Hi.

Was wondering about this setup. If you have a post with a stair resting on it. The post wants to fall over. The bottom of the post is connected but not a really strong (fixed) connection. Could you brace from stair to the bottom of the post to fix this predicament and if so which angle would be better?



1 is square to the slope and 2 is to the midpoint of the slope. I guess it would be necessary to have solid connection at the bottom of the slope too.

Mo, if the top of the stairs is attached/fixed to the post why would the post fall over? I would think the strongest connecting point/angle would be straight up. If the post bottom is fixed to the floor and the base of the stairs is also fixed to the floor you have created a triangle. Something would have to slip to have the post move. Angle 1 and 2 could take some spring out of the stairs if the stringers aren't stiff enough. Fix the fixed points. Maybe I'm seeing this wrong?

Tim

Hey Tim, No you aren't seeing it wrong. I probably am though. This is for a deck I am building and the cantilever is for a desired width and not being able to place a post in the middle of the HVAC unit further down. I was just looking at everything again and trying to figure out what is happening in each member. I had it designed so the bottom of the stair just rests on some block. I am beginning to think that this is not good though and needs to be fixed (pun intended). Without that connection at the bottom of the stair and some person running up the steps it seems it might not be good.

I guess what has me a little worried is that there is no second post in line with the stringer. Just the one, and a strut for the cantilever. So there is really nothing stabilizing the post. I keep placing a pencil on an angle on top of a short book standing on my desk. When I place some weight on the pencil the little book falls over.

Everything is poured for the posts already and no anchor was built for the bottom of the stair.

Do you think I should attach a level piece from post to stair towards the bottom to build the triangle? Or would it be better to somehow attach the bottom of the stair to the ground to maybe make the stringer a tie member in this situation? Or am I being over analytical?




Thanks

p.s. I dont like the post at tread 1 either.

Mo, I would say if you use a mechanical fastener at the bottom of the stair and the top is bound as well it can't move. Put some hot glue on the book and pencil and test that.

On icy decks I have been using 3", GRK, T-30 screws through the feet of the ladder to address a similar issue.

You have to fix the bottom of the post hard to the footing where it can resist several hundred pounds of side load from the strut. As the load from the cantilever flows through the strut, it becomes equal parts horizontal and vertical.

So with my 200 lbs plus the weight of the deck standing just over the top of the strut, you have 100 lbs plus half the dead load pushing sideways on the post through the brace. Imagine 4 people or more standing there. (That is the problem with decks -- they are prone to severe concentrated overloading by beer kegs and people and the like.)

You will also need to affix the stringer at both ends so that it can withstand tension. Because as the cantilever is trying to fall down, the stringer is what is holding the post vertical.

Personally, I don't like the cantilever. I wouldn't build this without an engineer reviewing it.

Thanks for the replies guys. I'll have to get some good hardware for this.

Gabel, I understand what you are saying. Especially about the load of suds.

When you explain the load forces, wouldn't half of the load be transmitted down and over only if the brace is 45 degrees. I am thinking that the closer I can bring this brace to plumb the more load will be transmitted down instead of over. If the x-force can be minimized than the stringer would not have to overcome as much tension. Am I thinking about this right?

yes, you're right about the 45 degrees. but, remember, as you move the bearing point of the brace in from the end of the cantilever the moment increases (leverage). I would have the brace maximized -- running from as low on the post as possible to as far out towards the end of the cantilever as possible.

not quite done, but strong, the big fella jumped on the corner w/o the brace and had minor deflection.


I removed wood from pieces so I don't feel too bad putting these on a timber frame forum. Over on the left you can see the unit. I like the cantilever.

It's good to see you two are closely monitored in every picture by your four legged supervisors! Nice work.

Thanks Paul. they didnt bark too much. nothing like retrievers.