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Old 09-06-2019, 12:19 AM   #1
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Garage Rafter Supports


I am in the process of adding ceiling joists to my unfinished garage (18x24) and am looking for advice on what (if anything) I can do with the existing rafter support.

Originally the roof was simply secured to the side wall top plate by 18-ft 2x4s. Off of the 2x4s there are some 1x6 pieces of wood secured to various pieces of ridge/rafter.

The house is nearly 70 and the original 2x4 ties had been serving double duty with some light garage storage.

I’ve decided to turn the attic space in the garage into usable space. I’ve added 2x10 ceiling joists to support the new attic floor and have now realized that the original 2x4 roof members were/are sagging about 4 inches in the middle.

I’d love to remove or minimize the existing supports - or at the least transfer their pod to the new 2x10s.

Is there a way to re-frame this to open up the middle section for storage?

And thoughts welcome. Thanks.

Ryan
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Old 09-06-2019, 01:17 AM   #2
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Re: Garage Rafter Supports


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Originally Posted by Ryanmatthews2 View Post
I am in the process of adding ceiling joists to my unfinished garage (18x24) and am looking for advice on what (if anything) I can do with the existing rafter support.

Originally the roof was simply secured to the side wall top plate by 18-ft 2x4s. Off of the 2x4s there are some 1x6 pieces of wood secured to various pieces of ridge/rafter.

The house is nearly 70 and the original 2x4 ties had been serving double duty with some light garage storage.

I’ve decided to turn the attic space in the garage into usable space. I’ve added 2x10 ceiling joists to support the new attic floor and have now realized that the original 2x4 roof members were/are sagging about 4 inches in the middle.

I’d love to remove or minimize the existing supports - or at the least transfer their pod to the new 2x10s.

Is there a way to re-frame this to open up the middle section for storage?

And thoughts welcome. Thanks.

Ryan
Did you find that the joists with those supports had less sag than the rest?
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Old 09-06-2019, 09:15 AM   #3
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Re: Garage Rafter Supports


Are the roof rafters (actual) 2x4s? Because comparing the proportion of edge compared to face width, they look more like (actual) 1x4s. From this perspective, it looks like there is a gable roof, some sort of end hip roof, and/or flat roof intersecting too?

It looks to me that the roof rafters are not sufficient for the load, and they sagged. At a later date, someone added (nominal) 1x4/1x6/1x8s as a horizontal mid support, the sorta king post, and some struts down to the rafter ties (old 2x4 ceiling joists you removed that were probably sagging too) to brace the sagging roof. The newer 1x sheathing boards were shimmed with plywood chunks to have a flat exterior plane.

My initial response from that pic is you don't want to remove any of those strut supports, and may need more.
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Old 09-06-2019, 01:17 PM   #4
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Re: Garage Rafter Supports


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Originally Posted by Nealtw View Post
Did you find that the joists with those supports had less sag than the rest?
Neal -

Thanks for chiming in. There were only 4 (2x4) rafter ties/ceiling joists spaced about 6 feet apart for the 24 foot run spanning the 18 foot wide garage. They are toe nailed into the top plate (not to a rafter).

Three of the 4 2x4 ceiling joists have some sort of rafter strut/support on them. The previous owners had placed some plywood across the 'joists' and used them for storage - so all three that had storage on them (and supports to the roof) had similar sag to them. They should never have had anything up there at all on a 2x4 spanning 18'!

The roof still seems solid - no visible sag from the exterior or even looking at the interior framing.

It was build in 1955 with redwood lumber - and these struts seem of the same age and are also present in other houses (same model/same subdivision). So I think that they are original to the framing of the original roof.

The question is can I replace them/re-route them to the new 'stronger' 2x10 joists that I put in?

When I place any pressure on the 1x6 and 1x8 struts that join the 2x4 to the ridge beam and rafters they don't seem to be supporting much if any load and are not under tension (possibly because I removed the stuff that had been resting on the 2x4 ceiling joists).

I've taken some more photos of the system that's in place and would welcome any more thoughts or questions.

Ryan
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Old 09-06-2019, 01:30 PM   #5
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Re: Garage Rafter Supports


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Originally Posted by 3onthetree View Post
Are the roof rafters (actual) 2x4s? Because comparing the proportion of edge compared to face width, they look more like (actual) 1x4s. From this perspective, it looks like there is a gable roof, some sort of end hip roof, and/or flat roof intersecting too?

