Dear Tiffany,
Thank you for sending photos and videos of your friend's house. You told me your friend plans to extend the existing deck and add a screened patio. He also ordered this platform sectional sofa for his future patio and wants to know the optimal locations for this furniture.
Please see my suggestions in the following sketches.
Before diving right into the furniture's location, I want to clarify the design parameter of the current deck plan. This project is considered an R5 residential building with a deck. The existing deck area is 420 square feet, with 330 square feet of deck extension. This single detached house is located in Arlington, Virginia. Typically, we can find our local design criteria on our jurisdiction's website. Here is the guide to all design codes used in Arlington County that I will use for the following discussion.
Furniture Location
First, to answer your primary concern about locating this 4-piece sectional furniture that you like.
From your photos, it looks like this house is situated in a green and woody area. In scheme A, putting your sectional platform sofa at the south corner of the "covered patio" can extend the indoor activities to outdoors and maximize the circulation area on the deck. Guests' primary focus will be on the gathering event and center around activities and conversation.
He could also go for a similar but smaller sectional seating that will fit on the north corners of the patio. In this arrangement, the seating at the north corner will be close to the outdoor grill, convenient for serving guests. Scheme B offers the best view towards the woody backyard. The unobstructed views of vegetation and serene moments will help guests regain mental restoration, relaxes them after intense work schedules.
(See our place for more science literature and how outdoor vegetation, onsite food, and social connection help our physical and mental well-being.)
This option extend the indoor activities to outdoors and maximize the circulation area on the deck.
This option offers the ample view of the woody backyard. The unobstructed views of vegetation will help guests regain mental restoration.
Covered Patio Area
Second, I suggest modifying the planned patio-covered area to match the existing railing posts and deck structure. So the load can directly transfer to the footing without much obstruction.
Other than the furniture placement and covered area, I want to highlight a few potential issues related to building codes so he can communicate with the contractor to ensure the best quality of his new patio.
The patio screen: Per AH 106.3 in IRC 2018, the extruded aluminum member of the screen enclosure shall be more than 0.04 inch, and the screen density shall be less than 20 threads per inch by 20 threads per inch. Though the screen is meant to block the insects from flying in, this design criteria is to ensure there will be adequate outside airflow within the covered area.
The patio strength: Per AH 105.1, the patio cover should be designed to resist the local's minimum wind load. Thus, we can use its judicial residential design perimeter to calculate the wind load. In this case, a designed wind load is 0.00256 (mph)2, which equals 33.856 PSF (115x115x0.00256).
The other issue worth noting is the local frost line. In this scenario, the local frost line is 24 inches, meaning the footing needs to be placed below 24 inches from the ground surface. (For more details on patio and deck structure, please see this article)
I hope you like this furniture layout and agree with my recommendations.
Your affectionate friend, Hepburn