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Sealing Wood End Grain

Window sill replacement

On decks or porches you can seal all rip cuts as they are installed and seal the end grain after the decking in in place.

Painting Wood End Grain

The end cuts in siding, deck boards and trim all need to be sealed at installation. 

The biggest reason for sealing wood end grain is because the wood end grain is exposed on an end cut and it absorbs liquids up to 250 times more rapidly than other wood surfaces.

Why Sealing End Grain Is Important

Grab a bunch of straws and hold them together – that is how I envision wood end grain.  These tiny straws wick up moisture over time from rain, snow and roof splash off.

The days of old growth lumber, “bullet proof”  lead paint, and leaky breathable house walls are gone.  All of these things help prevent or slow wood rot.

Today’s wood is different and not as insect and rot resistant, the paint is not nearly as durable and houses are constructed so tight that sidewall moisture problems are prevalent.

By sealing and back priming all wood trim or decking you are giving the trim or decking a better chance to endure the elements by slowing water infiltration.

Wood trim often rots due to improper installation methods, and from not priming or painting the end grain.  Trim wood exposed to the elements soak up water which start the rotting process.

Wood trim should be installed:

Wood trim and decking should:

Seal End Grain At Installation

Priming and sealing end grain during the wood siding, deck or trim installation can be easily accomplished and does little to slow down a job.   All it takes is a little can of paint or sealer.
Spray cans or primer or disposable cans and brushes with primer can be used to prime the end grain once installed.
Most of our exterior wood siding and trim comes pre-primed or finished with at least one coat from the factory so all we have to be concerned with is end grain.
 On our deck installations we seal all six sides but start by sealing only  the top, bottom and edges.  We do this on saw horses prior to the decking installation.   We seal the end grain after the deck boards are cut to final size or after the deck boards are fastened, if accessible.
On decks or porches you can often seal all rip cuts after they are installed.  Many times the carpenters will run the boards long and cut them in place –  sealing the end grain can then be done with the decking in in place.

A Better Product Lasts Longer

Best practices dictate sealing wood end grain – it doesn’t add on much time, just like adding strips of building paper behind the joints ad results in a better quality, longer lasting installation. 

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