After going through two warranty exchanges for sagging mattresses from Mattress Firm (ironic, right?) my wife and I decided to try a foam mattress. The problem was that it wouldn't work with a traditional metal frame, so we decided to build our own!

These plans are for a king size mattress from Tuft & Needle, but it should fit other brands as well. Please confirm the measurements of your mattress to ensure proper fit. Final dimensions are 76” wide by 80” head to foot. The legs can be adjusted to the height you need, but this height, combined with the new mattress, matched the height of our old frame, box spring, and mattress. These plans give you tons of room underneath for storing items in large plastic bins.

This frame will be *rock solid* and should last a long, long time. All of the materials are common to any chain store like Home Depot or Lowe's, and the cost should run close to but under $100.

Step 1: Gather Tools & Materials

Tools

Hand or Circular Saw
9/16 Wrench or Ratchet & Socket
Carpenter’s Square
Hammer
Phillips Screwdriver
Drill with small drill bit for drilling pilot holes and larger 3/8” drill bit for carriage bolt holes
Sandpaper

Wood

NOTE: These will be visible, so choose boards with a nice sanded surface for painting or staining

(4) 2x6 boards – 8 ft. length
(1) 4x4 post – 8 ft. length (I recommend having the store cut this into (4) 20” sections)

NOTE: These will NOT be visible, so just find the straightest boards you can – surface does not really matter

(3) 2x4 boards – 8 ft. length
(20) 1x3 spruce/pine furring strips – 8 ft. length

Hardware

(6) 2x4 joist hangers
(24) 1” wood screws (#8-10 size should work, just make sure they fit the holes in the joist hangers – these are usually sold in the small plastic bags of 6 or 8 per bag)
(8) 2.5" wood screws (2" will also work)
(12) 3/8” x 6” carriage bolts
(12) 3/8” washers
(12) 3/8” lock nuts
(1) box of 1.5” nails – you will need at least 60 in the box

Step 2: Make Your Cuts

Cut (2) of the 2x6 boards to 76” – these will be the head and foot

Cut (2) of the 2x6 boards to 77” – these will be the sides

Cut all (3) of the 2x4 boards to 77”

Cut all (20) of the 1x3 furring strips to 76”

Cut the 4x4 post into (4) 20” sections if you didn’t have the store do it for you

Sand all cut edges, especially the ends and surfaces of the furring strips since these will be supporting the mattress.

Step 3: Assemble Outer Frame

Lay the 2x6 boards in a square, with the head and foot boards (76”) overlapping the ends of the side boards (77”) as shown. Use a carpenter’s square to make sure the boards are lining up at a right angle. It’s okay if some of the boards have minor warping or twisting. They will square up as you connect each corner. Working one corner at a time, drill pilot holes for (2) of the 2.5” screws, drilling through the head/foot boards and into the end of the side boards. Screw the 2.5” screws into the pilot holes to connect the first corner, then repeat the process for the other 3 corners, making sure to square them up before drilling your pilot holes.

Step 4: Install Joist Hangers

Next, you will want to attach the 2x4 boards to the inside of the head and foot boards using the joist hangers as shown. The 2x4 boards are shown in purple and the joist hangers are shown in green. When installing these, have a friend hold the 2x4 so that the edge is flush with the top of the head and foot boards as shown below. Holding the joist hanger around the 2x4 board, mark the holes. Then pre-drill the holes and attach the joist hanger using the 1” wood screws (4 per joist hanger). The hangers should be installed on center at 19, 38, and 57 inches from either side, or 19” in between each one.

Step 5: Flip the Frame

At this point, remove the 2x4 boards from the joist hangers and carefully flip the entire frame upside-down. Installing the legs while the frame is upside-down will ensure that the top of the legs are flush with the top edges of the frame.

Step 6: Install Legs

Measure 3.5” from each corner and draw a vertical line on both the head/foot boards and the side boards. Along that line, measure 1.5” from the top and bottom of the side boards and mark it. These will be your holes for the carriage bolts on the side boards. On the head/foot boards, measure 3” from the top or bottom of the line you drew to find the center and mark it. This will be the hole for your carriage bolt on the head/foot boards. Have a friend hold one of the 4x4 legs up against the corner while you drill the holes, going all the way through the leg to the other side. NOTE: If you are doing this indoors on a carpeted surface, you may want to use a scrap of 2x6 board underneath each corner to make sure that the frame is flush with the 4x4 leg. After drilling the holes, install your carriage bolts through the holes, putting a washer on the inside, followed by a lock nut. Do this for all 12 bolts, then tighten them with your wrench or ratchet.

Step 7: Flip the Frame & Install Joists

Flip the bed back over, right-side up, and add your 2x4 boards back into the joist hangers.

Step 8: Add Slats

Line up one of the 1x3 furring strips with the corners of the frame, and make sure the edges are flush with the side boards. Using the 1.5” nails, put 1 nail in each end of the furring strip, driving the nail into the top edge of the side board. Add another nail in the center of each furring strip, driving the nail into the center 2x4 joist. Use a scrap of 2x4 on each end, between each furring strip as a spacer. This will give you the proper spacing for all 20 of the furring strips. Remove the 2x4 scrap after hammering in your nails and repeat for all of the furring strips.