Question about this truss system

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Nicholas
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Question about this truss system

Post by Nicholas »

Verancular [ver-nak-yuh-ler], noun;
a style of architecture exemplifying the commonest techniques, decorative features, and materials of a particular historical period, region, or group of people.

When we purchased this house I had the vision of finishing the attic as a decent space. This included moving the air handler from the middle of the attic to a more accessible location. Air handlers in attics in this area are suspended from the trusses, which I do not like. But this is how it is done, by code, with the drain running to the outside, as well as an overflow pan with cut off float switch hanging underneath.

The previous one was hung by chains, this new one has eye hooks and threaded rod. Then there is the ductwork. Since then we decided to leave as is, more of extra storage, we have a few boxes in one corner as there was plywood already there.

But...can somebody please tell me if what you are seeing here would be a normal, safe design of the period to begin with? I sometimes wonder what is holding this house together, but as my neighbor pointed out, it has probably seen a lot of hurricanes and is still standing.

Truss1.jpg
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If you notice, every other truss has either a 1 x 4 tying together, followed by 1 x 4 going from truss to ceiling joist, and of course no hurricane ties. The 1 x 4 is exactly that, as was done back in the day. The chip plywood you see on the far end, is at both ends, and was probably added with the AC to help insulate, as it is up against the exterior siding.

Although all appears straight from the outside, no sagging, I am considering adding supports with ties, going from joist to truss, similar to diagram I have included, but I will wait for cooler weather.
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Casey
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Re: Question about this truss system

Post by Casey »

It is very underbuilt by modern standards/codes. I will guess that the ceiling joists (attic floor joists) are 2x6? I will also guess that the W struts do not bear directly to a wall underneath, but are just carried by the 2x6's.
The good news is that you can sister all the rafters with new 6" LVL stock, and lots of bolts, and add a full set of collar ties with bolts, and get rid of the W-struts. Then the AC can safely hang from the new system. IDK why they hung it; noise control?
We have retro-engineered quite a few old roofs this way; of course, following the plan of a structural engineer.
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Re: Question about this truss system

Post by phil »

I think the plan as drawn would mess up a lot of valuable storage space. I'd rather have a little wall to separate it and add strength to the ceiling if you think you need it. That way you have the little triangular space for storage.

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Re: Question about this truss system

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Nicholas wrote:But...can somebody please tell me if what you are seeing here would be a normal, safe design of the period to begin with? I sometimes wonder what is holding this house together, but as my neighbor pointed out, it has probably seen a lot of hurricanes and is still standing.


Can't really say, but my attic has no trusses at all, but the roof is a very low slope. It was just rafters and battens for the slate, although it has decking and asphalt on it now. I know this house has been through at least four very powerful (100+mph) hurricanes (1915, 1947, 1965, 2005) and still had it's original roof when I purchased it in 2014. There wasn't any sign of major repair to the roof for all that time ... no sign of maintenance, either :shifty:

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Re: Question about this truss system

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Casey wrote:We have retro-engineered quite a few old roofs this way; of course, following the plan of a structural engineer.
Casey


Yes, not sure I want to mess with it without one. On the AC the tech said "that is the way it is done". Thing ways just over 100 pounds.

phil wrote:I think the plan as drawn would mess up a lot of valuable storage space. I'd rather have a little wall to separate it and add strength to the ceiling if you think you need it. That way you have the little triangular space for storage.


That diagram I showed was the detail of an open attic plan, which with the peak being over 6 feet high, would give me a long hallway, not going to do it, although I have seen it done.

kelt65 wrote:
Nicholas wrote:But...can somebody please tell me if what you are seeing here would be a normal, safe design of the period to begin with? I sometimes wonder what is holding this house together, but as my neighbor pointed out, it has probably seen a lot of hurricanes and is still standing.


Can't really say, but my attic has no trusses at all, but the roof is a very low slope. It was just rafters and battens for the slate, although it has decking and asphalt on it now. I know this house has been through at least four very powerful (100+mph) hurricanes (1915, 1947, 1965, 2005) and still had it's original roof when I purchased it in 2014. There wasn't any sign of major repair to the roof for all that time ... no sign of maintenance, either :shifty:


Well that is encouraging. The recent storms in this area were Jeanne and Francis in 2005
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Don M
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Re: Question about this truss system

Post by Don M »

Your roof system looks like it is typical for a stick built home. Truss systems are engineer designed using lighter construction with metal plates. They come pre-built and are installed on top of the top wall plate. They are not usually designed to provide living space. Your roof looks like it originally may have had wood shakes installed on skip sheathing to allow ventilation for the wood roofing. Your roof looks much like my 1830s vintage house roof. Mine still has the original wood shakes now covered by a 100+ year old standing seam metal roof.

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Re: Question about this truss system

Post by shazapple »

I would refer to those as roof rafters, not trusses. Trusses use smaller wood and engineered designs to carry the load where rafters are typically a single piece of wood. The allowable span depends on how far they are spaced apart, the size of the wood, and the snow load (if any) in your area. Most codes have tables that you can look at to determine if what you have meets the criteria.

I wouldn't be concerned as long as there are no signs of warping, cracking, or bowing.
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Nicholas
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Re: Question about this truss system

Post by Nicholas »

Don M wrote:Your roof system looks like it is typical for a stick built home. Truss systems are engineer designed using lighter construction with metal plates. They come pre-built and are installed on top of the top wall plate. They are not usually designed to provide living space. Your roof looks like it originally may have had wood shakes installed on skip sheathing to allow ventilation for the wood roofing. Your roof looks much like my 1830s vintage house roof. Mine still has the original wood shakes now covered by a 100+ year old standing seam metal roof.


That is very interesting, it never occurred to me what the original roof may have been. Right now it has the asphalt hurricane (split) shingles.

Thanks Don And Shazzaple.
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Re: Question about this truss system

Post by kelt65 »

Nicholas wrote:
Don M wrote:Your roof system looks like it is typical for a stick built home. Truss systems are engineer designed using lighter construction with metal plates. They come pre-built and are installed on top of the top wall plate. They are not usually designed to provide living space. Your roof looks like it originally may have had wood shakes installed on skip sheathing to allow ventilation for the wood roofing. Your roof looks much like my 1830s vintage house roof. Mine still has the original wood shakes now covered by a 100+ year old standing seam metal roof.


That is very interesting, it never occurred to me what the original roof may have been. Right now it has the asphalt hurricane (split) shingles.

Thanks Don And Shazzaple.


Almost certainly slate. I've never heard of wood shakes being used in the south.

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Re: Question about this truss system

Post by Nicholas »

kelt65 wrote:
Almost certainly slate. I've never heard of wood shakes being used in the south.


Kelt, although there are several old homes around here that still have the original slate, they are a lot fancier homes, not sure if this one would of had it.
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