How thick should render be for tiling?

[LankyPaddy]

How thick should a 1:5 render be on bare brick walls to accept 30cmx60cm ceramic wall tiles?

I don't have specific weights but they are these: http://www.toppstiles.co.uk/tprod2790/section269/Glossy-White-Flat-Wall-Tile-30X60.html

I need to render the walls as they are external cavity brick, and I've been told insulating/dry lining external walls is bad due to dew points.

Any advice hints/tips welcome.

Thanks

 

[Richard C]

A typical render base of 10-12mm will give a tile + addy weight of around 40kg/sqm tile weight but that really does depend on how well the render is applied & actually stuck to the brick/block work.

I can’t imagine your “Topps” tiles will exceed that but you have asked other questions which I cant answer now as I'm off for me dinner!

 

[Richard C]

I've been told insulating/dry lining external walls is bad due to dew points

Not really much to add from may last post but that’s brollocks unless you have a solid external brick walls. Dot & dab on external solid walls can be a real problem but dry lining done correctly is what’s normal to upgrade insulation to current standards. On cavity walls, it’s definitely not a problem &, much to my dismay, the majority of new housing estates are now built using dry lining, mostly dot & dab. You only need to consider what is best for you; traditional finish is always best IMO but if you want to save a few quid then you can still dry line, no problem but if you want to hang tiles of any signifiant weight use tile backer board rather than plaster board.

 

[LankyPaddy]

Thanks for the information Richard. It's good to know D&D is an option for us.

Because the room is quite small I think batons + foil backed insulation + hardiboard would be too thick.

However using Hardiboard + D&D with some through fixings to the brickwork might be thin enough, would we need a membrane of some sort behind the board?

Final option was rendering, I was going to rake a few mm of mortar out the joints and really work the render into the wall. I am slightly worried about it holding, hence the raking!

 

[jrplastering]

rakeing out the joints will help with the render but if you are still worried then hardi boards dot and dab and nice strong through fixings will be good should be nice and quick process for you too as you dnt have to wait hardly any time compared to render with regards to tileing on top.
you wnt need a membrane if you dab hardi on the walls.
im sure richard will be along with more info for ya if you need it hes the muts at knowing these fine details.

 

[Richard C]

If your fully tiling I’d go with a tile backer board, as JRP said your going to have to wait up to 4 weeks for render to dry before tiling. Any of the proprietary boards will support your tile weight but if you want to use plasterboard in the dry areas (MR only), you need to check the tile weight; raw plasterboard will take 32 kg/sqm but a skim (not necessary if tiling) will reduce that to 20 kg/sqm, including addy & grout.

 

[LankyPaddy]

For both speed and hassle reasons I think backerboard throughout is the way to go.

Would there be any issues with putting a layer of Soundcoat Plus under the boarding (both in the bathroom and elsewhere in the house on the D&D'd external walls). Just thinking that anything to reduce noise/heat/drafts through the bricks would be beneficial.

Thanks again for your both your help

 

[Richard C]

Personally never used it; had a quick look at the spec sheets but couldn’t find anything on drying times before you can D&D onto it. If drying time is not an issue & you’re fixing through into the blocks, I suppose it won’t do any harm but exactly how much improvement it will give on a cavity wall with backer board for all the extra work/expense involved, I’m a little sceptical.

 

[LankyPaddy]

Not an official spec sheet but I found this:
http://www.british-gypsum.com/pdf/HOMESPEC05_5_External_walls_02.pdf
Page 95 - "Gyproc plasterboard should be fixed using Gyproc Dri-Wall
Adhesive after Gyproc Soundcoat Plus has set – allow 120
minutes minimum setting time."

Any improvement would probably be minimal, but the psychological factor plays heavily

 

[plstering]

id render it 4:1 with a dash of water proofer 10mm min
or use hardwall
use plaster gage bead set it up in bays rule off as you goo

 

[Richard C]

id render it 4:1 with a dash of water proofer 10mm min

That was my initial thinking but if the OP renders, he’s going to have to wait for it to dry before tiling; with a base coat that could take up to 4 weeks. Backer boards are the quickest & easiest route in this case, particularly for floor to ceiling tiling & they will accept up to around 50kg/sqm, depending on make.

or use hardwall use plaster gage bead set it up in bays rule off as you goo

The OP has rather large format tiles which are going to be way in excess of the maximum acceptable tile weight 20kg/sqm for plaster. Additionally, “Hardwall” or any of the other base plasters are not suitable for tiling onto, BG say “Tough Coat” is the only acceptable base plaster for a tile base

 

[jrplastering]

ive use soundcoat loads of times but i cnt really see the benifit in doin it on the external walls as you have a cavity but you can do it on the internal walls if thier brick or block to help reduce sound, personally i love the stuff really easy to use and pefect for a diyer to have a go at reduceing sound levels.
if you want to dab soundcheck over the top of it you can and you dnt have to worry too much bout how the soundcoat looks either.
but in your bathroom if you want to try it on the internal walls you can but you will need even longer fixings then for your backer boards that your dabbing over the top just a thought.

 

[Richard C]

Reasonably quick then & JRP seems to like it but I would echo his thoughts regarding dubious benefit on cavity walls; your link just throws me the message “the file is damaged & could not be repaired”

 

[LankyPaddy]

Don't know why that link errors, works ok here - just imagine a shiny British Gypsum brochure!

Maybe I'll leave the external cavity walls and just Soundcoat the internal brick one. I'll loose 6mm, but it'll be a bonus to reduce the apparent noise of peoples morning ablutions...

Not having to wait 3-4 weeks for render to dry is really valuable time at the moment, also the "guaranteed" weight loading of backerboard vs my dodgy render is much appreciated.

 

[jrplastering]

good luck mate