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  1. #1

    Default Total Floor Dead Load Very Important Factor

    It is important for ceramic tile or stone to be installed on a code-conforming wood-framing system. Part of being a code-conforming substrate requires that the floor system to be designed with the appropriate Live Load AS WELL AS the Total Dead Load that includes the weight of the framing system below and the "installation method." Until recently, the weight of installation methods for TCNA Handbook methods had not been published.

    The 2011 TCNA Handbook contains an appendix with the typical weights of the various floor tile installation methods: http://www.tileusa.com/publication_main.htm

    This is an extremely valuable resource for folks interested in specifying and designing floors that will use tile or stone surfaces. Solid-sawn wood-joist floors that were to be covered with carpet etc. have been typically designed for a 10 psf total dead load for many decades. Inspection of the TCNA Handbook will review that total design dead load for tile applications is about 20 psf or more when the weight of the framing system is added to the TCNA Installation Method weights.

    Frank Woeste, Ph.D., P.E.
    Professor Emeritus
    Virginia Tech

  2. #2
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    Default Re: Total Floor Dead Load Very Important Factor

    I have become a bit concerned recently regarding huge stone loads installed in my homes on the 2nd floor over wood joists and floor trusses. We just installed a large solid stone fireplace surround in a room and I had to go back to the engineer to confirm it would support it. Of course I had no idea the weight of the surround.

    In all of our 2nd floor baths and utility rooms, the thickness of the mud base and tile is 1-7/8", so it is not insignificant.

    A few years ago, after a house was framed, the owner changed their 2nd floor material to 4" thick stone imported from France. It affected door heights, we had to raise all headers so the doors would fit, had to re-frame stairs for stone treads. We did have engineer certify that the wood truss system would support the stone.
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  3. #3

    Default Re: Total Floor Dead Load Very Important Factor

    Quote Originally Posted by Allan Edwards View Post
    In all of our 2nd floor baths and utility rooms, the thickness of the mud base and tile is 1-7/8", so it is not insignificant.
    .
    Allan:

    Thanks for your comments. Here is an article that gives some typical weights of some typical tile installations:

    http://dl.dropbox.com/u/26195443/Woo...ec.%202007.pdf

    Go to Table 1 and look at the total weights of tile methods F-141 and F145. Then, go to Table 2 and look at the rightmost column, TOTAL WEIGHT OF FLOOR AND CERAMIC TILE METHOD (psf), for methods F-141 and F145.

    Assuming that a joist system was designed for 10 psf dead load, and subsequently F-141 or F-145 was installed, the dead load would be off by as much as a factor of 3.93 or 2.47, respectively.

    This issue is important for tile installations because "creep" is related to sustained load level. Creep deflection is long-term deflection beyond the initial load deflection. The easiest place to possibly see creep is in a heavily loaded bookcase that is sagging.

    Frank Woeste
    Professor Emeritus
    http://www.cmec.wsu.edu/facultypages/WoesteResume.pdf

  4. #4
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    Default Re: Total Floor Dead Load Very Important Factor

    All good information, but one point that is continually overlooked by most builders, designers, and installers is that in spite of its many benefits, the TCNA Handbook methods are MINIMUM standards - not recommendations or best practices. Any builder or installer working to minimum standards should not be surprised when an installation is stressed, and becomes damaged, or worse, fails completely.

  5. #5
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    Default Re: Total Floor Dead Load Very Important Factor

    So Michael, where would you look for best practices?

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    Default Re: Total Floor Dead Load Very Important Factor

    Quote Originally Posted by charles View Post
    So Michael, where would you look for best practices?

    When in doubt over build

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    Default Re: Total Floor Dead Load Very Important Factor

    Michael does a fairly nice job of describing a few best practices in his latest book Tiling for Contractors. You all have the book - right?

    Don
    I started out with nothing. I still have most of it left.

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    Default Re: Total Floor Dead Load Very Important Factor

    Quote Originally Posted by DonMirabito View Post
    Michael does a fairly nice job of describing a few best practices in his latest book Tiling for Contractors. You all have the book - right?

    Don
    Yeah, but where did he get them? Is he the source? Not that I don't trust him completely.

  9. #9
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    Default Re: Total Floor Dead Load Very Important Factor

    Quote Originally Posted by DonMirabito View Post
    Michael does a fairly nice job of describing a few best practices in his latest book Tiling for Contractors. You all have the book - right?

    Don
    Michael writes books? :D
    Greg

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    Default Re: Total Floor Dead Load Very Important Factor

    Charles,
    The prime source for minimum standards is the ANSI A108.1, known officially as: American National Standard Specifications for the Installation of Ceramic Tile. The standards found in this booklet make their way into the TCNA Handbook. If you are installing tile as a professional, you need to reference both booklets (and if you don't use them, don't consider yourself a knowledgeable pro installer); if you are a DIY installer, you should have the TCNA handbook to guide you.

    One of the reasons I wrote TILING FOR CONTRACTORS is that I have been troubled for years about the tile industry publishing minimum standards: the point below which an installation will fail. As for the methods presented in my new book, they are my own, and have been developed over the 40+ years I have been installing tiles. But it is not rocket science to develop your own "upgrades". Do this by looking at minimums such as underlayment, joist or stud spacing, adhesives, and any other installation materials, and improve on them. Use 3/4-inch plywood instead of 1/2-inch, insist on 16-inch spacing (or less) for studs and floor joists, and use a latex (or polymer) modified thinset mortar instead of dry-set thinset mortar. It goes without saying that EVERY tile installation needs movement joints.

