Deck – Post and Girders

Post and Girders

You can install the girders in two ways:

  • If the posts and girders are not too long or heavy, you can pre-build the girders/post system, bolt or nail the entire thing together, and then move it as one large piece into place.
  • The other way is to build it piece by piece in place.

Determine with local building codes on which type of post/girder variation to use. There are two types, either 2 girders can be nailed or bolted to the post (see Figure A) or the girder can be placed on top of the posts and fastened with metal attachments (see figure B)

Figure A Figure B

Figure B variation allows you to cut cost out the wood. So decide on which type of girders you want to use with adherence to the local codes.

Cutting the posts

1. To determine post height (where in this project the top of the post is level with the bottom of the outer joist that you’ve installed earlier), go back to your two outer joists and check to be sure they are still exactly level.
2. Move the string that is on top of the joists (which you used to center your foundation pier holes) so that it is now connected on the bottoms of the joists. The level of the bottom of the joists is the same level as the top of the posts you are about to cut.
3. Measure from the top of each pier block (or metal fastener) to the string, and cut posts corresponding to each of these measurements.
4. Be sure you are accurate and that you make good straight cuts so the posts will sit smoothly on the pier blocks. Do so by marking around the circumference of the post, cut one side, and then rotate it and cut the sides adjacent to it.
5. Finally make one more cut on the side opposite the first cut.

    Cutting the girders

    After the posts are cut, cut your pieces of girder stock the specified length. This will be the length of the ledger plus 3”.

    Make sure you use one continuous piece of girder stock for each piece. If that is note possible, be sure the two pieces meet at a post so they can both be attached there.

    Make sure that all girder stock is extremely straight. Just like the outer joist, there can be a possibility that they are bowed. If the bow is small (1/2” over 12’), point it up toward the sky and it will settle down in time.

    With all your pieces cut you can now assemble posts and girders into one unit. Usually this is done with bolts, nails, or metal fasteners.

    If you are resting the girder on top of the posts, use metal fasteners. Be sure to always use hot dipped galvanized (HDG) fasteners, boils, or nails so they will not rust
    If you are bolting it together, drill your holes good and straight so the bolts will go through straight. Use a bit that is 1/8” larger than the bolt, to allow for final adjustments.

    Assemble the entire unit, then move it into place under the two outer joists. If you are assembling the pieces in place, the application is pretty much the same.

    Measure out from the wall to be sure the girder is the proper distance from the wall before toe nailing the outer joists to the top of the girder. Check to make sure the joists are still at right angles from the ledger and still level. Then nail the joists into the girders with 10d galvanized nails to use some special L-shaped metal fasteners.