How much weight can hemlock hold???

[shinnlinger]

Hi,

I cant find my load figures right off.  I am wondering how much weight a 8x10 hemlock beam 9'2" between posts can handle.    It is pretty clear with some small knots. 

I want to avoid running my chimney all the way into the basement and my floor system has 4x10 hemlock floor joists 16" OC.  I would pour a large hearth/chimney pad and catch 5 or 6 of the joists and the weight would transfer onto the hemlock carrying beam.  My over estimate for weight is about 4,300 lbs, but 35 foot of 8x8 chimney is less.

I can easily put a post in and cut the span in half.

Thanks.

[Jim_Rogers]

Have you learned how to use Don P's calculators here on the FF?
They are under the tool box link......

[shinnlinger]

Jim,

I did and it says I pass, but I was hoping to compare to a chart like in the back of timberframing books

[Tom]

check out The Wood Handbook.  There are all manner of stress and strength table in there, if you wnat something different than the Tool Box calculators.

It's probably in chapter 6 or 8.

[Jim_Rogers]

I would pour a large hearth/chimney pad and catch 5 or 6 of the joists and the weight would transfer onto the hemlock carrying beam. 

Will your building inspector allow this? What about your fire department? Will there be enough between the fire and the wood to prevent it from heating up and catching fire?

I was at a house party one new years eve and the house caught on fire because the hearth was laid on top of a plywood subfloor deck and the fire was hot and the plywood caught fire underneath..... Wasn't a fun time at all......

[shinnlinger]

Jim,

a 5 inch pad with a woodstove with sheilds on it I would think is OK.  What would you recomend???  My current house has a woodtove siting on concrete pavers.

In the "live free and die" part of the state I am in, inspections are not applicable, but that doesn't mean I want to burn my house down.

[beenthere]

If the wood is insulated from the heat, then you should be ok. If the wood is too hot to keep your hand on it, then it will cook (become very dry, and can begin to burn noticed first by charring). 

Neighbor burned through the wall behind his fireplace and didn't notice the damage until it finally burned through the outside siding. This happened over a fairly long period of time. Just a fire created enough heat to go through firebrick and 6" of solid concrete block backed by a conventional 2x4 stud wall, sheathing and wood siding (maybe if it had been vinyl siding, he would have noticed it melting before burn-through.

There are ways to make heat shields that have an air gap to upset the direct heat transfer. Some of the wood stove companies include these in their manuals along with Nat'l Bldg Code required distances (Vermont Castings did when I installed mine).

[shinnlinger]

OK,

I will work with my mason and woodstove provider to ensure I safely install the unit.

What I would like to know is can the beam hold the weight?  I ran it by Don P and it says IM OK, I think.  What I was hoping is someone would have chart handy or even run it by Don P again, to double check my specs from the first post.

Thanks.

[Tom]

Did you find the equations in the Wood Handbook?

[SwampDonkey]

Lots of variables go into it. Fatigue from load over time, moisture content, temperature in service, grain direction, knots and defect, weight of piece itself, length of span. Wood Handbook as Tom says has some figures. Otherwise it's a wild guess.

[mrnero]

Hi,

I cant find my load figures right off.  I am wondering how much weight a 8x10 hemlock beam 9'2" between posts can handle.    It is pretty clear with some small knots. 

I want to avoid running my chimney all the way into the basement and my floor system has 4x10 hemlock floor joists 16" OC.  I would pour a large hearth/chimney pad and catch 5 or 6 of the joists and the weight would transfer onto the hemlock carrying beam.  My over estimate for weight is about 4,300 lbs, but 35 foot of 8x8 chimney is less.

I can easily put a post in and cut the span in half.

Thanks.

Try a local lumber yard. They have charts what would be best size beam for your weight an span that you need. You do get more of a weight factor in using 2 X's nail together than a one solid wood beam or best is using an LVL beam. You also dont want a beam to sag over time. Just stating the facts from my previous experience.