of the joists have some slight rot in them - not too much just a few mm. Do I need to remove this completely or can I just lay the floor over top and glue + screw the floor into the joists to hold it all together?

Cheers,

Mark

[journeyman Mick]

Mark,
if it was my place I wouldn't use anything other than the 19mm cfc. You definitely need to remove all the rot. I would use some 100 x 50 joist material and just double it up next to the joists that have had the rot hacked out. It doesn't need to take long or look very neat, it just needs to have any rot removed and a firm level base provided for your floor sheeting.

Mick