Building sofits/ extending rafters

[Umby]

I have a ranch built in 1951 that has no overhang/sofits (i.e the roof just ends at the top of the exterior wall). Because of winter ice dams and summer overheating in the attic, I would like to build out sofits by extending and boxing-in the rafters, get rid of the can vents, and cut in ridge vents. Does this sound like overkill? Any tips or sites I should visit? Thanks

[mrcaptainbob]

That's a great plan. Use that styrafoam sheet with the ridges to keep the insulation from the new overhang and provide that important airgap. Go ahead and cut in the ridge vent, but I'd keep those cans as well. Make sure to provide plenty of venting along the soffit. There's a formula for how many sq. ft. of venting (in and out) per attic sq. footage. Don't know what it is, though!

[Umby]

Actually, after putting in soffit vents in my existing soffits, I got up in the attic, lit a cig, and saw little or no drift/draft. Then a buddy of mine told me about what he called 'soffit baffles'. After installing those, you could see the imediate effect and smell the fresh outside air coming in.

You say to leave the can vents? Won't those become intakes after the ridge vent is cut?

[mrcaptainbob]

A fine use of cigarette smoke!!! (HA)....Well, I would suppose that if the cans let the air in, or let the air out, either way would be a plus. I have heard about some ridge vents clogging up after a few years with dust. Supposedly happens on newer homes with all the fresh dust around. But again, if the cans let more air in or more air out, it's a good thing. The only thing left would be if they detract from the look of the house....there's several on our house, and truthfully, I don't care for the looks of them. But, I'm not about to climb on a two story roof just to change the 'looks'!!

[Umby]

My only fear was of rain or snow following a draft into the cans and on into the attic. Where can I get info on the sequence of steps to build soffits on an existing house?

[mrcaptainbob]

It's not likely, Umby, that rain or snow would be drafted back into thie roof mount cans. As for the building of the soffits, A friend did that with his place a few years ago and it turned out very well. He used four foot pieces for a two foot overhang. Having cut the correct vertical angle on the pieces first, he set one in place at each end of the roof edge, against the inside of the last rafter and made sure that each was extended the same distance. Having pulled a tight string between those two, he placed the remainders in place to line up on that string. Then he set the facia in place on the vertical ends of those boards. To cap off the soffit he used the vinyl 'f' strip on the house wall, the vinyl 'L' strip on the facia, and then used the perforated soffit panels for the air flow. It turned out very well. And, since that end of the rafters is exposed, that's the time to slide those airdams in place! Two tools to help/speed the job is an air nailer and a chopsaw. Rent, borrow, or (good time/excuse!!) to buy them!!!

[Umby]

Wow thank you, that was very helpful.
I was not sure how to line those rafter tails up for the facia without getting into game of shims, thanks. Are 'f' and 'L' strips used to hold the soffit panels? What did you mean by sliding air dam in place because of exposed rafters?

[mrcaptainbob]

The best time to install those air dams is right after you install the roof extensions. You'll be able to easily access the attic the same way you did to add those extensions. And it would save you from having to cramp yourself down into the narrowness of the roof from the attic side. Not a comfy place to be! As for the F and the L channels, yes, that's what holds the soffit panels in place. I set a carpenter's square against the wall and the bottom of the facia trim. That tells where the F channel goes. Again, mark at each end of the soffit, snap a chalk line between and line the BOTTOM flange of the F with that chalk line. After that, it's a simple task to measure between the F and the L channels, cut that length from the soffit boards and start snapping them in place...

[Umby]

I got up in the attic and looked at the end of the rafters where they sit on the rafter plates. Of the 5.25" these rafters are wide, they're only 3" above the plates (H.A.P ?). In other words they have been narrowed down as if they inteded to cut a bird mouth, but end at the facia. Kind of screwed up my plans. Will this be enough to work with when I go to nail in extensions to them?

