I am looking into a defect of cracking ceramic tiles on an exposed cast concrete deck which is used as a balcony. The deck is exposed beneath and the building is on the coast so exposure to salt water and freezing conditions is high. The initial complaint is of leaks to the area below and then cracking. On further investigation the tiles, when tapped, sound hollow as if laid on dots and dabs. It was the initial theory that the tiles had been laid incorrectly (ie on dabs) but on lifting a tile the adhesive was clearly laid to a full bed. However it was very crumbly and clearly not adhering. The deck was completed in 2008. I have to try to determin if this is a design or workmanship issue but I am mindful that the adhesive may not have performed as expected.
I am aware that last winter the deep frosts have caused a number of tile and slab failures and I wanted to gauge opinion from the forum as to whether this is a significant factor in respect to adhesive breakdown. I would also be grateful of any opinions as to the type of adhesive that should be reasonably specified in such an environment and finally the anticipated movement detail for a balcony 6.5m by 10m

The adhesive was granfix 1 part and the tiles were 10mm ceramic laid over asphalt.
Any observations please?

Hello and welcome, any pics..?

seems like a freeze and thaw issue diect bonding to a slab on a balcony is not recommended even with the mild winters we get in the uk, contact schluter systems technical helpline and they will give you the answers you are looking for

Roofing asphalt?

hi i use granfix products and touch wood have never had any problems ,correct me if i am wrong but
are you saying the tiles are ceramic and if so they should never have been laid whre the weather can
get at them,worth checking whether they are just ceramic tiles first,if so the frost may have blown them and then got through to the adhesive which then may have caused the problem,sounds like wrong tiles to me

Surely the roofing asphalt is to blame here.

hi Tabby just interested to know why you think it might be the asphalt

From what I can make out he has tiled directly to asphalt outside. With that kind of movement, I can't thnk of any adhesive that could cope with that.

Thank you all for your comments so far. If I can clarify some points. The layer below the tiles is the Granfix adhesive and then below this is a two coat asphalt then a concrete screed and then the concrete deck. I must admit I was surprised to hear that the tiles were ceramic but I understand they were chosen as there were external grade. My questions now are:
1. Is it reasonable for a designer to select ceramic tiles be used externally on a pedestrian deck?
2 If the deck is 10m by 6m how where and what form should the expansion take. (I would like some reference to BS 5387 if possible)
3. The adhesive manufacture seems to suggest that the product will disintegrate if it gets wet. Is this a common understanding within the industry? Are there products that dont do this.
Thanks again for your assistance

This is a test to check my last reply was sent as it does not appear to have been displayed.

Sometimes I do a post and forget to do post quick reply, just an age thing LOL

Hi just a couple of thoughts from down here in NZ, we don't have the extreme temps you have in the UK so thats not an area of expertise that I can help with, but I have tiled over asphalt or (torch on) bitumen membranes from time to time. There are very specific adhesives required to do this. So the first thing to do is Identify the membrane and you will find that there will be only one or two adhesives that will carry a warranty when used on the membrane. Often we find they are manufactured by the membrane company. And they are generally damn awful to use. You know the ones, throw away your mixing paddle and trowels after use. Hope this helps

I have some recent news. The manufacturer has confirmed that the adhesive breaks down if it gets wet. I find this confusing given it was advertised as water resistent and suitable for swimming pools. While I find the design is weak I cannot see how the material selection is at fault if the designer relied on the description of the technical leaflet. Part of the problem is that it is the ashpalt that is supposed to be the water proofing not the tiles yet the gullies are in line with the tiles. This means than water cannot filter to the outlets once it is past the tiles. I feel this is one of those OK in theory designs compounded by an OK in theory material. I think the designer should have had more regard for the level of exposure of the viewing gallery (it is exposed underneath) and should have made the drainage consistent with the principle he set up.

Thanks for the update may i ask which adh was used

I am told it was granfix Flexible 1 partGranfix tech info 001.jpgphoto 1.jpg

when you say cast deck can you explain is it poured concrete 1 piece or made up of sections

Its a pre cast plank (made up sections)

So i take it has cracked on the sections or joins.These joins should of been carried through the tile surface (as a movement joint or expansion joint)
The other thing you may want to consider is most pre cast slabs are formed in boxing molds witch are coated in a release agent (to save the boxing) was the slabs cleaned before tiling started

hope this helps