So I need to modify a couple of trusses that I had made. I was going to use the same style plates that they used to put them back together, but I the company wouldn't sell me the plates. I'm having a hard time locating them in the size I want, would it be the better choice to use the nailing plates instead? If so, should I use screws to fasten them, or nails?
Truss Repair
- Thread starter Big Ragu
- Start date
readhead
Well-known member
Trusses should not be modified without a specific procedure from an engineer or the truss company. The fact that you are asking about screws or nails tells me you don't have that. Modifying trusses is serious business and should not be taken lightly.
pattenp
Well-known member
Not getting into the do's and don't's about modifying the truss. But when using nailing plates it's best to use nails because nails have better shear strength than screws.
Leaflessshadetree
Well-known member
If they are the types of plates normally used to make trusses you would need to have the specialized equipment to install them.
signcrafter
Well-known member
- Joined
- May 9, 2012
- Messages
- 12,359
We need more details about how and why you need to modify these trusses. Trusses are an engineered thing and come with an engineer stamp saying they will do their job as intended. Once you cut or modify them that stamp is thrown out the window and if an inspector catches wind of this modification then he can make a big deal about it and make you replace them with factory engineered trusses. So, why do you need to modify these trusses and in what way do you need to modify them?
The nail plates also take a special clamp to install them to make them legit. This isn't something you can rent or borrow since the everyday DIYer isn't able to legally modify trusses. There are methods of doing this and even some ways to do it with plywood, adhesive, and nails. But again it needs to be designed right.
Here is some google images of the plate presses used for truss plates, https://www.google.com/search?q=tru...ved=0CAcQ_AUoAmoVChMIldO07I7jyAIVAugmCh3mbQZs
The nail plates also take a special clamp to install them to make them legit. This isn't something you can rent or borrow since the everyday DIYer isn't able to legally modify trusses. There are methods of doing this and even some ways to do it with plywood, adhesive, and nails. But again it needs to be designed right.
Here is some google images of the plate presses used for truss plates, https://www.google.com/search?q=tru...ved=0CAcQ_AUoAmoVChMIldO07I7jyAIVAugmCh3mbQZs
I have made small trusses for various projects using the plates available at the box/home centers. they are the type the truss mfgr's use, not nailing plates, but with the stamped "claws" you pound/press in. You should be able to find them where the joist hangers/rafter ties/simpson products are sold.
signcrafter
Well-known member
- Joined
- May 9, 2012
- Messages
- 12,359
Small trusses for projects can be fine. I just want to make sure the OP understands that modifying trusses can lead to big issues if it's getting inspected. Also technically, you can not install the claw plates without the special press approved for installing them. So even though you can buy the correct plates unless you have the expensive press to install them they won't meet approval. I'm not saying it can't be done or that if the average person does it that the whole building will fall down, just saying if an inspector finds out you modified trusses and he wants to make a big deal out of it then he can make your day ****.
I just was answering the question of where to get them...they had a large selection of many sizes at Menards...Not arguing for or against truss modification or design. I know my capabilities, and I presume the OP knows his--either way that's his business, IMO...
pattenp
Well-known member
I believe you are talking about splicing/mending plates and they are not approved for truss application. http://www.homedepot.com/p/Simpson-Strong-Tie-3-in-x-6-in-20-Gauge-Mending-Plate-MP36/100374920
yep, that's them. Not approved or tested for structural application, but same style as OP was asking about. work better than the nail through type, thought I've added a few nails/staples here and there as needed. I have seen builders use them for on-site building of trusses for dormers, and other things like sliding doors, porch trusses, etc., which is how I found out about them. they used a pneumatic air chisel with a big flat tamping bit to install them.
not saying I'd build a house with them, but they are quite handy when you need them.
Kevin54
MEMBER EMERITUS
Our local lumber company sells the plates just like on a factory truss. I'm fairly certain they sell them by individual piece.
imo by saying "not approved" he probably thinks oh its fine they are just not "approved"
OP, I have tried this many times. You simply cannot duplicate those plates that are on there. They look so simple like some guy beat them in with a hammer, they are not, they are perfectly stamped. They look so similar and so simple to put on your will undoubtedly do it and try it on your own, because I would to. The pressed ones if I had to guess are atleast 10 times more secure than those things.
If you want to go DIY, make a plate out of plywood. Google image it, common DIY method, and way better than those stupid plates you were going to buy.
that is totally false
screws and nails are just sticks made out of metal
Also sheer strength of the actual bolt is borderline irrelevant when making wood repairs. Nails and screws will almost always pull through the wood before they "sheer"
I agree with the plywood glued and nailed.
(And, yes, nails will bend when the typical black screws will break. The correct type of screws can be bought if you do not want to nail. You just need to look for them.)
"Approved" is a lawyer talk side step.
Lack of It has nothing to do with lack of strength.
(And, yes, nails will bend when the typical black screws will break. The correct type of screws can be bought if you do not want to nail. You just need to look for them.)
