MCA and Aluminum?

DFB · Apr 21, 2016

Micronized Copper Azole Preservative what gives...

I got some PT landscape timbers at the Orange box yesterday to make the frame for my HF greenhouse like they recommend to use and just now looking at the end tags it says "not for contact with aluminum"... oh well dang that's what the greenhouse frame is! :confused2:

Any how the HD product page description says MCA is the preservative and this HD page says micronized is ok with aluminum and so does this page onlne

But that's not what the lumber tag says :confused3:

Says its CA-C treated

So is the product supplied is not actually what is described...that would be correct.
(I never shop there if I can help it all and the only reason I went to there yesterday was it right next to the new HF store.)

And first I was thinking should I maybe use a strip a tar paper between the two but this page recommends at least 10 mil thickness of poly barrier

Dang it's 25 miles back to Home desperate too

GLyford · Apr 21, 2016

I've used the sticky rubber "flashing" like is used to install windows with pretty good results so far...used it on my trailer where the sides meet the front between the angle and the PT ply, and between the ledger and flashing on my back porch. The ledger flashing I took down looked like swiss cheese, but that was with the older CCA.

This Stuff:

Protecto Wrap BT25XL 6 in. x 5 ft. Window and Door Sealing Tape-D89726 - The Home Depot

SirReal63 · Apr 21, 2016

You don't want to use landscape timbers, they are not really pressure treated, that are treated to refusal. Landscape timbers typically come from peeler cores, which is what is left over after peeling veneers for plywood, they are not kiln dried, full of moisture and because they are still wet with water and chemicals when treated, the treatment doesn't penetrate and become fixed in the wood. This is why landscape timbers do not last, it is the worst possible piece of wood to treat and has become such a commodity that no one dries them prior to treating them as the cost would be too high.

Use a true 4x4 that is treated for ground contact and it will last, and probably also be treated with MCA instead of CA-C.

DFB · Apr 21, 2016

Stopped at my local lumber yard today the place I always do business and Ed "the counter guy" knew just what I was talking about but also said their in stock PT was all CA-C rated too.

I took his word for it and didn't go out in the yard to check labels.

And the smallest roll of an ice and water shield barrier they had on the shelf was 6" x 75' for $30 too.

I told them this my money I'm spending not my Boss's. :confused2:

The roll of sticky rubber at HD that was linked will be about the same cost difference of buying 4X4 PT material from there also. My GC bud used that stuff similar as GLyford did while exterior strapping and re-siding a mobile home a while back, plus it was recommended by the local Building Inspector to meet his requirements too.

So I freely admit I was cheaping out on the 3 x5 timbers vs some graded dimensional lumber but I was trying to wing it for a low budget project and figured they would probably last as long as the HF greenhouse itself. :laughing:

Just last week they were on sale for like 1.97 ea. go figure!

I knew the gal at checkout too (I said please, please give me the sale price)

Nope no deal she says...you should have bought them last week.

I said I didn't have a project last week.

Well supposed to rain to tomorrow so I will take the ride back to the box store (guess I'll stop for breakfast my fav lunch counter en route

) and then see exactly what they have for other inventory treatments. Really you could easily get by with just PT 2x6's framed up on edge. The aluminum sill plates are not very wide at all plus I have stack of leftover galvanized corner connecters from past jobs too.

Maybe I will go back HF too!

Thanks for the suggestions and advice