Need advice for boa enclosure

I am going to be building a 6x4x2 enclosure for my boa and need some help. First this is going to be heavy so it's going to sit on the floor, how would I heat thru the bottom (sealed plywood) It's going to have plexiglass front and sides and I'm going to frame around it, how thick should the plexi be? I was thinking half inch should be good. I also was playing with the idea of bio active substrate and plants. Pros? Cons? Any advice is greatly appreciated. I have some time she is only about 4 feet long now. Thanks, Mike.

Plants don't survive heavy-bodied snakes very well, and "bio active substrate and plants" with the needed warmth & humidity is the perfect medium for growing mold & all sorts of harmful pathogens, without the cleansing sunshine & air circulation that takes place in the great outdoors. No matter how nice & natural it looks, I wouldn't do that.
Are you sure you'll enjoy servicing a cage that's so heavy it has to rest on the floor? Also consider that floors are drafty- probably harder to heat the cage there.

Wood is a great insulator...heat from UTH doesn't get thru it very well without careful planning; keep safety foremost in your design, as some UTH requires air circulation so it doesn't over-heat. You don't want a cage (& house) fire. I personally prefer UTH but in this type of cage, you might be better advised to use RHP? Wood that is constantly heated also dries out & becomes more flammable in time...I'd never try to use UTH thru wood. Never.
One thing you might consider is using a kennel heat pad inside the cage: I used to have some that were designed for dogs whelping quarters etc, so they were insulated & safe with moisture etc. Don't know what's currently on the market, research thoroughly if you decide to try that. And of course, the 'pad' would have to be connected to a thermostat, goes without saying. The ones I had were plenty large & about 3/4" thick.
I think "pig blankets" are still on the market too, same idea, only for livestock.

If you use a suitable heat pad within the enclosure (instead of underneath the floor), another thing you might do is to make a frame for it to sit on & attach to, so that it sits about 5" off the floor. That way you'd provide a warm "hide" under it, plus a surface the snake could lay on top of or just crawl across: it expands the floor space & options, while heating the air too. (yes, I've done this before, on a smaller scale, with ceramic professional heat pads made for zoos-) And when I kept a large BCI, I did use UTH but made her a huge hide box that she used just as I described, ie. she loved basking on top, but also being inside of it; essentially, it's like a "loft". I made 2 rounded doorways in the one end so she could move in/out easier- that way your snake doesn't have to go all the way in to come out again...boas are heavy-bodied, it's harder to move in/out, this encourages them to 'cruise', or at least it had that effect on mine.

Thanks Caro, as for the floor I haven't decided if it is going to be plywood, is there a better alternative? if I used pvc or plexi would that be better? I am also going to have at least 1 shelf so I think the rhp would work better. Also this is going into my snake room so the radiant heat in there is 74-75 at all times so really I am just thinking about the hot spot. I am by no means a carpenter so thank you for responding.

I'm no carpenter either, but I've successfully modified a few cabinets for snakes to live in, though not for large boids, only for large colubrids.
I don't like plastics (like PVC), especially with heat that will promote the off-gassing of toxic vapor. No matter how slight it may seem, our snakes are enclosed 24/7 with it.
Here's a recent article about just one aspect of plastic as it relates to us & our food, & we're much bigger (resilient?) than our snakes. Plastics are everywhere in our lives, & while they are essential in many ways (like in medical devices & water pipes), we also take for granted that they are completely safe...that, IMO, is a fallacy, but you'll have to decide for yourself.
https://www.cnn.com/2018/03/29/healt...udy/index.html

The plastic/plexi will also scratch (even when wiped with paper towels when you clean), & those tiny scratches may not hurt appearances on the inside floor of a cage, but they allow bacteria to hang on. I've heard of people using tile or tile-board (like a shower is lined with)- whatever you use, it has to be moisture proof & preferably with minimal seams. Smooth wood finished with non-toxic (low/no VOC) products to waterproof seems to eventually break down (but could be re-done in time). Because I keep mostly colubrids, I really prefer glass (tanks with UTH) & while glass is heavy, it's easy to really clean (disinfect) and most of all, it's inert. (plywood is of course known to off-gas toxic formaldehyde- seal it well)
When I kept a large BCI (for years) I did so in a modified very large "aquarium"...call me "old-fashioned" but she was healthy. (she was a terrified defensive biter, a homeless rescue I took in, & after I calmed her down I hoped she'd stay a manageable size for me; she did for 12 years but after that I reluctantly re-homed her with friends who are into big snakes)

Thanks caro, looks likebi have alot of thinking to do. I got the wood for the frame for free which started this whols idea I was going to give her a whole spare room but decided against it when thinking of how long it would take to clean every week lol. One concern i have about glass is transporting it as i have a small car and 6x2 is a pretty big sheet. Thanks for all the tips, Mike.

Even if you had a truck to transport it, hauling tempered glass would be daunting, as would building a cage with it. I can see why many boa-keepers just go with the "plastic" cages, and you can buy kits to save on shipping if you put it together yourself. (Hint: the really large cages for heavy boas can use the extra support of a wood frame/platform.) I love your ideas of both a natural cage (with plants) & using a whole room, but sadly, neither one are practical unless you have no other life, lol.

There are one or 2 companies that use HDPE ("food safe") plastic for snake cages but even HDPE isn't designed to be heated 24/7...frozen food containers made from it specifically say "do not re-heat" because they break down with heat. Here's a link for one of many that discuss the "safety" of plastics, but it's a bit like climate change..."an inconvenient truth". Note what it says about PVC...the most toxic.
https://www.lifewithoutplastic.com/s...s_no_1_to_no_7
I have a feeling that some day scientists will admit that many of the cancers we now have are related to the rise of plastics everywhere...but probably not in my lifetime. Humans are reliably stubborn....I hope they can figure out a way to make plastics inert.

In the meantime, I still like glass. The "drawbacks" for boas can be dealt with: retaining humidity has nothing to do with the material (glass or plastic) because neither one lets air in...it's a matter of minimizing air flow with the kind of top you design, and
glass itself can be easily insulated on sides & back for both privacy and minimization of heat loss. I also prefer to offer my snakes "belly heat" and glass is perfect for using UTH (I use Flexwatt, if you're wondering). In your shoes, I'd personally make a sturdy stand with the wood & buy a giant aquarium (& have it delivered), but hey, that's me. My 2 cents...good luck! (I've been making my own tank lids for years too, not hard. And they are escape-proof: I install eye-bolts on the lid & stand in all 4 corners, & use chain & snap bolts from any hardware store, no way a snake can push that off, nor can other pets get in.)

I think I might scour craigslist for a big tank and just build a stand with the wood I already have. I still like the idea of building my own enclosure, maybe on a smaller scale. Thanks for all your help Caro, I really appreciate it.

You're welcome, I've been at this (keeping many snakes) for a while, & kicked around the same things, lol...

I once built a low stand for a large tank & made good storage use under it with some very nice salvaged matching drawers from an old refrigerator. Makes for a nice use of space- the drawers were a dark smoky color that visually blended with the dark stain of the wood, so they looked nice, were very functional (sturdy & slid easily) & held a lot. Creativity is both fun & functional. (I got the drawers for nothing from an appliance repair place- it kept them out of landfill)