Engineers - Ideas To Replace These Trusses?

[Willypu]

So we are ready to have the framing inspection done but I would like to see if there is a way to replace the wood trusses in the picture with possibly wood beams or steel beams.

My contractor is dragging his feet on this as he usually works just with wood trusses and not steel.

If we leave it the way it is, the ceiling height will be about 5'. If we could replace the wood truss with something else at the height where the 2x8's meet we would have a 7' ceiling and could make this area a bedroom and storage.

So, without all the drawings what is your opinion, can we replace the trusses with steel or wood beams? Any ideas are very welcome!

The floor is raised up as this is where the lift will go on the first floor.

The left dormer is where the issue is. The other sections have a 10' ceiling but because we put a lift in, this section has a 13' ceiling.

 

[LX-Markham]

As a structural engineer, I would suggest you consult your truss supplier with your proposed changes.


Really really nice looking garage BTW.

 

[manwithtools]

Should have thought about this much earlier on, it could have been far less painful. That being said, you'll likely need an engineer at this point to alter your approach. Lot's of arm chair engineers here (me included) could offer suggestions. None of them will be valid until the actual engineer with liability signs the alterations.

 

[Willypu]

Should have thought about this much earlier on, it could have been far less painful. That being said, you'll likely need an engineer at this point to alter your approach. Lot's of arm chair engineers here (me included) could offer suggestions. None of them will be valid until the actual engineer with liability signs the alterations.

I agree, we originally were going to use the area as storage so we did not pursue changing the truss design. However, once we actually saw what it looked like the idea of making it a livable space came up.

I am not an engineer, but it seems we should be able to create a support that would allow a taller ceiling.

Thanks for the input.

 

[rayra]

seems like an easy alteration given the huge chord of those rafters (2x10? 2x12?) and the small size of the box truss lumber (2x4?

Seems it could be re-engineered with a large (2x8?) crossbrace as an A-frame, its bottom at your desired 7' height, sistered to the existing rafter adn truss structure. Then pruning the existing truss framing to fit a new bottom chord on the truss frame, itself sistered to the new larger crossbrace and tied into the old truss web.
Talk to the original truss engineer (or another) to get proper mods figured. And kick your GC in the ***. Or yourself if the raise ceiling was your change order after the original design.

 

[manwithtools]

I agree, we originally were going to use the area as storage so we did not pursue changing the truss design. However, once we actually saw what it looked like the idea of making it a livable space came up.

I am not an engineer, but it seems we should be able to create a support that would allow a taller ceiling.

Thanks for the input.

Agreed, should not be a problem. It's all up to the guy's with calculator and checkbook......

 

[Stuart in MN]

As a structural engineer, I would suggest you consult your truss supplier with your proposed changes.

I agree. Unfortunately, any engineering advice you get on the Internet is worth what you paid for it.

It is a good looking place.

 

[n20junkie]

seems like an easy alteration given the huge chord of those rafters (2x10? 2x12?) and the small size of the box truss lumber (2x4?

Seems it could be re-engineered with a large (2x8?) crossbrace as an A-frame, its bottom at your desired 7' height, sistered to the existing rafter adn truss structure. Then pruning the existing truss framing to fit a new bottom chord on the truss frame, itself sistered to the new larger crossbrace and tied into the old truss web.
Talk to the original truss engineer (or another) to get proper mods figured. And kick your GC in the ***. Or yourself if the raise ceiling was your change order after the original design.

Look at the top chord again, it transitions to a much smaller size once it gets above the ceiling height.

What the OP is asking for will cost BIG money to change now. Nothing is impossible, but those requested changes are just not as easy as adding collar tie and moving on.

Half of the trusses job with that ceiling pocket is to take the spreading load. What you want to do will leave no way to acceptably handle those spreading loads without lower level engineering. You just can’t sister some 2x12’s and call it good.

 

[firebirdparts]

That is a beautiful building.

Not sure how rayra thinks this would be easy. Even if stick built it from scratch, it wouldn't have been too simple. That floor is not sitting on the walls. It's 4' above, hanging from the roof. It's an awkward design, and it may be that truss was never designed for normal living space loads either. After all that, the dormer knocks a chunk of it out.

We can't see what's below that, but if you're going to have a lift, evidently it's air.

 

[ez-duzit]

Should have thought about this much earlier on, it could have been far less painful...

This.

Now that it's already built you could get it engineered to replace the trusses with more traditional framing plus posts to transfer the vertical roof loads to the raised floor supports, where the new collars will end.

 

[Copymutt]

Could be replaced w/ scissors truss.

Expensive lesson.

 

[bczygan]

As a structural engineer, I would suggest you consult your truss supplier with your proposed changes.


Really really nice looking garage BTW.

This is the answer.

Truss designer will have all the design loads and parameters.

Bill

 

[bczygan]

First of all, that is a two piece truss design.

There is the main part with a small A shaped piece on top.

It is done that way so the trusses can be carried down the road. Otherwise they would be too big.

The main portion has all that small framing at the top that could be replaced with different framing with more headroom. It needs to be engineered.

Truss company would need to do it.

