Can anybody think of the DISADVANTAGES(s) of painting FC (two coats) after it is installed ? I have been putting one coat on when it is down and the final coat on after putting up.
I have been painting the cut edges and ends prior to putting it up but am thinking that I have been making a time-consumming mistake by painting as I described.
Thanks in Advance,
Eric S.
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Replies
Wood rots, of course, and expands and contracts with changes in moisture. If the back of wood siding has a different amount of moisture than the front the siding will warp. Also, the constant shrinking and swelling will eventually cause the paint film to separate from the wood. To slow down the uptake and release of moisture, wood siding is often painted on all sides.
Fibercement doesn't change size with moisture, so I would not expect there to be any need to paint the back, because it wouldn't matter if the back had a different moisture content than the face.
Here's the painting recommendations from James Hardie.
http://www.jameshardie.com/homeowner/prodhome/hardiplank_paintingtips.php
I did not download the full document so I don't know all it says.
Their caution against using any oil based paints is important. Oil will react with the alkalai in the siding and form soap. (Remember soap is made from fat and lye.) When paint turns to soap it won't stick. 100% acrylic primer and topcoats are the best choices.