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        posted
        I plan to build a 20' by 30' deck on the side of my house. The floor of the deck will be 10 feet off the ground. I have been in the planning stage for almost two years. I have two SPECIFIC questions that need SPECIFIC answers, NOT general answers. Forgive me for being blunt, but I have asked these questions on other websites and all I get is a lot of general information, which I already have, and no answers for my SPECIFIC questions.
        Before I ask my questions you need to know that I live near a rock quarry. This means there are occasional blasts from the quarry. The blasts cause my house to shake a little, but in almost eight years of living here the only thing that has happened is three drywall nails have popped loose as a result of blasting. Now for the questions.
        1. Should this deck be attached to the house or free standing?
        2. Because of the size of the planned deck and its distance off the ground I have decided the columns will be 8 X 8's. Should the columns be in post holes filled with concrete, or on top of concrete piers?
        If you need more information before answering my questions, contact me and I will get whatever information you need.
         
        Posts: 12 | Location: Clarksville, TN | Registered: Dec 03, 2008Reply With QuoteReport This Post
        posted Hide Post
        There are several options for deck construction. The best approach would be to build it with code in mind. Here is a site which should answer most of your questions.

        http://www.awc.org/publications/dca/dca6/dca6-09.pdf
         
        Posts: 1756 | Location: Applachain | Registered: Feb 27, 2006Reply With QuoteReport This Post
        posted Hide Post
        The document red pointed you to is very good and is now the reference document for Fairfax County VA, they had the best deck documentation I've found on the internet previously.

        The place to start is your local building department. There you'll find out how deep and wide your footings need to be based on your local conditions. What is good for code here is Cary, NC isn't sufficient in northern VA (Fairfax) due to different frost lines in our soils.

        To do your deck as a free standing deck will require additional Z bracing in both directions. I suspect with a 10' high elevation you'll need poured footings at least a foot down, and 2 foot square, but your local codes office will be the final approver. If your yard is fill you'll need to get down to native soil that doesn't give when the inspector probes it with a piece of rebar with a T-handle. Spacing on the footings and posts will depend on the load, the document Red linked to should cover that.

        6x6 posts should be sufficient. I prefer to bring my footings out of the ground and have the posts mounted on a galvanized post fastener instead of burying the end of the post in ground. Even though the PT wood is rated for ground contact keeping it out of the ground should help it resist rot longer.


        General Disclaimer

        Any advice given here is general in nature and is not necessarily valid for your given area. If in doubt check with your local codes enforcement department for what is required when doing electrical, plumbing or structural work on your house. Permits may or may not be required in your area and home owners may not be able to DIY some tasks. I have no way of knowing if you have the skills needed to complete the tasks you are asking about, when in doubt seek professional assistance.

        My advice may be worth exactly what you pay me for it. :-) For the record I did not stay in a Holiday Inn Express last night.
         
        Posts: 725 | Location: Cary, NC | Registered: Aug 17, 2006Reply With QuoteReport This Post
        posted Hide Post
        The reason your not getting " SPECIFIC answers" is because it's a matter of personal preference, then you have to add the codes that very from place to place.
        If you want my opinion I will give it.
        There is only three reasons why I would build a free standing deck.
        1. In a mobile home park, state park, etc., that dictates free standing.
        2. The customer prefers it to be.
        3. The deck is not near the house.

        The only time I have ever used 8"x 8"s, or pilings, was for commercial property. 6"x 6"s was more then enough for attached three story decks. If your going for a certain look ( curb appeal) by all means do use the 8"x 8"s.
        For decks I always use concrete footings. In my area the footing must be 32" deep and 3x the width/circumference of the column.
         
        Posts: 827 | Registered: Jan 29, 2010Reply With QuoteReport This Post
        posted Hide Post
        The purpose of my original post was to determine the best building methods in relation to my home's nearness to a rock quarry, and its occasional blasts and associated shaking. The use of 8 X 8's WAS recommended by the local codes department due to my proximity to the rock quarry. However, the codes department had no recommendation about my original two questions because no one else living near the quarry has ever applied for a deck permit.
        If anyone else responds, PLEASE consider my nearness to the quarry before you answer. Thank you.
         
        Posts: 12 | Location: Clarksville, TN | Registered: Dec 03, 2008Reply With QuoteReport This Post
        posted Hide Post
        I think to get anything more SPECIFIC you're going to have to actually PAY an ENGINEER for his advice. No one here is going to be able to give you SPECIFIC information.

        The 8x8's seem like overkill but I'm not an engineer, and I don't play one on TV.


        General Disclaimer

        Any advice given here is general in nature and is not necessarily valid for your given area. If in doubt check with your local codes enforcement department for what is required when doing electrical, plumbing or structural work on your house. Permits may or may not be required in your area and home owners may not be able to DIY some tasks. I have no way of knowing if you have the skills needed to complete the tasks you are asking about, when in doubt seek professional assistance.

        My advice may be worth exactly what you pay me for it. :-) For the record I did not stay in a Holiday Inn Express last night.
         
        Posts: 725 | Location: Cary, NC | Registered: Aug 17, 2006Reply With QuoteReport This Post
        Picture of Jaybee
        posted Hide Post
        First off, I'm in agreement with everyone's advice above. Especially the fact that your best source for answers will come from only from an on-site visit. Since your local code department cannot answer your questions and since you obviously have some valid concerns about the structure, it will be worth your while to hire a local engineer to make structural recommendations.

        On the flip side, I will specifically answer as I am a GC licensed in Tennessee and have many years building decks.

        1. Attach it to the house. All structures will move a little - a 10' tall deck more than most. Attach it to the house at several points just to keep the deck and house solid in relation to each other. However, do not use the house as the house-side structure of the deck. Think of it as doing the best of both choices - build the deck so that it is solid and free standing. Anchor it to the house just to keep the two in line.

        2. Piers. Always piers. Current code for most localities in TN specify an above ground concrete pier with the post sitting on a metal base to keep the end grain elevated. Footing depth in TN is shallow - even 12" deep will suffice as long as the pier is on solid compacted ground. With an 8' max pier spacing in all directions your piers can be 24" square, 8" to 12" thick with a cross of #4 rebar formed inside.

        The whole key to a good, solid deck is to brace your framing so that all the load continues to be applied straight down. For a 10' tall deck this means cross bracing to avoid side to side movement in all directions. Again, build the deck braced this way so that attaching it to the house is just an 'extra'. You do not want to use the house as the load bearing end of the deck.

        I will also repeat the mantra to hire a local expert to answer your questions. Even though I have built more than enough decks of your description to know that it will be solid, you just can only do so much working with a verbal description over the internet.


        Jaybee
         
        Posts: 10312 | Location: Knoxville, Tennessee | Registered: Sep 27, 2003Reply With QuoteReport This Post
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