# Over-Engineer Kills Project



## Anti-wingnut (Mar 12, 2009)

Is part of the problem that the client and /or architect wanted ICF's ? Seems like it would have been easier to get someone to build it if it was formed with bar, and poured or air-placed concrete used. Using ICF's just complicates things, when a regular old poured wall can be insulated as well.

But of coarse ICF has all that green cachet


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## Tom Struble (Mar 2, 2007)

Cjeff said:


> So then by your line of logic the more overbuilt the better? :blink:


 in who's opinion,thats my point:blink:


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## katoman (Apr 26, 2009)

tomstruble said:


> i understand Greg and not trying to be an a** but i can't help it sometimes:no:
> 
> but i haven't found the ''24k'' after your name in any professional degree abbreviations list:shifty:...i know that's not as important as experience to some but it is what it is


Tom, what's "24k" ?


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## Tom Struble (Mar 2, 2007)

lol i was talking to Greg...hope he dosn't take it the wrong way:shutup:


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## Tim Garrison PE (Oct 22, 2009)

Here are a few thoughts on several of your posts.

* Regarding SEs in other states, I don't know for sure the licensing requirements of other states but my guess is that most are similar to CA and WA, the two where I hold licenses. My original post could apply in either state - they're just about identical as far as licensing requirements. 

Also, a masters degree has little to no effect on a professional license. I went back and earned mine because I thought it might look good on a resume. Now, 20 years later, I question whether it was worthwhile. The most valuable education any engineer can get does not come from a classroom. It comes from EXPERIENCE. School teaches you *how to learn*.

* Regarding CMU with no space left for rebar. I've designed a lot of CMU and of all the structural materials, it makes me the most nervous. Code will allow goofy stuff like too much or too little rebar in the cells, in my opinion. A good design has to take into account buildability. Some engineers, especially those who've never strapped on a tool belt, have trouble with that concept.

* Regarding government jobs being overdesigned. I couldn't agree more. Why do engineers think that governments should spend more money than the private sector? I don't get it. It's OUR money for crying out loud. 

* Regarding ridge beams. This is one of the most misunderstood areas of framing and has been the subject of my writings several times. In short, if it's not a truss, there needs to be a *substantial* ridge beam. My next book, Green Framing - An Advanced Framing How-To Guide is due out in about a month and there's an actual example problem therein where I size a ridge beam. Tell you what - I'll pull that section out and post it in this forum. I think you'll be surprised.

* Regarding ICF vs formed concrete. I'm a big fan of ICF and have written about it, too. In short, I like it because it's easy for the builder to get the rebar in the right place. And, unlike CMU, there's plenty of room for rebar. Also, did you know that the compressive strength of regular CMU is about 750 psi and ICF is about 3,000? (4x weaker) Just writing those numbers makes me cringe at the thought of having to design with CMU again :-(

Thanks, everyone for taking the time to bring up these excellent points.


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## Tom Struble (Mar 2, 2007)

of course experience is important but experience with out the degree,well what good is it really if thats the area you want to practice in


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## NJ Brickie (Jan 31, 2009)

Tim Garrison PE said:


> Here are a few thoughts on several of your posts.
> 
> * Regarding SEs in other states, I don't know for sure the licensing requirements of other states but my guess is that most are similar to CA and WA, the two where I hold licenses. My original post could apply in either state - they're just about identical as far as licensing requirements.
> 
> ...


Maybe I feel differently about the last part of your post because I make my living in part with CMU's. I do not know what type of designing you usually do, but CMU's are by far a more verastile building material than ICF forms. I have nothing against ICF construction. I looked into it for my own house. But you make it seem like block is no longer a standard way to build. Also the PSI numbers you stated is kind of a half truth. A CMU may have a 750psi compressive strength rating, but a wall system properly designed with grout and rebar will far exceed that number. Which is closer to comparing apples to apples. That also brings us back to possibly over designing a wall.


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## Tinstaafl (Jan 6, 2008)

Tim Garrison PE said:


> * Regarding ridge beams. This is one of the most misunderstood areas of framing and has been the subject of my writings several times. In short, if it's not a truss, there needs to be a *substantial* ridge beam. My next book, Green Framing - An Advanced Framing How-To Guide is due out in about a month and there's an actual example problem therein where I size a ridge beam. Tell you what - I'll pull that section out and post it in this forum. I think you'll be surprised.


