Replies

1. 
   sapwood | May 21, 2014 11:23am | #1

   The few times I've done a dry pack floor, I've simply mixed all purpose sand with portland cement and a bit of water. Getting my mixture slightly too wet doesn't appreciably weaken it at all. The stuff you used is different, maybe. I don't know what's in the bags you talk about. In any case, since you are worried that you violated the doctrine of the johnbridge group I'd broach the subject with them. They are most helpful there. Two big thumbs up for them. 

1. 
   kvman | May 21, 2014 12:25pm | #2

   Thanks for your reply

   The Quickrete sand topping mix is a pre-mix of portland cement and sand to which I added general purpose sand (the same one referenced in the johnbridge link). My mix ratio is about 5:1 and from what I've been able to gleen from the web the mixture can range anywhere from 3:1 to 7:1.  The johnbridge link also recommends 5:1. The main concern for the strength of the base over time stems from the fact that the base will act as a pan for a 2nd floor washer and dryer - my old washing machine flooded and caused a huge amount of damage to the floors below so I've installed a drain and built a shower base to (hopefully) prevent a similar event from happening in the future.

   Now that the base has had time to dry it is definitely harder but it seems very grainy. Given the amount of sand added to the mix I assume this is normal, correct?

   As a side note, I find this site extremely helpful and it gives a place for us weekend warriors to tap into the wealth of knowledge that people like yourself freely give. Kudos to you and the other members!

1. 
   deadnuts | May 21, 2014 09:28pm | #4

   What kind of strength are you expecting out of it?

   Remember, a sloped mud set layer is not considered a structural element. It's simply acting as a sloping element for drainage. Your "strength" in tems of load bearing capacity and resistance to deflection will come from your floor framing and underlayments. TCA standards should be observed there.

1. 
   kvman | May 22, 2014 12:49pm | #7

   I agree with you - the structual integrity of the base comes from the construction below it. The area was originally built with a washer and dryer in mind so the underlying structure is sound. 

2. 
   sapwood | May 22, 2014 11:11am | #5

   I'm not a tile guy so take all this with a grain of... sand. 

   Normally, the tile does an effective job of spreading the load of your bare feet over sufficient area that high strength isn't really required in the supporting bed of dry pack. And this would be the case for your washer and dryer also except maybe because the washer jiggles a bit when not loaded right... you may need more. I'd still ask at john bridge. Those guys see a lot of tile jobs and unusual applications. But don't be concerned with the graininess of your mud bed, that's normal. The thinset will bond tenaciously to it and then the rough surface is a moot point. 

   Bottom line if it were me... If I was sure I had at least a 1:5 mix, then I'd tile away. 

1. 
   kvman | May 22, 2014 12:28pm | #6

   Thanks for your 2 cents. I found a lengthy thread specifically on this topic (unfortunately I can no longer find it). The conclusion was the same as yours - the degree of sandiness in my case shouldn't be a problem.

2. 
   deadnuts | May 22, 2014 01:26pm | #8

   Which advice are you giving?

   Sapewood-

   With all due respect, you do not seem like a "structural" guy either. First you say it's okay, then...maybe not, then...check with some else. What kind of advice is that? The bottom line is you (or I) have no idea what the OP is doing with tile in his house. First he's talking about a shower floor, then it morphs into a setting bed for a washer and dryer. Who knows what's going on or the specific conditions there. IMO, If you don't really know, then  it's best not to comment on what actually will work...or what won't.

   One thing I do know is that "strength" is that it is a relative term. It can refer to both tensile and compressive capacity...and it can relate to individual building compopents or entire composite building material assemblies. One thing to keep in mind when talking about strength:  tile mud setting beds act predominately in a compressive manner. Any defeincies in  supporting substructure  (such as inadequate floor joist or underlayment structure ) can adversly affect its performance...and telegraph through to the finish tile layer.  

   Another tiling tip: embedding poultry wire in your mud set will do more to counteract stresses due to vibration than any slight variations in your mud base mix.

   Cheers!

2. 
   deadnuts | May 21, 2014 07:42pm | #3

   3:1 ratio of concrete sand (rather than masonry sand) and portland cement.

   Adding some latex additive to the mix is a good idea as well. The dry pack for a floor should be mixed to a consistancy where it will hold form when balled up in your hand, but crumble away when you work your fingers through it.