tile substrate slope - any contradict...

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Author Message Anonymous   Posted on Wednesday, July 09, 2008 - 07:35 am:    ANSI A108.01 standard for tiling says in 2.2 Floor Drains: "...Slope in subfloor shall be specified in sections such as concrete or carpentry and not with the mortar setting bed. Mortar to be of uniform thickness". (2005 – trying to locate current edition to verify) ---HOWEVER--- TCNA says "A mortar bed, up to 2" in thickness, facilitates accurate slopes or planes in the finished tilework on floors..." (2008, pg 7) Which way do your firms or clients typically anticipate this going – for example in the case of a recessed concrete slab for thickset in an area with a floor drain, is the concrete substrate clearly indicated to provide the slope, or do you assume it can be flat to make life easier on the concrete installers and let the mortar make the slope? TCNA does not seem to currently address this except in a couple of tiling methods which specifically require sloping substrate, and the broad cross reference to ANSI A108. Many TCNA methods do not say anything about substrate slope even though they are recommended in the matrix for uses that frequently have floor drains. Some waterproofing membrane mfr literature appears to concur with ANSI more than with TCNA on this issue. Anonymous   Posted on Wednesday, July 09, 2008 - 08:52 am:    That same TCNA reference, later on, refers back to ANSI, so an absolute answer really is not there. Although slopes are "facilitated" it does not say that they should be done, necessarily-- just that they "can" be done. But sloping the substrate does add cost, and needs closer observation [in concrete] to ensure proper and uniform slopes. Nothing's easy! John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 925 Registered: 03-2002 Posted on Wednesday, July 09, 2008 - 09:09 am:    I think that the preparers of those documents are trying to 'scope' work between trades, and so are saying "we don't own slope to drain." However, I have always specified this in the tile section, using appropriate materials from the setting materials manufacturers, and have never had any trouble or push-back. The manufacturers have products for it, and reps have told me it should not be a problem. I prefer this approach because I can't see the concrete crews--having watched them in action--being willing or able to take the care at that point in the project to get the slope correct. After all, there aren't any partitions yet and they're working on wet concrete--layout would not be easy. A depressed slab may or may not be needed depending on the size and configuration of the space, drain locations, etc. I think the main thing is to decide how to approach it and indicate it clearly. George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 437 Registered: 11-2004 Posted on Wednesday, July 09, 2008 - 10:13 am:    Re: "Current Edition" 2008 ANSI A108.01 says the same thing as you quoted in your post. Dale Roberts CSI, CDT Senior Member Username: dale_roberts_csi Post Number: 54 Registered: 10-2005 Posted on Wednesday, July 09, 2008 - 10:21 am:    The 2005 ANSI states the exact same statement for 2.2 Floor drains. So technically it should be placed in the substrate but I have never seen it actually done this way. Insert the requirements in the tile section. This gives control of the substrate to the tile contractor who has to consider the size of the tile or stone they are installing. Also as a manufacture of waterproofing membranes we have no problem with tile contractors doing their own slope to drain. The waterproofing membrane should not be flat! The main concern is that they pre-sloped before they install the waterproofing. You do not want moisture trapped in the corners; you want the moisture to drain to the weep holes. Liquid applied membranes can be installed directly on top of the sloped mortar bed and you can adhere the tile directly to the liquid applied membrane. This keeps the moisture from penetrating the mortar bed. Nathan Woods, CCCA, LEED AP Senior Member Username: nwoods Post Number: 259 Registered: 08-2005 Posted on Wednesday, July 09, 2008 - 11:50 am:    To me, it seems that the approach stated by Dale Roberts accommodates both ANSI and TCNA. The actual mortar setting bed is uniform thickness, and the substrate is sloped by being built up above a flat surface, such as a slab on grade. We just need to make sure there is enough of a depression in the slab or sub-floor to accommodate it. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 798 Registered: 07-2002 Posted on Wednesday, July 09, 2008 - 02:26 pm:    I think the other issue is to make sure that SOMEONE is taking care of the slope and that they know it. You don't want the tile person assuming the substrate is sloped when it isn't or that the substrate can be dead flat when it needs to be sloped. Anonymous   Posted on Thursday, July 10, 2008 - 08:04 am:    What Dale is proposing is probably almost universally used in pratcice but I must disagree with Nathan's one statement, it is not at all like ANSI, which says slope must be in the conc or wood subfloor. If the subfloor is level and the mortar is not, how do you conclude the mortar is uniform thickness? ANSI's issue with this I am told is uneven curing of the mortar. Not sure whether mortar manufacturers acknowledge a problem with that or not - if this is so commonly done that all specifiers and architects I've talked with so far say not to specify the slope in the subfloor, then why does the industry standard say to do it? The other concern I heard from a sub and a rep is about ponding on the WP membrane if it is flat level on the subfloor. One more question- Is it not always possible to install the waterproofing membrane on top of the mortar? If it had to go under the mortar right on top of the subfloor, then I see their