This particularly piques my interest, because according to my experience and what I think I know, with properly done rafters and joists, you could virtually use a sheet of paper for a ridge beam. Assuming of course that it's a "standard" roof.


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## neolitic (Apr 20, 2006)

Tinstaafl said:


> This particularly piques my interest, because according to my experience and what I think I know, with properly done rafters and joists, you could virtually use a sheet of paper for a ridge beam. Assuming of course that it's a "standard" roof.


I can show you a great number
of 100+ year old houses with
roof in fine shape, and no ridge
boards at all. :thumbsup:


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## naptown CR (Feb 20, 2009)

I'm kind of curious about the ridge beam also I agree with Neo and Tin that in a typical construction it is not needed.


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## Elyrain (Dec 17, 2007)

Good thread, OP, I'm going through the same situation myself. Except we used a top notch engineer, and he designed this building to be like a darn hospital instead of a small office building.


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## katoman (Apr 26, 2009)

I agree with Tin, so the reason for large ridges should be interesting.

Of interest - In my jurisdiction, the City changed it's by-laws, so it would be less liable in construction. Now, everything needs an engineers' stamp.

My structural engineers' insurance quadrupled!!!! So perhaps it's more about cover your *** than anything else. This may be one reason for over engineering.


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## greg24k (May 19, 2007)

Ridge beams play its own part just like girders and headers. If we have a gable roof on the building that is 24 feet wide, ridge beam supports a tributary load of 12', this means the ridge should be strong enough to support the live load i.e snow load lets say:30 psf x 12 ft = 360 plf... roof dead load:10 psf x 12 ft = 120 plf, so the total load on ridge beam is = 480 plf in addition sometimes there other loads calculated i.e uplift loads and wind loads.
This just a small example of typical calculation to determine the load that is distributed to a ridge beam. Old days before states adopted building codes, ridge beams weren't required, today they are and there is no need to over design them unless its required.


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## Tom Struble (Mar 2, 2007)

you are a genius:notworthy:notworthyarty:


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## greg24k (May 19, 2007)

The guy who taught me is, I'm far away from being that, I never finished high school... but thanks for the compliment :thumbsup:


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## Tscarborough (Feb 25, 2006)

"Also, did you know that the compressive strength of regular CMU is about 750 psi and ICF is about 3,000? (4x weaker) Just writing those numbers makes me cringe at the thought of having to design with CMU again :-("


This part is so obviously wrong that it makes me doubt anything else that you say. Are you seriously going to tell me as an engineer that you do not know what the C-90 requirement for CMU compressive strength is?! And that itself is a joke since the majority of the CMU in the US test out way stronger than the ASTM standard!

I suggest that you print this out and study it:

http://www.ncmaetek.org/etek/pdf_brand.asp?pdf=TEK 01-01E.pdf&si=468.jpg

Pay particular attention to Table 3, "Strength and Absorption Requirements for Concrete Masonry Units, ASTM C 90 (ref. 3)A"


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## Tscarborough (Feb 25, 2006)

Also, when you state that the compressive 
PSI of ICF is 3000, I will assume that you mean the completed wall assembly, not the ICF unit itself? If so, then you should at a least compare the completed wall assembly of CMU, which I can assure you will be at least as strong as ICF if not considerably higher.


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## Tinstaafl (Jan 6, 2008)

greg24k said:


> If we have a gable roof on the building that is 24 feet wide, *ridge beam* supports a tributary load of 12', this means the *ridge* should be strong enough to support the live load i.e snow load lets say:30 psf x 12 ft = 360 plf...


Honestly not trolling for arguments here--after all, one of the main attractions of this forum is the abundance of information.

Can you (or Tim) explain why a ridge beam is necessary to support that load, versus rafter-opposing-rafter support? I just can't picture the forces requiring that.


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## katoman (Apr 26, 2009)

Exactly. Roof rafters on a gable roof in effect create a triangle. With the ceiling joists and collar ties. Then it is covered with roof boards, thus connecting all the rafters into one structural element.

What need is there of a ridge board, as the only area not loaded will be between the rafters, which are carried by the roof boards, same as the rest of the roof.


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## BrianFox (Apr 6, 2009)

greg24k said:


> Ridge beams play its own part just like girders and headers. If we have a gable roof on the building that is 24 feet wide, ridge beam supports a tributary load of 12', this means the ridge should be strong enough to support the live load i.e snow load lets say:30 psf x 12 ft = 360 plf... roof dead load:10 psf x 12 ft = 120 plf, so the total load on ridge beam is = 480 plf in addition sometimes there other loads calculated i.e uplift loads and wind loads.
> This just a small example of typical calculation to determine the load that is distributed to a ridge beam. Old days before states adopted building codes, ridge beams weren't required, today they are and there is no need to over design them unless its required.


