Need Help Figuring Out Rafter Lengths. - Carpentry - Page 2 - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Carpentry

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 11-09-2009, 01:52 PM   #16
Framing Contractor
 
Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000
Default

Need help figuring out rafter lengths.


Quote:
Originally Posted by CleIndiana View Post
Thanks joe for the drawing, its not going to be closed in I'm going to put in 6x6 post trying to utilize only 3 post. I plan on using 2x12 for the girders that way I get more span with less post. The porch doesnt have to be exactly the same hieght as the existing hieght but I would like to stay around 7ft for the hieght of the new porch. I'm not at home to measure but I would say the existing wall is aroung that same hieght once the pad is in place.

.
Your existing walls are only 7'? If so, is your house on a slab because 7' from the patio floor to the existing top plate is very low.

Advertisement

__________________
Joe Carola
Joe Carola is offline   Reply With Quote
Old 11-09-2009, 02:57 PM   #17
Newbie
 
Join Date: Nov 2009
Location: Indiana
Posts: 17
Rewards Points: 10
Default

Need help figuring out rafter lengths.


Quote:
Originally Posted by Joe Carola View Post
Your existing walls are only 7'? If so, is your house on a slab because 7' from the patio floor to the existing top plate is very low.

I should have mentioned I'm guessing. I'm not at home measure. My house is crawl space. I think what I meant was that when I get the patio floor powered it would be roughly 7 it maybe higher I haven't measured the height yet, I will when I get home tonight.

But from what I'm seeing all I should have to do is drop the patio girder height just 5/16 and that would get me to a 2/12?
CleIndiana is offline   Reply With Quote
Old 11-09-2009, 03:07 PM   #18
Framing Contractor
 
Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000
Default

Need help figuring out rafter lengths.


Quote:
Originally Posted by CleIndiana View Post
I should have mentioned I'm guessing. I'm not at home measure. My house is crawl space. I think what I meant was that when I get the patio floor powered it would be roughly 7 it maybe higher I haven't measured the height yet, I will when I get home tonight.

But from what I'm seeing all I should have to do is drop the patio girder height just 5/16 and that would get me to a 2/12?
5/16" for every foot of run.With the 10' span, you will have to drop the girder 4-5/8" to get a 2/12. This is based on the top of the girder being even with the top of the existing plate. If you can lower the girder, that would make the pitch higher. You really don't want a 2/12 pitch and put shingles on that. It definitely voids all warranties.

Have people done that, yes. You would run snow-ice shield the whole roof and instead of going 5" to the weather, you go 4". Still voids all warranties and isn't the right way to do this.
__________________
Joe Carola
Joe Carola is offline   Reply With Quote
Old 11-09-2009, 03:26 PM   #19
Newbie
 
Join Date: Nov 2009
Location: Indiana
Posts: 17
Rewards Points: 10
Default

Need help figuring out rafter lengths.


How far would I have to drop it if I wanted to get the 3/12 so that way no warranty is voided? I can handle inches, I just have to put into consideration how much the height will affect the entry. I dont want someone that is 6'6" coming over and knocking his head on the porch roof. I would love to get rid of the sky light, but my wife says no. I guess she wants to pay for it later when it starts leaking. I think I have grasped it, I would need to drop another inch along with 5/16 every ft so it would be 1' 1 1/8" and that would only leave me with and 6' 10 7/8" height for my porch roof? if the wall height is at 8ft, which i dont build houses so I dont know. But if have you cable tv questions I am your man. haha.

I went ouside tonight and measure the wall and it is 8'. So if i have to go 6' 10" that seems a little low. so it sounds like to me the sky light goes or I dont get the porch i want.

Last edited by CleIndiana; 11-09-2009 at 07:17 PM.
CleIndiana is offline   Reply With Quote
Old 11-09-2009, 07:56 PM   #20
Framing Contractor
 
Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000
Default

Need help figuring out rafter lengths.


Quote:
Originally Posted by CleIndiana View Post
How far would I have to drop it if I wanted to get the 3/12 so that way no warranty is voided? I can handle inches, I just have to put into consideration how much the height will affect the entry. I dont want someone that is 6'6" coming over and knocking his head on the porch roof. I would love to get rid of the sky light, but my wife says no. I guess she wants to pay for it later when it starts leaking. I think I have grasped it, I would need to drop another inch along with 5/16 every ft so it would be 1' 1 1/8" and that would only leave me with and 6' 10 7/8" height for my porch roof? if the wall height is at 8ft, which i dont build houses so I dont know. But if have you cable tv questions I am your man. haha.

