tiling - screw down plywood to floorboards

[DrGonzo]

I plan to tile my kitchen floor.
There is plywood over the floorboards on the main kitchen but not in the utility room.
I plan to put plywood over the boards in the utility room but a mate also suggested screwing in the plywood to the floorboards every 30cm or so over the whole floor to make sure it didn't move.

This worthwhile?
The floor is flat, or at least was so when I used my spirit measure on it, but maybe there are slight deflections over the floor in places...hard to tell

 

[Softus]

I plan to put plywood over the boards in the utility room but a mate also suggested screwing in the plywood to the floorboards every 30cm or so over the whole floor to make sure it didn't move.

This worthwhile?

Very much so, your only alternatives being to glue or to nail, both of which are less preferable.

The floor is flat, or at least was so when I used my spirit measure on it, but maybe there are slight deflections over the floor in places...hard to tell

Depending on what you mean by "slight", you can usually take up imperfections in the layer of tile adhesive.

 

[masona]

I plan to put plywood over the boards in the utility room but a mate also suggested screwing in the plywood to the floorboards every 30cm or so over the whole floor to make sure it didn't move.

That's the way to go, and make sure the plywood is not interior grade plus the screws are the correct lenght

The floor is flat, or at least was so when I used my spirit measure on it, but maybe there are slight deflections over the floor in places...hard to tell

You won't really noticed that much

 

[Softus]

...and make sure the plywood is not interior grade plus the screws are the correct lenght

...and are brass or galvanised.

 

[gcol]

Make sure the ply is 12mm and screw down every 200mm not 300mm.

 

[DrGonzo]

What length and what type screws should I get?
Brass?
and what 15mm into 12mm plywood or more than that ?

 

[gcol]

12mm ply + 18mm floorboards = 25mm screws
12mm ply + 22mm floorboards = 30mm screws

http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=18365&id=63457
http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=18749&id=98953

Forget brass screws - Softus really . They are very weak, require pilot holes drilling and aren't really available with pozi drive heads so you'd have to use a regular screwdriver (not fun when you've got hundreds to put in) or get a bit holder for you drill.

 

[DrGonzo]

Turns out the main room doesn't have plywood down...it is some sort of thin chipboard type stuff so I'm going to have to take that up and put 12mm plywood down.

DOes it matter if I put the plywood down in smaller sections rather than 1 big piece?
I assume I screw this down all over.

Is there anywhere to get plywood online & delivered? I can't get it to fit in the car if it's a sheet from Wickes, B&Q, etc.

 

[gcol]

Turns out the main room doesn't have plywood down...it is some sort of thin chipboard type stuff so I'm going to have to take that up and put 12mm plywood down.

Good.

DOes it matter if I put the plywood down in smaller sections rather than 1 big piece?

No it doesn't, but stagger the joints so that you don't have 4 corners meeting.

I assume I screw this down all over.

Yep, every 200mm.

Is there anywhere to get plywood online & delivered? I can't get it to fit in the car if it's a sheet from Wickes, B&Q, etc.

Call your local builders merchant.

 

[DrGonzo]

Need about 13m2 and the local builders suggested I needed 5 sheets at a total of £110.
Sound about right?

B&Q do sheets (can't remember exact size), but they're about £20.

 

[gcol]

The sheets should be 8' x 4' (or metric equivalent 2440 x 1220). 5 sheets sounds right.

 

[DrGonzo]

Right, in the DIY book I have it says to use 9mm plywood.
Thinking about it, I'm a bit worried that 12mm will be too thick as when you add that plus the thickness of tiles + adhesive, they may come above the level of the carpet in the hallway just before you get into the kitchen.

Will 9mm do the job?

 

[gcol]

I've never heard so many questions from one person. You can use what you like mate but for an extra 3mm, play it safe and use 12mm.
Go on surprise me and ask something else...... I dare you......no, I double dare you.

 

[DrGonzo]

Alright then!
Do I need to use batons running parallel to the walls? Everything I've seen says to place the centre tile and work it out so that you are left with a half tile against the wall. Surely, once you've done this, if you start from the corner of the room there will be a slight margin of error and the centre tile will no longer be exactly centred?

Seriously, I just wanna make sure I get this right as I only have one chance !

 

[gcol]

Ok I've added to the sticky to make it clear that you start from the middle. You did read the sticky didn't you?

Laying out
Find the centre of the floor you are tiling and mark it with a marker pen. Pick up a tile in each hand and working from the centre line, “walk” the tiles (hand over hand) to the edge of the floor. If the last tile is less than half a tile width, go back to the centre line and this time offer the first tile to the centre line so that the centre of the tile is on the line and “walk” the tiles again – you should now have a larger piece of tile at the edges. Generally rooms are not perfectly square so you should measure the centre line at the other end of the room too. Once you’re happy with that centre line for the whole room, you can mark it with some white tape.
Ok so now you have a start point in one direction you need to do the same in the other direction to give you a cross of white tape in the centre of the room. Once you have your start point and a cross of white tape, you can now start fitting the tiles. Starting from the middle of the room, you work outwards and in line with the tape to keep it square (see fixing tiles below).

Fixing Tiles
Tile the room in quarters and make sure you leave the quarter next to the outside door until last. Just put down the full tiles (leave the cut edges until last).

Anything else?