Installing Deck Posts & Beams



Before you begin framing your deck, you should have the ledger installed along the house and the concrete pads poured. These create the various supporting elements for your deck. Next to the house, the deck joists will be attached directly to the ledger. Meanwhile, the concrete pads hold up the posts, which support the girders (or beams) that the support the deck joists opposite of the ledger.

Time to complete this project depends on the size of the deck and the level of help available, the times listed here are for two people on a 10’x 30′ deck with the house defining two sides of the deck.

  • Beginner – 2 to 3 days
  • Intermediate – 1 to 2 days
  • Advanced – about 1 day



Refer to your deck plans and determine the height of each post. Add at least 6″ to the length of each and mark the appropriate dimension on each post. Cut the posts at the marks using a miter saw or circular saw.


Place the posts in the piers on top of the appropriate concrete pad. Using pieces of 1″ or 2″ thick wood, put 2 braces on each post at 90 degrees from each other. Drive a stake into the ground and screw the tail of the brace to the stake. Then use a level to make sure the post is perfectly plumb and screw the two braces to each post. Make sure the braces are below the area where you will be installing the deck beam.



Screw each post to its pier using a screw gun.



With the posts now in position, you need to determine the position of the top of the joists on each post. To do this, take a long straight 2″ x 4″ and rest it on the top of the ledger. Place a level on top of the 2″ x 4″. Hold the board level and then lower the board ½” for every 6′ of distance between the ledger and the post. This is to provide a slight slope for water runoff away from the house. Mark the post at the bottom of the 2″ x 4″board.



From the mark on each post, measure down the height of a joist and the height of the beam. Then use a square to mark all 4 sides of the post. This will be your cut line.



Cut each post to its marked height. Use a reciprocating saw and cut squarely across the lower mark on each post.



Install the post cap brackets on top of each post. Use the appropriates screw or lag bolts to securely anchor the brackets in place.



Measure and cut to length girders to length. Eyeball each girder to determine which way it crowns. Place each girder in position on top of the posts with the crown of the girder directed upwards. Screw the girders into place through the post cap brackets with screws and a screw gun.



Materials Needed

4″ x 4″ Posts

4″ x 6″ Girders

Brace boards

Wood stakes

Post cap brackets

Angle brackets

Lag bolts



Silicone caulk

Tools Needed

Miter saw

Circular saw



Screw gun

Plumb bob

Reciprocating Saw

Tape measure

Leave a Reply

Your email address will not be published. Required fields are marked *