Rendering for Mosaic Tiles

[shart3]

I was wondering if someone could help me out here.

I have looked around the site at rendering advice, but found nothing specific enough for my application.

I am building a pool/pond outdoors from dense concrete blocks and have rendered with one layer (10mm thick) of 3-1-1 Sand-cement-lime mix. I intend to tile the pool/pond with mosaic tiles.

My question(s) are: Do I need a second layer of render? I will be tiling onto the render with a waterproof adhesive and grouting so is there a need to have a top layer of render? If so, what would the mix be?

Thanks for your Help...

 

[roughcaster]

Hi shart3,
Any advice you are looking for on cement render to line a pool/pond,in permanently wet,submerged conditions,I am unable to give.There may be more to this than just mixing up the mortar.Special admixtures apart from the normal ones??? I don't know.This comment is only on the application of cement render.You say that you have already given the pool/pond one coat of render,and because you are tiling it,does it really need 2 coats? Depends what kind of job you made of the first coat of render? smooth n flat,rough n bumpy.As I have said before,2 coats are always best.To render with two coats, you will have had to scratch the first coat to make the key,if you haven't and you want to put another coat on,you would have to make a key.PVA in permanently wet conditions is of NO use.Even though you are tiling the finished surface with mosaics, it should still be fairly flat and even.I'm sure more advice on the overall project could be had by contacting firms that specialise in this type of work.Sorry I can't offer anymore than that.Anybody else?

Roughcaster.

 

[shart3]

Thanks for your reply...

I have made the first coat pretty flat and smooth. It is flat and smooth enough to tile mosaics onto I believe. I did also scratch the first coat thinking I may have to put a second coat on (and also it wouldn't hurt the tile adhesive).

It was then that got me thinking, you need more than one coat of render to protect against the elements - wind, rain, etc... But seeing as I will be tiling over the top, I thought it is as protected as it will get (having tiles and a waterproof layer between the water and the render. So is there a need for a 2nd coat?

 

[roughcaster]

Hi S'3
Thanks for your update.If you are happy with one coat of render with your tiles,then that's all that matters.As you say,if it's nice and flat and has a good key for your tiles and you use a good waterproof adhesive and grout,then it should be ok.

Roughcaster.