Tiling on various surfaces - priming help/advice please

[DRon]

Here I go.

Completely stripped out bathroom and have just bought these tiles:

http://www.homebase.co.uk/webapp/wc...ay?langId=110&storeId=10151&partNumber=087711

(Porcelain, 30x60, 4kg per tile, 10mm thick)

1 wall is stripped back to the cement render
- I'm guessing I can just tile straight onto this? I just need to know if I need to prime it?

2 walls are patchy painted plaster/cement render
- patches of plaster have fallen off, remaining plaster is solid so I will scratch off paint, fill the patches and tile straight on top. Do I need to prime?
- these are the walls which will have the shower/bath on.

1 wall is painted plasterboard
-not 100% sure what to do here. I've heard both arguments for / against pva on plasterboard?

Be really appreciated to get some advice

Thanks alot
[/b]

 

[Richard C]

Completely stripped out bathroom and have just bought these tiles:
http://www.homebase.co.uk/webapp/wc...ay?langId=110&storeId=10151&partNumber=087711
(Porcelain, 30x60, 4kg per tile, 10mm thick)

Big tiles, what is the weight/sqm? They may be too heavy for plaster.

1 wall is stripped back to the cement render
- I'm guessing I can just tile straight onto this? I just need to know if I need to prime it?

As long as the render is sound yes; you should be OK with the weight on render. You need to use cement powder adhesive not tub ready mix; primer not normally required as it can affect adhesion but if dusty use an acrylic primer NOT PVA.

2 walls are patchy painted plaster/cement render
- patches of plaster have fallen off, remaining plaster is solid so I will scratch off paint, fill the patches and tile straight on top. Do I need to prime?
- these are the walls which will have the shower/bath on.

Again cement based adhesive but plaster has a 20 kg/sqm weight limit (including 4 kg/sqm for addy & grout) so if your tiles weigh more than around 18 kg/sqm (I’ve allowed a 10% safety factor) your over the top for plaster & they could pull the skim off. Using cement addy on gypsum plaster or plasterboard you need to use an acrylic primer to avoid a reaction between the gypsum & cement in the addy. That’s assuming your tiles are within weight limit.

1 wall is painted plasterboard
-not 100% sure what to do here. I've heard both arguments for / against pva on plasterboard?

What sort of paint is it? Don’t plaster it, unplastered plaster board will take 32 kg/sqm so you should be OK with the weight but check. Same as above, prime with acrylic primer never use standard PVA on a tile base as a primer, it’s water soluble & if it ever gets wet your tiles will fall off; whoever advised you to use PVA to prime a tile base is an idiot.

Use only quality trade tiling products of the correct type for your tile base & tiles; own brand & DIY products are mostly crap. Read the tiling sticky & forum archive posts, it may prevent you making disastrous & potentially expensive mistakes – like using standard PVA as a tile primer!

 

[Richard C]

Sorry just spotted the tile weight; I make that 22.2 kg/sqm + 4 for the addy/grout. That’s a total of over 26 kg/sqm & well over the top for plaster.

 

[DRon]

1 wall is stripped back to the cement render
- Ok, straight forward application

2 walls are patchy painted plaster/cement render
- so as 26kg/psm is over the limit I will need to remove the plaster

1 wall is painted plasterboard
-not sure what paint it is, I'll make sure to prime it.


Do powder and ready mixed addy set at the same time as I'm not the fastest tiler so wanted to use ready mixed if possible? Might be easiest if I just mix up a small amount of addy and top it up/mix up more as I use it!

One more question, does ply need priming for the same type of tiles as above? Doing the floor aswell!

Thanks alot Richard

 

[Richard C]

2 walls are patchy painted plaster/cement render
- so as 26kg/psm is over the limit I will need to remove the plaster

Problem with that is it will most likely leave you with a very uneven surface (what's the other one like?) & with tiles that size you need to get the tile base as flat as possible or it will be very difficult for you to avoid excessive lippage & get them looking good. It will probably be easier & quicker to overboard what you have with tile backer board mechanically fixed. If you can’t suffer loosing the 12mm, another option would be to remove the lot & then fix tile backer board directly to the block/brick.

1 wall is painted plasterboard
-not sure what paint it is, I'll make sure to prime it.

Before you go priming it & sticking tiles on it, let me know what type of paint it is?

