Laying porcelain tiles externally

[Adsibob]

I’m considering some large format porcelain tiles to lay externally. We have a cement slab outside, but it needs to be built up by about 90mm before we lay the porcelain tiles. What build up should I use:

flow screed?

sand and cement screed?

something else?

ditra matting?

 

Do I need to make sure the build up is dry/cured before the porcelain goes down or does it not matter for external purposes?

 

[Mr Punter]

90mm is a fair amount.  Concrete may be best.  Yes, it needs to cure / dry before tiling.  Another option is the pedestals but they may be more problematic / expensive.

[Adsibob]

29 minutes ago, Mr Punter said:

90mm is a fair amount.  Concrete may be best.  Yes, it needs to cure / dry before tiling.  Another option is the pedestals but they may be more problematic / expensive.

If I pour concrete, how long will that take to cure? It will take a few days to lay 30m2 of porcelain, even using the large format tiles we are using, it will be about 30 tiles. Do I need to wait for a dry spell, or does it matter if it rains in between days? I’m wondering how  anybody lays a patio in this country…

[Russdl]

1 hour ago, Mr Punter said:

Another option is the pedestals but they may be more problematic / expensive.

Pedestals would definitely do

it, and on a concrete slab I wouldn’t have thought it would

be too problematic. I’ve used pedestals on a compacted base of type 1 and a bit of

sand to level than as we didn’t have the articulated pedestals.
 

Whilst it’s taken me an age, problems haven’t been too many.

 

They’re not cheap, but not massively expensive either, however if you change your mind about any aspect of your patio (which we have) it’s really easy to start over, for example we decided to remove two tiles and put plants there instead, we dug out the type one to make a hole, lined it with some leftover geo textile membrane and planted away. Really easy to do with pedestals and equally easy to reverse.

 

(It’s still a work in progress, but the olive tree has been pruned!) 

 

[Mr Punter]

It doesn't matter if the concrete has completely dried.

 

Your tiler may even be up for laying the tiles into a thick bed of sand / cement and forgoing the concrete.

[Adsibob]

1 hour ago, Mr Punter said:

It doesn't matter if the concrete has completely dried.

 

Your tiler may even be up for laying the tiles into a thick bed of sand / cement and forgoing the concrete.

So whatever build up I go for could be poured one day and then tiled over the next, regardless of whether it is more concrete or sand and cement screed?

[markc]

2 minutes ago, Adsibob said:

So whatever build up I go for could be poured one day and then tiled over the next, regardless of whether it is more concrete or sand and cement screed?

Yes, externally this is fine - always plenty of air circulation to take the moisture away

[Adam2]

pedestals - need to watch tile size and thickness. Largest I could see were 600x600 x 20 thick to use on pedestals - @Russdl your look bigger which is nice:-)

 

concrete base - we found the void filler (Cemex but I guess they all do it) was good to work with in filling err voids but has a C20 rating I think so plenty for paving and was quite cost effective if you don't need a pump to get it where you need it. Think maybe of drainage under the raised deck if using concrete - maybe a few holes or do it to a slight fall?

[Pocster]

I need to do this also and was initially going down the pedestal and tile route . Thickness of tiles required and lots of cuts make it a pita for me . Decided instead on pedestals with engineered decking .

[Dan F]

We have 14mm 1200x600mm porcelain tiles that we want to lay externally.  (Technically 20mm is advised externally, but given this is for the rear gaden where there will only be light traffic shouldn't be an issue with 14mm from a strength perspective)

 

Have been getting some quotes in, but getting very different opinions on how best to lay it:

1) 125mm Concrete slab + sand/cement bed.

2) 150mm Concrete slab + tile adhesive

3) 50mm screed with some kind of mesh

4) Sand+cement

5) Fuga-Pave

 

Not considered the pedestal, but might not be ideal only support large 14mm tiles on corners.

 

Given tiles are 14mm and not 20mm some contractors want to avoid basic sand+cement approach, but 150mm concrete slab just seems overkill to me.  @Adsibob What approach did you use in the end?  Or what have others done?

 

Edited June 10, 2022 by Dan F

[Adsibob]

We already had a concrete slab already, but needed to make up an additional 75mm or so in height, so we just did a sand and cement screed, with a aluminium profile in the middle to create a fall line from. The sand and cement screed went down about 4 weeks ago, and we will be laying the tiles in a week or so. It’s probably will not have  fully cured by then, but I think @nod and others have said that for outdoors, it didn’t matter so much if the substrate is not fully dry.

20 hours ago, Dan F said:

Technically 20mm is advised externally

Where is this from? We’ve gone with 1500 x 750 x 9.5mm tiles made by marrazzi which are “frost proof” and anti slip, so I had understood they were fine for an outdoor patio.

[Adsibob]

On 06/04/2022 at 12:10, markc said:

Yes, externally this is fine - always plenty of air circulation to take the moisture away

But what about cracking in the sand and cement screed. Ours was poured about 3.5 weeks ago and the main contractor wants to commence tiling in a couple of days. If the screed cracks in a month or two’s time (as our internal sand and cement screed did on month 5) then will we have cracks in the porcelain? Internally we had already run the UFH for quite while whereas externally we obviously don’t have that, although London temperatures have fluctuated between about 10C and 22C over the last 3.5 weeks or so. I should add that we don’t have space for a decoupling membrane, unless it’s possible to find one that can be laid externally and is only 1mm thick.

Edited June 12, 2022 by Adsibob

[Dan F]

On 11/06/2022 at 15:19, Adsibob said:

Where is this from? We’ve gone with 1500 x 750 x 9.5mm tiles made by marrazzi which are “frost proof” and anti slip, so I had understood they were fine for an outdoor patio.

 

Just that almost all contractors I've spoken to has been unhappy about using anything less than 20mm unless laying directly on concrete with tile adhesive.  Something about:

i) being too fragil to bed down properly on sand/cement based with mallet

ii) while tiles are frost resistent, unless tiles are bedded perfectly, water can get under tiles and there is potential from cracking due to this in freeing conditions.

 

Our are 14mm, not 10mm so tempted to insist on not using any concrete and just have them laid on screed on top of compacted MOT1, but not sure.   Being quoted £200-230/m2+ assuming; sub-base, 125mm reinforced concrete slab, adhesive and grout etc. (excluding tiles).

 

 

[Pocster]

It’s a surprising amount of work to get the frame level with pedestals !

[Pocster]

Yes it’s my paddling pool 

[SiBee]

No expert here but I’ve laid a few patios using various products. I don’t understand why a sand and cement mix would be used on a product that isn’t porous? For a wet bed of sand and cement to bond, the product needs some suction ie be porous, doesn’t it? Maybe okay for a short time.

I used thin granite pavers on my patio but to aid adhesion the back of the pavers received a coating of SBR/cement slurry mix before bedding them down. This I was the instruction from the specialist supplier we used.

Some areas I switched to a tile addy just for the experience. All laid on a dry concrete base five years ago with no hollows or loose pavers.