Sizing and laying out a deck

Almost every deck conversation starts with a size that came from nowhere. Sixteen by twenty, because that sounds right. The trouble is that a deck too small for the furniture is useless and a deck too big is expensive, and both mistakes are permanent in a way that a paint color is not.

There are four inputs that should set the footprint, and they should be worked in this order.

1. The recorded plat

Before anything else, find out where you cannot build. Meridian subdivision lots carry recorded easements, and the city's typical figures are 10 feet across the rear yard, 5 feet along an interior side yard, and 15 feet on the street side of a corner lot. The city is explicit that a structure in the required rear yard is likely encroaching, and that if a beneficiary needs access it may have to be moved and replaced at the owner's expense.

On a Meridian lot with a 40 foot deep back yard, a 10 foot rear easement removes a quarter of it. That is a bigger constraint than any design preference, and it is knowable in ten minutes from the plat.

2. The furniture

Measure what you own or what you intend to buy, then add circulation. Working figures:

• Six seat dining table with chairs pulled out: about 12 by 12 feet of clear floor.
• Four seat lounge grouping around a low table: roughly 10 by 12 feet.
• Grill: three feet of clearance in front and to each side, and not directly under a low pergola beam.
• Circulation past a seated person: three feet minimum, or people stop using the route.

A household that wants dining and lounging and a grill needs somewhere between 300 and 420 square feet done honestly. Most Meridian decks land in that band, and the ones that end up unused are usually the ones sized at 200 because the quote looked better.

3. The door and the height

Where the door sits above the finished ground decides more than most people realize. Three cases:

• Under 30 inches. No guard is required. Cheaper, and visually far more open, because nothing stands between the kitchen window and the lawn. On flat Meridian ground this is often achievable by stepping the deck down one level from the door.
• 30 inches to 4 feet. Guard required, and a stair run of four or more risers which brings a handrail with it. This is where rail becomes 20 to 30 percent of the budget.
• Over 4 feet. Taller posts, bigger footings, longer stair, possible landing, skirting to consider. Common on Boise and Eagle foothills lots, rare in flat Meridian.

Stepping down to stay under 30 inches is worth pricing as an option even when the door is higher, because the saving on rail and stair can be several thousand dollars. The railing guide covers the code side of that decision.

4. Which way it faces

In this valley, orientation determines whether the deck gets used. A west-facing back yard at 2,600 feet with a July normal high near 93 degrees is uncomfortable from roughly two until seven in the afternoon, which is exactly when a household would otherwise be outside.

If the yard faces west or southwest, plan the shade at the same time as the footprint. That might be a solid roof over part of it, a pergola, or simply positioning the seating zone where the house casts a shadow in late afternoon. All three are design decisions, and all three are cheaper now than later. The shade guide works through them.

Shapes that work

The simple rectangle. Cheapest per square foot, and it is the right answer more often than designers admit. Square-ish proportions also cost less to rail than long thin ones, because rail is priced on perimeter.

Two zones with a step between. A dining area at door level and a lounge or fire pit area one step down. More framing, but it defines spaces without walls and it keeps the lower zone under 30 inches, which can remove a guard from part of the run.

The wrap. Turning a corner of the house to catch a different aspect. Useful where the back yard faces west and a side yard faces north, giving somewhere to sit in the afternoon. Expensive per square foot because of the extra perimeter and framing complexity.

What to avoid: long narrow strips. A 6 by 40 foot deck has the same area as a 15 by 16 and roughly double the rail, and nothing fits on it.

Sketch it on the ground

Before anyone quotes, mark the footprint in the yard with a hose, some spray marking paint, or a few stakes and string, and put the actual furniture in it for an evening. It costs nothing and it settles arguments that a drawing cannot. It also shows immediately whether the grill is in a doorway and whether the route to the gate still works.

Once the shape is settled, the cost estimator will put a range around it in about thirty seconds, and the cost guide explains what each line in that range is doing.