Have you already secured materials for this project?

Could you sketch out a quick plan showing house, deck, existing retaining wall and where you propose to add on to it. (I don't quite understand your explanation.) It doesn't need to be to scale ... just reasonably proportionate. pencil on paper.

Since there is not current design for the wall addition, I'm speculating that the contractor is over-estimating what is needed and the cost, adhering to the CYA principle. 2' deep and 3' high sounds a bit overblown from what I'm guessing. I'm wondering if you couldn't use an altogether different (modular block) system and build an entirely new wall (with a curve or corner at where I think they might join) ... and save some money.

https://drive.google.com/file/d/0By1rlumPGq9ecFZkUzVkemtqck0/view?usp=sharing

Thanks. Sorry I was having trouble uploading my landscape design sketch. Try this?

I've only been given a proposal but haven't bought materials yet.

It's the case that in order to understand the particulars, it's necessary to understand the overall, which I cannot do from your picture. At first, I thought the wall was extending to the left (as facing the slope) and continuing on below the fence, where you have "planters" marked on the plan. Now I'm thinking it is at the right where you have an elevation differential ...?? In order to understand this better, you need to show the whole back yard from the view point of back of house at center of wall, using a series of slightly overlapping photos that pan from left to right.

Now I think I understand why you were speaking about such a large wall for the proposed portion. From my perspective, still without knowing much, this seems like an inefficient plan. Maybe I'll find out I'm wrong, but that's where it seems like it's going as of now. I don't know how true to the plan you intend to be, but there are errors in the way you are designing the patio edge, both in the way the edge intersects with the wall and in the surplus of tight radius curves along one side. It's going to be better to simplify/smooth that line.

Thanks for the insight. Sorry it is a long but not a deep backyard and cant be captured in one pic. As mentioned, the new wall to built is to contain the slope dropoff that cuts near the center of the yard. The paver border shown here may have a lot of room for adjustment. I might go with straighter lines which probably agrees more with my modern-transitional style.

When the words, plan and pictures correlate, many details that are explained in words, but misunderstood, are clarified.

"... it is a long but not a deep backyard and cant be captured in one pic." The way you capture this long, shallow back yard is to stand at the back center of your house and begin by aiming the camera straight left (such as in your first picture above.) Then PIVOT the camera slightly rightward and take a second picture that SLIGHTLY OVERLAPS with the first. Continue pivoting the camera rightward while taking slightly overlapping pictures until you have completed panning the whole yard, where the camera is looking in the opposite direction as it was in the first picture. Post the individual pictures. Don't make a panorama out of them. If you do this, we CAN SEE your whole back yard. It is important NOT to change the camera location while taking the series of pictures.

Thanks for your thoughts on the slope in the lower yard - valid point. The lower part of the yard never had a retaining wall... just a slope on that end with no defined ending point, thanks to the previous homeowner of 40 years. OK, I'm attaching a photo of the left part of the retaining wall and the right part of the wall where it ends (see garden hose). That's where there is a straight line dropoff from the plateau 2.5 ft down to the lower patio. I'm actually considering a modern style horizontal wood retaining wall against the existing brick retaining wall... and continuing it at the 90-deg wall as well - integrate some bench seating and planters centered around that corner.

Hope that helps you picture what's going on.

To answer your questions:

Yes the new wall (perpendicular to existing wall) will be approx 18"H on that side, 30"H from the lower yard/patio.

Where is this project located and how deep is the frost line? Los Gatos, CA (by San Jose) - so we don't quite get to freezing temps.

Will the BBQ grill's home be on the wood deck, or somewhere else? Grill will likely sit on the new deck.

These are half the pictures that are needed. You need to return to the exact position where the camera was and continue with overlapping pictures to the far right and far left, so that the scene connects with the house at each side. In landscaping, one does not know if they can do something until they know how it affects what is next to it. We have not seen the far right of the yard. We can't use the original (first) picture with the new one because the camera position is different resulting in different focal lengths, i.e., the pictures (new and old) cannot be reassembled into a single scene.

Built-in seating needs to relate to where people will be milling about. Near the putting green makes sense, but why 30" height seating? It seems very high for that purpose. Too, the putting green area has positive view potential (from viewpoint of the deck) so why kill some of that with a low wall?

Good that there is no frost line to worry about. Consequently, a wall footing does not need to be very deep.