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Old Pergola wet rot question

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Forum topic by japenrod posted 05-12-2021 02:26 PM 258 views 0 times favorited 6 replies Add to Favorites Watch
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japenrod

4 posts in 33 days


05-12-2021 02:26 PM

Hello all,

I have an old wooden pergola in my back yard I am trying to refurbish. I removed the rotting 2” x 2”’s from the rafter beams and ordered alumawood pergola lattice to replace the rotten boards. My issue is, the 4” x 8” x 20’ Rafter Boards have terrible rot on top where the 2” x 2”s were attached. I would like to remove the tops down about 2” to get down to healthy wood for painting.

My question is:

Is it possible to rip cut 2 inches off the top off of a 4” x 8” x 20’ rafter beam with it in place? Tools required? How would it be done? It is 9 and a half feet off the ground.

I appreciate any input.

Thanks.


6 replies so far

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tvrgeek

1934 posts in 2763 days


#1 posted 05-12-2021 03:18 PM

Possible, but not smart. With a big enough hammer ( chainsaw, circ saw, sawsall, bow saw, adz) anything is possible but a 20 foot span! No way would I reduce it to a 4×6 from a 4×8. It is your head of course and a pergola won’t have much load.

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splintergroup

5271 posts in 2337 days


#2 posted 05-12-2021 03:42 PM

Alternatively you can cap the tops of the rafters with metal flashing that extends down past the rot. It’s still there, but protected from the weather and “out of sight, out of mind”

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japenrod

4 posts in 33 days


#3 posted 05-12-2021 04:16 PM

@TVRGEEK – Thanks for responding! Yes, does seem like a good bit of work. I’ll look at other options.

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japenrod

4 posts in 33 days


#4 posted 05-12-2021 04:18 PM

@SPLINTERGROUP – I Like the way you think? This looks like an easy optionwith the added benefit of moisture not affecting the flashing beneath the Lattice. Should i bore out the wet rot removing the loose material and apply a drying agent before applying the flashing?

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splintergroup

5271 posts in 2337 days


#5 posted 05-12-2021 06:12 PM

You should have everything at least dry before covering, removing any “nastiness” is also prudent, but you want to keep support under any flashing where the lattice attaches to avoid the flashing being pushed down into a void when the lattice is attached. The points where the fasteners penetrate the flashing is a potential point of moisture intrusion and if there is a divot there, the moisture can pool and seep in through the fastener hole.

Alternatively you could scarf out the rot in the areas where the lattice attaches and replace with sized “chunks” of 2×4 material to re-level with the top of the beam and provide a secure fastening point. The fasteners in either situation need to penetrate far enough to grip into solid wood

Basically it all comes down to your budget and time.

Best fix is of course to just replace the beam, the flashing simply keeps further moisture from collecting in the beam top, extending its life. Not a permanent fix, but probably the easiest to take on with the best cost/benefit ratio.

This technique is common for the tops of cabin logs that are exposed to sitting moisture (snow, etc.) and often is decorative (made from copper)

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japenrod

4 posts in 33 days


#6 posted 05-13-2021 01:47 AM

@Splintergroup – Thanks so much for all of your input and advice. I’ll probably just go with replacing the rafterbeams. Seems the most prudent. Followed by a really good paintjob for the whole thing. Your helpfulness is very sincerely appreciated!

Joe

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