Oak Stain: Rust or natural?

irlrobins

Hey all,

In the process of purchasing a new house. House has a front porch roof, supported by two painted oak beams, one short, one full height. The both have stains that look like rust. Builder is saying it's not rust but rather the stain is a natural "weeping" of the oak. He's saying it's pointless to repaint as the oak will contain to weep for sometime.

Anyone know what this weeping is? Does it need treatment or will eventually dry up and then can be painted?

Pics attached

Double Barrel

Tannin bleed.
Tannin bleeding is when the oils in the wood seep through the paint. The only way to stop this is to use an alkyd/oil based sealing primer.

irlrobins

Thanks for reply. So recommended action would be to sand down existing paint, use a sealing primer and reapply top coat?

Double Barrel

irlrobins wrote: »

Thanks for reply. So recommended action would be to sand down existing paint, use a sealing primer and reapply top coat?

Correct. Maybe two coats of primer.

Extractives ( bleed) include tannins and other polyphenolics, coloring oils, resins, and gums. Water-soluble extractives will cause stain discoloration. Nonwater-soluble extractives such as pitch and resin may bleed through the surface and harden there when the solvent evaporates. Naturally occurring chemicals in the wood itself can migrate to the surface and discolor the finish. The chance of getting discoloration depends on many factors, including wood species, moisture content, and construction practices.

A product containing oxalic acid such as Liberon Wood Bleacher or Ruskins Bleach will remove the stain.

Good luck.

tabby aspreme

What finish is on the L bracket under the wood, and what type of metal is the L bracket made from, the tannin from the wood is acidic so it will continue to rust the bracket if it is mild steel, also Oak will turn black where it is in contact with mild steel

irlrobins

I'm not sure to be honest. I'll have to ask the builder when I'm next on site.