  11. #11
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    Default Re: Total Floor Dead Load Very Important Factor

    Hey Michael,

    Use a polymer modified thinset- except around a firebox, right?

    I enjoyed your latest book, learned a few good tricks. Some questions though.

    Floor tiling over plywood- 3/4 over 3/4 with Titebond 3, why cement board screws? Seems like overkill. It would seem to me that if one is troweling a glue that strong that regular screws- heck probably staples, would be adequate.

    Stone mosaics over floorheat- why no foam at the tub before slu pour? I see the soft joint between the tile and the tub, I didn't think it was ok to lock in the tub with SLU.


    Last question was alluded to above. No modified thinset or grout around a firebox? I don't even know where to find unmodified grout.

  12. #12
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    Default Re: Total Floor Dead Load Very Important Factor

    Matt,
    You are right about using dry-set thinset instead of a latex or polymer. Not so much for bond strength as much as eliminating the possibility of odors coming off the heated thinset.

    Why BB screws? The main reason is that for the standup gun I use, bb screws are no more expensive than other magazine-loaded screws (at least in my area). My experience with drywall screws is that they were designed for use with soft drywall. I have seen numerous double-layer plywood floor installations where drywall screw heads broke off the body of the screw. When this happens, there is nothing to hold the board down. Staples? Staples on plywood (and OSB) floors I have inspected tend to buckle the surface of the plywood enough to require sanding whereas BB screws cut a countersink with a minimum of fuzz sticking up. Since I always follow plywood floors with a membrane - and because I want the membrane as flat as possible - I use screws. The main reason, though, is strength.

    As for overkill, if you have read my new book, you should have noticed in the "How to use this book" section (page vii) that I write about what minimum standards mean: they are the point below which a failure will occur. As I say in seminars and discussions, would you be happy if your kids came home with D+ report cards? Minimum standards are D+. I don't consider using heavy duty screws on a double-layer plywood floor as overkill, but rather as providing the customer with a reasonable level of performance. If you think the plywood floor installation is overkill, you should see how I put together a premium quality floor.

    Like all technical books, mine has omissions. With over three hundred pages and almost 700 graphics, the number of details that went into the book drove one editor mad and one writer crazy. If you have attended any of my seminars, you know I hound people about movement joints. What I should have included with this installation was the reason why I did not put a movement joint against the tub: the height of the SCU was flush with the bottom of the tub. At the sides of the floor, the top of the finished tiles was below the bottom of the paneling. I did place a movement joint at the bathroom's threshold because the tiles abutted a wood plank floor. Another factor is that the stones used on this floor are very soft. It was a judgement call and after at least 8-years of service, there have been no problems where the tiles meet the tub.

    Your is a good point, though, and you caught me with my pants down - I should have known that if there was an omission, you would be the one to find it.

  13. #13
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    Default Re: Total Floor Dead Load Very Important Factor

    I'm not ok with a D+! But I can live with an A-. Your spec is for A+++.

    I thought I read somewhere that staples with glue is ok, I will have to try and find that. I use the same simpson gun you have- took your advice from an old post.

    The problem I seem to face most is fighting transitions. The best way to build a floor always seems too thick. My current job is a mid-century house with 5/8" subfloor. The subfloor is the old form boards for the foundation- no panel is bigger than 2'x4'. Butted tight. Compromised from the concrete? Who knows. Can't pull them, radiant tacked underneath.

    What to do here? I insisted on 5/8" AC underlayment with a paint on membrane. So I'm way thicker than the bamboo floor and have gotten called out by several carpenters at the site for overkill, now I'm looking bad to the homeowner.

  14. #14
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    Default Re: Total Floor Dead Load Very Important Factor

    Matt,
    I think the best approach on installations where height is an issue is to inform the HO that there will be a height issue, if you thin down the underlayment, the installation will fail, and finally,suggest several alternatives to the threshold. I tell customers that I can: (1) Bevel or round over the edge of the tile where it meets the outside flooring; (2) Insert a raised threshold (usually of marble) whose top surface lies above both floors; or (3) Insert a sloped threshold (also usually marble) that smoothly transitions one floor to another.

    As for the carpenters, I suggest that if they knew what they were talking about, they would be installing tile - not wood. It will not do you any good if these guys become negative "salesmen" for your company. Without making it seem like a confrontation or a pissing contest, have a talk with these guys and ask them: where they get their information; if they have TCNA or ANSI A108 Handbooks on which to base their claims; if they would be OK with their kids getting D+. I would also explain the concept of minimum standards as applied to tile, and encourage them to get a TCNA Handbook, so when they are building for tile, they can make informed decisions.

    Are these carpenters independents or employees? If they are employees, I would have a talk with their boss and tell him or her about how criticizing you for doing a reasonable job is bad for both businesses. You might also give the boss a TCNA Handbook, or at least show the boss a copy of yours, or photocopy the appropriate page and let the boss read for himself.

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    Default Re: Total Floor Dead Load Very Important Factor

    MB, why is marble so commonly used for tile thresholds?

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