Cutting Down a Roof Ridge (A LOT) 1

jerseyshore · Mar 3, 2023

As I mentioned in my other thread, the real reason I went out to this house was because they framed the roof ridge 9" too high. We have to cut down the roof ridge and the contractor was throwing out some options on how to do it. It's a low slope roof so 9" of vertical cut is 5'-5" horizontally.

The challenge here, besides the obvious, is that they:

1. Already sheathed the entire thing, so they want to save the 2x8 rafters as currently positioned, just cut off at that max height mark
2. Also have to keep 7' ceiling height to keep this a finished space for appraisal

The only way to keep this 7' ceiling height is to use 2x6's at the flat portion. Here is what the contractor described:

Option 1: lap 2x6 on each side of the now cut rafter pair, thru-bolt together
Option 2: Similar to OPT 1, but add a structural ridge beam down the center and hang the 2x6's off of it. Would need a triple 2x6 hanger since it'll be 3 ply wide basically.

My original repair included marrying new 2x8's end to end and using a plywood gusset (like a steel bent frame), but that won't give them 7' clear and the contractor doesn't think he can make the cuts that nice at the joints. I've included that below also.

Thoughts on this dilemma we have here? Any suggestions are greatly appreciated.

SWComposites · Mar 3, 2023

Seriously?
Is the owner going to accept a flat roof top?
Where is the 7’ clearance measured? Only in the center part? This is an attic?
I’m not a CE, but those 3 fastener joints in Options 1 and 2 look awful.
Was the whole house built too high? Or were the plans wrong?

jerseyshore · Mar 3, 2023

7' is measured only under the flat portion in the center. Need it to be 7' to be considered finished space, otherwise it would just be an attic. This 3rd floor is partial attic partial finished space.

The owner is partially running the job, has a builder too, but he's kind of the GC.

He took a laser measuring tape, walked to the telephone pole and held it up at the flood elevation mark. Shined it onto the house and had someone mark that line. That is what they used as a baseline for the 3rd floor roof ridge.

Well guess what, 3rd grade geometry tells you that even a fraction of a degree off over 20 ft adds up to a much larger number. Never used a laser level, just eyeballed it. Close enough = 9 inches off by the time you get to the highest roof peak.

No one else ever re-measured or checked. Never had the surveyor back out until the whole thing was built.

You know what they say, measure ~~twice~~ once, build a whole house.

phamENG · Mar 3, 2023

You are too patient for your own good, jersheyshore. I'd probably laugh at these guys and walk away. I would not want my name associated with these clowns in any way, shape, or form.

If the ridge beam works, great. Maybe you can make a go of that. Otherwise, would 2x6's work as a full length, flat rafter? If the answer is no, the top one is no good unless your 2x6 is actually a 6" steel channel.

jhnblgr · Mar 3, 2023

Out of curiosity is the roof height the top of the roof in the legal definition or the median height? If so you might not have any issues at all

jerseyshore · Mar 4, 2023

When the housing market is hot, you get a lot of clowns in residential construction. That comes with the territory.

The 2x6's on the flat would work because the span is only 6ft or so.

Comes down to the connections. I have 30 psf SL, 15 psf DL, plus wind uplift. I normally don't like to mess around with low slope & flat roofs, both of which I now have here, so tying everything together at the joints is a challenge.

jhnblgr, since this house is in a flood zone, all elevations are measured off of BFE. It's not a terribly uncommon issue around here since so many houses are raised up and people try to squeeze every vertical inch out of it. I'd say probably 90% of new houses that raised up a full story are within an inch of that max height allowed in their town. This is one is as bad as I've seen tho.

phamENG · Mar 4, 2023

jerseyshore said:
The 2x6's on the flat would work because the span is only 6ft or so.

I disagree. This is no longer a simple rafter system. Your span is 18' and you're using a moment spliced beam. Maximum moment will still be 9' from the support, right at the middle of the 2x6.

Yes, circus level housing markets do bring the clowns out of the woodwork (or into it, really)....but that doesn't mean we should help them in their shenanigans. If they have to rip this thing down and totally redo it, they'll either a) not have enough money to get back in the game and we'll be down a clown, b) they'll come back in with a greater appreciation for the right way to do things and we'll be down a clown, or c) they're too dense to learn and it won't matter.

WinelandV · Mar 4, 2023

I don't like any of the options. I think the flat in the middle will sag over time and you'll have nothing but water issues there.

The owner will likely have to accept something less than what he wants - unless he's willing to tear down to at least to the second story and cut out 9" from there, I don't see how you make this work.

Please note that is a "v" (as in Violin) not a "y".

Enable · Mar 4, 2023

I'm with the others that my immediate reaction is revulsion. The entire enterprise hinges on developing true moment connections in wood, which is a dubious prospect in the best of times and nye impossible when your builder is this bad.