"Approved" is a lawyer talk side step.
Lack of It has nothing to do with lack of strength.
pattenp
Well-known member
The metal that screws and nails are made of is not the same. Nails can tolerate more bending force than a typical screw can. Screws are more brittle than nails. There are more structural screws now available. There is a place for each. Screws have more tensile strength but nails have more shear strength. As for nailing plates used for trusses I believe nails are better because of shear strength. Or use the specified screw fastener by the manufacturer for the plate.
*
Last edited:
So I wasn't really interested in getting into the "why" I'm modifying them, I know no matter how I explain it, it will yield the "I knew a guy that modified a truss once, 2 weeks later BOOM! Herpes". But anyway, I ordered a set of trusses that in the end, were built wrong. The company won't make it right and I cannot afford to pay another $1000 to have them remade. My repair will in fact make them stronger, but I need to be able to put the mods back together. I removed a plate and reattached it with horrible results. That is certainly not an answer. I can order the same style plates but I don't have the means to use them. Now I'm thinking nail plates, but plywood and glue may be the answer? I want what's strongest, not easier.
PugetDude
ALLIANCE MEMBER
rlitman
Well-known member
While both screws and nails are just sticks made out of metal, when you choose the largest screw and the largest nail that can fit into a specific hole, the nail will be stronger in shear.
As for pull through, have you seen what good coated framing nails shot in with a gun can do nowadays. I've used a puller that grabs them by the shank, and have had the shanks fail in tension, after first having the heads rip off.
readhead
Well-known member
Big Ragu you are missing the point. The splices are no problem. Plywood, glue and nails. Been done for decades. It is the actual design of the truss and how you may be modifying the load paths that is a concern.
I didn't miss the point. The question was about the splice, not the modification. The new design has been looked at by a structural engineer and deemed OK to use.
pstnbly
Well-known member
There are screws rated for mending plates and hangers. Check the bins near the hangers and you will find them.
So the pitch of the new truss is wrong. It needed to be considerable sharper, unfortunately it was not. My initial thought was they need to make it right, they would not. Basically the project stalled for a few months due to time issues and I've had the trusses for about 4 months. I recently erected the walls, laid a truss up, and found the issue. My next thought is, gotta repair the truss. I took my ideas to a couple structural engineers, they agreed that it will work. However, this is going to be a bit of work, as tearing these plates apart, reassembling, etc is a bit of a task. Maybe what I need to do is come up with a solution that will allow me to use them, as they are.
This is going to be difficult to explain without a pic, but what I'm doing is rebuilding an addition. It was not originally built with trusses, but everything on the original addition failed. From roof to floor. I have rebuilt everything to the original dimensions, however when I set the truss up, the pitch difference showed up. So basically, at the tip of the truss, the roof is below the house roof (by roughly 5"). At the ends, because the pitch is wrong, the addition roof will sit about the house roof, by roughly 5" (roughly, again this is going by memory).
Now, I'm not a home builder, I'm a metal guy. Generally speaking if I can't weld it together I'm not interested in it. I've overbuilt everything on this addition as I do not want to have to do it again, but I am learning as I go. So if I ask the wrong question, or say something wrong, remember that I am not well versed in home construction.
This is going to be difficult to explain without a pic, but what I'm doing is rebuilding an addition. It was not originally built with trusses, but everything on the original addition failed. From roof to floor. I have rebuilt everything to the original dimensions, however when I set the truss up, the pitch difference showed up. So basically, at the tip of the truss, the roof is below the house roof (by roughly 5"). At the ends, because the pitch is wrong, the addition roof will sit about the house roof, by roughly 5" (roughly, again this is going by memory).
Now, I'm not a home builder, I'm a metal guy. Generally speaking if I can't weld it together I'm not interested in it. I've overbuilt everything on this addition as I do not want to have to do it again, but I am learning as I go. So if I ask the wrong question, or say something wrong, remember that I am not well versed in home construction.
Last edited:
readhead
Well-known member
Ok, now we have the whole picture. I would think the engineer would provide a procedure for the modifications. I would think that sistering a 2 x8 on the side of the trusses to get the proper pitch would be the easiest solution. Set the first truss next to the existing house to get the proper layout and use that to modify the rest of the trusses. Don't forget to allow for the sheeting. This is only a internet guess and I would still run it by an engineer.
I should have painted the whole picture up front, I apologize for that. It just seemed difficult to relay to words. The manufacturer of the truss was not willing to help in any way, even though it's their screw up. So, I took my repair plan to an engineer at a company I used to work for (that manufactures timber frame homes) and he agreed it would be sound. If push came to shove I could have him provide a stamped drawing, but he was helping me out as a friend and I didn't ask for all that. And before anyone asks, I ran their maintenance department, overseeing machinery, buildings, rolling stock, etc. I had nothing to do with the manufacturing, design, etc.
Anyway, maybe this is not the way to go about it, maybe I'm making it harder than it needs to be. Sister a 2x8 onto the truss? Please explain further.