I went ouside tonight and measure the wall and it is 8'. So if i have to go 6' 10" that seems a little low. so it sounds like to me the sky light goes or I dont get the porch i want.
I still say that the top of the girder can be lower than the existing top plate and if you can give me that height difference that would help alot. Also, you don't have to loose the skylight if you bring the new rafters to the existing ridge. You just remove the skylight and frame a new opening in the new roof above the existing opening and frame a small shaft from the top of the existing double rafters to the bottom of the new doubled up rafters for the new skylight opening.

If you can't save the skylight and flashing you might have to buy another skylight. If you give me the height difference from the top of the new girder to the top of the existing top plate, I will draw the new rafters going to the top of the existing ridge for you and tell you what pitch you will have. It might be close depending how much lower the top of the girder is from the top of the existing top p[late. Also making it a little shorter than 10' might get you to a 3/12 pitch.
__________________
Joe Carola
Joe Carola is offline   Reply With Quote
Old 11-09-2009, 09:21 PM   #21
We pick these?
 
Join Date: Jun 2009
Location: Indiana, Texas, Florida
Posts: 136
Rewards Points: 75
Default

Need help figuring out rafter lengths.


I'm also a framing contractor, btw. I was going to explain that you could drop the height of the beam or shorten the run, but it seemed like without some kind of visual example I would have confused you more than strictly necessary... Thankfully J.Carola is on the ball with that for you.

You could take out the skylight, put in your new shed roof, and re-install the skylight on top of it. You'd have some drywall work to fix up inside, but it would get you up into 4/12 pitch-range and your wife keeps the skylight. Your labor is FREE, right? Also, if you didn't mind a step-down onto the porch you could pick up the rise by going lower than the plate-height of the existing structure with your porch beams. I didn't catch how high up your crawlspace/stem-wall has you off the ground, I'm guessing you might have a foot or so to work with? Anyway if you pick up that much you could leave the skylight how it is and get the minimum pitch. Exceeding the minimum is better in this case, IMO.
NailedIt is offline   Reply With Quote
Old 11-09-2009, 09:36 PM   #22
Newbie
 
Join Date: Nov 2009
Location: Indiana
Posts: 17
Rewards Points: 10
Default

Need help figuring out rafter lengths.


nailedit or joe, what if i shortened the run by a foot or two and then kept the same height with the top plate and my new girder? would i still be able to stay 7" below the sky light. I dont want to drop thee girder to low because people will have to walk under it to get to the front door. I'm going to draw out a rough plan of what the front of the house looks like.

skip the drawing

Last edited by CleIndiana; 11-09-2009 at 10:17 PM.
CleIndiana is offline   Reply With Quote
Old 11-09-2009, 10:48 PM   #23
We pick these?
 
Join Date: Jun 2009
Location: Indiana, Texas, Florida
Posts: 136
Rewards Points: 75
Default

Need help figuring out rafter lengths.


If you could live with an 8' porch with a few more posts... You could use smaller beams to effectively lower the tail-end of the rafters and get a steeper pitch. Going from 2x12 down to 2x8 gets you 4" more rise overall.

Leaving the same headroom under the beam, that is...
NailedIt is offline   Reply With Quote
Old 11-10-2009, 08:10 AM   #24
Newbie
 
Join Date: Nov 2009
Location: Indiana
Posts: 17
Rewards Points: 10
Default

Need help figuring out rafter lengths.


Quote:
Originally Posted by NailedIt View Post
If you could live with an 8' porch with a few more posts... You could use smaller beams to effectively lower the tail-end of the rafters and get a steeper pitch. Going from 2x12 down to 2x8 gets you 4" more rise overall.

Leaving the same headroom under the beam, that is...


I'm not sure i understand because if i use a 2x12 i will place it to the same height as the existing top plate nd i would do the same for the 2x8. So both would measure the same wall height.
CleIndiana is offline   Reply With Quote
Old 11-10-2009, 11:51 AM   #25
Framing Contractor
 
Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000
Default

Need help figuring out rafter lengths.


Quote:
Originally Posted by CleIndiana View Post
I'm not sure i understand because if i use a 2x12 i will place it to the same height as the existing top plate nd i would do the same for the 2x8. So both would measure the same wall height.
You would gain 4" at the bottom for headroom underneath the girder. If the top of your 2x12 is 7' from the top of the patio for example, you will have 6' 1/2" to the bottom of the 2x12 for headroom. If you use a 2x8, you will have 6' 4-1/2" to the bottom.

