Cutting trusses

[JackOfDiamonds]

I want to put a big ladder to my attic, which uses 24" on center prefab trusses.

I thought you could cut the bottom chord of a truss, as long as you frame it properly. I expected the truss company to tell me how to do this. They must deal with this all the time, right?

Instead, they said it's impossible to cut the bottom chord and wouldn't help me with the engineering. Yet, I see that I can buy 25" and 30" wide ladders all day long.

I'm thinking about buying a 25" ladder and just shifting a truss over a couple inches, but nobody will tell me this is OK either.

 

[whateg01]

This is a joke, right?

 

[ptt49er]

The PO cut the trusses to install the attic ladder in our house.

I spoke with a structural engineer and there are ways to frame a diaphragm of plywood around the penetration.

I haven't gotten a stamped plan from him but have installed ply around the opening.

Find a local residential structural PE, they'll likely be able to help.

 

[Uncle murph]

This is a joke, right?

I want to put a big ladder to my attic, which uses 24" on center prefab trusses.

I thought you could cut the bottom chord of a truss, as long as you frame it properly. I expected the truss company to tell me how to do this. They must deal with this all the time, right?

Instead, they said it's impossible to cut the bottom chord and wouldn't help me with the engineering. Yet, I see that I can buy 25" and 30" wide ladders all day long.

I'm thinking about buying a 25" ladder and just shifting a truss over a couple inches, but nobody will tell me this is OK either.

You’ve got 22.5” between your trusses,buy a ladder that fits.

 

[PCustoms]

The PO cut the trusses to install the attic ladder in our house.

One of mine is cut, thankfully in a low load spot (cantilever, cut spot is past the support). The ceiling was sagging over an inch until I re-framed it.

 

[BurtEggley]

I had to cut a truss to put in a whole house fan. Needed an engineering drawing with a stamp to get it approved, and when the city came out to inspect it, they even verified the nail size, type and placement on that part of the drawing. The engineer wanted a lot more than just the plywood sistering I was suggesting.

As suggested, I'd look for a ladder that fits.

 

[tarmy]

Cut and trusses are not two words that should be used in the same question

As noted, get or build something that fits in between them.

 

[TRWham]

We have modified or repaired trusses per engineer instruction, but not very often. You would need some path to carry that tension without just transferring it to the adjacent trusses, and the connections would be critical.

 

[mike93lx]

Is this building done? If so, how are you planning to move a truss over?

If not, get the trusses designed for this need, or just buy a ladder that fits

 

[PCustoms]

I'm thinking about buying a 25" ladder

Got a link?

 

[LopezBart]

Some quick estimate numbers to show why this is not simple: each 16p common nail is good for ~130 lbs in single shear; douglas fir is rated for ~300 psi in tension. Sistering in a 2x4 bottom member would then take 12 16p nails at each end, a 2x6 obviously more. Plywood, unless glued as well as nailed, would fail in bearing unless many many nails are used.

Getting 1.5" inches more width is pretty doable, but you need an engineered solution. More gets harder quickly.

 

[wssix99]

Instead, they said it's impossible to cut the bottom chord and wouldn't help me with the engineering.

Here is the translation of this statement from your truss company to English:
"We are sorry but our engineering services and help come free of charge with new truss purchases.

If you desire additional support and assistance beyond warranty repairs, you will need to pound sand and go hire your own engineer.

I want to hang up on you now so I can go fishing."

 

[JackOfDiamonds]

Here is the translation of this statement from your truss company to English:
"We are sorry but our engineering services and help come free of charge with new truss purchases.

If you desire additional support and assistance beyond warranty repairs, you will need to pound sand and go hire your own engineer.

I want to hang up on you now so I can go fishing."

Well I was asking for the $3000 worth of trusses I have on order with them.

This must be a regional thing. I swear back east all you had to do was ask and the truss companies would give you a pre-engineered framing plan for an attic staircase. But things generally get more lawyerfied over time so maybe that's a bygone era.

 

[mike93lx]

Well I was asking for the $3000 worth of trusses I have on order with them.

This must be a regional thing. I swear back east all you had to do was ask and the truss companies would give you a pre-engineered framing plan for an attic staircase. But things generally get more lawyerfied over time so maybe that's a bygone era.

Do they already have them in production? If not, they **** for not working with you on a solution

 

[wssix99]

Do they already have them in production? If not, they **** for not working with you on a solution

+1 If not in production, I would talk to your salesman.