Anyway, maybe this is not the way to go about it, maybe I'm making it harder than it needs to be. Sister a 2x8 onto the truss? Please explain further.
Denwood
Well-known member
This truss building guide has details of plywood truss plates and nails for some approved designs. It's hosted on a Province of Ontario site, so these designs are likely to code in Ontario as well.
http://www.cps.gov.on.ca/english/plans/E9000/9101/M-9101L.pdf
The gussets use 3/4" fir plywood nailed with 3" spiral concrete nails to reduce the number of nails required.
Free plans including truss designs are here: http://www.cps.gov.on.ca/english/planmenu.htm
http://www.cps.gov.on.ca/english/plans/E9000/9101/M-9101L.pdf
The gussets use 3/4" fir plywood nailed with 3" spiral concrete nails to reduce the number of nails required.
Free plans including truss designs are here: http://www.cps.gov.on.ca/english/planmenu.htm
Last edited:
larry4406
Well-known member
I've built houses that truss pitch was wrong. We used the truss as is and sheated roof. Then did an over build to correct the pitch (similar to putting gable valley sets on main roof sheathing). Lastly cut ventilation holes in the truss sheathing to ensure proper function of soffit and ridge vents.
MagKarl
Well-known member
"Sistering" usually means to attach another framing member to the side of an existing member. In this case, attaching a rafter to the side of your truss top chord, skewed to correct the pitch.
Another idea might be to cut tapered rafters to stack on top of the top chords and then plate the sides with plywood.
Another idea might be to cut tapered rafters to stack on top of the top chords and then plate the sides with plywood.
pattenp
Well-known member
"Originally Posted by pattenp
Not getting into the do's and don't's about modifying the truss. But when using nailing plates it's best to use nails because nails have better shear strength than screws."
I'm very well aware of that. I made that point in follow-up post #16. My original comment, which I should have clarified, was about common nails vs. typical wood screws.
Not getting into the do's and don't's about modifying the truss. But when using nailing plates it's best to use nails because nails have better shear strength than screws."
I'm very well aware of that. I made that point in follow-up post #16. My original comment, which I should have clarified, was about common nails vs. typical wood screws.
signcrafter
Well-known member
- Joined
- May 9, 2012
- Messages
- 12,359
I've ran into this a couple of times. What I've done is take a 2x and snap a line, in your case about 5" at one end and tapers down to nothing at the other end. Then cut them with a circular saw and just add them to the top of the truss. If needed add some plywood supports on the sides to keep them from coming off the original truss. Or you can also sister like mentioned but would need 2x8 or 2x10s. If you just add a 2x on top like I did you will only need 2x6. Either way isn't really a truss modification. A truss modification is when you cut it and redo part of it. That's the reason you got so many warning posts when you said modification.
Thank you. Originally, and I haven't ruled it out, I was going to cut my trusses all up and change the pitch and reinforce. That was the modification I had in mind. But you guys have given me something to think about, I like the idea of adding to the truss.
bczygan
Well-known member
OMG!
This and some other "FIXES" are...........well, I just don't have the words!
We have gotten the wrong pitch trusses on a job. The truss mfg. sent a rep out toot sweet, and got a rush job of replacing them at their cost.No way an owner should get anything other than what was on the plans.
I would order the proper trusses and sue the original truss company for the damages.
Or, you said there is an engineer involved? Then just do exactly as he specifies. If he's good, he will tell you exactly what methods and materials will be needed, and he will specify readily available and cost effective ones.
Bill
I don't have time for that. This is NY, it's getting cold. Thanks for the input though.
Denwood
Well-known member
We did in-place restructuring of existing 50ft trusses in our building reno. One section went from 8 ft ceiling to 11ft vault.
Engineering concerns aside, the easy way to do this is cut the new top chord (and possible webs), and sister it to the existing truss with plywood, along the entire length, glued and nailed both sides. If anything, your truss will be a lot stronger when complete.
This is a different application than yours, but same idea (bottom sketch). The vault section is about 20ft wide. We have high snow loads here, so this may be overkill in your application.
[/IMG]
Engineering concerns aside, the easy way to do this is cut the new top chord (and possible webs), and sister it to the existing truss with plywood, along the entire length, glued and nailed both sides. If anything, your truss will be a lot stronger when complete.
This is a different application than yours, but same idea (bottom sketch). The vault section is about 20ft wide. We have high snow loads here, so this may be overkill in your application.
Last edited:
We did in-place restructuring of existing 50ft trusses in our building reno. One section went from 8 ft ceiling to 11ft vault.
Engineering concerns aside, the easy way to do this is cut the new top chord (and possible webs), and sister it to the existing truss with plywood, along the entire length, glued and nailed both sides. If anything, your truss will be a lot stronger when complete.
This is a different application than yours, but same idea (bottom sketch). The vault section is about 20ft wide. We have high snow loads here, so this may be overkill in your application.
[/IMG]
Man, I wish I could zoom in on the pic. I'd like to see exactly what you have going on there.