If for some reason I felt compelled to come up with a solution though, I would look into supplementing the existing with a CFS moment frame thing between every truss. If you have any prospect of making this work I feel a CFS structure with moment connections at the change in slope is your best bet. Surely we'd have a lot more confidence in the moment connections at least. You may want to look into circular bolt patterns as I know there is some literature on that and using the self-drilling fasteners can be dubious for moment connections in CFS (still better than wood I feel though).

No matter which route you go you still have sag / flat roof issues. So if you do go ahead with something make sure the owner puts it in writing that they are taking an increased serviceability risk / maintenance schedule.

jerseyshore · Mar 4, 2023

phamEng, you are 1000% right. I originally checked this as a new roof and it needed 2x6 LVLs @ 5" o/c to work for that span. When I modeled this yesterday I realized I checked it as pin-pin instead of pin-roller. It needs to be supported in the middle.

Running it with a ridge beam would give me about 490 lb-ft at the joint. I don't see any way of making that work with a couple of thru bolts in a 2x6-2x8-2x6 sandwich.

I have no problem being the bad guy on things, especially now working for myself, all the liability is solely on me. But on residential construction you get a lot of "how can we make it work" type scenarios. I try my best to look at all the options and work with these guys as long as I can prove it on paper.

I think a gusset-type connection with at least 2x8 depth would be the only way to even have potential to work assuming I could get enough nails in there with proper edge/end/spacing distances.

jerseyshore · Mar 4, 2023

Enable, thanks for that sketch. A true wood moment connection is something I've never recommended before and I don't want to start now.

Of course my first thought when seeing this issue was a steel frame, but CFS would certainly be better than wood, although I can't think of the last time I did any CFS moment connection either, if ever.

You guys want to know what the builder was going to do if I wasn't involved? Instead of putting 2x6's on that flat area, he was just going to use two 1/4" x 5.5" x approx 6' long steel plates (vertically) and bolt them to the end of the 2x8s! Talk about someone who has no concept of structure. That thing would've collapsed under its own weight.

I appreciate all the comments that reinforce my idea that this isn't going to work.

SWComposites · Mar 4, 2023

I suggest adding two big ridge beams, one at each intersection of the sloping rafters and the flat joists, angled half between the rafter slope and flat. Can use hangers on both sides. And double or more the number of flat roof joists. Tie the ridge beams well into the end gables.

What do they plan to do for roofing on the flat area? Can’t use shingles.

phamENG · Mar 4, 2023

I had a thought. Ostensibly this design was reviewed and approved, meaning if the ridge is 9" too high, the first floor must be 9" higher than required, right? So...

Get a house lifter to shore the house and disconnect it from the piles. Cut the piles down 9" (using a surveyor to set elevations this time), let the house, reconnect to the piles.

Boom. No fancy structural magic that won't last me than any 5 years or one big storm.

jerseyshore · Mar 4, 2023

I suggested that this morning. The issue with this is that one of the two ridge beams falls just in the middle of the space so they don't want to add any columns since it's tight enough already. And I have to keep those ridges to 2x6 flitch beams max because of the depth restriction.

They were contacting the roofer to see what he recommended, probably fiberglass.

That was my very first comment to this whole situation. Evidently the first floor is at the correct elevation. So is the 2nd floor. The surveyor checked them as well.
The architect ONLY shows 9' ceiling, 8' ceiling, 7' ceiling for the 3 levels, but nothing else dimension-wise besides labeling the maximum height above BFE. No roof slopes or floor-to-floor dimensions. So my guess is that the dimensions are forced or maybe his drawing isn't to scale. So yes they messed up by building first then measuring second, but even still, the design drawings just didn't actually work as shown.

Funny you said that because I just spoke to a house lifter client of mine yesterday and told them what happened and they said they've done that before (cutting down studs not the piles) to bring a house under compliance.

jerseyshore · Mar 5, 2023

I told these guys this evening that there is no solution to splice members together.

The builder goes: "I ordered the material already. You said it would work."

Yeah don't think I ever said that. In fact I make it a point to never give definite answers in the field. I said what I always say "let me run some numbers and see what we can do."

So for this "finished" 3rd floor space they will remove the entire roof area and replace with a new structural ridge and new rafters, just at a lower slope.

---------------
What I didn't realize the first time I was out there was that EVERY ridge is at the same height, thus also needing to be cut down by 9 inches.

In the front of the house, there is no attic above the master bedroom so they deleted the ceiling joists to make a high ceiling.

You think these guys added in raised rafter ties in that bottom third of ceiling height? Ha, no.

Now just the collar ties remain up there to resist the thrust. Can anyone guess how close they are to the ridge? A third of the way down right? Well you guessed it, 9 inches below the ridge nailer.

But it's okay, they say it doesn't snow down the shore...

SWComposites · Mar 5, 2023

It’s probably cheaper to just bribe the surveyor to say its compliant. This is Jersey, right?

jerseyshore · Mar 5, 2023

Okay so I lied. The very first thing I said was I hope you have a friend who's a surveyor.

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