[riffdex]

Attic has rafter ties at chest level throughout. It is my belief at this point that the house has ceiling joist below the subfloor, which effectively tie the roof together and prevent outward pressure on the walls, and that the rafter ties are present, but not necessary.

if you look at the photo I attached, I believe the house has Ceiling Joists (green in photo) below the subfloor and the rafter ties in question are “mid span rafter ties” as labeled by the photo - and unnecessary.

Of course, I am going to consult with a structural engineer and have him sign off any modifications to this setup, but I’m curious if my interpretation of this structure would be correct.

To be clear, I’m not asking for anybody to provide any expert advice on structural engineering. I’d like to know if the presence of ceiling joists tying together the roof rafters would indicate these rafter ties are redundant, all theoretically speaking of course.

If you believe they are absolutely essential, would there be any alternatives you could recommend to make the attic space walkable? Structural ridge beam attached to vertical posts, knee walls, or other ideas that could replace the necessity of the rafter ties.

I uploaded a few videos of my attic as well:

 

[Nealtw]

Rafter ties are ceiling joists that sit on the wall or can be moved up as high as 1/3 the height of the attic.
Collar ties stop wind lift and tie the the rafters together near the peak and can be anywhere in the upper 1/3 of the attic.
Your ties do not seem to fit in either description.
If you do not have collar ties now I would install them before attacking your ties.

 

[riffdex]

Rafter ties are ceiling joists that sit on the wall or can be moved up as high as 1/3 the height of the attic.
Collar ties stop wind lift and tie the the rafters together near the peak and can be anywhere in the upper 1/3 of the attic.
Your ties do not seem to fit in either description.
If you do not have collar ties now I would install them before attacking your ties.

Okay, I’m not opposed to adding collar ties if it’s necessary and advisable. Is it your opinion that the current rafter ties are not providing the function of “ceiling joists”?

 

[Nealtw]

Okay, I’m not opposed to adding collar ties if it’s necessary and advisable. Is it your opinion that the current rafter ties are not providing the function of “ceiling joists”?

You have ceiling ties at ceiling heights, so I don't know what those mid height ties are for.
Rafters would not bend out mid span, and there is no way they would stop them from bending in.
The problem with roof structure, what ever was put in we tend to think that guy knew what he was doing so leave it.
But in this case it was more likely something to stand on while he nailed the rafter to the ridge board.

 

[riffdex]

You have ceiling ties at ceiling heights, so I don't know what those mid height ties are for.
Rafters would not bend out mid span, and there is no way they would stop them from bending in.
The problem with roof structure, what ever was put in we tend to think that guy knew what he was doing so leave it.
But in this case it was more likely something to stand on while he nailed the rafter to the ridge board.

Well, just to be clear, I presume I have ceiling ties under the subfloor but haven’t verified. So now that we’re on the same page, would the next step be to hire a structural engineer simply to confirm my theory about the roof’s design? Otherwise, is there any way I could confirm it myself - short of ripping up the subfloor? It certainly appears the rafters are tied into the ceiling when viewing the house from the exterior, although I’m definitely not expert. Would it be a good idea to try and track down the original building plans? The homes were built in the 1930s but surely there must be some record that exists for the house, right? How would I go about finding those?

on a side note, other houses in the neighborhood have attics with the rafter ties removed and haven’t collapsed yet, although it doesn’t mean they haven’t done some other structural modifications to compensate for their removal.

 

[Nealtw]

Well, just to be clear, I presume I have ceiling ties under the subfloor but haven’t verified. So now that we’re on the same page, would the next step be to hire a structural engineer simply to confirm my theory about the roof’s design? Otherwise, is there any way I could confirm it myself - short of ripping up the subfloor? It certainly appears the rafters are tied into the ceiling when viewing the house from the exterior, although I’m definitely not expert. Would it be a good idea to try and track down the original building plans? The homes were built in the 1930s but surely there must be some record that exists for the house, right? How would I go about finding those?

on a side note, other houses in the neighborhood have attics with the rafter ties removed and haven’t collapsed yet, although it doesn’t mean they haven’t done some other structural modifications to compensate for their removal.

