Armchair Builder

Building Decks? Don’t Do This!

A Quality Deck. Photo by

A lot of folks will be building decks this spring.  Why not.  It’s a great project for the DIY’er.  A deck is relatively simple to build and can be completed in just a few weekends.  And as for the savings…they can be in the thousands.  Unfortunately, I have seen quite a few of these DIY projects end badly.  Here are four things you should never do when building decks.

Build it and then decide to put a kiddie pool on it (or hot tub).   Any idea how much water weighs?  I’ll save your fingers the workout on the Google search…62 pounds per cubic foot.  So, let’s say your pool is eight feet across (in diameter).  We are talking about a kiddie pool here…you know, one of those plastic pools you buy at Walmart for $30.  If you fill it with a foot of water, it will weigh in at 3114 lbs or a little over 1.5 tons!!!!!  That’s the weight of a Honda Accord!  The million dollar question is..Is the typical deck designed to support this kind of weight?  Typically not.  Don’t forget, the weight of the pool is concentrated in one place.  So if you decide to try it, make sure nobody is underneath when you fill it up.

But who would put a kiddie pool on a deck?  A person I built a house for that’s who.  Luckily for me, the homeowner built the deck after closing (and nobody was hurt when it fell).  The moral of this story is…design your deck for your most demanding intended purpose.

Forget to check the frost depth in your area   Do you know what happens if you are building decks in a cold climate and the footings aren’t deep enough?  Bad things happen.  The deck can heave and put stresses on the framing…it can rack, cause deck boards to pop, and can bind up the door above it…just to name a few.  If you live in a location that has any potential for freezing temperatures, you need to dig the footers to the appropriate frost depth.  Check with your local building department for the depth they use.  You will typically have a footing inspection to check this as long as you have pulled a permit.  Be sure to pull a permit.

Failure to secure it to the house properly   Many homes built in the last ten to fifteen years have manufactured floor joists.  These have some great benefits.  However, they many times come with an OSB (oriented strand board) rim board around the perimeter of the home.  This works fine unless you’re building decks.  If you have this in your home, be sure to provide solid backing or fasten directly into the framing studs and not just into the rim board.  You can also add more posts and a beam and forget about securing to the house altogether.Flashing for Deck

Forget to install flashing   This simple lapse of judgement can cost you dearly.  If moisture gets into your walls, over time you will have damaged materials and possibly mold.  The simple diagram above shows “Z” flashing installed over top of the deck ledger board attached to the house.  The ledger board is the board that all of the joists connect into to support the deck.  The top of the vertical piece of the flashing should be taped directly to the house sheathing (not the housewrap) all along its length.  I know you are thinking to yourself...But there is siding above the deck board, I shouldn’t have to install flashing.  Doesn’t matter.  Water gets behind siding all the time.  And when it does, it can travel down the wall, hit the holes from your fasteners and run back into your home.  This deck flashing can be found at any home improvement store for $10-$20.

Hopefully those of you building decks this spring will follow these simple tips.  They should help you avoid future hassles.


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6 Comments for Building Decks? Don’t Do This!

Danell | April 15, 2012 at 9:07 am

That’s a mighty big kiddie pool at 350 gallons! Lots of small inflatable kiddie pools hold quite a bit less and should be safe on an adequately built deck, yes?

Author comment by armchairbuilder | April 15, 2012 at 11:59 am

That calculation is for a pool that is 8 feet in diameter and the water…1 foot deep. Sure, there are smaller pools out there. But this size is pretty common…we just want people to be aware of the weight of water and take proper precautions before placing one on a deck that may or may not hold the weight. The example we used of the homeowner whose deck fell was close in size.

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