Do powder and ready mixed addy set at the same time as I'm not the fastest tiler so wanted to use ready mixed if possible?

No you can’t use ready mix; it relies on evaporative cure & will take an absolute age to set behind large tiles or may never set at all & your tiles will fall off. Cement based adhesive is chemical cure.

Might be easiest if I just mix up a small amount of addy and top it up/mix up more as I use it!

You will need flexible adhesive/grout over boards but standard is OK for render. Depending on how much of each you need, it may be more cost effective to use Flexy all over. A Rapidest/Rapidset flexible will go off in 45 mins so only mix up what you can use in 30 mins, leaving time to wash down your bucket & tools before mixing the next batch (you must do this or the new mix will go off even quicker. Mixing in batches, the time factor should not be a problem but if you’re unhappy with it, you can get cement powder adhesive with a much longer pot life. Lay on a solid adhesive bed only (deep, round notch trowel). What adhesive/grout were you thinking of using?

One more question, does ply need priming for the same type of tiles as above? Doing the floor as well!

Generally no but tiling over a suspended floor needs particular care & consideration in preparation, too much flex & it will fail within just a few months. What ply have you used? How thick is it? Have you over boarded or replaced an existing floor? How did you fix? Did you acrylic seal the back & edges of the ply before you laid it?

 

[DRon]

2 walls are patchy painted plaster/cement render

It will probably be easier & quicker to overboard what you have with tile backer board mechanically fixed.

- I will take off plaster, if surface is too uneven then use cement aquapanel. Just read a post from a while back to use drywall to stick aquapanel to wall and then screw it to wall.

1 wall is painted plasterboard
Before you go priming it & sticking tiles on it, let me know what type of paint it is?
- really not sure, looks just like standard paint!?

you can get cement powder adhesive with a much longer pot life.

- which is a good one to get?


Does ply need priming for the same type of tiles as above? Doing the floor as well!
- I was simply going to screw WBP 12mm ply to floorboards this weekend, sounds like it needs priming all over before fixing? Just going to use flexible addy and a dark grout!


This tiling business is a pain, thought I would just pull off old tiles and stick up new ones

 

[Richard C]

I will take off plaster, if surface is too uneven then use cement aquapanel. Just read a post from a while back to use drywall to stick aquapanel to wall and then screw it to wall.

Was it one of mine? I usually say exactly how to do it.

- really not sure, looks just like standard paint!?

Does it look like just matt emulsion? If you throw water at it does it soak in or run off ? Quiet important with that size tile; might need extra prep especially with silk emulsion or oil based paint. Do a tape test; stick some 50mm masking tape on the wall & pull it off briskly, if the paint comes off with the tape, you've a problem as you can't hang tiles off that; think about it If the masking tape works try the same with Gaffa tape, if the paint still stays put it should be OK, if not

you can get cement powder adhesive with a much longer pot life.

Which is a good one to get?

Personally I always use BAL Rapidset Flexible; Single part flexible or Wall & Professional will give you 5 hours but I’m not sure how well it grabs & holds large format tiles on walls & you have to wait a min 16 hours to grout.

I was simply going to screw WBP 12mm ply to floorboards this weekend, sounds like it needs priming all over before fixing? Just going to use flexible addy and a dark grout!

Personally I prefer to replace with 18-25mm WBP, exact thickness I use depends on size/pitch/span of joists. Fix the ply through into the joists (check for pipes/cables) every 150mm (check for pipes/cables) not just into the top of the original floor boards & make sure they are well fixed down. Just prime the underside & edges NOT the tile surface. Use a quality addy such as BAL Single Part Flexible or Rapidset Flexible if you can stand the 45 minute pot life; Microflex grout. I notice your tiles are porcelain; some porcs need sealing to avoid staining by addy/grout but it doesn’t say on the web site, does it say on the pack? If not do a water test; blob of water wait & see if it soaks in.

This tiling business is a pain, thought I would just pull off old tiles and stick up new ones

It was never quiet as simple as that but wasn’t too much of a problem when 6 x 6 tiles were considered large but now everyone wants to stick paving slabs on their walls; you have to get it right or you’ll have problems. It’s not rocket science, you just need to understand the materials you’re using, their suitability & their limitations under certain circumstances.

 

[DRon]

Was it one of mine? I usually say exactly how to do it.

