We are 95% sure its Kwila, its not had an oiling in a VERY long time, its about 12 years old. The wood is hard and nails dont seem to pop up which is a plus. We have tried 3 brand name deck cleaners and none of them have removed the silvering, its clean, but it has patchy silvering. Is the only fix to the problem to sand before oiling? If so is a stand up belt style floor sander the best to hire and use? Its about 60sqm all up.

Challenging conditions: a) -35c in winter b) On a slope, 3 ft difference c) New house, the ground still on settlement d) I never build a deck [img]https://cimg3.ibsrv.net/gimg/www.doityourselft.com-vbulletin/1024x227/img_8584_3dda2d2205bb7c01260a487cab6e62940ada7657.jpg[/img] [i]the slope and the current stair ...[/i] [b]The plan[/b] [img]https://cimg8.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x1081/screenshot_2022_09_18_at_00_32_21_b9fa21b2226ea90091ec144b729d0205ce37a8fa.png[/img] [img]https://cimg5.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x669/screenshot_2022_09_18_at_00_34_29_41c21e9809f2dc89fe59a7d5b5080c78d779fe28.png[/img] [b]Plan A - Separate into 3 frame[/b] Frame#1: [use 2x6] connect to the stair, supported by 2 concrete footing (pad) (problem: cannot adjust the height). Frame#2: [use 2x6] support by concrete footing. TWO of them with height adjustable bracket, TWO without (problem: cannot adjust). Frame#3: [use 2x8] Supported by 6 adjustable screw piles and ledger board which attached the house. [b]Plan B - one big frame[/b] THREE on the left is concrete footing (pad, not adjustable), the rest is screw pile [b]Ideas and problems:[/b] 1. As there is only 10" in height from the ground on the stair side, it's not possible to use any adjustable post. Has to build it as low as possible to connect to the last step of the existing stair, otherwise, I have to build steps/ stair with handrail ... I try to avoid it by install railing on the new deck up to the current stair, make it the only way to the sod. That makes Plan B not quite work as it's too low to use 2x8. 2. Not sure about the structure of PlanA: Frame#2. I stopped after drawing the Joists, how about the beam? no height for both beam and joist, and not sure how to calculate the loads with similar structure on Fram#1 ... stuck here. 3. If I used screw pile on every post (9 of them) in Plan B, is it a proper design, especially the joist with ledger? would it be too long? (the code states: 10 ft joist with 3[2x8] as beam.) 4. It is really expensive to install 9 screw piles ... ($200 for 1), but it's simple, 10 ft pile passes the frost line and adjustable on every post. I am really struggling now. Any advice would be welcome. Thanks.