*swish*


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## Ayerzee (Jan 4, 2009)

Tinstaafl said:


> Honestly not trolling for arguments here--after all, one of the main attractions of this forum is the abundance of information.
> 
> Can you (or Tim) explain why a ridge beam is necessary to support that load, versus rafter-opposing-rafter support? I just can't picture the forces requiring that.


I can't picture it either...My only guess would be that it would allow a stronger connection between the two and would transfer the stress from the rafters to the ridge beam itself...but that's a little abstract :blink:


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## Tom Struble (Mar 2, 2007)

unless there talking vaulted,structural ridge?i dunno:turned:


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## BrianFox (Apr 6, 2009)

tomstruble said:


> unless there talking vaulted,structural ridge?i dunno:turned:



A vaulted ceiling is more likely to require an actual ridge beam, because it would have no means of resisting outward thrust at the bottoms of the rafters. When the rafters are carried by a ridge beam, there is no outward thrust.


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## Rio (Oct 13, 2009)

I know from bitter experience that if the roof is less than 3:12, by the newer codes, it has to be designed as a flat roof with a ridge beam. If it's 3:12 or more than you don't need a ridge beam as far as I know with conventional construction (rafters opposing each other and collar ties).


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## Ayerzee (Jan 4, 2009)

BrianFox said:


> A vaulted ceiling is more likely to require an actual ridge beam, because it would have no means of resisting outward thrust at the bottoms of the rafters. When the rafters are carried by a ridge beam, there is no outward thrust.


Isn't that what the collar-ties are for? I'm still not able to picture why the ridge beam itself would resist outward thrust...


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## katoman (Apr 26, 2009)

Brian is talking about a cathedral ceiling where there will be no collar ties and no ceiling joists. He is correct in that now, the ridge becomes a beam.

I'm still waiting for the PE to explain why a ridge is required on a conventional roof. I build as per code and we do put in a proper ridge, but this is perhaps not structurally required?


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## greg24k (May 19, 2007)

In my experience I know one thing for sure, in every larger home that I built where home is anywhere between 3,500 and 4,500 SF, the design criteria called not only for the ridge beam but also the ridge beam support columns that distribute weight to the walls bellow and down to the footings. The picture I showed before, was the perfect example...above in the attic there was a ridge support column which was supporting the ridge. I calculated that the total point load on that header bellow where you see the jack on the first floor, was (if I remember correctly) little over 10,000LB. So lets say we have a home that has a large open room going from one side of the home to the other and in todays designs we have open Master bedrooms cover half of the house, ridge beam and ridge beam support columns play an important role when tying the whole roof structure with the rest of the house. Roof must be supported by a beam along the ridge of the roof. Because if there is no walls bellow, ridge has to be strong enough not to allow roof to sag in the area of the open room. This beam is also need to be supported by extra supports within the wall cavity, I call them support columns. I'm sure everyone seen them in the wall cavity , when you have three or more 2by studs together and they located at the end of each wall of the open room span and they tie the whole system together. So the ridge carries the roof load and creates a point load on this columns and the whole weight is passed through them to the foundation and footings. Maybe allot of people don't realize this, but the size of the footings have lots to do with the point loads that ridge beam carries and distributes the load bellow through the support columns so the greater the load they larger the footing should be.


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## Tom Struble (Mar 2, 2007)

well then there goes the idea that the gable end is not a supporting wall


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## katoman (Apr 26, 2009)

Greg - are we discussing the same roof here? We're talking about a simple conventional gable roof, not a cathedral.

If you're talking about a cathedral/vaulted roof, then yes, of course the ridge is a beam.


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## greg24k (May 19, 2007)

katoman said:


> Greg - are we discussing the same roof here? We're talking about a simple conventional gable roof, not a cathedral.
> 
> If you're talking about a cathedral/vaulted roof, then yes, of course the ridge is a beam.


I was talking about regular conventional roof, the few pictures I showed (I didn't take any from the outside) had a convectional roof and the way house was laid out, it needed a ridge support beam in the attic resting on the wall of the second floor wall, which carried the load to the first floor wall...after they opened the first floor wall to make a bigger opening, they didn't realized how much weight that wall was carrying, so they put the wrong sized header...the header was 2/2x10 and the load bowed the header.


