Sunday, July 23, 2017

Carport Post Rot

Our home has a carport supported by four 4"x4" cedar posts, and one 4"x6" cedar post. One of the 4"x4" posts, and the 4"x6" post, are exhibiting severe dry rot at their bottom ends. Here are views of the 4"x6" post's problem.

That's what happens when a paint film fails and acquires little fissures that can admit rain water. Water wicks in readily, but the largely intact paint film prevents the water from evaporating readily. What you have is a situation where the paint is actually worse than useless. Naked cedar would at least dry out quickly after being wetted, and wouldn't be nearly as inclined to rot.

I wouldn't care to have to replace that entire post. The post is quite tall; jacking the peak of the carport's roof to accommodate post replacement would be problematic, to say the least.

So, I went with reinforcement of the post's base by way of 2' lengths of pressure-treated 2"x4" and carriage bolts. Here's a view of the the reinforcement applied to two sides.

And here it is with all four sides' reinforcements installed.

That still leaves me with exposed voids at the very bottom corners. I'll fill those with expanding foam, then prime and paint the whole repair.

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And here it is filled and primed.

The primer is Behr No. 436, exterior primer & sealer.

The results I got from the expanding foam are not great. I was unable to trim the stuff nicely in those corners.

I wish I could have come up with a better scheme for dealing with the voids, but expanding foam was all I could think of. It will have to do.

Here's the first coat of green enamel.

That's Behr No.4300 deep base exterior flat tinted Mountain Spruce.

And here it is recoated and the masking tape removed.

I expect that to be a long-lasting repair, and it was far more economical of effort and material than post replacement would have been.

The other rotted post, a 4"x4", had to be replaced entirely, though. See this post for an outline of that procedure.

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