It looks to me that the roof rafters are not sufficient for the load, and they sagged. At a later date, someone added (nominal) 1x4/1x6/1x8s as a horizontal mid support, the sorta king post, and some struts down to the rafter ties (old 2x4 ceiling joists you removed that were probably sagging too) to brace the sagging roof. The newer 1x sheathing boards were shimmed with plywood chunks to have a flat exterior plane.

My initial response from that pic is you don't want to remove any of those strut supports, and may need more.

3onthetree - Thanks for the reply.

The roof rafters are definitely 2x4s. I went up there and measured just to be sure. (actual measurement 3.5x1.75)

The house is a Cape Cod with both roof directions joining together in the middle of the garage (picture attached) - so there seems to be alot going on where the two 'roofs' meet (house and garage)

The rafter supports to the 2x4 ceiling joists appear to be original to the construction as they are of same age redwood and are present in other models of this home in the subdivision.

The whole garage only has 4 original 'ceiling joists' that were toe nailed into the top plate (presumably to simply keep the walls together to support the rafters from spreading out) - and then they have this king post setup - but its made up of 1x8 redwood and doesn't seemingly have much tension or weight to it.

I've taken some more photos if they might help.
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Garage Rafter Supports-img_7399.jpg   Garage Rafter Supports-img_7403.jpg   Garage Rafter Supports-img_7407.jpg   Garage Rafter Supports-img_7408.jpg  

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Old 09-06-2019, 01:58 PM   #6
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Re: Garage Rafter Supports


Even your 2x10s are 2 ft over span, we had an engineer who thought we could double up 2x10 12" on center for 20 ft and they sagged 1 1/2" before we finished building the house.

I think those boards were put there to hold up the 2x4s so taking them out would be no big deal. That said, I am not an engineer and don't play one on the web.
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Old 09-06-2019, 02:41 PM   #7
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Re: Garage Rafter Supports


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Originally Posted by Nealtw View Post
Even your 2x10s are 2 ft over span, we had an engineer who thought we could double up 2x10 12" on center for 20 ft and they sagged 1 1/2" before we finished building the house.

I think those boards were put there to hold up the 2x4s so taking them out would be no big deal. That said, I am not an engineer and don't play one on the web.
Neal -

Thank you. Yes for a second story floor definitely would have gone with 2x12 - but this is simply for some attic storage and garage miscellaneous. There isn't more than 48" at the peak so its just going to be xmas decos and camping gear and such - nothing too heavy up there. If it were going to be a living space - definitely would have gone with 2x12 - but I didn't want to give up another couple of inches of headroom since its just going to be 'stuff'.

I tend to agree with you that those supports seemed more likely to support the 2x4 than for the roof.

Will see if anyone else has thoughts on that.

Cheers.
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Old 09-06-2019, 03:59 PM   #8
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Re: Garage Rafter Supports


More pictures, aha! Roof purlins, not shimming, and plywood sheathing! I better get thicker reading glasses or increase the brightness of my screen!

My thought is with the 2x4 rafters, I would want to keep the struts as designed for tension (a la king post). Although it seems a bit light on how many struts there are, they had the midpoint rafter purlin and there probably was an "L" purlin (binder) across the top of the 2x4 ceiling joists that the king post(s) tied to (as it was helping hold them up). So think of this framing as sort of a truss. Besides, with all the competing roof slopes, multiple hip rafters tying in at various places of a ridge board, errant struts, etc I can not figure this roof out and honestly it's a hodge podge of framing.

Even with upsizing to 2x10 ceiling joists, I wouldn't want to change the structure to a compression design by relying on these 2x10s to support the roof. You would need new calculations and they would probably come up short, especially considering dead load of storage. Be prepared to be hammered by others on the size and spacing of the 2x10s.
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Old 09-06-2019, 05:31 PM   #9
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Quote:
Originally Posted by 3onthetree View Post
More pictures, aha! Roof purlins, not shimming, and plywood sheathing! I better get thicker reading glasses or increase the brightness of my screen!

My thought is with the 2x4 rafters, I would want to keep the struts as designed for tension (a la king post). Although it seems a bit light on how many struts there are, they had the midpoint rafter purlin and there probably was an "L" purlin (binder) across the top of the 2x4 ceiling joists that the king post(s) tied to (as it was helping hold them up). So think of this framing as sort of a truss. Besides, with all the competing roof slopes, multiple hip rafters tying in at various places of a ridge board, errant struts, etc I can not figure this roof out and honestly it's a hodge podge of framing.

Even with upsizing to 2x10 ceiling joists, I wouldn't want to change the structure to a compression design by relying on these 2x10s to support the roof. You would need new calculations and they would probably come up short, especially considering dead load of storage. Be prepared to be hammered by others on the size and spacing of the 2x10s.