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## Rocket Red (Jan 28, 2010)

I'm not sure if I can lend any help here, but to answer a general theme.

A ridge beam is required when there is no method of resisting the outward thrust at the bottm of the rafters.

Just imagine setting two cut rafters, end to end, without attaching them to the wall, the bottom ends will slide away from each other. That is essentially what a collar tie does. If the ridge beam was there, then they would set atop it and their load would land in 2 places.

To utilize the ceiling joists or a collar tie, the thrust must be calculated and the attachment between the collar tie and the rafter should be detailed for construction. You are in essence creating a truss, which bears on the exterior walls, nothing else. The higher (above the floor) the collar tie is the greater the thrust load to resist, plus there are a multitude of other issues to account for and the harder it is to detail.

I have done a lot of little projects in years past where owners wanted to turn an old 2x4 truss into a "cathedral' ceiling, but cutting out the web and bottom chord of the truss, and adding a collar tie half-way up it somewhere. It never worked the way they wanted. The simplest solution usually was to cut in for a ridge beam and then they could put their ceiling height whereever they wanted it. It would always require tearing out sheetrock so that they could post the new ridge beam to the foundation.


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## Rocket Red (Jan 28, 2010)

greg24k said:


> I remember a while back I was looking at a small addition, it was a little cape-cod they wanted to attach one car garage. Simple addition, like building a shed. The architect who is a distant relative of theirs, did the design, from what they told me he designs stadiums, and that what he did, he included a piece of that stadium in that one car garage addition...I will not go in to all details what was on the plans, but to give you one example...The main roof of the house is 2X6 rafters with 2x8 ridge, the new roof over the garage is to have a ridge beam 3 1/2 X 11 1/2" para-lam with 2x10 rafters :shutup: and you see more and more of this.
> 
> This is why they get the big $$$ :whistling


I also wanted to address this one, you never qualified your post by stating what the spans were. I assume that you meant the spans for the garage were matching the house gable, so they were the same as the house spans. If so, you didn't state when the house was built, and if it was more than 10 years ago, then we are talking what 3 code revisions? 

I could not say if it was over designed, or if it just meets the current span tables based on the current IRC or IBC. It seems like that project may have a vaulted ceiling, or why wouldn't they just buy a truss system?

An 11 1/2" ridge beam could not be spanning very far before deflection becomes an issue.


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## Tinstaafl (Jan 6, 2008)

Thanks, guys. I think we're all actually on the same page as long as we can figure out who's talking apples and who's talking oranges. :thumbsup:


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## neolitic (Apr 20, 2006)

Tinstaafl said:


> Thanks, guys. I think we're all actually on the same page as long as we can figure out who's talking apples and who's talking oranges. :thumbsup:


Keep your hands off my apples! :hammer:


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## Tinstaafl (Jan 6, 2008)

neolitic said:


> Keep your hands off my apples! :hammer:


Hammering out a little hard cider there, Neo?

Okay, but you have to share.


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## neolitic (Apr 20, 2006)

Tinstaafl said:


> Hammering out a little hard cider there, Neo?
> 
> Okay, but you have to share.


My Kiddo makes a fine cider indeed!
Knows how to keep his oldman happy. :thumbsup:


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## cbrew (Feb 16, 2010)

*over engineer*

I have heard an Engineer say that they over engineer because they think contractors will only do half of what they call for.

Apex Carpentry


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## Tim Garrison PE (Oct 22, 2009)

What a great thread!

Here are a couple more thoughts.

First, in response to NJBrickie that I'm giving CMU a bad rap. Sorry, I didn't mean to do that. What I meant was that CMU can be difficult to engineer because the strength values are low compared to concrete. The 750 psi compressive strength I mentioned is for grouted CMU with rebar. Code allows double that if special inspection is provided. But who wants to pay for and endure the hassle of special inspection? And even then it's only half of concrete's strength. The point is, engineers kind of feel penalized when designing with CMU because codes treat it so harshly.

But, designing with CMU is only troublesome when it's highly stressed, for example: tall walls; walls with lots of doors and windows; and retaining walls. There is no problem at all in other, more standard, applications. 

Truth be told, I love the look of split-face CMU, especially when different colors are tastefully used. It is a great product for many applications.

