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-   -   Rafter tie adjustment (http://www.diychatroom.com/f19/rafter-tie-adjustment-87091/)

albanello 11-18-2010 08:21 PM

Rafter tie adjustment
 
2 Attachment(s)
My Garage originally had ONLY three Rafter Ties to hold the walls together see picture Old.jpg (Original construction 45 year old house). I have recently added I-Jousts to construct a ceiling I can insulate and drywall. When the people did the work they put the attic access (4' by 2') under one of the 3 existing Rafter Ties See New.jpg, which reduced the attic access by 3 inches on the 2' side (4' by 1'9"), pictures are attached.

I would like to offset the 4' section of the Rafter Tie, the section over the attic access, with a plywood spacer (3") and reconnect the Rafter Tie through the plywood spacer with another piece of lumber of the same dimension as the existing Rafter Ties.

The new Rafter Tie will be tied to the spacers with bolts. Not sure of size and number of bolts was thinking 4 bolts 1/2" size (for each spacer), at each end of rafter plywood spacer connection.

The plywood spacer will be 4 pieces of 3/4 inch plywood glued and screwed together.

Hope this text along with the picture is clear. Trying to come up with solution that will work and be professional ?

The new I-Joust should help to keep the walls from spreading along with the two unchanged rafter ties and the proposed fix of the third rafter tie.

All comments and questions welcome.

Thanks
albanello

PS old.jpg is the first picture. New.jpg is the second picture

Bondo 11-19-2010 04:09 PM

Ayuh,.... From your post, 'n pictures,...(can't see the tie's ends)
I think if it were me, I'd move that rafter tie down to the next rafter, 'n not look back....
Probably add a vertical up to the ridge just for the 'ell of it too...

albanello 11-19-2010 07:14 PM

Thanks for the reply

I thought of that also but to get a 21+ foot long piece of lumber in the area over the garage and then get it nailed to the next rafter properly. may not be possible. It would be near impossible to get that length of lumber though the attic access, because of the angles I have to work with.

Do you think what I am suggesting would work or do you have another suggestion as to how I can rework the exiting rafter. The only other thing I can think of is to tie the existing rafter to the LVL below it.

Was my description of what I am proposing clear.

Thanks again

Gary in WA 11-19-2010 09:26 PM

Check with your local B.D about the strapping. 3" + 1-1/2" (rafter tie thickness) is 4-1/2" - 24" = 1'7-1/2", but I'm using old math.....lol It's net free area:
SECTION R807 ATTIC ACCESS


R807.1 Attic access.
Buildings with combustible ceiling or roof construction shall have an attic access opening to attic areas that exceed 30 square feet (2.8 m2) and have a vertical height of 30 inches (762 mm) or greater. The vertical height shall be measured from the top of the ceiling framing members to the underside of the roof framing members.

The rough-framed opening shall not be less than 22 inches by 30 inches (559 mm by 762 mm) and shall be located in a hallway or other readily accessible location. When located in a wall, the opening shall be a minimum of 22 inches wide by 30 inches high. When the access is located in a ceiling, minimum unobstructed headroom in the attic space shall be 30 inches (762 mm) at some point above the access measured vertically from the bottom of ceiling framing members. See Section M1305.1.3 for access requirements where mechanical equipment is located in attics.

Gary

albanello 11-19-2010 10:09 PM

Thanks GBR

You are correct on the amount of lost clearence as a result of the Rafter Tie.

4' by (2'-0.375') = 4' by 1.625' = 6.5 square feet that is no where near the 30 square feet state in the section you posted. 30 square feet is a lot bigger than a pull down ladder access....this is giving me a headach. The 30 inch height is no problem I have about 4 feet in head room clearance.


Thanks
albanello

Gary in WA 11-19-2010 11:06 PM

"attic areas that exceed 30 square feet" ------- Your garage footprint (outside walls) 16' x 21" (?) would equal 336 sq.ft. - bigger than the 30 sq.ft. minimum.

Gary

albanello 11-20-2010 07:01 AM

Thanks GBR

I must have been asleep when I first read the section you sent, sorry

"........shall have an attic access opening to attic areas that exceed 30 square feet........"
My Garage "attic area" is 21' by 21' = 441 square feet........SO I need a attic access. I have one.

"........have a vertical height of 30 inches (762 mm) or greater........"
My "vertical height" is 48"........SO I'm OK

"........shall not be less than 22 inches by 30 inches........"
My "attic access" is 4' by (2'-0.375') = 4' by 1.625' = 48" by 19.5"........SO my opening is to small. If I move the rafter tie obstuction I would have a opening of 4' by 2' = 48" by 24"........SO I would be OK

Thanks again for the attic access code requirements.

Now I just need to come up with a way to move the obstruction. So far I have three possible solutions.
1) The one I proposed in Post #1
2) The one "Bondo" proposed in Post #2
3) The other one I proposed in Post #3

Do you think my first proposal would be acceptable ? Or is there another solution I'm not thinking of.

Thanks again
albanello

Bondo 11-20-2010 08:51 AM

Ayuh,... Just to clarify abit,...
I'm thinkin' you could use the Same tie that's there Now,....
Just move it Over a rafter...

If you insist on new wood,... 2, 12'ers will still bridge the distance, with plenty of over-lap for strength...

The offset arangement in your 1st post, sounds like a real cobb-job to me...

albanello 11-20-2010 01:46 PM

Bondo

Thanks for your reply

Moving the existing rafter tie would be a nightmare as for as I am concerned. Look at the 1st picture, there is a 2" by 6" nailed to the top of the rafter tie, plus all the old rafter tie have sag in them (the red line you see shows how much sag there is) Plus now I have I-Joists 16"oc under the rafter ties. It is sure NOT a job I could do by myself.

Based on GBRs post I only need to offset the rafter tie by 2.5". The only thing I'm not sure of is, after the offset is done does the modified rafter tie still have enough integrity to help hold the rafters together ? Remember now there are also I-joists 16" oc tied to the walls, to help.

Thanks again
albanello

creamaster 11-20-2010 03:38 PM

1 Attachment(s)
I beleive the purpose of the rafter tie is to help prevent the rafters from sagging and therefore help prevent the walls from spreading apart, this happened in my garage due to previous owner building a loft not supported right and without proper rafter ties.

The rafter ties work best in the bottom third of the rafter. You could likely cut out the section of this original rafter tie thats in your way, then you could install a rafter tie above this ceiling you constructed and still be within the bottom third of the rafter. Do like Bondo suggested and move it over 1 rafter to clear the attic access. Also I would think your I joists are keeping the walls from spreading apart too.

In my pic I added 5 rafter ties and a cable to pull walls together. These ties are in the bottom third of the rafter and have been working great. Your original ties are tied in at or near your wall plates if they are 21 feet long, you could therefore use a 16 foot length like I did and possibly get it up through the access.

albanello 11-20-2010 10:26 PM

creamaster

Thanks for your post and pictures.

I'm not sure what I'm going to do. But what I am sure of is the only way to get a piece of lumber greater then 10 ft is to cut out the drywall in the ceiling. The I-joists are 11 7/8 inches deep and the pitch of the roof is 4:12. the access is 2' from the wall. There is no way to slide a piece of lumber in the attic because of the angle it would have to go in at. A 10 foot piece of lumber hits the roof before the board is fully in the access hole.

Good luck with your project and thanks again
albanello


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