point about ponding. TCNA 2008 on page 11 seems to be saying some membranes have to go on bottom and some have to go on top, depending on type, or I guess mfr instructions. Incidentally every TCNA detail appears to show the membrane on bottom. I am having trouble accepting the solution of continuing to allow structural specs to let recessed subfloor be level in spite of ANSI just because it is easier and hoping WP membrane can be used on top to solve one of the two cited problems even though TCNA always shows it on bottom yet they say some types can go on top. Which types?!. What should a specifier do when common sense and trade practice seem to be at odds with industry standards? Expecting only common trade practice but referencing the standard in the spec that now appears above the norm seems to give opportunity for debate on the jobsite between substrate installer/GC and tile installer. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 926 Registered: 03-2002 Posted on Thursday, July 10, 2008 - 11:21 am:    The specifier must require what makes sense for the project. There are many standards that have aspects of them that specifiers do not agree with, and that are focused on issues other than performance of a system. I have not heard that ANSI's concern was uneven curing--it was described to me as 'jurisdictional,' though I don't know for sure. Since the setting materials manufacturers have been telling me for years that it is acceptable to use their products (generally polymer modified mortar) to create a slope, over which I apply a waterproof membrane (by same manufacturer), then I am not too worried about what the ANSI standard may say. They are not concerned about uneven curing. As I reread the A108.01 standard, the key seems to me to be the term "mortar setting bed." What posters have been describing in this thread is, in fact, a separately installed sloped mortar (cured), followed by a thin-set tile installation. I'm not sure there's any conflict at all. See definitions in A108.01 section 3.0. Nathan Woods, CCCA, LEED AP Senior Member Username: nwoods Post Number: 260 Registered: 08-2005 Posted on Thursday, July 10, 2008 - 11:40 am:    Annon, my opinion that it meets ANSI is by providing the following: 1. Flat concrete sub-floor 2. Built-up mortar substrate, sloping towards drain. 3. Waterproofing membrane on top of sloping substrate 4. Uniform thickness mortar bed with tile. Christopher E. Grimm, CSI, CCS, LEED®-AP, MAI, RLA Senior Member Username: tsugaguy Post Number: 147 Registered: 06-2005 Posted on Thursday, July 10, 2008 - 11:53 am:    Anon, I think Nathan is saying there can be two different mortars in this assembly - the first one being the thickset mudbed that does vary in thickness; then waterproofing membrane, then the second one being a thinset mortar that is uniform thickness which is used as the setting bed - therefore eliminating most of the ANSI conflict because it specifically says the slope shall not be with the "mortar setting bed". Dale Roberts CSI, CCPR, CTC Senior Member Username: dale_roberts_csi Post Number: 55 Registered: 10-2005 Posted on Thursday, July 10, 2008 - 03:57 pm:    Anonymous There are several TCNA details showing waterproofing on top i.e. F-122 (for concrete or cured mortar bed substrate), F-101, F102, F-103, F-104, RH-111, RH-112, RH-122, RH-123, F-180, Yes, In a perfect world we would like to see the mortar bed be of a uniform thickness. You will receive the maximum performance from a wire reinforced mortar bed this way. Does sloping the substrate have a negative impact on the substrate compared to the advantage of a uniform thickness mortar bed? You can also have a flat substrate and then have the waterproofing installers installing the pre-slope (think of a traditional hot mop installation in a shower. The hot mopper starts with a flat concrete floor he then pre-sloped the corners, and then installed the hot mop over this pre-slope). The mortar bed is then installed over this pre-sloped waterproofing installation. This is the way you would treat an underlayment that goes under the mortar bed on a flat substrate. In this installation you have to remember to use the proper mortar bed to allow drainage through the mortar bed to the weep holes in the drain. Even then the mortar bed is not going to be of an exact uniform thickness. With the waterproofing on top of a cured mortar bed you do not hold as much water in the system because it drains and dries quicker than if it is in the mortar bed. A small amount of water can create a lot of damage, the closer it is to the top of the assembly the quicker it will evaporate. Regarding ponding, you never want standing water that never drains from a mortar bed, the moisture can cause a lot of damage to the mortar bed and waterproofing. Remember most wet areas (Gang Showers, showers, saunas, commercial kitchens, Restaurants floors that are saturated every night for cleaning) in buildings see more moisture in the southwest region than your roofs every do. Most roofing manufactures have a clause similar to this “the accumulate moisture must be free from the roof surface within 48 hours of a rainfall. Standing water that remains on the surface beyond 48 hours of rainfall poses serious threats to the deck system. This would also be a good clause for your tile or stone assembly. Bob Woodburn, RA CSI CCS CCCA LEED AP Senior Member Username: bwoodburn Post Number: 256 Registered: 01-2005 Posted on Thursday, July 10, 2008 - 04:18 pm:    "You can also have a flat substrate and then have the waterproofing installers installing the pre-slope (think of a traditional hot mop installation in a shower. The hot mopper starts with a flat concrete floor he then pre-sloped the corners, and then installed the hot mop over this pre-slope)" Dale, what does this "pre-slope" involve? What is it? How is it accomplished? Is it cementitious, bituminous, or what?