Regarding engineers overdoing it because they don't trust builders. That mentality does exist, for sure. What's unfortunate is that engineers rarely give builders credit when they save their bacon. For example, I, not being perfect, will occasionally design something that isn't quite right, or may look iffy. I LOVE it when the builder calls and asks, "Tim, is that really what you intended? Seems a little shaky to me." This is why I'm careful to never break my pick with a builder. I WANT that phone call. No one is perfect, but together we can get close. 

On the topic of a an engineer overdesigning in fear of a builder "not building it right," the IBC has factor of safety in everything - approximately 2.5 for stick-framed construction. That means, if built to code, it's 150% stronger than it needs to be. That's huge! So for an engineer to design more conservatively that code minimum, for whatever reason, is just plain ludicrous. It's anti-green and costs big bucks.


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## Ayerzee (Jan 4, 2009)

Tim I'll agree with code being more than adequate for most things (I'm sure most will disagree). But what about things like decks where you will want extra capacity? Do you just beef up the F.S. for something like that?


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## katoman (Apr 26, 2009)

Tim - can you give us the info on why a ridge is req'd on a conventional roof where rafters oppose each other and there are ceiling joists and collar ties and roof boards?

As I've said, of course we put in a ridge board, just like to know the structural reasoning behind this. Thanks.


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## Tom Struble (Mar 2, 2007)

i used to a have an aunty greenarty:


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## Tim Garrison PE (Oct 22, 2009)

Regarding decks or anything else you want stronger than code. Certainly you can beef things up. Building code is a minimum standard. The rub comes in knowing what to beef up and what not. If, for example, you're trying to accommodate a hot tub, you don't need to overdo everything, just the area supporting the tub. And don't forget that seismic forces go up with increased weight, so you need to think about more lateral bracing as well as bigger joists, beams, posts, and footings.

Regarding the rest of the ridge beam story, I'm in the process of making that post this morning. There are 6 sketches, so I can't post it here (3 max on this forum). It'll be on my home site's blog. But I'll give you that link when I finish.


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## neolitic (Apr 20, 2006)

katoman said:


> Tim - can you give us the info on why a ridge is req'd on a conventional roof where rafters oppose each other and there are ceiling joists and collar ties and roof boards?
> 
> As I've said, of course we put in a ridge board, just like to know the structural reasoning behind this. Thanks.


:shifty: Psssst!:shifty:

**Top secret.
Hush hush!**

:shifty:

In your scenario?



The ridge board is there,
because it makes it easier to frame that way.


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## Tscarborough (Feb 25, 2006)

The only reference I can find to 700 PSI CMU is for ungrouted hollow units (as an aloowable stress for the emperical method of design). the infomation I have, shows a low of 1500 to a high of 4500 for grouted cell 8" CMU. Could you list your source?


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## Tim Garrison PE (Oct 22, 2009)

Okay, the article on ridge beams and collar ties is up:

http://www.constructioncalc.com/blog/structural-design/collar-ties-and-ridge-beams/

I'll start a new thread on it here, too. Please look at the article there and let's discuss it in the new thread here.


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## greg24k (May 19, 2007)

Rocket Red said:


> I also wanted to address this one, you never qualified your post by stating what the spans were. I assume that you meant the spans for the garage were matching the house gable, so they were the same as the house spans. If so, you didn't state when the house was built, and if it was more than 10 years ago, then we are talking what 3 code revisions?
> 
> I could not say if it was over designed, or if it just meets the current span tables based on the current IRC or IBC. It seems like that project may have a vaulted ceiling, or why wouldn't they just buy a truss system?
> 
> An 11 1/2" ridge beam could not be spanning very far before deflection becomes an issue.


Addition was 10' by 20'...the continuation of existing ridge was 10'6" to match the existing roof line. Basic gable roof 5/12 pitch, one car garage, ceiling, collar ties... Not over designed with 11 1/2" para-lam and 2/10 rafters 16" OC? :no:


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## Tim Garrison PE (Oct 22, 2009)

What is the snow load?

What is the span of the ridge beam, inside of bearing to inside of bearing?

Tell me those and I'll calc it for you. However, you can calc it yourself in about one minute, for free, using ConstructionCalc ProBeam demo. That demo has a five day free trial period.


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## katoman (Apr 26, 2009)

Unfair. That is not a true representation of any roof I have ever seen.

The cieling joists are 2x6. They can't be spanned 24'. There would normally be a centre bearing wall.

You have not explained the difference between loads applied to a roof with and without ridge board. NOT ridge beam.