You climbed up the attic thru a hole between ceiling joists, are those ceiling joists at the top of the wall height.
They are ceiling joists and having a floor on them may be questionable but that has nothing to do with the ties you would like to remove.
O doubt you would find original plans and extras inside the structure would not likely be in the plans.
There are others here that understand roofs, give it some time and see if others have a different thought about your extra ties.

 

[riffdex]

You climbed up the attic thru a hole between ceiling joists, are those ceiling joists at the top of the wall height.
They are ceiling joists and having a floor on them may be questionable but that has nothing to do with the ties you would like to remove.
O doubt you would find original plans and extras inside the structure would not likely be in the plans.
There are others here that understand roofs, give it some time and see if others have a different thought about your extra ties.

Oh absolutely, i without a doubt have ceiling joists, I meant that I’m not certain that the roof is tied to the ceiling joists, in effect providing the tension required for the roof to stay together - If that makes sense.

 

[icerabbit]

The key thing not shown is what is happening where your roof meets the top of the wall and your ceiling joists.

What part of the country do you live in? Snow load? Lots of tropical weather with high wind?

Personally, if it was me tackling this - DIY - I'd crawl to the eaves, take a very good look around, what meets what, how is it fastened, if need be add structural screws or bolts, or even structural clips; that takes care of things down low; then up higher collar ties everywhere, properly fastened ... as low as you can to not bump your head? ... 6ft something (don't know how much space there is ... ).

And, if there's snow load and or high winds; to stiffen it all up, I'd be considering some vertical studs to mimic a knee wall ( if storage is highly critical I wonder if you could do like every other one ) and probably some boards length wise where those mid height boards were ... I guess blocking as spacers could work too. But, yeah, it really is a bit strange to have those boards at that height.

 

[Nealtw]

Oh absolutely, i without a doubt have ceiling joists, I meant that I’m not certain that the roof is tied to the ceiling joists, in effect providing the tension required for the roof to stay together - If that makes sense.

The ceiling joists are tied to the wall and the rafters are tied to the wall and most likely the rafters are tied to the joists.
I think you are going to need an engineer to feel comfortable doing anything.

 

[colin123]

If It were me I would just go for it. It looks like your rafters are 2x4, maybe the middle ties were added to stiffen them up for snow loads? A knee wall would do a better job of that and would make finishing the space easier.

 

[Half-fast eddie]

Just rip them all down. The builder wasted hours and hours of time, and all that lumber and nails for no purpose. He should have known you would want to use the space. Nothing bad will happen to your house. Trust me.

 

[SpentPenny]

If you leave the engineering aside just ask yourself why the designer/builder would add extra parts to your roofing system? Those "extra" ties added some cost to the build and I know of a few builders that may inflate cost now and then, but none that actually go to the trouble to add a series of parts not needed for something. It just makes no sense.

 

[riffdex]

The key thing not shown is what is happening where your roof meets the top of the wall and your ceiling joists.

What part of the country do you live in? Snow load? Lots of tropical weather with high wind?

Personally, if it was me tackling this - DIY - I'd crawl to the eaves, take a very good look around, what meets what, how is it fastened, if need be add structural screws or bolts, or even structural clips; that takes care of things down low; then up higher collar ties everywhere, properly fastened ... as low as you can to not bump your head? ... 6ft something (don't know how much space there is ... ).

And, if there's snow load and or high winds; to stiffen it all up, I'd be considering some vertical studs to mimic a knee wall ( if storage is highly critical I wonder if you could do like every other one ) and probably some boards length wise where those mid height boards were ... I guess blocking as spacers could work too. But, yeah, it really is a bit strange to have those boards at that height.

I’m located in Guilford County, NC. So we get one or two good shows a year typically, and I wouldn’t describe us as particularly tropical but we get some wind from time to time.

 

[icerabbit]

So, you're not dealing with snow, no uneven loads from snow drifts, no continuous exposure to very strong wind, ...

How much interior height do you have, to the ridge beam?
Can you do the high collar tie and get enough head clearance?

I think there have to be options to reframe this in a smart way, improve what you have and achieve what you want to do. Even if you have lift up some of the plywood, or come up with a variation on like a scissor truss ... if there is serious concern. Other than wind load I can't really see why those ties are where they are. But if one see the attic truss system, that's basically what you're after in some way. You already have somewhat of a knee wall area. Maybe skip a bay, alternating so you can maintain storage usefulness ...