I draw it out for you later with the rafters to the top of the existing ridge what your pitch will be. You will never get a 3/12 underneath the skylight without dropping the header down and coming in with the wall less the 10' at least 2-3'.
__________________
Joe Carola
Joe Carola is offline   Reply With Quote
Old 11-10-2009, 01:59 PM   #26
We pick these?
 
Join Date: Jun 2009
Location: Indiana, Texas, Florida
Posts: 136
Rewards Points: 75
Default

Need help figuring out rafter lengths.


I concur... except I was saying that you could keep the post height the same, so you'd actually be dropping the top of the beam if you switched to a double 2x8. If you did so your eaves wouldn't match up exactly(as far as overhang) if you're tying them together at an inside corner, but I'd opt for that vs. not getting the pitch I need. You'd have to add a couple posts to use 2x8, but that's your call. You don't have to have matching plate-heights where the beam ties in so long as you make the connection properly, though that's the usual way of doing these things. Joe's suggestion of going up to the ridge is actually the better looking and stronger way to do this kind of addition on your particular house, IMHO. I would draw you up a pic of what I'm saying with the beam thing, however I gotta git to the hospital, 1st baby's about to be born today... HAHA
NailedIt is offline   Reply With Quote
Old 11-10-2009, 05:16 PM   #27
Framing Contractor
 
Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000
Default

Need help figuring out rafter lengths.


Here's a drawing using the 10 span with the top of the girder that's 7' off the patio and flush with the top of the existing plate and running the roof into the existing ridge flush at the top. It only gets to around 2-1/8:12 pitch.

I also drew the roof with a 3/12 pitch with the shed rafters flush at the top of the existing ridge. You will see as the angle carries out to a girder, your span is only 8'1". This puts the top of the girder at 5' 11-1/4" off the top of the patio.

You can switch to 2x8's, but use a triple 2x8 so that you have to use less posts and drop the top down 4" as NailedIt said. that will gain a little more pitch.
Attached Thumbnails
Need help figuring out rafter lengths.-porch-shed-roof-diy-2.jpg  
__________________
Joe Carola
Joe Carola is offline   Reply With Quote
Old 11-10-2009, 05:18 PM   #28
Framing Contractor
 
Join Date: Apr 2006
Location: Caldwell, NJ
Posts: 1,758
Rewards Points: 1,000
Default

Need help figuring out rafter lengths.


Quote:
Originally Posted by NailedIt View Post
however I gotta git to the hospital, 1st baby's about to be born today... HAHA
Congratulations my friend!!!!!

Best thing that could ever happen for you and your wife.
__________________
Joe Carola
Joe Carola is offline   Reply With Quote
Old 11-11-2009, 08:41 AM   #29
Newbie
 
Join Date: Nov 2009
Location: Indiana
Posts: 17
Rewards Points: 10
Default

Need help figuring out rafter lengths.


Quote:
Originally Posted by Joe Carola View Post
Congratulations my friend!!!!!

Best thing that could ever happen for you and your wife.

Yes congratulations , and thansk you guys for all your in put and help. I will look over your drawings Joe. I think going all way up to the existing ridge plate would not be a bad idea and it doesnt seem there is to much work involved to raise the sky light. Thanks again guys.
CleIndiana is offline   Reply With Quote
Old 11-15-2009, 01:08 PM   #30
Newbie
 
Join Date: Nov 2009
Location: Indiana
Posts: 17
Rewards Points: 10
Default

Need help figuring out rafter lengths.


Hopefully your still following this Joe, because I just came up with a new idea. I was driving around my neighbor hood and saw a house with the same style porch that i want. From what I could tell you would build up and off the existing ridge board. so the way it looked to me was that the whole front section of the roof is lifted about a couple of feet and that seemed to be how they got the right pitch. I wish I could have a drawing for you but sketch it isnt letting me open your drawing that you had fr me.


well i made a drawing on sketch it but i cant get the file name type to change.

Advertisement


Last edited by CleIndiana; 11-15-2009 at 01:23 PM.
CleIndiana is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
how to find rafter lengths countryboy Building & Construction 3 12-07-2008 07:25 PM
Moving Attic Access -- Same Rafter or Different ?? wrldruler Carpentry 1 10-19-2008 07:03 PM
need some rafter help feralfreak Carpentry 5 07-30-2008 07:48 AM
rafter questions - structural rtoni Carpentry 11 09-13-2007 06:40 AM




Top of Page | View New Posts