A Question for Contractors

[CurlyDave]

I have to confess, I didn't design the deck myself. The general contractor who built it just made it that strong, possibly because he had worked with me for a few months before he built the deck.

The deck certainly seems stable, but I know that doesn't really mean very much.

I think its stability comes from the fact that there is an OSB diaphram under the concrete and tile. It acts just like a shear wall, lying on its side instead of standing upright. This stiffens the deck in the horizontal plane, preventing the outboard edge from moving in a direction parallel to the inboard edge. Cross bracing the posts would certainly be another way to get stiffness in this plane, but I think the OSB is sufficient.

There is a very substantial retaining wall/foundation along the south side of the house, which can be seen in the picture which includes the garage doors. Even though the wall is very tall, it was engineered and then I asked the subcontractor who built it to double the amount of re-bar in it. He balked at that, because it would involve a huge number of pieces, so we compromised. Everywhere the engineer called for #4 bar we used #5, and where he wanted #5, we used #6.

The floor inside the house is at he same level as the deck and again acts as a diaphram stiffening the structure of the house at exactly the attachment plane of the deck.

One of the pictures shows the attachment detail of the header to the retaining wall. There is a heavy steel seat for the beam, secured to the retaining wall by eight 3/4" bolts. I think the weakest part is that the beam itself is only secured to the bracket with two 3/4" bolts through the bracket.

The place where the grout is deteriorating the worst is very near where the beam is attached to the retaining wall, which is the spot I would expect the least movement in the deck.

If anyone can educate me as to why I am wrong, I would love to hear it, because it would solve the problem.

 

[Cap-n-Cray]

Dave,

I am a general contractor and I do all the work myself. I too stand by my work as your contractor is doing. It is nice to hear about a good contractor for a change. You are being very fair to him.

One thought is epoxy grout. I did some research for a client, but we decided not to use it. It is water proof, but expensive. It may cost less than the grout you mentioned. I think expansion may be an issue too. When installing Hardiboard you leave an 1/8 inch gap between boards for expansion.

I have used a material on concrete floors for fracture control that is a peel and stick type of material that cushions the tile. Clients have dropped wine glasses on the tile floors with this material installed without the glass breaking.

Also I use a product called Flexibond which is a flexible ceramic tile adhesive with good results.

Cary

 

[marimus]

We had a deck built in a manner pretty similar to yours on a house a few years back. Similar size too, with tile over plywood.

Before tiling, the entire area (of plywood) was primed and painted with a flexible waterproofing membrane, reinforced with fibreglass matt, which wrapped up the wall about 1 foot, and over the outer edge.

The tiles were then laid onto this waterproofing membrane with a 2-part flexible acrylic tile adhesive especially for use in areas subject to movement. The product we used was called Kemflex from memory, and carried a 25 year guarantee.

The grout was treated/mixed with another product that gave it flexability, i'm not sure what it was called, but you used a regular floor grout and instead of water you mixed it with this which both waterproofed the grout and provided the flex.

10 years on it still looks great, although some of the grout does have fine cracks (none is loose though) and no tiles have come loose.

 

[MarkV]

Boy Dave this just isn't your year for houses. The new house is very nice by the way.

As to the original question I think you are being fair by paying for the materials. It is also good to hear that the tile guy and contractor are working to fix the problem with you. I do kind of wonder if the thin set/grout manufacture who recommended the material that is failing should not be called into the mix.

Here for outdoor wet applications the thin set of choice would be epoxy based. It is the same material used to tile swimming pools and has a proven track record. I have used it and it is not as easy to work with but it sure does hold once it is down.

Someone mentioned the compatibility of the waterproofing agent, Redguard, and the thin set used. That would be something to check out in my opinion. I see Reguard used often and tile is set directly on it but I believe you can't use all types of thin set over it. Worth checking.

Dave check out Sheet Membranes & Shower Installation Products for Tile & Stone They offer tile materials for outdoor applications and have some PFD detail files worth looking at. The tile guys I work with think highly of the Noble products.

MarkV

 

[EddieWalker]

Dave,

Thanks for the explanation. It sounds like you way over built it and have everything covered. I'm out of ideas and now fall into the clueless category. The tile coming loose near the cement wall really destroyed all my theories as I agree with you that is where there would be the very least movement.

Since it sure sounds like nothing is moving on you, then it goes back to the thinset being the issue. There are a variety of brands and types designed for different applications. I can't believe you had two bad batches of it, or that he used the same type the second time that failed the first time, so it all comes back to the test area and trying another type of thinset.

Keep us posted, it's an interesting situating where everything sounds like it was done right, and then some.

Eddie

 

[dmccarty]

The place where the grout is deteriorating the worst is very near where the beam is attached to the retaining wall, which is the spot I would expect the least movement in the deck.

Could water be getting trapped or pooled at that spot and then freezing?

Since we are really running out of ideas..... Could you put a gauge on the deck to measure if it is moving? Since I have no idea how much this would cost is it time to call in a PE with experience in this sort of thing? If the deck is not moving then it seems like a water issue?

Very pretty deck and the view is not bad either.

Later,
Dan