I would expect that if you want wider spacing, they would NOT give you a repair solution for new trusses. (They would only want to engineer intact trusses for your installation from a liability perspective.) That being said, they should be able to re-design your trusses for wider spacing, but that will likely cost you more money (for hefty trusses) and could change the shape of your roof to make the options economical.

 

[TurnipTruck]

I seriously doubt that truss loading doesn’t have at least a small safety margin such that you couldn’t scoot one truss over 2 or 3 inches to make room for your stairway. Blocking and sheathing will have to accommodate the odd spacing, of course. **** it’s OK****

I would FAR prefer to scoot rather than cut or modify a stressed truss member.

I asked my truss designer friend to design a four foot gap in my 40’ trusses for a spiral staircase; the attic truss (LEFT) merely required the nail plates to be upsized ($8) while the other side he just doubled the standard truss.

 

[PCustoms]

Got a link?

 

[Stuart in MN]

It's not worth the truss company's time to do the engineering for one homeowner to modify one truss, plus there's the potential liability if the modified truss fails. That's why they said no. You may be able to find a structural engineer who's willing to do an initial inspection, then do the calculations and make drawings, then do a final inspection, but most will either decline the work or charge you more than you think it's worth. I was a consulting engineer for many years, unfortunately that's how it works for small jobs like this.

 

[carlaisle]

Easy button:

https://www.stairwayshop.com/american-stairways-husky-800-1200-series-aluminum-attic-ladders-door-upgrades.html

 

[Two Door]

I'm thinking about buying a 25" ladder and just shifting a truss over a couple inches, but nobody will tell me this is OK either.

Are you planning to custom-size or re-orient the sheetrock and decking to accomodate this?

 

[finn]

I have a narrow pull down ladder similar to that to get to my attic storage. In a word, it *****.

The narrow opening is too restrictive to get anything with any bulk through the opening, the stairs are too steep to safely navigate while carrying anything, and the stairs depth is too short to comfortably fit your feet where the plywood closure sheet closes in the raised stairs.

I’ve said it before, but the money I spent for the storage trusses and aluminum stairs is largely wasted in my opinion.

You’d be better off adding a foot or two to the footprint with that money and put up metal shelving on your concrete floor.

 

[mike93lx]

It's not worth the truss company's time to do the engineering for one homeowner to modify one truss

It's not a modification, it would be a new truss and it's their job.

Not all truss companies want to only deal with big jobs. I got trusses for a 16x16 shed and two local companies were happy to quote exactly the details I wanted, without trying to get me to go to anything "standard"

This company would lose my business over that response

 

[Skooterj]

If the building hasn't been built yet, and you are just getting the trusses ordered, changing the spacing between just 2 of the trusses should be a non issue. If your truss company won't do that simple engineering, find another truss company. If the building has already been built, or the trusses already been manufactured, you are going to need to hire your own structural engineer to modify your existing trusses.

 

[BillK]

I want to put a big ladder to my attic, which uses 24" on center prefab trusses.

What do you mean by a "ladder" ???? And how wide do you want it to be ?? You can buy pull down stairs for 24" OC trusses almost anywhere. I have them on both of my garages.

 

[johninct]

What are you going to put up there? That weight matters.

 

[CraigStu]

I framed a hole between 2 trusses 4ft long. Then I put a hinged cover over it on the top of trusses w/ a rope going through pulleys up to the roof area and over one to a hanging weight. Got the weight so I could push the lid up w/ my little finger or my head. Then I bought a 10ft step ladder. I hung the top of the ladder from 2 eyebolts. I ran a rope from the bottom of the ladder to a pulley in the ceiling to another pulley at the wall and down to a cleat on the wall. I would undo the rope at the cleat, drop the ladder, open the ladder so it sit on it's normal 4 feet so no stress on the eyebolts while I was climbing. both the rope from eyebolt to eyebolt and the rope to the bottom of the ladder attached w/ dog leash hooks. So I could undo the ladder and carry it anywhere else I needed it. Storing it against the ceiling kept it out of the way. The step ladder was WAY better than a pull down ladder in the previous house.

 

[Innovate1]

Well I was asking for the $3000 worth of trusses I have on order with them.

This must be a regional thing. I swear back east all you had to do was ask and the truss companies would give you a pre-engineered framing plan for an attic staircase. But things generally get more lawyerfied over time so maybe that's a bygone era.

Have you committed to getting them? They may have already started on making them. This is something that should have been discussed up front and not tacked on after you ordered them. Guessing a bit on exactly what "have on order" means...

