The main concern when replacing the wooden surround on an existing hot tub is the weight involved. A hot tub and its operating equipment weighs around 318 Kilogram. Depending on the depth and width of the tub, you can add another 1361 Kilogram for the water. When building the new frame, think of it like building a load-bearing wall in a house: a lot of the surrounding structure relies on it for support. Construct the new frame with solid, sound lumber regardless of the wood used for the old frame.
Expose the old frame. Locate the nails or screws holding the wooden skirt to the frame. Set the nails with a nail set and hammer or back out the screws with a variable speed drill and a Philips head screw tip.
Cut the nails in the corners. Check the four corners of the frame to discover how they are secured to each other. Slip the metal cutting blade of the reciprocating saw between the corner pieces of the frame. Cut the nails holding the corners together. If they are secured with screws, back them out if possible.
Take note of the frame construction. Each frame has two horizontal pieces at the top and bottom with studs that install vertically between them. Two of the existing frames will have wood attached to them that runs underneath the tub. Label them as sides with runners. Replace these two frames last.
Measure and cut the first frame. Measure the width of one of the two frames with no runners and cut two pieces from the 2-by-4-by-96-inch lumber with the electric mitre saw for the bottom and top of the frame. Measure the height of the frame from the ground up to the bottom side of the tub and subtract three inches to allow for the top and bottom of the frame. Cut one stud for every foot of the width, plus one extra stud, with the electric mitre saw. For example, if the frame is five feet wide, then cut six studs.
Assemble the frame. Place the studs between the top and bottom pieces of the frame. Secure the studs on the ends of the frame first with the deck screws. Secure the remaining studs in the same manner, about 12 inches apart.
Replace the old with the new. Remove the old frame for which you built the replacement. Stand the new frame in place. Repeat this process for the other frame with no runners.
Install the last two frames. Measure and cut parts for the last two frames in the same manner as the others. Cut the nails holding the runners to the existing frames with the reciprocating saw, if necessary. Build the new frames, remove the old ones and set the new ones in place. Secure the corners with deck screws.
Swap out runners and cover the frames. Pull one of the runners out from under the tub and cut one to match its length. Put it in place and secure it to the frames. Repeat this for each runner. Cut the skirt from the 48-by-96-by-3/8-inch wood siding with a circular saw. Secure the skirt to the frames with drywall screws.
Use the same method for surrounds with wood on top, saving the old top pieces to use as patterns to cut the new pieces.
Do not damage the pipes around the hot tub while building the new surround.