It was one of yours. Full explanation was there, use drywall to stick aquapanel to wall and use long fixings to screw aquapanel to wall - I'm hoping I don't need to do this though!

Does it look like just matt emulsion? If you throw water at it does it soak in or run off ? Quiet important with that size tile; might need extra prep especially with silk emulsion or oil based paint. Do a tape test; stick some 50mm masking tape on the wall & pull it off briskly, if the paint comes off with the tape, you've a problem as you can't hang tiles off that; think about it If the masking tape works try the same with Gaffa tape, if the paint still stays put it should be OK, if not

I will try this tonight and let you know - makes sense!!! Worse case, what will I need to do if paint does come off?

Personally I always use BAL Rapidset Flexible; Single part flexible or Wall & Professional will give you 5 hours but I’m not sure how well it grabs & holds large format tiles on walls & you have to wait a min 16 hours to grout.

16hours wont be a problem!

I notice your tiles are porcelain; some porcs need sealing to avoid staining by addy/grout but it doesn’t say on the web site, does it say on the pack? If not do a water test; blob of water wait & see if it soaks in.

I will check, thanks for the heads up! What would you seal them with?


When would you use ready mixed addy then? Sounds like it isn't suitable for many jobs? I thought for the floor tiles it would be ok?

As for tiling on top of under coat plaster, does this have the same limitations as skim? (20kg/psm & use acrylic primer with cement addy )

 

[Richard C]

Worse case, what will I need to do if paint does come off?

You could tile over it with the best adhesive money can buy but the tile bond strength (support) will only be as good as the paint has to the wall Given you’re already in trouble with tile weight, the easiest solution would be to replace it with 12mm tile backer board, kills two birds etc.

I will check, thanks for the heads up! What would you seal them with?

http://www.bal-adhesives.co.uk/products/protective-sealer
Or Lithofin make some good sealers.

When would you use ready mixed addy then? Sounds like it isn't suitable for many jobs? I thought for the floor tiles it would be ok?

On the contrary, there is nothing wrong with a good tub mix. I use BAL White Star a lot & it’s very good stuff, it’s just not suitable for large format or heavy tiles. BAL say up to 300 a 300mm is OK & I’ve done 300 x 200mm with it but I usually consider switching to powder on anything larger & generally above 250 x 250mm; again it’s all about knowing the suitability & limitations of the products you’re using.

As for tiling on top of under coat plaster, does this have the same limitations as skim? (20kg/psm & use acrylic primer with cement addy )

More bad news I’m afraid, base plasters (as opposed to render) are not a suitable tiling base at all; Plaster manufacturer & Tile Association say no!

 

[DRon]

You could tile over it with the best adhesive money can buy but the tile bond strength (support) will only be as good as the paint has to the wall Given you’re already in trouble with tile weight, the easiest solution would be to replace it with 12mm tile backer board, kills two birds etc.

What would happen if I scratched the surface to create a key for tile to bond to? It isn't a water exposed wall.

More bad news I’m afraid, base plasters (as opposed to render) are not a suitable tiling base at all; Plaster manufacturer & Tile Association say no!

ok no problem, was just thinking of ways to make the wall good once I take the plaster off to avoid putting up aquapanels! (what sort of fixings would you use to fix aqua panel to wall?)
Sorry for all the questions, really appreciate your help/quick reply Rich!

I just read that others have used adhesives to make a rendered wall good, (to fill gaps etc) would this be an idea if the wall isn't in too bad a shape? Suppose it wouldn't need priming either. (what about Bal quick set render?)

Think I'm nearly there!

 

[Richard C]

What would happen if I scratched the surface to create a key for tile to bond to? It isn't a water exposed wall.

Wet area or not, won’t make any difference; you will still be relying on the bond strength of the paint to the wall to hold the tile in place, scratches in the surface will help a little but not much. Still not sure if this is paint directly onto unplastered PB or paint over skimmed PB; if it’s paint over skim, you still have a fundamental problem that your tiles weigh in at over 26 kg/sqm which is way over the limit for plaster skim. Do you really want to risk it

If it’s a dry area, just replace the PB with new MR PB & tile straight onto that. If it’s a stud wall it’s a doddle to replace if its dot & dab you could ether fix new over the top or rip the old stuff off & fix directly to the wall. If its dot & dab, you will have to provide additional mechanical fixings through into the wall behind (say on a 300 x 400mm grid) When tiling, do not rely on the adhesive fixing alone (particularly with heavy tiles) or it could all end up on the floor.

ok no problem, was just thinking of ways to make the wall good once I take the plaster off to avoid putting up aquapanels! (what sort of fixings would you use to fix aqua panel to wall?)

