What is your climate? And any activities you want for each terrace? Dining? Kids' play space? A water feature of some sort would be lovely. Could add some fake lawn (putting green even!) for part. This product has come a long way!

As far as spacing between the pavers, you want a minimum of 3mm or ⅛ an inch, but the ideal spacing really depends on the whole space and how you want to fill the space between pavers. If you are thinking about pea gravel or sand, you probably want less space between to help keep your costs down and make it easier to power wash. If you are looking to add greenery then more space between the pavers gives you more green, creating a more natural-looking space. If you do decide to go the gravel route, you can apply a clear coat of something like gravel-lok. It acts like glue, keeping the gravel in place. It may not be able to take the full force of a power washing, but it will certainly hold the gravel in place better than not having gravel-lok. If you do want to go for a green option, grass could work, You could also look into small succulents, moss, or clover. With any green option, you will have a little more maintenance in the form of trimming and watering, but the look is stunning! You absolutely can put grass between the pavers. It will actually help stabilize and hold the pavers not move them. (if installed correctly) I would space it 4” apart and use netfin or a similar subsurface drip line to water the grass underneath the soil. This look is probably my favorite but you could also use a crushed aggregate in between too. Gravel is a terrible idea because it doesn’t stay in place. Here are some ideas from our projects of all kinds of paver designs:

Red tall grass is reed grass. The low broad leaved plant is day lily and the low one is opiopogon.

Hi Namrata - The grass height doesn't matter as much as the grass density (i.e. the number of stitches per sq meter) - higher the better. The below balcony from one of my projects uses turf with a height of 25 mm and density of 18000 stitches/ m2 . Hope this helps!