What size slide do you need for a 4 ft or 5 ft deck?

The short answer

Buy the slide made for your deck height, not the one with the right length. Home slides sold for a 4 foot deck have 74 to 91 inches of chute and reach 5.5 to 6.3 feet out from the deck. Most slides for a 5 foot deck have 100 to 119 inches and reach 6 feet 9 inches to 8 feet. Then keep 6 feet of clear, surfaced ground past the end of the exit².

The rule people quote, a slide twice the deck height, is roughly right for the chute and wrong for the yard. The chute is the long side of a triangle. The ground it covers is 1.35 to 1.6 times the deck height in the slides below that publish it, and the clear zone past the exit comes on top.

The CPSC slope rule behind the numbers

The public handbook does not set a slide length. It sets a slope: for preschool and school-age children the chute's average incline should be no more than 30 degrees, which it states as a height to horizontal ratio that "does not exceed 0.577"¹. For toddlers the limit is 24 degrees, a ratio of 0.445¹. The height in that ratio is the platform's height above the exit, not above the ground, and the horizontal distance runs from the start of the chute to the exit¹.

The exit itself has numbers too. It should be at least 11 inches long and nearly flat, no more than 11 inches above the surfacing on slides 4 feet high or less, and between 7 and 15 inches above it on taller slides¹.

Two things follow. A lower exit means a longer slide: drop the exit of a 5 foot slide to 7 inches and the sloped run rises to 92 inches. And a toddler slide is far longer for its height. A 3 foot toddler deck with the exit at the handbook's 6 inch maximum has a 30 inch drop, and 30 divided by 0.445 is 67 inches of run, more than twice the drop¹.

None of this is law for a backyard. Publication 325 is guidance for public playgrounds, and the home handbook gives no slide angle at all². Home equipment is built to ASTM F1148, a paid standard not read for this page. CPSC, ASTM and how the rules work explains the difference, and slide safety covers the rest of the chute geometry.

Seventeen slides, by deck height

Four patterns stand out.

• The 4 foot chutes cluster at 74 to 91 inches³⁴⁷⁸⁹, and most 5 foot ones at 100 to 119 inches^51011121419. Gorilla's Super Scoop is the exception at 84 inches for 5 feet, a scoop that comes out 81 inches¹³. No chute reaches twice its deck height.
• The ground run is 1.35 to 1.6 times the deck height on every straight, wave or scoop home slide that gives one: 66 in from a 48 in deck, 72 and 76 in from 4 foot decks, 81 and 96 in from 5 foot decks, 108 in from 6 feet and 132 in from 7 feet³⁴⁵⁶¹³.
• The commercial slide runs longer. The Starglide reaches 9 feet 6-1/2 inches from a 5 foot deck, 1.9 times the height¹⁷.
• A spiral saves length, not area. Backyard Discovery's 5 foot spiral tube comes out only 4 feet 7 inches from the fort, but it is 61 inches wide and 55 inches deep¹⁶.

"Length" means three different things

"Length" is the sliding surface on PlayStar's pages³, the assembled chute on most of Gorilla's, and the installed ground run on the Starglide¹⁷. Gorilla lists its Summit slide at 91.5 inches and, on the same page, at 44.25 inches, its packaged length⁹.

Only one figure matters for the yard: how far the exit lands from the deck. PlayStar calls it horizontal distance; Gorilla answers "How far from the fort does the slide come out?"³¹³. Where it is not printed, plan on 1.6 times the deck height, the top of the range above.

How much ground the whole slide needs

Add 6 feet of clear ground past the end of the exit. The home handbook asks for at least 6 feet of play area around every piece of equipment and says a slide should not exit in front of a swing². The public handbook asks for 6 feet in front of the exit on slides up to 6 feet high, and for taller slides a distance equal to the slide's height, up to a maximum of 8 feet¹.

The whole strip gets protective surfacing. A slide's fall height is its platform above the surfacing¹, so the deck sets the depth for the entire run: the depth and fall height chart gives it, backyard surfacing compares materials, and the mulch calculator gives cubic yards. Recheck the exit height once the fill is in, since it is measured to the surfacing, and slide exits are where the handbook says loose fill is displaced most¹. Surfacing under swings covers the same problem under the seats.

Small yards and replacement slides

If the strip does not fit, lower the deck: each foot of deck height adds about 1.5 feet of run. A spiral shortens the run at the cost of width¹⁶. Aim the exit along the long side of the yard and away from the swings, whose zone runs twice the beam height front and back. Small yards covers the other trade-offs, and the playset fit checker adds up the footprint.

A replacement slide is a deck height question first: buy inside the new slide's fitting range, and check what mounting lumber the box leaves out (Backyard Discovery's kit needs a board¹⁵). Repairs and replacement parts covers sourcing, and buying a used playset what to check on an old slide.

Where this stops applying

These figures are for plastic home slides mounted on a deck. A freestanding slide also needs 6 feet in front of its ladder and at both sides¹. Toddler slides follow the stricter 24 degree limit and need a longer run for their height¹; playsets for toddlers covers under-fives. The public handbook asks for shade on bare metal slides¹, and heat and burn risk explains why. If your manual gives a larger clear zone, use its figure.

What to do next

Measure the deck, find the slide's fitting range and ground run (or use 1.6 times the deck height), add 6 feet and stake the strip clear of the swings and every fence. Then compare chute types in slides and check the finished exit against slide safety.