If discussed early I don't see why they shouldn't be able to design trusses for whatever spacing you want. Truss companies around here seem to be pretty willing to do such things although mine were pretty standard and they may want more money for engineering for complex cases. They could even do 2 heavier trusses for a bigger spacing (double normal spacing for example) and the framing between them for a bigger ceiling opening and support for roof framing between. Then again, maybe your truss company only does fairly standard truss designs - you can order standard trusses from some lumber companies and even Menards here in the midwest but you don't get any extra engineering from Menards. Might need to go to a different truss supplier.

You can't just cut the lower member of the truss. It has serious tension stress. And as others have noted bracing to other trusses isn't enough unless they are designed for the extra load and the bracing is done properly.

 

[firebirdparts]

You cannot cut the bottom chord of a truss, ever (that would be insane), but if all you want is 24" on center, then obviously that's not very difficult. I mean it's not difficult for a wooden structure to hold up 25" of roof. I daresay they would happily give you a framing plan that involved uncut trusses. I could be wrong.

 

[firebirdparts]

Are you planning to custom-size or re-orient the sheetrock and decking to accomodate this?

Any sane person would make appropriate accommodations of a 24" spacing stuck somewhere in an 18" building.

 

[Bert_]

Pretty common to laminate a couple trusses on either side of a large opening. Then you just frame in support for your roof sheathing

 

[larry4406]

OP states 24" O/C trusses in the opening thread. Wants a presumed folding ladder.

As many have said, there are many premade folding ladders that slip right in the 22.5" net spacing which results from 24" OC trusses. Standard off the shelf product.

Seems like a trolling thread...

 

[mike93lx]

To be fair, 22" attic ladders make it really hard to move stuff. If I was starting from scratch, I'd also be looking at something at least 30"

 

[sjvicker]

Easy button:

https://www.stairwayshop.com/american-stairways-husky-800-1200-series-aluminum-attic-ladders-door-upgrades.html

This is the way

 

[larry4406]

To be fair, 22" attic ladders make it really hard to move stuff. If I was starting from scratch, I'd also be looking at something at least 30"

It was also asked if the trusses were ordered such that they could accommodate storage and I don't recall an answer ever posted.

Asking to modify non-storage rated trusses for a wider stair opening to then add storage to, I can see why a truss vendor would not want to advise.

 

[whateg01]

To be fair, 22" attic ladders make it really hard to move stuff. If I was starting from scratch, I'd also be looking at something at least 30"

Yeah but op says he's thinking of buying a 25" ladder. Easier to use than 22.5 but a long ways from 30

 

[mike93lx]

Yeah but op says he's thinking of buying a 25" ladder. Easier to use than 22.5 but a long ways from 30

I bet he said 25 thinking it would be a simplish mod.

 

[mm08822]

It was also asked if the trusses were ordered such that they could accommodate storage and I don't recall an answer ever posted.

Asking to modify non-storage rated trusses for a wider stair opening to then add storage to, I can see why a truss vendor would not want to advise.

I hope the truss mfr was given floor loading as part of the design input.......otherwise, I bet they were only planning on holding up sheetrock with the bottom chord.

 

[mm08822]

Yeah but op says he's thinking of buying a 25" ladder. Easier to use than 22.5 but a long ways from 30

Still doable @ 22.5" RO, IF the trusses can support storage. Storage capability is the bigger red flag for me.

 

[mm08822]

It was also asked if the trusses were ordered such that they could accommodate storage and I don't recall an answer ever posted.

Asking to modify non-storage rated trusses for a wider stair opening to then add storage to, I can see why a truss vendor would not want to advise.

That's when 16" or 19.2"OC could come into play aside from each truss being upgraded.

 

[Innovate1]

Storage loading has been brought up and that's typically what happens with easy access like a folding stair. I put cross pieces just above the insulation in my shop attached to the center 2 diagonals and then put some sheeting on for a walkway and easy access to things like wiring. It's not easy enough to get there that storage isn't practical. St. Louis county has a rule that if the bottom cord isn't rated slightly more than minimum (I forget what the needed loading is) they require you to attach framing around the upper side of the opening to make openings small enough that storage (and a person getting in to do anything) is nearly impossible and a warning sign about no storage allowed. I was planning to build there so asked the truss company to add that so I could have reasonable access. Turns out the trusses already met that so they just had to add a note to the drawings. I didn't end up moving there but built the shop where I currently live with those trusses even though the requirements here were minimal.

I didn't see where the OP ever clarified if the trusses were already ordered and committed to.