Mapei's white unsanded will work. Of course, the warm grey unsanded would show off that brick pattern alot better. :-)

Elephant in the Room: "...we are having a friend do the install..." This is fine with flooring (as in hallways, bedrooms, etc) but not a great idea with stairs. As everyone has said (and I will repeat myself) stairs are EXPENSIVE because they deal with CODE. A 'friend' will have to be willing to take ALL LEGAL RESPONSIBILITY should the product that s/he applies cause A. injury or B. fail code. Most friends aren't that excited to be on the hook for 'helping out'. Carpets HIDE the WORST MATERIALS in the building world. By worst I mean CHEAP and POORLY made. That NORMALLY includes OSB. OSB can be the cheapest of the cheap. It is made up of 'chips' of wood glued together with a waxy substance. The very make up of OSB PREVENTS stuff from being GLUED to the surface. Enter: Vinyl stair covering. Vinyl planks/nosing MUST BE GLUED to the stair's substrate. Imagine the substrate as the WORST OSB possible. Stairs need to be strong and meet minimum code. Builders LOVE to use the CHEAPEST MATERIALS on stairs because stairs are INHERENTLY expensive. So....save $300 on the stairs and you have $300 in your pocket (the GC/Builder). So long as stairs are DESIGNED to be carpeted the architect and builder have NO INCENTIVE to make it out of anything other than OSB. I know this is all new to you. So I will spell this out for you: your assumption about plywood (plywood is EXPENSIVE = saved for places where it is NEEDED) is, sadly, a problem. A plywood stair would be AWESOME for your situation. But I would bet dollars to doughnuts you have OSB. And the subfloor UPSTAIRS is probably going to be OSB as well (see discussion about costs of plywood). OSB does VERY WELL under carpet. Carpet can cover hills and valleys and sagging sections of the subfloor (OSB does ALL of those things and MORE). As soon as you want to put down a rigid floor (where carpet used to be) you MUST ASSUME a LOT of patch/repair. Again, this is where the COST of the repair comes in. I have told my clients to BUDGET $2-$4/sf worth of SUBFLOOR REPAIR when removing carpet. Yes. That is the same price as the vinyl planks themselves. The subfloor repair can DOUBLE the cost of your project. Now ask your friend if s/he is GOING to do the 8-16 hours worth of work to PROPERLY prepare the subfloor upstairs. This is when using a friend gets tricky. So long as you are paying them FULL MARKET VALUE for their labour/skills, your friendship will remain solid. If they are doing this for beer and pizza, then things are going to get VERY tense. I know this is new to you, so be PREPARED for MUCH BIGGER project costs than you originally anticipated. If you have to repair the upstairs subfloor AND REBUILD (remove the OSB and then lay down NEW PLYWOOD on) the stairs you are in for a MASSIVE bill. Rebuilding stairs is worth the same price of the vinyl AND the cost of labour to repair the upstairs subfloor. It runs in the THOUSANDS of dollars. Just so you know.

Thought it might be useful to post the original program we provided to the architect… Character and Style of Home Modern, sleek lines, tall one‐story, as much light as possible ‐ light is of the essence. High ceilings throughout. All windows are BLACK frame (no brown). House is mostly white stucco. Anywhere there is windows and neighbors (North/South), we want to obscure views of the neighbors through the use of foliage or other means. From the moment you enter the wider than normal front‐door (i.e., double doors or other), we would like to see through the main living area out through the sliders out into our backyard area which includes a simple, sleek lines, pool. In addition to the pool, the outdoor living area includes a partially‐covered U‐Shaped area that somehow still allows light into the home (i.e., skylights, plexiglass, louvers, etc. to avoid the typical darkness that you might have from a covered outside area). The home has 3 ensuite bedrooms with the master bedroom separated from the other bedrooms. There is an office with glass doors and a IT/communications closet. There is a 1/2 bath powder room for guests near the great room. The kitchen should be open to the great room. There is no formal separate dining room but a space off the side of the kitchen for a sizeable table that seats up to 10 people. The modern sleek‐lined kitchen includes a large island (all one‐level), all pull‐out drawers and no cabinets above (sleek lined shelves ‐ Kat understands). There is one large nook where the oven and hidden vent hood resides. There is a separate coffee station area which can also be in an open nook. There is a sub‐zero wine fridge, fridge/freezer combo (industrial stainless) and a built‐in oven with warming drawer. Microwave can be with the oven or hidden somewhere else in the island. All bathrooms except the powder room must have open nooks for linens, towels, etc. Powder room has a floating sink / cabinet combo that will suffice for powder room toiletries. The other bathrooms also have floating sink/cabinet combos. All closets lighting automatically turns on and off when the occupent opens / closes the door and/or enters / leaves the space. Laundry / mud room has a closet(s) that has space for hanging coats, cubbies for bags, cubbies for shoe storage, etc. Master bedroom DOES NOT have to be enormous ‐ consistent with your other homes. Our current MBR is 16x18 and we find that adequate. We don't want a separate pool bath but we do want an outdoor rinse‐off shower that doesn't have to be a closed room. At the front of the house, we prefer to have a gradual step up with longer treads versus a standard stair. We would like to have the front of the house walled‐in for privacy and so we can let our small 10 lb dog out in the front and not worry that he runs into the road. The home has an oversized 2 car deep garage with plenty of storage in the rear. A propane tank is buried near the street to heat the pool, any gas fireplace features, and the outdoor weber grill. The home is very energy efficient maximizing the use of green technologies, etc. The outdoor U‐shaped area includes some Ipe hardwood decking.

I can’t name one reputable manufacturer that has it in writing that this is an acceptable installation - LVP has its place just make sure the subfloor is properly prepped. Shaw Floorte - Flooring can be installed over most existing hard–surface floor coverings, provided that the existing floor surface is fully adhered, clean, flat dry structurally sound and free of deflection. Lifeproof LVP - APPROVED SUBFLOORS Concrete, Plywood, OSB, Particleboard, Chipboard, Hardwood (Solid, Engineered, Parquet), Tile (Ceramic, Terrazzo, Stone, Asbestos, Peel and Stick), Non-Cushion Sheet Vinyl, Metal, VCT, DRIcore Smartcore Ultra - Flooring can be installed over most existing hard–surface floor coverings, provided that the existing floor surface is fully adhered, clean, flat, dry, structurally sound and free of deflection. Coretec - Acceptable Subfloor Types: • CDX Underlayment Grade Plywood (at least ½” thick) • Underlayment Grade Particleboard • OSB (at least ¾” thick) • Existing Wood or Laminate Floor • Resilient Tile • Concrete Slab • Ceramic Tile • Non-Cushioned Sheet Vinyl Karndean - Types of subfloor • Timber Floors: These should be solid with minimal flexibility. All loose boards must be firmly fastened, gaps filled and undulations removed. Where necessary, overlay floorboards with flooring grade plywood or similar underlay. • Woodblock/Parquet Floors: Make sure these floors are solid and fix any loose or broken areas. Wood block floors laid direct to earth/bitumen/pitch must be removed prior to installation Mohawk - These vinyl flooring products can be installed directly over most existing floor coverings, EXCLUDING carpet (including needle felt), floating laminate, floating floor systems, lauan and cushioned vinyl flooring.