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Post and Library Installation

Types of Posts

Although there are certainly different choices when it comes to posts, such as fir or cedar, or even a straight section of a tree trunk, we typically recommend purchasing a standard 8'x4"x4" pressure-treated post from Home Depot or Lowe's. Most standard-size libraries require a single post with either supports or a post topper. In this article we will explain our preferred method for installing your library using a single post with side by side supports.  


Tools and Materials Needed


To Assemble Post

One 8'x4"x4" Treated Post

Two 3/8"x12" Galvanized Steel Carriage Bolts with Nuts & Washers

12" long 3/8" Wood Drill Bit

12" Bar Clamp (or larger)

Corded Drill

Hand or Circular Saw (capable of cutting 4x4 post)

Tape Measure

Ratchet with 9/16" Deep Socket (or open end or adjustable wrench)

To Install Post

Post Hole Digger


Tape Measure

Tamp Bar or equivalent (optional)

One 60lb bag of fast-drying concrete (optional)

Trowel (optional)

5 gal bucket or wheelbarrow (optional)

To Install Library

Mounting Board

Seven 3" Deck Screws (typically star or square bit)

Four 1/4"x2" Galvanized Steel Carriage Bolts with Nuts & Washers

Ratchet with 7/16" Deep Socket (or open end or adjustable wrench)

Cordless Drill (with bit matching Deck Screws)

1/4" Wood Drill Bit

Tape Measure


Pick a Spot for Your Library and Call 811

Choose a spot for your library (see our article Deciding Where to Put Your Library) and contact your local utility locating service at least two or three business days before you plan to dig. They will arrange for representatives of your local electric, gas, water, phone, cable and other services to come out and mark any nearby utility lines. This service is FREE to homeowners and as they say, it's not only smart, it's the law! In most areas you can contact them by calling 811 or you can request their services online. They will ask you to describe where the spot you intend to dig is located and request that you mark the spot with something white. This can be anything from a white flag to a white piece of paper with a rock on it. If you're undecided about the exact spot you can ask them to mark a larger area.

Cut and Assemble Your Post

Cut and Assemble Your Post

Cut your 4x4 post into one 4-1/2' (54") piece and two 1-1/2' (18") pieces. Cut a 45 degree angle off the end of each of the two smaller pieces as shown below. (Tip: Treated lumber is typically very wet and heavy when first purchased so the longer you store it before cutting the drier and lighter it will become.)

Safety Warning: Always wear gloves, safety goggles and a dust mask when working with pressure-treated lumber. Cut treated wood outdoors, not in an enclosed space.

Post Cut.jpg

Stack the pieces as shown below, being sure that the "tops" (left side in photo) line up evenly, then clamp.


Leaving clamp in place, elevate entire project off the ground then drill two 3/8" holes completely through all three pieces as shown. (Tip: I save leftover pieces of 4x4s and place one under the left side and two under the right, then use my foot to steady the project while drilling.)


BEFORE removing clamp, insert a 12" carriage bolt through each hole (using a hammer if necessary) then secure with washer and nut and firmly tighten with ratchet using 7/16" deep socket. Remove clamp. 

Install Post

Unless you have loose, sandy soil or snow plows are a concern, it is not necessary to use concrete when installing your post.

Installing your post without concrete:

Dig an 18" deep hole with your post hole digger keeping the hole as narrow as possible. Place your post in the hole, back-fill with several inches with dirt and tamp down. Ensure your post is level and squarely facing the correct direction, then continue back-filling a few inches at a time while tamping and rechecking the post as you go.

Installing your post with concrete:

Dig an 18" deep hole with your post hole digger and widen the hole to 12" diameter. 

(Optional: Dig out another two inches from the bottom of your hole and add two inches of compacted gravel.)

Back-fill with several inches of dirt and tamp down to help hold post in place. Mix concrete in a wheelbarrow or 5 gal. bucket according to manufacturer's directions. Ensure your post is level and squarely facing the correct direction, then fill hole with concrete to about 3 inches below ground level. Poke concrete with a shovel or stick to remove air pockets and distribute evenly. Recheck that post is level and slope the top of the concrete with a trowel to direct water away from post. 

Wait at least four hours for concrete to dry then add dirt or sod to ground level.

Install Library

Install Library

On BOTTOM of prepared mounting board¹ mark four spots two inches from each corner as shown below.

2 inches.jpg

   ¹ If you do not already have a prepared mounting board, see our article How to Cut and Prep a Mounting Board.

Center mounting board on top of post. Drive a 3" deck screw into center until tight and top of screw head is flush with top of mounting board. Recheck that mounting board is centered and squarely facing the proper direction, then continue driving remaining deck screws in a pattern similar to that shown below.

screw holes.jpg

Place library on mounting board and center being careful that entire library door opening is in front of the mounting board.  While holding library firmly in place, from BELOW mounting board drill a 1/4" hole upward through mounting board and library floor at each of the four marked spots. Being careful to continue holding library firmly in place, from INSIDE of library insert a 2" carriage bolt into each of the four holes. Tap each bolt head with a hammer so that bottom of bolt head is flush with top of library floor. From BELOW library, add a washer to each bolt and secure with nut using a ratchet with 7/16" deep socket to firmly tighten.

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