Thickness of spruce ladder legs?

[Jan Bianchi]

I am making a 5 foot tall ladder for a storage area in my cabin from Sitka Spruce that I have milled from a windfall on my property. I don't know how to determine how thick the sides should be. It needs to be as light as possible since it will be portable. Most wooden step ladder legs are 3/4" thick and purport to support a load of 250 lbs, but are made of fir or hemlock. Sitka spruce is supposed to be very strong for its weight.

One inch by 5 inches would be great since I already have some milled to that thickness, but maybe it should be 1 1/2? The steps will be 1" thick, dadoed 3/8" into the legs, but won't have the wire understrap that wooden step ladders have. This ladder will not be subject to weather, but might have to support up to a 250 lb. load. How does one determine this?

[Brian Millspaw]

I make a ton of rolling library ladders for a local company. The sides are 1 1/8" x 3 1/4" and the steps are 3/4" x 4 1/4" dado 3/16" into each side. They do get the tie rod underneath, but i have made these over 10' tall in many different wood species with no problem.

-Brian

[Dave Richards]

Years ago my father made a ladder to get into the attic of the house I grew up in. He used 2x2 SPF for it. It was plenty strong.

[Jan Bianchi]

Do you think they need the tie rod? Have the steps broken to your knowledge? I would think that they would have more to do with the step than the sides.

[Brian Millspaw]

I highly doubt a step would break. I think that they are more for holding the sides together, as they don't even touch the step underneath. I wouldn't worry to much about it on a ladder that is only 5' tall. The ones that I make are sold to the general public by a commercial company, so maybe it's just assurance against liability issues.

[Mike Nolan]

How thick the steps need to be depends on how long they are. You can make them much stronger by adding a lip on them. It is important to use wood with no knots.

[Bob Michaels]

Even a short 5' ladder is a leg breaker. I think your biggest risk is the sides separating and the steps pulling out of the dado's. I like the tie rod or some other mechanical means of making sure the steps don't pull out.