Setting Posts in Deck Construction:
Using Fast-Setting Concrete Mix and a Construction Laser Level
© 2008 by Kelly Smith all rights reserved; content may not be copied, rewritten, or republished without author’s written permission
Welcome to the fifth in a series of deck design and construction articles. This one covers
installing your ledger board, digging the footings, and setting your posts in fast-setting concrete
and leveling.
The URLs of the previous article topics are listed at the bottom of this one.
Part of this information concerns the issue of the geographical area where your deck is being built;
some areas get colder than others and need deeper post holes determined by the frost line.
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Before starting a structural project like this, always be sure to check your local building code.
Start with the Ledger Board
If your deck is going to be an attached deck, the first thing to do is install your ledger board.
It must be secured to your home’s
exterior wall studs
using lag screws. If you’re dealing with flat
siding, keep your ledger off your siding by using 1/2” exterior-grade plywood spacers in the places
where the screws penetrate.
3” wide is sufficient and should be tapered at on the top side to facilitate
water run-off. Take the time to soak them in a wood preservative and then wrap them with roofing felt.
On the other hand, if you have lap siding, it should be cut away before attaching your ledger board.
Next, slide some galvanized metal flashing up under your siding, then attach your ledger,
and finally bend the flashing over it.
Note: It’s critical that your ledger is level; the levelness of the entire
deck will flow away from it.
Next, Dig Your Footings for the Posts
You learned how to mark your post hole locations in the previous article. You’ll use your shovel
or post-hole digger to make your holes at these spots. They need to be 10” wide at the top and then
“bell outּ to 16” at the base. The depth is important and depends on local wintertime weather.
If you live in an area that doesn’t freeze, 24” deep enough. If it does freeze,
your hole needs to be 8” below the frost line. This will make strong footing posts.
Note: Add 5” to the depth to allow for a bed of pea gravel.
Now Set Your Posts
Begin by pouring 5” of pea gravel into each hole; the purpose is for drainage away from the base
of the wood. Use your string lines from the prior layout article as guides to ensure that your support
poles will line up properly.
Stand a post in every hole. Then, use your 4’ level to make them stand plumb in both
directions and then stake them securely. Your posts need to be higher than the finish height.
Pour fast-setting concrete mix around each one. The mix is simple to use since water is added in
right in the hole; no mixing wheelbarrow is needed.
QUIKRETE Concrete
makes the best one in my humble opinion,
and you can find it at Home Depot, Lowes, and most other home improvement stores.
Build a Level Deck
Now we’ll make sure that your completed deck will be nice and level. You have three ways available
to you to accomplish this. The best method is to make use of a construction laser level. You can
transfer the elevation from the top of your ledger to each post, mark them using a pencil, and then saw
them flush.
When you determine your posts height, recall that your joists butt into your ledger, but set on the
top of your beams.
The second most accurate method to transfer elevation marks is by using a
water level. In theory
this would be the most accurate method but it’s a bit slower and may involve human error if you're
using a helper.
A water level is just a clear plastic tube filled with water. The water level on one end will be
the same as on the other end (as long as there are no bubbles in the tube and the water temperature
is consistent).
The third (and least accurate) method is to use the string line with a line level.
Follow Kelly Smith
Here’s the article line-up for the deck-building series!
- Part 1: Wood Deck Design Fundamentals
- Part 2: Deck Design and Framing Concepts
- Part 3: Lumber Sizes And Spacing for Deck Building
- Part 4: Deck Design and Post Hole Layout
- Part 5: Setting Posts in Deck Construction
- Part 6: Deck Building: Beams and Joists
- Part 7: Trex Composite or Aluminum Decking vs Natural Wood
- Part 8: Popular Deck Board Patterns and Decking Installation Instructions
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