External concrete slab for 20mm porcelaine - TilersForums.com

[Deleted member 51481]

Hello All,
After a few months respite I'm back. Some of you may recall my pre-Christmas dilemma with laying 30+sqm porcelain on what I thought was a unlevel slab. Well I heeded everyone's advice and got a professional tiler in who did a superb job and it turned out the floor was only 5mm lower in one section so saved myself a few quid by not having to get the screeders in. I (my tiler) even managed to get the thresholds bang on so am a very happy customer.

Fast forward five months and now I'm going external with the same tiles but 20mm instead of 10mm.

The coffers are dry so am planning to do everything myself this time round as the weather is good, no tight deadlines like before and is its external it doesn't have to be 100% perfect.

I've read and been advised by my tiler that the recommended method is to lay porcelain on a concrete slab which I'm preparing currently - which is 40 sqm - sqm on the front of a building and 20 sqm on the left so there is a right angle corner.

I've created a fall on the shuttering by using a long spirit level and made sure the bubble sits proud on the little line in the bubble window – sorry but I am a lay man – I hope this is enough fall!

My question is am I doing this right because what I’m worried about is when I pour the concrete it will sink to the lowest point.

Also due to access issues am I going to mix the concrete with an oversized mixer and wheel barrow it into place. In my simple mind I will do it in sections too, am I mad to do it this like this?

Attached are pics.

Thanks.

 

[Time's Ran Out]

You’d be better off getting a ready mix pour and doing it in 1section on the side and 2 sections on the back - that way you will only have 2 expansion joints and if you work it out correctly get them in line with a tile joint.

 

[Ck1]

Thanks for the advice but what I'm worried about is achieving a fall with the actual concrete rather than doing it with tile adhesive. Everywhere I look concrete slab are flat so am wondering if my strategy is going to work or not.

 

[Italy]

if I understand correctly,
do you want to glue the tiles over the concrete?
do you want to lay the concrete with the slopes for laying the tiles?
that procedure is not correct.
first you have to make the concrete with wire mesh armor
and after a layer of sand and cement with the correct slopes,
slope changes depend on the size of the tiles,
but the most correct thing is to take the corner of the house
and make a 45 ° cut

 

[ck1]

Thanks Antonio and yes I do wish to stick the tiles to the concrete. This is what happened internally so why would the procedure be any different externally please?
PLease can you also elaborate more on the 45 degree cut as I can visualise what you mean.

 

[Deleted member 51481]

Thanks Antonio and yes I do wish to stick the tiles to the concrete. This is what happened internally so why would the procedure be any different externally please?
PLease can you also elaborate more on the 45 degree cut as I can visualise what you mean.

 

[Italy]

........

 

[Spare Tool]

External tiling takes much more extremity's of weather than internal, a drainage/uncoupling mat should be incorporated under the tiles, it will cost more initially but will save you from a more than probable failure in a year or two and wasting £2-£3000 pounds worth of tiles in the long run.
Imo would be as well laying the screed level around 10-20mm lower than you need, and sorting out the falls with an external slc and fixing a mat like ditra drain before tiling.. As in Antonios diagram the 45 degree cut away from corners of the building will allow the appropriate falls to turn round the corners...

 

[Concrete guy]

This seems like an awful lot of work to lay some slabs.

Why just not lay them like paving slabs in sand/cement rather than fit them like tiles with mats and all the palaver that comes with it? As long as the back of each slab has a slurry primer they will be fine.

Don't think of this stuff as 20mm thick tiles, think of them as paving slabs and fit them accordingly.

 

[Tony_C]

if you are dead set on it being more tiles you could also consider the outdoor pedestal tiling. If you are DIY'n this then it could save you dealing with adhesive and make drainage a bit easier also. I don't have any experience in this but i'm sure i actually seen some pictures that @antonio done?

Installing Outdoor Slab Tiles Using Adjustable Support Pedestals - Tile Mountain - https://www.tilemountain.co.uk/blog/installing-outdoor-slab-tiles-using-adjustable-support-pedestals/