the type of mix you should use is call a sand topping mix and it should be clumpable(if thats a word) in your hand as far a consistancy goes.I just built one a few months ago so I may be able to help with any questions you have
Not sure if cement type is as important as to type floor it lays over. Is it a cement slab, or a wooden floor? If a cement, there is less chance of movement and the type you use is less important. If over a wood floor, which is prone to movement, use a fiber-filled cement product or, after laying and roughing in the new cement, press a nylon or steel mesh into the mix to prevent cracks that will open and seperate. Cracks are not critical, but cracks that open and seperate are. That's what you want to prevent.
To minimize cracks, maintain a 2" minimum depth (even at the drain throat) and deeper the further you get from the drain to establish slope for the water to be gravity driven to the drain.
Slope can be established by the new cement alone, or by a wood underlayment, then surfaced over with a consistant 2" depth of cement (use a nail poking as you go to ensure depth is consistant). If no wooden slope, the cement must be deeper as you get further from the drain.
For a wood slope, let's use an example of a 4' x 4' shower. Lay a 2 x 2 around the entire perimeter. Cut 3/4" CDX the size of the shower floor, then cut it from corner to corner with your circular saw (the intersection crosses over the drain location. If the drain is not centered, adjust the cross cuts to intersect over the drain.). Cut the sharp tips off an inch or so from around the drain opening, shim appropriately so the plywood doesn't sag (liquid nail the shims in place), fasten ply to suit (liquid nails to cement, screws to wood, etc., smooth the joints then lay your rubber mat over the top of it with enough excess to climb up under the wall sheathing and now you're ready for the cement. CLASACT was right on when he said to make sure its clumpy. Otherwise it will begin to sag and "fall" toward the drain. Make sure to keep it 2" thick & you'll be good to go!
Thanks to both for the great information. This is a wood (plywood) floor. I have been trying to calculate the quantity of concrete for this task. For a shower with an area of 8.2 square feet, I have calculated approximately 8 cubic yards of concrete which translates to about 7 40# bags. Am I in the ballpark on this?
I would say your pretty close if not a bag over which never hurts.I think I used 12 or 14 bags on mine but its like 14sqft and about 6 inches thick.I had to make it thicker to account for a pipe (thats another story).Make sure you have enough suport under it to account for the weight of the shower water and a person.Get all you slopes correct before you mix the cement (its a pain when it starts to dry) and dont forget your water proof membrian afert it sets.Good luck if you do it right you will love it
I went to the site suggested above. It does refer to the sand topping mix from Home Depot suggested by CLASACT. Did you add sand to this? The site suggests: "There are pre-mixed mortar products that contain only sand and portland, and these can be used to make deck mud. Most of them will have to be thinned down just a bit by adding additional sand, as the cement content of the pre-mixes is too high (about 3:1, usually). One popular product is Sand Topping Mix. You can find Sand Topping Mix at Home Depot. I use it frequently for small jobs like single shower floors. I buy a couple 50-pound sacks of Play Sand, which can be added to the Sand Topping Mix to weaken it and make it more appropriate for shower floors."
We have gotten a good idea about the consistency--"clumpable" is a good term.
We sure appreciate all of this information.
If your worried about it then go ahead and put an additive in.I had made a mesh piece for around my drain so I didnt think I needed any added strength but it cant hurt.I think the most important parts are getting to mix right,gettin the slope right,letting it cure properly and makeing sure when you put your membrain in it has no holes and tucks in the corner neatly and comes up the side I would say about a foot to 18 inches then have the sides over lap it
1st layer of concrete finished. My husband said the consistency was perfect to work with. We did mix in some sand--3/4 of a 50 lb bag of play sand to 2- 60 lb bags of the sand topping mix, with 3 pints of latex additive diluted 50:50 with water. We added more water to get the "clumpable" consistency. We did lay down felt roofing paper first, then some mesh. It looks very good. How long should this layer "cure" before we continue to the next step?
We are going out to buy the Wonderboard today so we are ready for a little break anyway.
if it is only say 2 inches thick it should be pretty well dry in a day press on it to make sure you have no give if you dont feel any its ok to work around it and move on but normally 24-48 hours and your ready
The shower pan is finished! Wonderboard on the walls with the joints thinset/taped. We had purchased premixed thinset with latex added for this portion. We read on the container that this product should not be used where moisture would be a problem--a shower floor? This thinset mix that we purchased with our tile from the Tile store--recommended by the Tile store--is a dry mix but already has the latex added--just add water. Is there something different that we should be using for the floor?
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