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bobkat
new deck materials
bobkat

I just bought a new mobile and am ready to put in two new decks outside. I am using composite decking but because of the size of the decks and the expense of the materials (12x6 and 6x6) my friend suggested that he could build the foundation for the deck not using composite lumber. He suggested pretreated lumber but my question is why pretreated and not treated ?? What would suggest in my situation, I already have 3600.00 in composite decking and rails and although I am not want to do something cheap and wrong I just want to know the best way. Thanks so much, love your show (and you can come build my decks if you wish lol. I am in Roswell, New Mexico, Alien Town.

Also forgot to mention I am using ArmorPoxy Renew for the old part of a deck I have and the concrete slabs and am running out of money but still want things right and with little maintenance as I am not able to do this myself and have to rely on friends and handymen I pay.

A. Spruce
Re: new deck materials
A. Spruce

I've never heard of "pretreated" lumber, possibly your friend meant "P" treated, as in PT, or pressure treated?

What you use will be dependent upon the environment that it is in, if it's protected from the elements, then normal lumber for the framing will suffice, if the deck will be exposed to rain and high levels of moisture, then pressure treated lumber is the way to go. I'd hazard a guess that with you being in NM, you do not have the rot problems that colder, wetter climates have, which means less expensive normal lumber, as opposed to pressure treated, could be used.

bobkat
Re: new deck materials
bobkat

Thank you for your answer and you are right about the pressure "not pretreated", sorry, this is a learning experience for me for sure. This has been an exceptional year for the monsoons, normally we do not have that much rain/snow/humidity so am hoping the cheaper will suffice. Again, thanks for the prompt answer and keep up the good work.

dj1
Re: new deck materials
dj1

At least, use PT for the posts in the ground. The rest of the framing can be regular construction lumber with composite top boards.

In some areas they place PT posts in the dirt. Around here we place them in concrete, or place SIMPSON anchors in the concrete and have the posts connected to the anchors.

Termites are everywhere and they attack most lumbers out there, even lumber known to resist termites like cedar, cypress and redwood.

If you intend living there for a long time, and not afraid of making an investment, consider lumber types like IPE or Mahogany.

A. Spruce
Re: new deck materials
A. Spruce

I would further recommend laying 2" wide strips of 30# roofing felt over each joist, regardless of what you use to frame with, as this will add another layer of protection.

Last caution is to make sure that the framing is absolutely no more than the manufacturer's recommended spacing to support their decking product. Trex, and similar composites do not have the structural strength or stability to span much distance, which means that joist spacing must be closer together than you'd see for wood decking materials. This caution extends to the fasteners used as well, zinc coated screws have a tendency to stain composites. Lastly, predrill all screw holes through the composite, including space for the screw head. This type of drill bit is very common, you can find them at any lumber supply/big box/hardware store.

Mastercarpentry
Re: new deck materials
Mastercarpentry

Most composite decking says youcan use standard 16" joist spacing but you'll do a lot better to go 12" O.C. instead because composite has a lot more flex than natural woods of equal thickness.

Phil

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