Please try again. :thumbsup:


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## Tom Struble (Mar 2, 2007)

so i guess it's overbuild sometimes,don't other times...got it:thumbsup:


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## katoman (Apr 26, 2009)

I just re-read this section. Tim never discussed ridge boards, he was talking about ridge beams, which I think we all know are required for vaulted ceilings. 

I hope he will still give us an engineering perspective on the issue of ridge boards as I have previously described.


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## Tom Struble (Mar 2, 2007)

I'd like a second opinion


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## NJ Brickie (Jan 31, 2009)

Tscarborough said:


> The only reference I can find to 700 PSI CMU is for ungrouted hollow units (as an aloowable stress for the emperical method of design). the infomation I have, shows a low of 1500 to a high of 4500 for grouted cell 8" CMU. Could you list your source?


750 psi seemed low to me but I figured I would take the word of an engineer. Learned my lesson. Did alittle research and found numbers similar to yours.


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## Ayerzee (Jan 4, 2009)

katoman said:


> I just re-read this section. Tim never discussed ridge boards, he was talking about ridge beams, which I think we all know are required for vaulted ceilings.
> 
> I hope he will still give us an engineering perspective on the issue of ridge boards as I have previously described.


I thought they were the same thing....:shutup:

(Only stick framed roof I've ever done was a shed dormer roof though) :jester:


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## katoman (Apr 26, 2009)

Ayerzee said:


> I thought they were the same thing....:shutup:
> 
> (Only stick framed roof I've ever done was a shed dormer roof though) :jester:


A ridge board is installed between your rafters. Typically 2" larger than the rafter dimension. There are a number of reasons it's there - helps keep everything straight, aids in the connection of the opposing rafters, and can be supported from below. But it is not in itself a 'structural' element, for lack of a better description.

On the other hand, a ridge beam, is just that. A beam, which will take weight. Think of it as a floor beam that you will hang floor joists off of. With a ridge beam you are hanging the rafters off it.

My question for Tim has been that I do not understand the structural significance of a ridge board. My ignorance, looking to learn something.


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## Tscarborough (Feb 25, 2006)

Never take the word of an engineer, a doctor, or a lawyer. They get so used to people taking their word that they begin to believe their own words too.


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## parkers5150 (Dec 5, 2008)

Katoman, i'm no engineer, in fact i've only ever been on a train twice, but:whistling in my humble opinion one of the structural reasons for ridge boards (rafters) ridge blocks (trusses) is for nailing(sheer). everyone is talking about the roof two dimensionally or the "triangle" when in fact as a three dimensional structure it is actually two squares or rectangles laid up against each other. the ridge board or blocks complete the diaphram in the square dimension which might not translate much into the "spread" factor but is definitely a link in the complete structural frame


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## Tom Struble (Mar 2, 2007)

well if there is no load at the ridge BOARD why do you need a shear connection there?


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## katoman (Apr 26, 2009)

parkers5150 said:


> Katoman, i'm no engineer, in fact i've only ever been on a train twice, but:whistling in my humble opinion one of the structural reasons for ridge boards (rafters) ridge blocks (trusses) is for nailing(sheer). everyone is talking about the roof two dimensionally or the "triangle" when in fact as a three dimensional structure it is actually two squares or rectangles laid up against each other. the ridge board or blocks complete the diaphram in the square dimension which might not translate much into the "spread" factor but is definitely a link in the complete structural frame


I understand what you are saying. But if the roof is covered with plywood, or roof boards, what benefit or need is there for the ridge board. As another poster stated, I have seen many older homes with no ridge boards, but full one inch roof boards, that were just fine.

As I've said, I'm looking for a detailed, comprehensive explanation from the engineer, explaining the loads involved and the need for the ridge board.


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## greg24k (May 19, 2007)

Question for Tim Garrison PE ...Straight gable roof, width of the building is 20' Ridge 10'6". What is the maximum rafter span for a 2X6 DF #2, 5/12 pitch, having 20LB LL and 10LB DL no ceiling attached to rafters? Thanks :thumbsup:


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## Ayerzee (Jan 4, 2009)

See if this helps.
http://docs.google.com/viewer?a=v&q...b8RPg0&sig=AHIEtbTDLkGcIPFC0vRK5ZyOCQOsbAEx4A

If not the Calcs for simply supported beams are pretty simple but I don't know if rafters are calc'd the same way as floor joists/girders. I think they are but may have to wait on an engineer to help you.

Edit - I'm not seeing any species/grade on the website so maybe it won't help you..sorry.


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