I use these;
http://www.diy.com/diy/jsp/bq/nav.j...cificationsSpecificProductType=plugs___screws
You must wait for the adhesive to set (overnight) & the fixings must go through the adhesive dabs or you will distort/crack the boards; how to do it should be in my old post.

I just read that others have used adhesives to make a rendered wall good, (to fill gaps etc) would this be an idea if the wall isn't in too bad a shape? Suppose it wouldn't need priming either. (what about Bal quick set render?)

Yes I frequently use powder adhesive to fill/level off or you can use quickset render as well. You need to be confident you can get a nice flat base which you will need if those large tiles are to look good when they are up; the larger the tile, the more critical this is & you will need to use a thick bed solid bed trowel.

 

[onlinetileshop]

Completely stripped out bathroom and have just bought these tiles:
http://www.homebase.co.uk/webapp/wc...ay?langId=110&storeId=10151&partNumber=087711
(Porcelain, 30x60, 4kg per tile, 10mm thick)

Big tiles, what is the weight/sqm? They may be too heavy for plaster.

1 wall is stripped back to the cement render
- I'm guessing I can just tile straight onto this? I just need to know if I need to prime it?

As long as the render is sound yes; you should be OK with the weight on render. You need to use cement powder adhesive not tub ready mix; primer not normally required as it can affect adhesion but if dusty use an acrylic primer NOT PVA.

2 walls are patchy painted plaster/cement render
- patches of plaster have fallen off, remaining plaster is solid so I will scratch off paint, fill the patches and tile straight on top. Do I need to prime?
- these are the walls which will have the shower/bath on.

Again cement based adhesive but plaster has a 20 kg/sqm weight limit (including 4 kg/sqm for addy & grout) so if your tiles weigh more than around 18 kg/sqm (I’ve allowed a 10% safety factor) your over the top for plaster & they could pull the skim off. Using cement addy on gypsum plaster or plasterboard you need to use an acrylic primer to avoid a reaction between the gypsum & cement in the addy. That’s assuming your tiles are within weight limit.

1 wall is painted plasterboard
-not 100% sure what to do here. I've heard both arguments for / against pva on plasterboard?

What sort of paint is it? Don’t plaster it, unplastered plaster board will take 32 kg/sqm so you should be OK with the weight but check. Same as above, prime with acrylic primer never use standard PVA on a tile base as a primer, it’s water soluble & if it ever gets wet your tiles will fall off; whoever advised you to use PVA to prime a tile base is an idiot.

Use only quality trade tiling products of the correct type for your tile base & tiles; own brand & DIY products are mostly crap. Read the tiling sticky & forum archive posts, it may prevent you making disastrous & potentially expensive mistakes – like using standard PVA as a tile primer!

This is probally your best bet, allot of it will come down to weight and how much your walls can take.

 

[DRon]

The plasterboard wall, I ripped down and was left with flat rendered wall - result!

The 2 patchy plastered walls, I took some time to remove the plaster, didn't take too long as it was old and most fell off, so left with 2 flat rendered walls, excellent.

So now Im left with pretty much a blank canvas and should be straight forward (ish) to tile straight onto rendered walls.

1 question I removed a big bit of boxing in the bathroom that has exposed concrete breeze blocks, I need to put render on top of these to bring the wall flush with render already on the majority of the wall. Can I simply use Bal quick set render? )The amount I need to render is about 1 metre wide and then the height of the room.) How long before I can tile onto this?

Thanks again for all your help Richard

 

[Richard C]

If you want to render it out then use quickset render, you can tile over it after 2 hours; if you use conventional sand/cement render, you will have to wait up to 4 weeks. It’s comparatively expensive though & another way of doing it would be to fix/pack out flush tile backer board in to the recess & then fill any gaps with powder adhesive & tape before you tile.

With large tiles it’s important the tile base is nice & flat or the finish could be uneven with excessive lippage which will look terrible.