Bill

 

[LX-Markham]

All i’ll say is that’s a weird hybrid of a design that i’ve never seen before. Would be easier to understand how it works by looking at the design drawings. But I suspect it’s going to be difficult (expensive) to raise the top section any significant amount.

 

[Leaflessshadetree]

I don't see a lot of actual space to be gained there. Just how wide will the area with a 7' ceiling be? From the pics it appears like about 6' wide. It also looks like the floor is probably about at the bottom of the windows in the dormers.
Open framing always looks bigger than it will be with insulation, walls and a ceiling.

 

[yeldogt]

First -- are you sure with the change you could actually code that as livable space ? I agree -- it's an odd design. But, you were asking for an unusual change to the building -- was that a truss designed standard layout? If so .. they would have needed an exception engineering design -- your best bet is to go back to that same guy and ask.

I wonder why they cut down the rafters --- what did they do on the other side? Is the floor the truss on the other side ? If so .. you will have an issue.

 

[PCustoms]

I wonder why they cut down the rafters --- what did they do on the other side? Is the floor the truss on the other side ? If so .. you will have an issue.

Good questions, i would think a framed rafyer would have been easier, and given the headroom. After reading this comment I went back and looked at the first post again.

OP, What is in your plans?

Did someone engineer this?

Was it built on site?

I see some things in that first picture that make me think this was built upon site, and the differences from truss to truss make me think at minimum the framer may not have followed plan 100%. Worst he "engineered" it on the fly.

The more I look at that back window the more the whole things looks crooked....

 

[LXCam]

I say rock it as is and rent it out to a family of midgets


Nice job on the garage, that's gorgeous.

 

[manwithtools]

Guys, you need to see his build thread to fully understand the issue and construction.

https://www.garagejournal.com/forum/showthread.php?t=402633

It's a two piece truss as Bill points out, which explains the changes in top cord sizes. There are undoubtedly ways to regain the lost headroom, it's just not going to be simple at this point. It might take posts and further beams which could spoil the design of the rest of the space.

For as much money the OP has invested at this point, a little more with an architect and engineer could be money well spent.

 

[yeldogt]

After reading this I went back and looked at it again.

What is in your plans?

Did someone engineer this?

Was it built on site?

I see some things in that first picture that make me think this was built upon site, and the differences from truss to truss make me think at minimum the framer may not have followed plan 100%. Worst he "engineered" it on the fly.

The more I look at that back window the more the whole things looks crooked....

This I not my build ....

 

[yeldogt]

Guys, you need to see his build thread to fully understand the issue and construction.

https://www.garagejournal.com/forum/showthread.php?t=402633

It's a two piece truss as Bill points out, which explains the changes in top cord sizes. There are undoubtedly ways to regain the lost headroom, it's just not going to be simple at this point. It might take posts and further beams which could spoil the design of the rest of the space.

For as much money the OP has invested at this point, a little more with an architect and engineer could be money well spent.

Good catch -- I guess a structural ridge could have done it ... but they tend to be large and would have been expensive for that span. I recently had to do a 30' and it was expensive to design and hide.

I'm wondering why they did not design the raised area of the building using the raised ffloor as the bottom of the truss.

 

[PCustoms]

This I not my build ....

I know, your post just made me go back and look

 

[Ironcrow]

I'd find an engineer and come up with steel flitch plate to add to both sides of the existing joists. Run continuous plate up over the apex. Sister them up, bolt them through and cut out the wooden collar ties.

 

[Handyfarmer]

if it was mine, and I wanted to do that,

take a 2x12 or what ever the rafter is, and run it along the side of the of the current rafter and 2x4 truss ****, to the peak and bolt and glue it to the existing rafter with at least a 4 foot lap, on to the existing rafter, when it is in and attached cut out the 2x4 junk, if wanted do both sides, why they just didn't do the 2x12 rafter to the peak amazes me,

my two cents,

 

[Ironcrow]

if it was mine, and I wanted to do that,

take a 2x12 or what ever the rafter is, and run it along the side of the of the current rafter and 2x4 truss ****, to the peak and bolt and glue it to the existing rafter with at least a 4 foot lap, on to the existing rafter, when it is in and attached cut out the 2x4 junk, if wanted do both sides, why they just didn't do the 2x12 rafter to the peak amazes me,

my two cents,

The idea of a steel flitch plate is you need a moment resisting element at the joist apex to resist spread forces OR if you do it with extended joists like you describe also add a tension member continuously from joist to joist just under the raised floor surface.

 

[holdover]

In essence your truss work tying in the rafters are acting as collar beams. I believe the code now says that collar beams must be in the lower 1/3 of the cathedral, which will mess up your ceiling height, BUT if it is engineered it may pass the building inspector visit. The rafter spacing looks 3' or more. Also your truss manufacturer/engineer is putting a-lot of trust in those lower gang nail plates and 2 X 4 beams.

 

[Ironcrow]

... if it is engineered it may pass the building inspector visit...

WILL pass. The engineer's stamp supersedes both the building code and the inspector's opinion.

 

[rayra]

Look at the top chord again, it transitions to a much smaller size once it gets above the ceiling height.

