Type IV construction (Heavy Timber) - MAXIMAL SPAN?


I would like to ask if somebody know the maximal span between loaded walls for the normal ceiling on the first floor when there are 2 and a flat roof.

Type IV construction (Heavy Timber).

Thank you in advance.

May 26, 19 1:57 pm

what type of gravitational environment is this in?

May 26, 19 2:50 pm

On billion solar mass black hole


Only type IX construction is allowed on celestial bodies with mass exceeding 500,000,000 sol, so high density ceramic carbon fiber composite should be used. Max span 32^-10 parsec.

Non Sequitur

what’s the depth of the structure?

May 26, 19 3:06 pm
Superfluous Squirrel

Really far

See the Richmond Olympic Oval:

May 26, 19 4:00 pm


There isn't a precise stipulated maximum theoretical span. If the beam is deep enough and sufficiently wide enough it can span a trillion miles. However, in reality, it isn't that simple. There are practical considerations. Glulam can span quite some distance but then you can span bigger distances with timber space frames like lamella roofs with sufficient sized individual members so the length to depth ration isn't exceeded. 

There are material properties, sectional properties requirements, etc. that you'll have to meet. Basically.... timber structural engineering.

May 27, 19 2:44 am

Thank you very much RickB-Astoria.

But I still have questions. 

I am not a specialist in wood, usually I used to work with concrete. But now I make planning for type IV. Could you let me know please. Should I place any columns between walls with a 70' span? 

If yes, on what distance would be good?

Thank you very much again. 


I'm not following what you are saying. Glulams typically span and are supported at the ends of each Glulam beam. A Glulam beam can span similar spans to many types of trusses. These are specially pre-engineered wood products not just solid hewn timber that is hewn from the logs harvested from the woods. These logs have an effective length of between 20 to 26 ft. give or take. It comes from the way wood is harvested from the wood. To achieve longer spans than 20 to 26 ft., you have to laminate the wood pieces in interconnecting strips that typically forms a beam bigger than typically found in nature and longer than you may typically find hauled down the road in logging trucks. The logging trucks just can't accommodate hauling a full length douglas fir of 100 plus ft tall tree. They cut it into segment that they can haul. The depth of a wood beam's cross section is critical to a beam's span especially when you consider how much deflection of the beam under load is acceptable not only per the code's safety requirements but also under consideration of user requirements. A 12x16 douglas fir beam could (end to end) span 15 to 20 ft so you would want a suitable (12x12 column under it). 15 ft. would likely be a fair span with suitable spacing between for an academic building. However, in a stadium, you may approach the design differently from a conventional post and beam configuration for spanning across a court like a basketball court or something. There is a lot that I can't just teach this over the forum. There is some books that is good and covers it. Some from the 1950s and 60s which are still useful for understanding the principles even though some of the calculation formulas maybe updated or modified. This might be helpful:


There are some other books and resources which you may at least want to read on the subject. I have some books on this. I usually am not designing for some of the more extreme spans for the types of buildings for residential application.

There is also resources that gives you information about modulus of elasticity and other pertinent properties of various wood species and grades of timber/lumber. You can use that information and calculate cross section requirements and span limits and devise a solution for your project.

Thanks everybody!

May 27, 19 5:40 am
Non Sequitur

columns every 10’ is typical. You can get away with 20’ spacing if you bribe the right AHJ. 

May 27, 19 5:46 am

There's not enough information in your question to give an informed answer.

The replies above are either jokes or speculation based on the limited info available. They're mostly useless.

10'-12' though, as a rule of thumb.

May 28, 19 5:06 pm

There are certain minimum dimensions in the building code for heavy timber cross sections...

May 28, 19 6:19 pm

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