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How to repair pulled out / rotten knots?

Started by kreyszig, August 26, 2018, 11:03:47 AM

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kreyszig

Hi,

I have planks on my tudor-style house that have pulled out / rotten knots. What is the best method to repair them (prepare the surface, back fill and seal)? The planks are most likely spruce and they are covered by a solid stain. Thanks!

Texas Ranger

Study up on "dutchmans" in wood repair, may be a better fix than just back filling.  Amounts to opening the knot out to solid wood, and fitting a "plug" into it with exterior glue.  I have done it with other knots to fit in better.
The Ranger, home of Texas Forestry

kreyszig

Quote from: Texas Ranger on August 26, 2018, 01:58:02 PM
Study up on "dutchmans" in wood repair, may be a better fix than just back filling.  Amounts to opening the knot out to solid wood, and fitting a "plug" into it with exterior glue.  I have done it with other knots to fit in better.
How does the durability of the result compare with grinding the inside of the knot until good solid wood is found and using plastic wood?

Texas Ranger

plastic wood is easier, but doesn't match the wood.  And it does last.
The Ranger, home of Texas Forestry

kreyszig

Quote from: Texas Ranger on August 26, 2018, 08:24:52 PM
plastic wood is easier, but doesn't match the wood.  And it does last.
Thanks. For this application with the solid stain the repair does not need to match the wood. So if the plastic wood lasts as well, I guess it might be the best solution?

low_48

Wood moves seasonally, plastic filler does not. If you insist on a filler, investigate renovation materials that use a stabilizing resin to harden the wood fibers, then a two part product to fill voids. I prefer a wood dutchman. 

1938farmall

X2 on the dutchman & use spruce if that's what was used for the plank.  the wood hardener & resins will fill the hole but seasonal movement of the wood will make the repair obvious in 3-4 years.
aka oldnorskie

bluthum

I've had great luck with bondo, plain ol' auto body filler. Small holes filled with it look like the knots it replaced and you can tool the surface for a texture before it cures if you have rough sawn siding.

I've always used it with the belief it is flexible and moves with the wood and have yet to be disappointed. If you have giant knots [say 2" or bigger] you will have to do more than 1 application and probably back up the resin with some hardware cloth pressed into the hole. A repair that size won't be invisible but if your siding has such huge knots they are already less than invisible. 

Anyway who wants wood siding that doesn't look like wood?

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