Aluminum Frames in flat construction

Hey all, I've been semi-conscripted to design/build set for a show going into one of my cities more proffesional theatres.
One of the pieces is a flat which must resemble a tree on one side and house on the other. The design brief insists that they be light enough for one person to lift and turn in a few seconds but be 2.5-3 metres tall.
Due to their irregular shape I think we're going with plywood surfaces but to keep the weight down im considering making aluminium frames. This is a slightly more exspensive option but after lifting the approximate weight of a timber frame yesterday I think it has to be done this way.
The problem is that ive never used alumininum before. Don't know its stength capabilities etc etc. and don't really have the luxury of stuffing up to many times. Any advice on this type of construction would be greatly appreciated or even any other tips for keeping the weight down.
do you have the capability to weld aluminum? if you do then it is fairly simple to build a frame of rods.


Senior Team
Senior Team
Premium Member
is the flat square, rectagular? also when you say plywood what thickness?... are you talking more of luan?... because if you have something 9' tall and lets say 4' wide and you put a sheet of ply on each side of it (even thinner ply) your going to have a 100 lb flat.... luan is the way to go if you need it to be durrable and still be light.... as far as construction is concerned you could build what is called a space frame.... do a google of it and you should be able to find a few examples... you can make it out of mechanical steel which is cheaper and easier to work with then aluminum


Senior Team Emeritus
Premium Member
By turned, we mean a double sided flat turned around, not turned as in struck from the stage fast?

I assume you mean by irregular shapes that it’s not square or rectangular. What’s the approximate width of this flat?

I agree with what is it 5.2mm Luan mahagony plywood for the best balance of weight and strength for it’s face. Might even be able to get it in a thinner thickness.

A sandwiched ply welded frame in aluminum or steel could work well. Say 1x1x1/8" wall aluminum structural tubing might be the norm. You might save some money and weight on 1/16" wall or if possible 3/32" wall if available. Challenge would be in balancing strength and burn thru with the benefit of weight. This would be something to do a test mockup with before the production run.

Another option might be a 18ga box steel in the same or perhaps even 3/4" size. 16Ga box steel in 1" would be more normal but as with the above test, this might be sufficient.

A final solution might be to use #3 rough sawn believe it’s Western or is it Cypress but I could be wrong - specifically not Red Cedar in lumber. Very light weight and often inexpensive. As long as not too dry and supported well enough, it can be fairly strong in a flat and very light weight. Red Cedar is very dense and heavy. Say a flat made of 1x3 nominal stock. Otherwise there is some luan mahogany lumber out there which should also be very light and fairly strong. As long as a part of a glued and double faced flat, this stock should be strong enough.
thanks heaps guys. struggling a bit to make the conversions from 'US' jargon to my own. So confused by feet, inches, and pounds, not to mention the fractions.

Unfortunatly, I doubt we have the capabilities to weld as this would be the perfect solution. Also, yeah, by turn i mean turned around on stage, setting changes from forest to town so some clever design work will occur (when i have some time) to figure out some ambigous tree/town shapes.

On reflection I'm gonna plead with the producer to let me put them on castors (ill promise they are really quiet) but if that doesnt work i'll try to work with only one sheet of ply/luan and work the framework into the town design.

Its times like this I realise I really need some actual training in this stuff or im going to get myself into real trouble.


Active Member
What about steel studs like they use in some newer buildings? Those you can just screw together and screw the plywood into. You could also stretch fabric across the front and paint that.

How were you planning on supporting the flat if it has to turn around? A loose hanging leg?


I would recomend sandwiching rigid styrofoam between 2 layers of luan. If you stagger the seams enough, it should be quite strong and light. A layer of muslin glued over it will add strenth and an exelent paint surface.


Active Member
ive seen oversized lazy susan casters before that are used for packing ans shipping dept. Might work real well if you just happen to monut it on there...then it doesnt matter about weight, just turn it around and put a lock pin if it moves at all. and if it actually needs to leave the stage at all, just get two guys on it to lift her up.

Users who are viewing this thread