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Loft Bed #1: Initial design requirement and a joinery concept

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Blog entry by coloradoclimber posted 2129 days ago 3514 reads 0 times favorited 3 comments Add to Favorites Watch
no previous part Part 1 of Loft Bed series Part 2: wedged half dovetail and a concept assembly »

My kids are getting bigger and they need more floor space in their rooms. We’ve decided loft beds might be the way to go. Get the beds up in the air, create some desk space under the bed, and free up some of the rest of the floor space.

I’m in the early design / concept phase right now. Some of my criteria include:

- fits a standard single bed mattress
- strong enough to hold a full size man, say 200+ lbs
- robust joinery, kids / teenagers can be tough on furniture
- knock down joinery, if they ever leave for college they might want to take them with them, and if they don’t want to take them I’ll want to be able to break them down for storage.

It will be a fairly standard loft bed, bed on the top, desk space underneath. Function over form. Not a lot of fancy rails or balusters. Easy to get into and out of.

My first thoughts are a simple frame, rails across the back and ends.

Simplified Frame Outline with just the side rails and posts

simple frame

I want to avoid gluing the rails to the posts. I want the entire bed to be able to be broken down in to a bundle of sticks.

I want the joints to be strong but able to be tightened if they loosen through use. This eliminates nails, screws, and lag bolts in my mind. Carriage or through bolts would likely work ok.

It needs to be reasonably easy to disassemble. Simple tools and not a lot of complex joints.

Think of something you could have broken down and put in the back of a covered wagon, hauled across the country, set back up when you got to California using only simple tools, and had it last for at least 3 generations.

The above requirements lead me toward some kind of a wedged joint. Something that will tighten up when the wedges are driven home, that can be further tightened by seating the wedges more, and can be disassembled by driving the wedges out of the joint. It also needs to be strong in use.

I considered a wedge pinned mortise and tenon. Basically a large mortise and tenon with a wedge shaped side pin through the tenon. I think it would work but I don’t care for the looks of the through wedge.

simple frame

Another thought is a wedged through tenon. Extend the tenon through the end of the mortise and put the wedge outside of the tenon. Again suffers from aesthetics. (drive a wedge in the hole in the rail)

simple frame

The direction I’m leaning toward is a Wedged Half Dovetail. The joint is pretty simple, it should lock pretty tight, it can be tightened by driving the wedge in, it can be disassembled by knocking the wedges out.

simple frame

simple frame

I drew the picture with the top and bottom of the mortise with sides at 7 degrees. Looking at it I think 7 degrees is probably ok for the half tail but is probably too steep for the top wedge. I need the top wedge to lock when driven in. I’m thinking maybe 3 degrees might be a better angle. I’ll play with some concepts and probably prototype up some and see how they fare.

And I figure if things to too far wrong I can always drill a hole and pin them tight with a cross through carriage bolt through the tenon.

simple frame

I’m open to other ideas. What else have you tried? No glue, locks tight, can be further tightened, knocks down easily, strong enough to last multiple generations.



3 comments so far

View RobH's profile

RobH

465 posts in 2645 days


#1 posted 2129 days ago

I am not sure about any of the methods other that the second one. I will have to defer that option to someone who has a little more experience with that type of joinery.

If it were me, though, I would either half-lap and use bolts through the joints. It is a loft bed for a college student. I am quite sure that no one will appreciate the non-use of metal in the joints. Plus, that makes is easier on you. Also, with bolts, you will not have to worry as much about said college student keeping an eye on the joint tightness. I know when I would have tightened the joint. Yep, when I fell out of the air one night.

Just my $0.02.

-- -- Rob Hix, King George, VA

View Derek Lyons's profile

Derek Lyons

584 posts in 2163 days


#2 posted 2129 days ago

If the kids want to take it to college, might they want a more conventional bed by that point? I’d consider modifying the design to allow for the bed and desk to be assembled in a more conventional fashion as well as ‘lofty’.

-- Derek, Bremerton WA --

View Doug S.'s profile

Doug S.

295 posts in 2303 days


#3 posted 2128 days ago

If I were building it I think I’d not want to cut away 2/3rd’s the thickness of the rails for a through joint, but rather a straight or dovetailed halflap then decent looking hardware through the halflap and post. Or even just butt joints with cross dowels or other knockdown hardware. Something about thinning the rail ends down would just worry me, but then I tend to overbuild things anyway.

-- Use the fence Luke

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