Prep for 10mm floor tiles on Indoor/Outdoor Concrete Slab

Thanks All!

That definitely clears a few things up on the tiling. All makes sense :)

The tiles are actually hexagonal (of course it couldn't be simple) so no long side as such. I'm aiming to avoid any air pockets if possible though as mentioned above. I'll ensure the initial ridges align with any fall if there is any (although I was thinking to make the floor level).

I was looking at some different types of adhesive. I see a few on screwfix.ie which mention that they are suitable for outdoor use. However, they don't all specifically mention frost-resistance. I would have assumed that the outdoor variants would have taken frost into account….. until I seen the one that specifically mentioned it. Has anyone had any experience with these:

The first one what was recommended to me was UltraTile ProFlex SPES Standard Set Tile Adhesive. However, this doesn't seem to mention frost.

I did see this Mapei Keraquick Wall & Floor Rapid-Set Flexible Tile Adhesive which does specify frost resistance but only has one review.

There is also one very reasonably priced option that has reviews ranging from brilliant to terrible. I'm guessing the results depend on skill level.

Any experience with either for outdoor use?

Also, should I be looking at some kind of uncoupling membrane to help with cracking / frost protection?

It wasn't my choice believe me. For some reason, not matter what the possibilities are, my better half always seems to choose the most complicated version without knowing.

The slab is 6m x 3m so I was planning an expansion joint.

I was planning a standard 5mm joint width. I thought the jointing options on AJ's site, (as well as the rest of his tiling advice), was aimed at 20mm paving tiles. I wanted this to be like an internal floor.

I have seen the separation membrane recommended here.

I have also seen a recommendation for a waterproofing membrane (RedGard) here.

I don't think either or these have taken Irish weather into account but something like the RedGard seems to make sense.

Most other countries seem have it easy when it comes to outdoor living spaces.

Thanks Shoog,

That was an option I was considering but was unfortunately over-ruled :-/

I have it dug out anyway and waiting for the pour. I just need to make sure I have brought the sub-base up to the right starting height to make sure I don't mess up my levels after all this work.

Tiling aside, I'm just wondering which of the following layer arrangements I would be better off aiming for:

Hi Lumen,

This is a glass veranda with each wall fully retractable. The supporting structure is made of a few aliminium posts with everything else being glass. It is neither fully indoor nor fully outdoor. It can be both. See the following pic.

In my case the grass will go right up to the front of the new slab and the paved area on the right is the new tiled patio I put in during the summer. This is the existing level I need to meet.

Apologies but I don't understand what you mean when you say "it can't be the case that you're putting new tiles outdoors".
I have already put new 20mm porcelain tiles on a mortar bed as the fully outdoor section (to the right of the structure in the above pic) of the patio area. I'm simply trying to get the layers (and therefore finished height) correct for the new slab/floor and tiles for the indoor/outdoor section so it meets the existing level of the patio and grass area.

So if, for example, it would be recommended to add a 50mm screed on top of the slab, then I'll have to finish my sub-base layer 50mm lower than I would if a screed is not recommended.

Does that clarify things at all?

Thanks very much for the input Mellor.

I'm not finishing the concrete myself. I have someone who has some experience to give me a hand but not sure whether our expectations are the same on how flat the finished surface should be, especially considering previous comments about differences in drying rates affecting the final flatness.

So would you recommend putting the DPM between the slab and the screed? If FFL is at ground level then would finishing the concrete 40mm below that increase the chances of issues with damp. I realise it is an indoor / outdoor but that may change in future depending on the lifespan of the veranda. Either way I'd like to aim for it to be as dry and warm as possible. I may not be sitting out in it in the subzero winter but there will be some furnishings / decor that I'd like to last.

Thanks Mellor,

That's an interesting point about the DPM. When I removed the existing paving flags and material to clear the way for the slab I could see the existing DPM from the house was buried loose and just crumpled in a bunch at the corner in a way that it was acting as a kind of bowl holding water. One of the guys that was helping me cut it off with a blade in one section about 1m long from the corner exposing the bare blocks behind. I was doubting whether that was the right thing to do but not much I can do about it now. I am left with a flap of DPM coming down under the plinth in that 1m section but there is enough to tuck behind the new slab. The rest is still buried along the wall and not sure how far down it goes (probably not much judging by the section that was cut off).

I'm planning to put another layer of DPM under the slab wrapping the entirety of the bottom and sides. Here's a diagram to try to explain:

Is that flap coming down under the plinth what you were referring to?

For completeness, here's a version with screed and additional DPM to make sure we are on the same page if I end up going that route:

Thanks again for taking the time to help me clarify my thoughts.

Thanks Mellor.

So first, when you say I can bond to the existing flap - would you recommend using something like DPM tape all along the wall that the slab is connected to?

Indeed, that new flap between the grass and the slab is something I was worrying about. I'm still not sure what do do about it wanted to get the slab in first. Initially I was wondering whether I could lap it in under the tiles but I very much doubt I would get this to bond without some kind of glue. Someone suggested some kind of paint on or melt on water proofing that I could potentially use but I have yet to do the research on that.

If you (or anyone) knows of any standard methods that could be used then I'd appreciate any input there.

Hi Greebo,

Fair points. Let's just call it a space attached to back of the house that I have spent a long time saving for and have put considerable effort into in an attempt to try to make it as useful as possible for as much of the year as I can, within reason. I would hope I wouldn't end up with something that feels like a shed. I'm aiming for few more levels up on the cosy-ometer.

To achieve that goal I am trying to do what I can up front to take precautions to minimise negative effects of weather where possible and practical.

This is a temporary structure. Down the line when my situation changes I may wan to turn it into a proper conservatory if possible and keep the floor so I'm trying to plan ahead now with that in mind.

The back door remains as it is. The ACO drain at the edge is a good idea but I wanted to avoid that if possible as I think they can be pretty ugly. The other option I could think of was a slot drain but they are difficult access in the case of blockages. I will absolutely consider installing one of these types of drains if I have no other option but at this stage of the process I am trying to focus on what I can account for before pouring the slab as I can't do anything to it after. I have added a 50mm boarder to the edge of the slab in front of the sliding rail in a very basic attempt to buffer the garden from the sliding door rail. I can try to lap the DPM under that and try to tile over it but then I'm presuming the water will be able to get under the outer tiles.

I'm surely not the first to do this though. Perhaps it is just not something that is done in our climate?..….

Hi all,

Had a heavy week there and wasn't logged in. Just to clarify, I'm not worried about water getting into the existing back door. As Mellor has said, the floor for the new space (veranda) is lower than that of the house. It is level with the garden and existing patio. What I'm worried about is the fact that I'm planning to tile this with standard 10mm floor tiles that are rated for both indoor and outdoor use. The main issue I was warned about was water / damp potentially loosening the bond under the tiles or freezing popping them off.

I'm open to anything I can do during construction of the slab to counteract that. I'm looking to pour in the next 2 weeks. Winter is coming!!!