Spray Deck Blisters Every Year, Any Suggestions?

[QingGuy]

Every year my spray deck (Preferred Deck System) blisters. To my contractor's credit, he comes back and fixes it every year (built pool in 2015). First two years he spot fixed. This last year they sanded my entire decking (roughly 2,200 sq ft), treated it, I think they sealed it and reapplied. It's back again this year, in some areas worse than ever. Has anyone seen anything like this?

The blistering is not confined to a single area. It's all over my deck. The only place it hasn't blistered is on the concrete that was poured with the house. That area has never blistered. I'm starting to think there was something wrong with the batch of concrete I received. Spoke with a plumber who said something about bad sand in concrete could cause it.

Any suggestions? I've included pictures for review?

Thanks in advance for any advice provided.

 

[sktn77a]

Well, if it only does it on the new concrete, then there's the cause. Could be water seeping up through a very porous mix or some other factor relating to the original concrete mix or ground preparation causing the blistering. Pity as it spoils an otherwise beautiful deck.

 

[ajw22]

If this is what you have - Pref Deck - then it is an acrylic coating over concrete. I suspect you have moisture coming up from under the concrete causing a lack of adhesion and the blisters. All the sealing from the top will not stop moisture coming up.

I don’t know how the ground under the concrete was prepared, what drainage you have in the area, or if you have irrigation introducing moisture.

Concrete is porous. I don’t think the concrete itself is the problem. I think it is poor preparation of the base under the concrete. Did the spray deck contractor pour the concrete deck? Or did he spray on existing concrete?

 

[QingGuy]

@ajw22 - Spray deck contractor poured the concrete as well.

What's strange is there is blistering in areas where the concrete was poured over the shotcrete (cantilever). I've circled a few of those areas in the picture below. If it was poor preparation, would it happen over the shotcrete too?

Thanks for your input.

 

[QingGuy]

Spoke with the contractor and he wants to remove a piece of concrete and test efflorescence levels. Also mentioned it could be the soil. 7 of my 9 neighbors have spray deck and I'm the only one with this issue (lucky me) so I'm doubting it's the soil. Also, decking that was poured when house was built in 2008 has never blistered.

 

[splashpad]

Spoke with the contractor and he wants to remove a piece of concrete and test efflorescence levels. Also mentioned it could be the soil. 7 of my 9 neighbors have spray deck and I'm the only one with this issue (lucky me) so I'm doubting it's the soil. Also, decking that was poured when house was built in 2008 has never blistered.

Does it blister in the exact same areas? Or just "random" places of the new concrete?

 

[QingGuy]

Does it blister in the exact same areas? Or just "random" places of the new concrete?

Some areas are the same, three new areas this year. Places that they've repaired in the past seem fine . . . so far.

 

[ajw22]

Spoke with the contractor and he wants to remove a piece of concrete and test efflorescence levels. Also mentioned it could be the soil. 7 of my 9 neighbors have spray deck and I'm the only one with this issue (lucky me) so I'm doubting it's the soil. Also, decking that was poured when house was built in 2008 has never blistered.

Sounds like contractor is also now thinking moisture is coming up through concrete.

Soil under decking that was poured when house was built may have been prepared with better drainage using a layer of crushed stone and gravel then the problem areas. Moisture flows and wicks in strange ways.

 

[jmikeb]

i would agree that it’s a ground moisture problem. that makes me wonder what the source of the moisture is. plumbing leak (house or pool), moisture from a/c units, sprinkler system leak?

 

[QingGuy]

i would agree that it’s a ground moisture problem. that makes me wonder what the source of the moisture is. plumbing leak (house or pool), moisture from a/c units, sprinkler system leak?

Tested pool for leaks and nothing. A couple of the spots where I'm experiencing blistering are not near any plumbing or yard irrigation, or the house for that matter. Very strange.