Thanks for the additional insight. Yes - there’s a single Perlin on the outside (non house) side of the roof - and yes - it’s a hodgepodge of framing up there.

Would you suggest simply tying the existing “king post” to the new 2x10 ceiling joist. Clearly that would be stronger than the sagging/failing 2x4 it is currently nailed to.

Is 1x6 inch lumber the typical (Or was typical) lumber to use for such a seemingly important part of a roof structure. These boards look like leftover scrap with knot holes my son can fit his hands through.

Thanks again.

Ryan
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Old 09-07-2019, 12:13 AM   #10
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Re: Garage Rafter Supports


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Originally Posted by Ryanmatthews2 View Post
Would you suggest simply tying the existing “king post” to the new 2x10 ceiling joist.
Is 1x6 inch lumber the typical (Or was typical) lumber to use for such a seemingly important part of a roof structure
That era of attic I've come across 1x's, 2x's, and even T&G flooring used for bracing - hey, whatever's laying around! So if you are able to deduce and want to replace knotty/add back in what was removed at some point, by using the same dimensional lumber, that's your call. What I will say is that if done today, the 2x4 rafters could only span about 6' to 8' and the purlins and struts would be minimum 2x4.

As I said before the framing is confusing, it looks like there's no end support for hip rafters or opposing king rafters, roof planes changing slope without ridge beams, etc. So I can't give specific advice on this situation. But if it were a simple 18x24 gable roof, the framing would probably have:
- 2x4 continuous purlin near midpoint of underside of rafter (or wherever 45d angled strut will hit)
- 2x4 purlin strut @4'o.c. down to a center continuous binder (or strongback) on top of ceiling joist
- 1x4 collar tie @4'o.c.

The binder (or strongback) would be made of 2x6's (to accept the diagonal cut of a 2x4), one laying flat and one nailed into it standing up to create an "L". The ceiling joists would be sized according to span tables for attic storage, so there would be no king studs.
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Old 09-07-2019, 05:08 AM   #11
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Re: Garage Rafter Supports


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Originally Posted by 3onthetree View Post
That era of attic I've come across 1x's, 2x's, and even T&G flooring used for bracing - hey, whatever's laying around! So if you are able to deduce and want to replace knotty/add back in what was removed at some point, by using the same dimensional lumber, that's your call. What I will say is that if done today, the 2x4 rafters could only span about 6' to 8' and the purlins and struts would be minimum 2x4.

As I said before the framing is confusing, it looks like there's no end support for hip rafters or opposing king rafters, roof planes changing slope without ridge beams, etc. So I can't give specific advice on this situation. But if it were a simple 18x24 gable roof, the framing would probably have:
- 2x4 continuous purlin near midpoint of underside of rafter (or wherever 45d angled strut will hit)
- 2x4 purlin strut @4'o.c. down to a center continuous binder (or strongback) on top of ceiling joist
- 1x4 collar tie @4'o.c.

The binder (or strongback) would be made of 2x6's (to accept the diagonal cut of a 2x4), one laying flat and one nailed into it standing up to create an "L". The ceiling joists would be sized according to span tables for attic storage, so there would be no king studs.
I have never seen rafter supports that do not go to bearing walls. So I think these board were put there just to support the rafter ties. Even back when this was built the 2x4s ties were over spanned.
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Old 09-07-2019, 10:50 AM   #12
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Re: Garage Rafter Supports


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I have never seen rafter supports that do not go to bearing walls. So I think these board were put there just to support the rafter ties. Even back when this was built the 2x4s ties were over spanned.
Yes the king posts were supporting the rafter ties.

His 2x4 rafters are inadequate, so to break that span you surely would run your braces to a bearing wall. Back then, in a garage with no middle bearing wall like the house would have, they would run them to a strongback. There probably was one at some point that was taken out.

There's a lot of names for that, like catwalk, binder, strongback, so its hard to find pictures.
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Old 09-09-2019, 08:23 AM   #13
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Re: Garage Rafter Supports


Actually, the king post would be in compression.

(You're also assuming each member is zero dimension.)
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Old 09-09-2019, 11:44 AM   #14
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Re: Garage Rafter Supports


The rafters are in compression. A vertical kingpost would be in tension, as is the ceiling joists. Maybe you're thinking with a ridge beam.
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Old 09-10-2019, 09:00 AM   #15
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Re: Garage Rafter Supports


Are you assuming the members are weightless, and that the only load on the roof is due to the roof covering?
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