BALAU WOOD FOR OUTDOOR OCEAN BEACH AREA STAIRCASE

[PT99]

I need to find allowable stresses for Balau wood, there is some information at Wood Data Base online, with some properties given, so how would you compare for allowable bending and shear stress.

Information at website
Modulus of Rupture
Specific Gravity
Elastic Modulus

 

[hokie66]

Information from an Australian website.

https://www.woodsolutions.com.au/Wood-Species/shorea-albida

 

[PT99]

Thanks Hokie66

My question is can you use some of these properties listed in my question to come up with an allowable stress, for example compare the same properties with Douglas Fir #2, I've got this situation (for treads) where if calculated with Douglas Fir #2, it does not meet structural requirements.

They already built this outdoor stair with Balau treads, and shifted stair stringers inward from the usual tread edges, so now the treads have cantilevered ends on both sides which is the problem. It looks nice to the owner, so they want to keep it, but it doesn't figure, unless allowables are a lot more. And of course I am saying its NG, and I assuming the local DOB will say the same, unless calcs can show otherwise.

 

[hokie66]

That website is Australian, and shows the stress grades applicable here for that timber. I would hope that if the timber is commercially available in the US, you would have a grading system which would control. I can give you assurance that any grade of Balau would be stronger and, if the heartwood is used, much more durable than Douglas Fir, but my asssurance is not worth much.

 

[BAretired]

You are too modest, hokie66.

BA

 

[dik]

Most 'rainforest' types of lumber have extractives that make them far more decay resistant... assuming that's what it is.

Dik

 

[thaidavid40]

The online information I am seeing for balau wood says that it is stronger than teak wood. Could you just use the published physical properties for teak as conservative bottom-floor values?
Dave

Thaidavid

 

[PT99]

Good idea, but teak is not listed in the NDS Design Value Publication.

 

[dhengr]

PT99:
This particular wood may have come in as dunnage, with some equip. shipment, but how do you know the particular/exact species, and nothing else? Where did your client buy the lumber, what lumber yard or supplier? Then, who was their supplier, and then that distributors ultimate importing source/supplier, etc. Can any of them provide general data on the material they are selling or do they just sell funny wood by the ton, with no particular use intended? Check with some exotic wood importers for potential sources of Balau. I would follow up on the link Hokie gave you, he seems aware that it is used in Australia and there abouts, and he seems to have some confidence in a reasonable strength level when compared with other woods they use over there. Does Hokie have any wood design codes/specs. which show/allow the use of this material? I wouldn’t be afraid to hang my hat on that code if it was a respected one, even though not a U.S. code. That link seems to go a little deeper than I can read at the moment, but you may have to subscribe or buy the info. from them. Finally, some form of grading will be an important issue, and then you put your neck on the line, saying you will act as insurer of last result, so they can use six or eight 2.5 x 12 x 6' treads which they think look nice. A $500 fee, and your insur. premium, for $300 worth of new material and some stain/preservative.

You might also try the Forest Products Lab., U.S. Dept. of Ag., in Madison, WI, they know about as much about various wood species as anyone in the world. They might have some basic info. on Balau. Whoever is selling that wood into the world market should have (would need to know) the info. you need, if the matr’l. is going to be used structurally, or they wouldn’t be selling much except as dunnage or for furniture making and veneer and the like.

 

[hokie66]

A bit more information from a Malaysian site, and that is where this rainforest timber comes from.

http://mtc.com.my/wizards/mtc_tud/items/report(95).php

You probably won't find that the timber is formally graded. I know some of it is used in Australia for decking, somewhat interchangeably with merbau, meranti, etc. Hard to tell what species you actually get unless you deal with a reputable timber merchant rather than a hardware store.

It seems to me that if your stair is not strong enough if built with DF, you can reject it based on it being built with an unknown quality material. On the other hand, if the treads are 2" thick hardwood, I think some engineering judgment would come to bear.