Wedi Tilebacker Board Query

[Thespanishtiler]

IMO you should not be trimming joists..?..

You can get trays that are now only 22mm thick and span the joists without the need to board out between the joists for support.

But you deffo DO NOT trim joists down in thickness/depth etc..

IMO timming say 6 mm off the top of a joist then running 3''x2'' along both sides screwed at 75mm through from both sides is no issue what so ever.

I am well aware of and used most of all the tray formers available on the market and would in such a case use say a shower stone or showerlay former BUT this guy specified he was to use a fundo former so I have offered my advice as such.

if he wants he can slap it straight to the floor and lay 40mm wedi all round but the door step may not be too attractive.

lets do the maths

floor 22mm

hb board on spf 8mm

ufh in slc 6mm

ci on spf 4mm

total 40mm NO NEED TO TRIM JOISTS

above scenario without ufh and slc

Total 34mm TRIM 6MM OFF JOISTS

If you where to overlay a 22mm floor with hb on spf and lay ufh in slc with ci on top you would have to raise your 22mm former by 8 mm to get a level threshold

the choice is yours

 

[Thespanishtiler]

and another point

its very rare to find the joists under your tray location are all level and true so are generaly not so usefull to fix direct to unless you want a tray that drains away from the gully

 

[DHTiling]

Each to their own Rob.. 🙂.. but when i trained in C&G joinery as a Teen , you never trimmed joists like that.. 🙂🙂.. if joists are different levels for a tray to sit flat then you frame the insides of the joists to level up.. Taking depth from joists is weakening them... but if it works for you then that is great.. ..

I agree that a tray does need to sit flat and true for flow rate on the tray drain.. these 40mm trays are old school now IMO.. plenty other options to keep heights down...

 

[Thespanishtiler]

the point is dave that by trimming lets say 5mm off a 150mm x 50mm joist over 900mm length you loose 3.33% of its volume
by adding 2 new 3'' x 2'' joists at either side you then increase it by 75 %

0ver 50 wetrooms installed and never a failure or a call back

more than happy with my working practices cheers

and so are my many clients

 

[DHTiling]

Ahhh you didn't say you were adding strengthening after trimming you sly devil you..:lol:...

 

[Thespanishtiler]

 

[Pebble]

Thanks guys for your help with this..