Intro and Construction Questions

[lady_mariko]

Hi Everyone! New here and have been spending a lot of time reading this forum. Would like to thank everyone for sharing your design and build stories as they have helped us quite a bit. We are now in the design process and I have a few questions that I hoped y'all could answer:

1) Why do many of you use cement board AND Trex on the bottom of your islands? Why not go with just Trex on the bottom and skip the cement board?

2) I understand you are supposed to tape and seal any seams where two pieces of cement board come together. Does that include seams where the boards meet at a 90 degree angle (e.g. where the front piece and a side piece come together)?

3) I like the idea of using rivets instead of screws to assemble the metal framing but have never used a rivet gun. Does that process require drilling holes and then installing the rivets, or is there a tool that punches the hole and installs the rivet at the same time?

Thank you so much for your help! Will post pictures once we break ground (and once I learn how to post pictures. ).

l_m

 

[Aurik]

Mariko,

I'm no expert, but from what I've read from these guys here's my take on the questions:

1) The cement board (hardie or otherwise) on the bottom both provides a floor to put stuff on, prevents the ingress of undesirables (rodents, insects, etc), and provides a bit of extra stability to the island.

2) A 90 degree seam is still a seam. Tape & thinset it.

3) AFAIK (as far as I know) there isn't some magic tool that drills & sets rivets at the same time. Predrill your holes and then punch the rivets through.

 

[lady_mariko]

Thank you so much for the reply Aurik. Regarding number 1), I guess my question was couldn't a sheet of Trex board attached to the bottom of the frame do all of those things (provide a floor, keep insects and rodents out, and provide additional support for the structure)? I'm not clear why you need to have both the hardi board AND the trex board for that.

As for 2) and 3), I guess that was just wishful thinking on my part. Thanks again for your help.

 

[denalio]

The trex board is merely a way to elevate the bottom of the island off the ground so the steel stud does not come into contact with the ground and any water. Some people use trex 4" x 4" feet, other use a strip all the way along the bottom perimeter. I see no reason you could not use a trex sheet(if they make one) on the bottom of the island instead of cement board. There are industrial rivet setters that punch through the steel or aluminum id you have a few thousand dollars to spare

 

[lady_mariko]

Ohhhh....I was making a huge assumption thinking that Trex was available in sheets. Not a brilliant move on my part. :-? I guess that would explain why people don't use it!

And sadly no, I do not have any thousands of dollars to spare on an industrial rivet gun. If I did I'd probably use it to hire a pro to do this job.

Thanks for the info!

 

[Stevereno]

lady mariko - Trex is essentially a synthetic replacement for wooden deck boards. It is quite a bit more expensive than say the pressure treated pine that is used quite a bit by some for their deck boards. It would be quite costly (if available in sheets) compared with the hardiebacker / trex feet approach that most folks are using for this application.

 

[vinper]

forget rivets , use the self tapping tek screw , on metal framing hold it together with vise grips .. very easy

 

[SkipDaddy]

Yes, the self tapping screws work great. You get in to a groove after a while. By the time my 1000th screw was in, it was second nature.