Advice before laying my porcelain tiles

[STEVEROG]

Before I go off half-cocked I wanted to check a few things before starting to tile my small bathroom.

Here is the basic overview of the job.

1. Floor is 4x2 inch timber joist floor. I have added boat loads of bracing and extra dwarf walls and grip-filled all bracing joints.

2. I have laid 18mm WBP over joist floor and glued and screwed this down with total screw overkill.

3. I plan to use BAL fastflex one part or two-part adhesive. Is this the correct adhesive for porcelain tiles 300mm x 300mm size. Make is Niro Granite.

4. What preparation do I need to do on the WBP plywood? Maybe this info is provided by BAL with the Fastflex?

5. I assume the fastflex is applied with a defined notched trowel?

6. How 'FLAT' does the surface of the plywood need to be?

7. How do I ensure the tiles I lay end up with even spacing and are all the same height relative to each other.

Aplogies for lame questions up front. I am a tiling FNG if it was not already apparent !

Steve

[doug boardley]

steve I've already replied to your adhesive query. I'm a bit concerned about tour floor joist dimensions, they seem very undersized, have you put these in yourself!?

[david campbell]

Before I go off half-cocked I wanted to check a few things before starting to tile my small bathroom.

Here is the basic overview of the job.

1. Floor is 4x2 inch timber joist floor. I have added boat loads of bracing and extra dwarf walls and grip-filled all bracing joints.

2. I have laid 18mm WBP over joist floor and glued and screwed this down with total screw overkill.

3. I plan to use BAL fastflex one part or two-part adhesive. Is this the correct adhesive for porcelain tiles 300mm x 300mm size. Make is Niro Granite.

4. What preparation do I need to do on the WBP plywood? Maybe this info is provided by BAL with the Fastflex?

5. I assume the fastflex is applied with a defined notched trowel?

6. How 'FLAT' does the surface of the plywood need to be?

7. How do I ensure the tiles I lay end up with even spacing and are all the same height relative to each other.

Aplogies for lame questions up front. I am a tiling FNG if it was not already apparent !

Steve

i generally add a coat of primer before tiling onto ply,i know some adhesives so theres no need but you cant go wrong,bal rapidflex should be enough,and how flat your ply is depends on the depth of your trowel,ie if the floor is realy flat i will use a 6mm trowel if not then its a 10mm

[STEVEROG]

Regarding my joist sizes.

They are definately 4x2 inch size joists. They are from original build in 1930's. Note that the bathroom is an en-suite that is simply the partitioned-off end of a bedroom in my bungalow. The floor area is very small. Its basically a 'T' shape with the top (horizontal) of the 'T' being about 3m long by only 0.75m wide. The joists run across the short 0.75m gap of the room so the span of the joists in this area is only 0.75m. In the vertical part of the 'T' (where the door opens into the room) the vertical length of the 'T' is about 1.5m so the joists are a bit longer at about 1.5m. However there is a dwarf wall at the 0.75m point so again the max span is 0.75m. I guess that the 4x2 inch joists are definately not up to regs or up to the job for spans say over a couple of metres but hopefully they should be ok for my tiny spans? However, now this has been pointed out I think it may be worthwhile to sister up each joist with another 4x2. What do you think?

Steve

Steve

[Alan.P]

I think it may be worthwhile to sister up each joist with another 4x2. What do you think?

Steve

Steve

Before you go to all the trouble of ripping up your work, a far easier question first. Is there ANY movement in the floor when you walk on it ? Is the floor both level and flat ?

[lucius]

Hi Steve your joists are good enough at .750mm the rule of thumb in old money is half the span plus two so even if you called .750 three feet that would be one and a half feet plus two equals three and a half inches depth of joist so four inches is more than enough but just jump up and down on it and make your own mind up.
Andy

[STEVEROG]

Lucius & Alan,

Thanks for your suggestions and input. The floor seems to be pretty damn solid to me. However, It wont be too much hassle to add a bit more timber as the plywood is not down yet.

Steve

[365drills]

Get it "as flat as you can get it"

But remember as you apply the adhesive you can move the tiles within the thickness of the ridges to get the perfect flat floor.

This is done by applying the adhesive like this:



300x300 are not that big. With large format tiles its critical to get the levels right.

[STEVEROG]

Thanks for the tip on adjusting the heights.

Steve

[cornish_crofter]

Steve may not need to do this but often with ground floor suspended floors you have the option of putting in more sleeper walls.

By that I mean blockwork to support the joists mid span. I would consider this over and above adding more timber.

Just thought it was worth a mention

[beanz]

Did you prime the back and sides of the Ply? It's usually recommended to stop moisture getting into the Ply from behind.
You can either space the tiles by eye, or use spacers. What size grout lines are you going for?

[STEVEROG]

"Cornish - Crofter" ...... Yes, your bang on the money with the sleeper walls. Some monkey had actually removed a couple of these so I have re-built these plus the requisite DPC. This has made a big difference.

I have also added a lot of noggins which are screwed and glued.

"Beanz"............. I have not yet fixed the ply down. I will be coating the edges and the back of the ply with either BAL APD or BAL bond SBR as recommended in another post.

Thanks Gents.

Steve