Even the most veteran of weekend warriors may blanch at the thought of an oval deck, with all its mysterious mitered angles and oddsized pieces. Well, fear no more. As with most things mathematical, there is a straightforward, stepbystep method. To keep things simple, "dekblock" floating piers have been substituted for the hole digging and concrete work usually associated with setting deck posts.
Things You'll Need
 Tape measure
 2by6inch treated lumber
 4by4 treated posts
 Dekpost floating piers
 3inch lagbolts
 Joist hangers
 Cordless drill
 1 1/4inch treated deck screws
 Circular saw
 Miter saw, powered if possible
Measure Your Pool

Measure the distance of both straight sides and width at beginning of curvediameter, probably 12, 14 or 16 feet. We'll use a pool 10 feet across for example.

Multiply diameter measurement by 3.14. Divide this in half. (10 x 3.14=31.4 divided by 2 = 15.52 or 15 feet, 6 inches) That is the outside measurementcircumference of the round end of your pool.

Decide how deep your deck should be from pool to outside rail. Add this measurement for each side to diameter, multiply by pi and divide by two. (e.g., 10 + 6 feet on each side = 22 x 3.14 = 69.8 divided by two = 34.54) This is the outside circumference of the round ends of your deck.
Building the Sides

Make a rectangle of 2by6inch treated lumber the length of the pools straight edge and as wide as the depth of your deck. Attach it to four 4by4inch posts, one inside each corner, at desired height using 3inch lagbolts. Attach one post centered on each long edge. Use joist hangers and 1 1/4inch treated deck screws to add 2by6 joists every 16 inches, perpendicular to pool.

Place one dekblock under each post. Level per manufacturer's instructions. Cut posts, using circular saw, on pool side even with top of frame; cut outside posts to length when adding rail.

Repeat steps 1 and 2 for opposite side.
Building the Ends

Divide pool end circumference by 9. Round up to nearest inch. (e.g., 15 feet 6 inches divided by 9 rounded up to nearest inch = 21 inches), subtract 3 inches; using a power miter (rent if you don't own) cut 9 pieces 2 by 6, on edge, with outside to outside 10 degree miters, with cuts angled away from center at each end. Repeat with outside deck circumference (e.g., 34.54 divided by 9 rounded up = 46 inches) Build trapezoid framea wedge shape with a flat nosefrom 2 by 6 using one short mitered piece and one long. Cut sides same as short side of rectangles from last section. (e.g., 72 inches) Attach, overlapping mitered pieces. (e.g., 46 inches tapering to 21 inches, 72inch sides)

Build nine trapezoids, attach with bolts, nuts and washers starting from one end of side rectangle. Leg same as rectangles. Add sections and adjust before adding two cross members, evenly spaced, in each trapezoid.

Repeat Steps 1 and 2 for opposite end. Add decking, prefab stair stringers and railings for a finished splash deck.This method also works for round pools, just exclude side rectangles.
Tips & Warnings
 Get the free plans from deckplans.com for inspiration.
 Measure twice, cut once.