Replies

1. 
   RyanBrant | May 10, 2005 08:56am | #1

   Check in to using steel.  We've used square steel tube with all thread running vertically through the tube and into concrete.  Then two nuts to adjust the tube to elevation and a large washer- two nuts tightened against each other prevent the nuts from vibrating loose and down.  And finally a nut on top of the steel.  The all thread and footings should spaced close enough the steel doesn't deflect.  We've only done it twice, but over 14' with 3" steel, 5-6 footings should be enough.  We decided on site by experimenting with the steel.

   Then we used 4x4's as joists with corner braces (or L brackets or angle irons, as some call them).  Pre-drill the steel, then self-tapping sheet metal screws.  Wood screws attach the bracket to the joist.  Remember, all this has to be minimum hot-dipped galvy nowadays.

   A 3" square steel tube with a 4x4 is 6.5" - a lot less than a 4x6 beam and 2x6 joists.  But because the joists are now only 3.5" deep, the steel beams need to be closer center-to-center.  This means yet more steel.  It adds up ($$), but it does save inches.

2. 
   Gumshoe | May 10, 2005 09:19am | #2

   http://www.askthebuilder.com by Tim Carter

   DEAR TIM: I have a problem. I want to build a deck close to the ground. In some places the joists will actually touch the soil. I realize that the joists can't just rest on the ground. How do I support them? Should I install a vapor barrier under the deck? What are the best decking fasteners to use? Steve K. Waverly, Iowa

   DEAR STEVE: Ground level decks are known to stump many people. Everyone seems to have the image of the beam supported by posts stuck in their head. I have seen people who actually buried a wood beam and posts in the ground to support the deck joists. Guess what? They were on the right track. They simply took the wrong turn.

   Deck joists need to have a firm support system not unlike those within your house or on a traditional deck. Beams are used for this purpose. A beam is simply a level or nearly level structural member that will support the joists with minimal or acceptable bending. Beams are most often made from wood, steel, and reinforced concrete. A ground level deck, in my opinion, can be most easily supported by using steel reinforced concrete grade beams.

   You will need a minimum of 2 grade beams, if your deck will not be connected to your house. The beams will be parallel with one another. They can be at the ends of the joists or they can actually be tucked under the edge of the deck for appearance sake. The beams must be at the same height and in the same plane so that the deck is level once finished. It is very wise to consult with a residential structural engineer. This qualified person will tell you exactly what you need.

   Grade beam are usually constructed by digging a trench at least 8 inches wide. A beam depth of 10 inches is generally suitable. The bottom of the beam will be supported by the soil. If you live in an area where the soil freezes each winter, you must dig piers at the bottom of the beam trench. The piers can be 10 or 12 inches in diameter and spaced no further apart than 6 feet. The bottom of the piers must extend to the frost depth in your area. Your building department will be able to tell you how deep to dig. Be sure that you flare the bottoms of the pier holes. The flared bottom serves two purposes. It increases the surface area of the pier helping to distribute weight. The flared bottom also makes it very difficult for the frost to heave the beam and the piers.

3. 
   dIrishInMe | May 10, 2005 11:34am | #3

   If you must build an on-ground deck, use a flush girder (beam) rather than a drop girder.  The flush girder will sit directly on the footers.  If necessary, you can form the footers up slightly above grade.  I'm at a bit of a disadvantage here though because you did not give a an actual deck height, nor do I know what area you live in.  The method of an on the footer beam is for climates where the frost line (hence the footer depth) is minimal - say 18" or less.

   Really though, why would anyone want to build a very low deck?  It's just a place for water, natural debris (leaves, etc) and insects to collect...  Build a masonry or concrete patio - the cost will be the less or the same and will require little maintenance, and if done properly, a patio will last longer.  For as little as $2.50 a sq ft (installed) you could have a low maintenance plain concrete patio as compared to $10 (min) a sq ft for wood which will need to be re-stained every 2 to 3 years.    Around here you can get a first class really sharp looking stamped concrete patio for around $9 a sq foot, although it does require periodic re-sealing.  There are some pretty cool concrete pavers available that can be laid in a myriad of patterns (see attached pic), or you can get creative with standard brick pavers too.  Stone is another option.
    

   Matt
1. 
   BryanSayer | May 10, 2005 06:17pm | #4

   One reason for a ground level deck is when the ground slopes significantly, particularly sloping to the side. So the deck is really only ground level for part of the way, and somewhat above ground level the rest of the way. We did this at our former house.

1. 
   Gumshoe | May 10, 2005 07:31pm | #6

   View Image

   Edited 5/10/2005 2:06 pm ET by Huck

2. 
   Isamemon | May 10, 2005 06:50pm | #5

   Dirihinme,

   If that is a stamped concrete patio and you can produce that for $9 a sq foot, bring your tools, Around here, that pattern, color variance, and labor would easily out price $9, maybe nearer 15

    

   sorry, I guess thats pavers

   oregon

   Edited 5/10/2005 11:52 am ET by Isamemon

1. 
   dIrishInMe | May 11, 2005 02:48am | #8

   Yes, the pic is pavers.

   We have stamped concrete around our pool, which we paid $6 a sq ft for about 4 years ago.  All one color.  Some people have mistook it for slate - but these were untrained eyes...

    Matt

4. 
   madmadscientist | May 11, 2005 02:14am | #7

   We did the basically ground level deck thing.

   http://www.madmadscientist.com/galleries/deck/index.htm

   If you scroll thru the pictures there are a bunch that show the ground level framing.  We made sure that the joists never actually touched the ground but they are close.  I can fit my work gloved fingers under them but just barely.  We also made sure that around the edges we built in an air gap between the deck and the retaining walls. We dug the dirt down in the deck area and covered it with clean drain rock also.

   I can answer why you would want to put in a ground level deck. We thought about the concrete patio-paver thing but we just didn't like the look. The way our deck is set up now its almost exactly the same height as the grass so moving from one to the other is not a problem.

   http://www.madmadscientist.com/pond/

   Shows some shots of the finished deck/grass/garden

    

   Daniel Neuman

   Oakland CA

   Crazy Home Owner