Safely Pressure Wash a Timber Deck or Fence

18-Nov-2018 By BWS

Safely Pressure Wash a Timber Deck or Wooden Fence

Here are four main points of note for safely pressure washing a wooden deck or fence:

1.  Keep the water pressure low, while still being effective (eg 500 psi to begin, then test increase if needed).

2.  Use a wide angle spray tip  (eg 40 - 60 degrees).  

3.  Keep the spray-end of the wand steady at your preferred distance from the surface (eg, 60 cm). 

4.  Test out the pressure first where feasible, eg on the back of the fence or the steps to the deck.

Wooden fencing and decks can be pressure washed safely with excellent results!  This includes those built from softer woods such as pine, and those constructed years ago, but if these timbers have not been sealed it is easy to remove more of the surface layer than you intended.  Damage from water pressure that is set too high can include:
-  Loose pieces of wood lifting out, leaving gaps.  
-  Gaps expanding with the water pressure and opening up to the weather. 
-  That leading in turn to warping and cupping of the wood.
-  Nails loosening as the wood expands.
However, as long as due care is taken when you pressure wash, all will go brilliantly well.  

Some suggestions for a smooth, even finish:

1.  When you start, do so at the beginning or end of a board, not half way along it.

2.  Use a steady, sweeping movement and begin from the side of the deck closest to the house. 

3.  Each sweep of the sprayer can overlap the one before, so that no 'cleaning line' borders appear.

4.  Work along the length of each board, going with the grain of the wood.

5.  Keep a steady, even spray over all the deck. Don't pause for long over any one part of the decking.

6.  When you stop the spray do so at the end of a board rather than some way along it.

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