 

[riffdex]

So, you're not dealing with snow, no uneven loads from snow drifts, no continuous exposure to very strong wind, ...

How much interior height do you have, to the ridge beam?
Can you do the high collar tie and get enough head clearance?

I think there have to be options to reframe this in a smart way, improve what you have and achieve what you want to do. Even if you have lift up some of the plywood, or come up with a variation on like a scissor truss ... if there is serious concern. Other than wind load I can't really see why those ties are where they are. But if one see the attic truss system, that's basically what you're after in some way. You already have somewhat of a knee wall area. Maybe skip a bay, alternating so you can maintain storage usefulness ...

I don’t have an exact measurement to the ridge off the top of my head (not at home right now), but I could certainly get that if it’s helpful. As for the general question - can I put high collar ties and still have head clearance? - the answer to that is yes. In fact, other houses in the neighborhood have removed their rafter ties that I’m complaining about and did have collar ties installed at the peak.

Yeah there is basically a knee wall structure in place already, but the roof rafters do not appear to be attached to it. And the knee wall is not a problem whatsoever. I mean I wouldn’t mind retaining some storage space behind the knee wall, but I’m okay with losing all that walkable space as long as the center of the attic has walkable space.

 

[icerabbit]

Note, I'm not an engineer, saying just go for it. I DIY have gone to code and beyond to well beyomd for a few things. I like things to be safe and durable. Good to hear a few of your neighbors have modified things to suit their needs ... Could be that some builder put up a whole lot of homes in the neighborhood that way, and everybody who moves in decades later - with more storage needs - is like: Ha?

I would ask a neigbor or two if you could take a peek at the solution they came up with or had a contractor do.

 

[riffdex]

Note, I'm not an engineer, saying just go for it. I DIY have gone to code and beyond to well beyomd for a few things. I like things to be safe and durable. Good to hear a few of your neighbors have modified things to suit their needs ... Could be that some builder put up a whole lot of homes in the neighborhood that way, and everybody who moves in decades later - with more storage needs - is like: Ha?

I would ask a neigbor or two if you could take a peek at the solution they came up with or had a contractor do.

I just took some measurements of the location of the ties in question as well as the distance to the bottom of the ridge board. The ties in question are about 51.5” from the floor to the bottom of the ties, 54.75” from the floor to the middle of the ties, and about 57” from the floor to the top of the ties. The bottom of the ridge board is about 7’ (84”) from the floor of the attic.
Therefore, they don’t meet the specifications that “rafter ties” would be required to meet. Rafter ties must be in the bottom 1/3 of the rafters. Collar ties must be in the top 1/3 of the rafters. If we are to take the middle measurement of these boards they are 54.75” from the floor, which is about 65% of the way from the floor to the peak. The top of the boards are at 57” which is 67.8% of the way from the floor to the peak. I must conclude that these are indeed collar ties and can be replaced with collar ties at the top, and/or appropriate ridge strips.

Any flaws in my reasoning here?
I kind of assumed the entirety of collar ties needed to be in the top 1/3, not just the top edge of collar ties being in the top third. Perhaps they are collar ties that were technically placed slightly too low, but collar ties indeed?

 

[Nealtw]

The collar tie can be right up against the ridge board so no limit on how high you want to go as long as it is in the upper third.

 

[riffdex]

The collar tie can be right up against the ridge board so no limit on how high you want to go as long as it is in the upper third.
View attachment 702060

I get that much. I was just saying the current boards are barely in the top third - only the top edge of the board is in the top third and the rest of it is lower. Is this an acceptable placement that they had it in - presuming they are indeed meant to be collar ties?

 

[Nealtw]

I get that much. I was just saying the current boards are barely in the top third - only the top edge of the board is in the top third and the rest of it is lower. Is this an acceptable placement that they had it in - presuming they are indeed meant to be collar ties?

Collar tie may have been different back then or just miss understood at the time. But you will do no harm by adding new and taking all that junk out.
The wall if important would be on bearing wall below, they would be fine if you were dividing the space but as they are they do nothing.