what type of wood is this?

You don't want T&G for a deck because the water will sit on it and rot the wood because the water cant escape. It will just sit on top. That is the main reason why there is a small space left between decking boards. Decking is typically 2x6. You can use 2x4 if the supporting joists are close enough together like 16" on center. If the joists are further apart, you should use a 2x6.

Use white cedar or redwood. These days people are mostly using composite decking because bugs wont eat it and water doesn't damage it.

Check out timbertech.com or correctdeck.com

It's not at all a good idea to use any kind of tongue and groove wood for an outside deck, even if it is pressure-treated. The problem is that water will get into the cracks between the boards and sit there, causing it to rot, and it will rot even if it is pressure treated. For exterior decks you need about a 1/4" gap between the boards to allow water to evaporate; don't butt them tigthtly together as this is asking for trouble.

If it is used on a porch that is sheltered by a roof, that is a different story, and you can get 1x3 T&G fir for this purpose, running it perpendicular to the wall of the house.

I am not sure if you can get a tongue and groove for out side use as a decking. You may want to check with your near by home center to see if there is such a thing that can be ordered. This would not be something you will find in the store if it's available.

You could use pressure treated lumber that is smaller in width and put them closer together, still allowing some space between each board.

As suggested it isn't common, though in the past was widely used on covered porches, and primarily painted to aid in it's life span.

Certainly composites are available in narrow "Board" styles, and may not need the same spacing as even PT lumber, but the other issue as suggested, even if you were to get long term service from the deck, is NO drainage. Composites would help with the decay factor, but hold water on the surface.

No offense to your Style at all, but what you suggest is totally impractical.

You can of course use 2 x 4 stock as opposed to 6/8/10, but you'd still need some drainage spacing. You could use decking lumber at 5/8~ 7/8, perhaps at 5 3/4 wide. Then there is the issue you don't state, about finishing the decking.

Steven Wolf

AKA: The Deck Doc

Cedar is a good choice although the quality has gone down in recent years due to the price pressure from big box stores like Home Depot. High quality cedar is quite expensive but very durable. I build a lot of decks and try not to use tight knotted cedar because inevitably you will get variations in quality and color that sometimes can be quite drastic and ugly. As for exotic hardwoods yes they are an excellent choice but to agree with the other poster you must be careful with where they come from. I do not believe that any Mahogany foresting is sustainable due to the 3rd world country's that own these forests and their sometimes less than honest sustainable designations. If you are having trouble affording the material of your choice might I suggest building the deck on multiple levels stepping down as you get farther from the house. That way you can build the first section smaller than the eventual size and add on as budget permits. At least that way you can get the material you want and eventually have the surface area you desire.

Lumber yards still stock tongue and groove. I bought some last summer. It is what was used on porch floors in the old, pre-pressure-treated days. The most common wood is fir, but you can also sometimes find yellow pine. I have used both on my porches, and found the fir to be much more durable and stable.

I agree it will last much better under a roof, as on a traditional porch.

Use 5/4X4 pressure treated decking. On porches where I come from they used 1X4 boards for the flooring. They ran straight out from the house, had a space between them and were painted(usually gray). The 5/4 looks the same. More elaborate porches had a different way but I think that is what you want.

You don't use tongue and groove on a deck. The boards need space in between to drain, also to expand and contract. I don't know how wide you are talking about but they make treated deck boards with rounded edges that is basically a 1x5.5.