When I started woodworking, I didn't know squat. I have progressed in 30 years - now I do know squat.
A king sized bed without a center support is going to require a really, really, really stout structure to avoid sagging and bouncing and cracking apart. (And I mean just from normal movement, "mattress olympics' aside) They are even common on queen sized at this point.
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The most expensive tool is the one you buy "cheaply" and often...
Agree with Jim. My method would be a wood cube or two UNDER the bed .
I used two side to side supports equally spaced with an adjustable foot. Use nylon foot, not rubber. Rubbed stained an area rug. Top of the Support can be designed with same height as side supports so your 3/4 osb can go on top, no slats. Brian
Brian
I remember a couple of bed building videos posted by Charles Neil a few years ago that had some good info. He made T-slats that were super strong and eliminated the need for a center post. I used the idea a few months back to build slats for a friend's queen size bed and they really worked. He also has a good video on using bed bolts.
Yes, you would need two, just like the box springs for a king sized bed. The advantage of two units is there will be a double rib down the centerline where they meet, adding to the stiffness. And, if desired, it would be easy to add an adjustable center support, or anywhere else, by means of a dado in one of the center ribs into which the support is bolted or screwed before adding the other torsion box. Adding a spline or other means to join the two boxes together would make them behave as one unit, too.
John
I would not use OSB or similar for this kind of project for multiple reasons...splintery which can damage a mattress being one of them. While most mattresses today are designed to work fine on platforms, having ventilation under them is also a good thing which is why slats are so popular. The slats can be heavy Tee-shaped like was mentioned eariler to handle more load, but even then, I remain convinced that a center support for something as large as a king sized bed is a good idea. The robotic vacuum will deal with it just fine.
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The most expensive tool is the one you buy "cheaply" and often...
I made a queen size bed with hickory. The side rails of the main frame are 8/4 x 12" wide boards. The headboard and footboard are also 8/4 hickory using frame and panel construction. The side rails attach to the foot and headboard with mortised bedrail hardware from Rockler...just slide in to lock. I have only four legs with no center leg. My slats are 4/4 poplar boards. In the mid-span I have a 8/4 x 8" wide white oak board going from the head to foot. It attaches with sliding dovetails to the center of the header & footer and supports the slats very well. The bed is SOLID. I'm quite sure I could park a car on it. I don't know what it weighs, but probably hundreds of pounds.
SB
I used one of these for a king size bed as support under the slats. We are a few years into that bed and so far so good.
https://www.knickerbockerbedframe.co...l-slat-system/
- After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off
- It's above my pay grade. Mongo only pawn in game of life.
I've made 7 beds that I remember all platform beds without a boxed spring. I built a torsion box structure for one my son and his wife now use and it is very firm. I don't know what they weigh but neither of them is small. But that requires more height. I built the bed to a plan that assumed a boxed spring so the torsion box used up that space. My more recent beds have had either slats or 3/4 plywood to support the mattress but never both. 5 of the beds I've made are queen size, no kings. I haven't done the calculations but I think the plywood deflects more. I haven't had any issue due to the lower "breathing" of the plywood support under the mattress. I've never put in a center support. I haven't made a king yet but my daughter and son-in-law are talking about one.
I think your ash slats are plenty stout and may not need to be T shaped. I don't think bed slats need to be as sturdy as a shelf or a house floor. If it deflects 3/4 inch I don't think you'd know it. The resulting angle is slight. But less deflection will translate into a firmer feeling bed. So I think it depends some on how soft your mattress is and how firm you want the bed to be. If you want to put something on top of the slats you can but I would not do it for structural reasons. You might even think of using 1/4 masonite or 5mm plywood. T shaped ash slats are going to give you a very firm bed. If you space them around an inch apart I don't think you really need anything but the mattress on top. I made my daughter a full sized bed with 3/4 baltic birch slats spaced about an inch apart when she was still in college. That bed is now in her guest room and my ex wife and I slept on it. The bed was small for the two of us but there was no noticable deflection due to our >350 lbs combined weight. I'm sure they deflected some but we did not notice it.