Hi, amiwhere. I also selected IPE to build my own deck. Absolutely no regrets now after about 6 months. (I built that one and only one deck... IPE Deck link below. It doesn't make me an expert like the contractors that build many decks and see many failures.) I used Anchorseal to avoid checking as is typically recommended. I put it on immediately after each cut. I was concerned about how it made the ends dark. Ironically, the sealer (Woodrich) didn't stain the ends as much. Now they are lighter. It looks ok and will likely be even less noticeable after the next staining. I just checked for checking. There is none at all. I didn't mind paying for the IPE but the idea of drilling into the face of it, at the price, seemed to be a sin. They say that plugs look "clean". I see IPE damaged with many spots... http://blog.eastteak.com/index.php/2009/05/qa-i-want-to-screw-and-plug-my-ipe-deck-what-do-i-need-to-know/ I had planned to fix problem spots with screws through the face but ended up avoiding that as well. I used Deckmaster underfasteners for overhangs such as the front of each step. It worked well but was very hard work. I had to use a rachet many times... not easy. The screws were able to screw into the IPE on their own because they are thick enough. However, IPE is so dense that the wood has nowhere to go. It cracks (mostly heard cracks, didn't see cracks) to make room for the screws. So I predrilled pilot holes. The screws were then able to drive through the fastener and IPE to poke up through the face. It takes some patience to drive them in just enough. I fastened most of the decking with Tigerclaw TC-Gs after using a router to cut groves for them. Some comment that they will fail over time. I don't have any failures to know what they are talking about yet. It apparently hasn't been long enough for mine to fail. I also don't understand exactly how the TC-Gs are suppose to fail. If the screws loosen up over time then they would likely be supplied with longer screws. Tigerclaw TC-Gs seem to be developed more recent then other clip designs. They seem to be thicker, SS, etc. Also, I was encouraged by how Timbertech endorsed them by starting to sell them as their Consealoc brand. TC-Gs automatically create a 3/16'' gap. I learned to like that given that moist air needs to escape out from under the boards to avoid cupping. The 3/16'' was apparently very consistent because I planned using that dimension and reality worked out to be the same. Something doesn't seem right about your comment of dirt and sand building up in the cracks so that weeds grow up. Are the boards so low to the ground that rain doesn't wash dirt away from the boards? IPE will cup if there isn't enough airflow under the boards. And, sand and dirt should be able to easily wash away to that space under the boards. Here is a link that might be useful: IPE Deck

There are several aspects of a deck that make it feel solid. Joist width is just one, and according to the AWC chart you're ok up to 13 feet even with 24" OC spacing. To make it solid, space the joists closer together, put blocking in at mid-point, put diagonal bracing between the posts and beams/joists if it's high off the ground. I think a 2x12 would be overkill, though it certainly wouldn't hurt. Here is a link that might be useful: AWC Guide (see page 3 for joist table)

Lots of questions here so I'll try to give my answers based on my experience in playing with both biscuit types and CAMO, as well as my customer feedback. I'm now leaning towards preferring CAMO as a hidden fastener because I think it gives you the best stability possible out of all types of hidden fasteners. With CAMO, you are putting two screws into each joist at a 55-degree angle. With a biscuit system, only one screw. I also like the fact that if you do have problems with a board, you can remove the CAMO fastener and remove the board and replace. It's much harder to do with a clip system and even then you have to plug the replacement board on one end according their own instructions. The gap is a little wider but I don't think you will be able to tell much of a difference with a 6" board. They have a 4" jig out now. How much airflow do you have under the deck? How high is it off the ground? These factors are important if you ware worried about cupping. Most cupping I've seen is due to no airflow underneath and the deck is low to the ground with a moisture imbalance. A thicker and narrower board helps prevent this, so 5/4 thickness would offer more stability than 4/4 if it works for your budget, but I've seen CAMO used numerous times on 1x6. The screw hole will ride a little higher on the eased edge of a 5/4 board but still very minimal aesthetic. You can see the screw holes if you re looking at them from an angle, but over the top they are barely noticable. Since Ipe is darker, especially if put a finish on it, I don't even think you'd notice them. CAMO's stainless steel screws are 316 stainless (vs. 305) which is what you would want for a salt environment. They are more expensive, but if you do the math with CAMO vs. clip system, CAMO comes out less expensive and I think it's more secure. Finally, PRE-DRILL your holes. Stainless Steel is soft and you will strip out more scews than you care to if you don't pre-drill...and let the screw do the work, don't push down on it. CAMO says you don't have to pre-drill but they do recommend that you do for hardwoods. I concur on this with my testing, especially when you are close to the end of the board. I was able to set the stainless screws without pre-drilling, but I stripped out or broke the head off of 1/3 of them and the boards cracked where I tried to fasten them at the ends. On my pre-drilling tests, they set perfectly. Also, if you decide to go with the CAMO, get the PRO jigs since they have screw guides on both sides, making it easier to install without moving the jig. And get two jigs so you can properly space your boards, as well as a BoWrench to make sure they are snug when you are fastening. Start with the outside part of the board (pushing back inwards to your boards already laid), then fasten the inside edge to keep them snug. I built a little 2x2 sample deck out of Garapa using the CAMO sytem that I can send you some pictures of if you want to see them. If CAMO was available when I built my dad's Ipe deck, I would have used it (we face-screwed and plugged it). Every person I have talked to who has used CAMO has loved it, even an installer I know that hates clip style hidden fasteners but now uses CAMO on every job. I've only had one installer say that he didn't like it, I think becuase he was pretty set in his ways and did't want to take the time to get used to it. So I recommend that you practice on some scrap pieces before you use it on your main boards. I think CAMO just cut a deal with Lowe's so you may see them in the store soon. There are plenty of online retailers to buy from, so maybe buy one jig and a small 100pc package to play with them to see if you like it. If not, keep the jig packaging, clean it off and send it back. Minimal investment to test it out. Sorry this is long but it's my .02. Hope this helps.

Retaining walls retain things like dirt/rain.Normaly they have nothing to do with the House structure. It very well could have been the walls were put in because the basement would flood out during a heavy rain bringing all the dirt with it. Your right that is part of landscaping. If you decide to take em out anyway the piers for your deck support should go below the leval of the missing walls. Geting cross ventalation depends on the final deck plan. Its a deal with skirting I have taken to runing the skirting right into the ground because if I dont the Wallet yells at me because it dosent look finished. This happened so many times now I just do it as drill. Its not a good idea>> the skirting soaks up water,the weed eater hits it,dirt builds up around it things like that