Building a Mezzanine - QUESTIONS

[Hirnsausen]

Hi,

I am intending to build a mezzanine, using ltreated umber (not steel).

The main beams (legs and frame) would be so-called 4x4 beams (in reality 3.5x3.5), and the beams inside the frame that carries the deck would be 68 inch long, 3.75 inch tall, and 1.75 inch wide ( = 2x4x68). The mezzanine main frame (96 inch above ground) would measure 75 inch by 120 inch. The deck is made from the red-edged "construction type" plyboard.

The mezzanine would just carry a small table on the one small side, and a shelf on the one long side. I expect one or maximum two persons using it at a time.

My questions are:
1.
Having a distance of 113 inch between the vertical beams, can the long beams manage that weight or should there be one more vertical beam in the middle?
2
What should be the distance between the 2x4x68 beams that are below the deck to distribute weight well enough?

 

[EddieWalker]

treated 4x4's here in the US have changed how they are made and they are horrible at remaining straight. Even treated 4x6's twist more often then not. I personally only use 6x6's now because they are so much better at remaining straight after a year of drying out.

NEVER use a 2x4 as a joist or beam to support a load. 2x6's would be the minimum for your short span, and if the long span is supporting the short span, then double 2x8's would be the minimum size lumber that I would use. If you are using 3/4 inch pylwood, then you need your 2x6's to be 24 inches apart or closer. If you are using anything thinner then 3/4 of an inch, you need to have your 2x6's spaced closer together. Half inch should have joists at 16 inches. A foot would be even better!!! I would only use 3/4 inch plywood, and if it was me, and such a small structure, I would space my 2x6's every 18 inches.

Remember that if you do not rest lumber on top of lumber, that you need metal hangars to support the load. Toe nailing, or even worse, nailing into the end grain will always lead to failure when supporting a load.

 

[Hirnsausen]

That's a good insight you have, my appreciation for your advise! Yes, those lumbers are taken nowadays from younger trees, and curve easier than before. I got plenty of these 2x4 joists, enought o have one each 13.5 inches apart.

On the one long side, there is a shelf with its own beams that touches the long beam from below and prevents bending. For the other long side, I think i am strengthening that beam with an additional 12 inch wide board (that would also be useful for the railing that comers then).

On top of that 3/4 inch plyboard, there will be an additional thinner decorative plyboard simulating deck planks.

The metal ends for the joists that we can buy here in Jamaica, do not allow for any joists higher than 4 inch. That's why I decided to place the joists closer to each other.

 

[Tractor Seabee]

Why are you using treated lumber? It has less structural strength than standard lumber Fasteners do not hold as well either as treating softens the fibers.

Ron

 

[Hirnsausen]

Thanks again. I did not know that. :-(
The problem here in Jamaica as a tropical country is, that we have termites all over, especially now during the tropical rain season, and all hardware shops recommend to use therefore treated lumber only (selling it even at a higher price). Under frame conditions like that, and without own firm knowledge, it is hard to make the best decision.

Having purchased all the lumber now, I have to go ahead with that.
But in regards to the annual termite invasions, i think, it is probably the slightly better decision, not sure.

 

[Tractor Seabee]

Thanks again. I did not know that. :-(
The problem here in Jamaica as a tropical country is, that we have termites all over, especially now during the tropical rain season, and all hardware shops recommend to use therefore treated lumber only (selling it even at a higher price). Under frame conditions like that, and without own firm knowledge, it is hard to make the best decision.

Having purchased all the lumber now, I have to go ahead with that.
But in regards to the annual termite invasions, i think, it is probably the slightly better decision, not sure.

That's what I get for not looking at your location. I did construction in Hawaii so am well aware of the destructive effect of tropical termites. They have the Formosa variety and they even tunnel in concrete.

Ron

 

[dmccarty]

Since you are using treated wood, make sure that the fasteners and connectors are rated for the pressure treatment used for the wood.

Later,
Dan

 

[Hirnsausen]

Thanks for the advise about the rating. But: no rating available for the lumber one gets in Jamaica. They simply never had established such standards (importing standards), or soem lobbies have diminished ay attempts of implementing such standards. Jamaican politicians are easily purchasable for money, that's a known fact. Jamaicans don't like to go by rules, and jamaica as a country has not as many rules and laws as normal countries that are ruled by normal politicians.

That's why I was posting here, and inquired about the distance between the joists. It seems, this is the only way to get some expertise for me. I appreciate dearly the assistance and good will of all of you here who answered me.

 

[2LaneCruzer]

I was told that if you take, like two, twoX8's and sandwich metal flashing between them, that it is much stronger and keeps them from sagging under heavy loads. Anyone ever heard of this?

 

[dougtrr2]

A metal plate, maybe, but I can't think that flashing would add much to the equation.

Doug in SW IA