What the OP is asking for will cost BIG money to change now. Nothing is impossible, but those requested changes are just not as easy as adding collar tie and moving on.

Half of the trusses job with that ceiling pocket is to take the spreading load. What you want to do will leave no way to acceptably handle those spreading loads without lower level engineering. You just can’t sister some 2x12’s and call it good.

Nonsense. Just talking about moving up the height of the bottom chord of the truss and increasing its strength, not removing it. Those rafters and a suitably sistered larger bottom chord will easily accomplish the change.
And the attic joists are already helping prevent spread, too.

OP, it's an easy thing to engineer. Don't let the doomsayers and fear-merchants deter you. Talk to the original engineer or see if you can find one with enough nutsack to modify somebody else's design.

 

[Innovate1]

The floor joists seem to cover the spreading forces. It seems to me the main issue is side forces on the roof will tend to push one side down and the other will go up, racking the trusses. The bracing above the ceiling prevents that. The very top is a separate piece as some others have noted and doesn't add any strength to preventing this. If the ceiling is raised to the end of the 2 x 12s then likely a larger cross piece would be needed to handle the inward forces but does nothing for the racking. Larger lumber could be lapped onto the 2 x 12s and run to the ridge to handle the racking forces. The side walls could be brought in to add bracing there but not sure how much that would really strengthen things.

I don't see where steel is the answer. As others have stated this needs to be engineered and the original truss company should be able to tell you what is needed for a reasonable cost (engineering only). Then a decision can be made if it is worth the cost of actually doing the changes.

 

[Innovate1]

The fly over video linked in the other thread gives some good views of the structure.

I grew up near the coast in this area. VERY nice looking place!

 

[86turbodsl]

I am an engineer and my opinion would be to seek out a structural engineer willing to work in steel. I think you could weld up a structure in-situ and remove those members to gain some headroom, but my opinion is only worth what you paid for it. You WILL need to get engineering signoff on whatever you end up doing.

 

[Willypu]

Hi Everyone, I am the OP, somehow I was not getting updates to the thread so I "assumed" nobody was answering. Thank you all for the great comments and suggestions.

Here is where we are, the original truss engineer explained that the primary purpose of these trusses is not only to support the roof but hold the walls from bowing out. He has been super busy (as most builders in the area) and is just getting back to look at our situation. He is trying to design a steel replacement that will not only provide support but also allow 7' of head room.

If we are able to obtain the 7' of head room that would create a useable 15'x18'x7' room. It was listed as a bedroom on the original plans and has been signed off as such. Cost? Well, as one post pointed out, I am in pretty deep now so I am willing (and hopefully able) to cover that expense.

We are really close to being ready for drywall etc, so I am hoping we can get this resolved in the next few weeks.

Thanks again for the input, and yes, I totally know about answers on the internet about engineering and doctors, but I was able to send some of the suggestions on to the builder and engineer and they were appreciated.

Have a look as the build so far. I will keep you updated and check in here now that I think I have the thread subscription setup.

Thanks again,

 

[theoldwizard1]

Here is where we are, the original truss engineer explained that the primary purpose of these trusses is not only to support the roof but hold the walls from bowing out.

This is true on the bottom chord of a full truss, as well as rafter ties, collar ties and even ceiling joists on a non-trussed roof !

He has been super busy (as most builders in the area) and is just getting back to look at our situation. He is trying to design a steel replacement that will not only provide support but also allow 7' of head room.

One big issue is, are the rafters strong enough that, if the existing rafter and collar tie are replaced with a single steel collar tie, will the rafters (and their connection to the top plate) hold the walls in AND still hold the designed roof deck load (including snow).

There are usually additional requirements for an "occupied" room above a garage.

 

[Road_runner]

I am also an engineer and agree with LX Markham. At this stage, you need to talk to the truss company.

 

[Willypu]

Just wanted to follow up on this. The truss company engineers took a look at the original plans and their calculations. The basically said they over built the trusses and what they plan to do is remove the portion of the truss, replace some of the structure with 2x4s and then sandwich the entire upper part of each modified truss with plywood. This will provide a 7'2" ceiling 15' wide by 18' deep. The engineer plans to be on site Monday to talk to the build crew so they understand what materials to use and how to modify each truss.

I will provide pictures (hopefully) in a few days for you all to see.

Thanks for all the comments, they helped in my conversation with the truss company.

 

[Willypu]

A sloution has been found, approved and stamped by the truss engineer. The fix is to cut off the lower 20" of the truss, replace 2x4's and sheet both sides with 3/4" plywood and add several supports to the existing load bearing support on the first floor. the fix should take the guys a week to complete and then we can get the framing inspection completed and move on to insulation and drywall.

Here is the post the shows the pictures of what we are doing.
https://www.garagejournal.com/forum/showthread.php?p=7750824#post7750824

 

[firebirdparts]

Good deal.

 

[greg13]

I think I would learn to live with it.
It might be easier and cheaper to take 12" out of your legs if you really want to walk in there.

 

[firebirdparts]

I was thinking more like they'd be done in a couple of hours.

 

[Willypu]

First section took a little longer as they were making templates for the next section.