[mrcaptainbob]

I think so, Umby. Can you mimick the birdsmouth of what's there? Would be great if you had a template of that and cut them on the ground. If you went with the 2x6 existing, then you'd have a fair size vertical end for a facia, translates to a bit more strength for a larger facia board and gutters. If you're doing a two foot overhang, you could get 14' boards, cut the bias in the middle. You have a nice 5 foot overlap, and the 2' extension. Cut the birdmouth where you need it. You may also want to set that bird mouth more than the 2', by the way. THe only correct ones would be the first and last boards. All the rest would want to be over-extended. That's where you'll need to revise that 'string' we spoke of earlier. A bit more work, but it's the right way...Once all the over-extended boards are in place, snap your chalk line between first and last, then cut off the excess according to a template you made to get the vertical. Mark them all, then cut. And yep, this is the time for using one of those neat 'trim' saws. Unless you have a good wrist to hold the 'full-power' corded saws!!! By the way, this projcect is a great excuse to build your arsenal of toy....er....tools.....(Air-nailer, chop saw, battery operated tool kit with 'trim' saw!)...

[Umby]

Yes I could mimick the bird mouth and create a template. But I fear variations in the other rafters may cause my tails on the outside go 'up and down' with respect to each other. I'm not concern with length outside, I can just over extend and rectify with a chalk line. However your taught string idea may still come in handy. I'll install the first and last tails and then tack a taught string accross the tops of them. Then as I go to install the remaining tails, I'll adjust them 'up' to meet the string and nail into place and plum trim (with my new toys!). Does this sound like it would work?
Thanks for all of the help, this project will occurr during the week of 23JUL - 31JUL, and I don't think I could prepare enough. I would like to send/post the sequence of steps (about 30 of them) that I would take to achieve this effort. Would you mind taking a look at them and warn me of any out-of-sequence nightmares I could cause myself? Thanks again Cap'n for all of the help.

[mrcaptainbob]

That's a great idea using the string to keep it all level. Hopefully the roof is such that you'll be able to do that. I agree with the preparation. Always was a believer in gettin' the ducks in order. Glad to help. I'd like to see the 30 steps. Sounds like a plan-in-progress...

[Umby]

Here's the sequence I think it should be done, but please note the questions along the way and thanks again.
1. Have tarps ready...
2. Tear off gutters and drip edge (carefully for reuse)
3. Remove top two tiers of aluminum siding
4. Cut third tier in half long-wise leaving makeshift tabs to re-secure with nails
5. (or not? I may just install the nailer to this third tier of siding...?)
6. Remove old facia board (or whatever exists) to expose the rafters, pull back insulation inside attic
7. Measure existing rafters for their bird mouth dimensions and create a template
8. Cut and sister-in two new rafter tails to the existing rafters at both ends of the sofit with (say) 2' overhang
9. (Rafter tails inside the attic around 5')
10. Cut and sister-in all of the rest of the rafter tails with a greater than 2' overhang
11. (Use taught string ran between, and on top of, the first and last rafter to align the remaining rafters)
12. (What about old roofing nails keeping me from getting the two rafters to align?)
13. Snap a chalk line fastened between, and on top of, the ends of the first and last rafter tails
14. Plum cut all rafter tails (with my new trim saw!)
15. Push insulation in attic back into place and insert new air dams in between rafters from outside
16. Nail 2x4 (or 2x6) sub-facia accross the rafter ends flush with their bottoms
17. Level measure from bottom of sub-facia to wall at both ends of soffit and mark on wall
18. Snap a chalk line between these two marks
19. Horzontally nail up 2x4 nailers to the wall with their bottom edge flush with the chalk line
20. At every rafter, measure and cut 2x4 lookouts to be toe-nailed to the nailer and nailed to the rafter tails
21. Nail on 1x6 facia board, possibly vinyl, but certaininly painted or treated, to the sub-facia
22. (Carefull placement of the facia to allow for sheathing to clear and overhang a little)
23. Measure, cut and nail-on, plywood sheathing to the tops of the rafter tails
24. (Maybe I should use the entire 4' width of the new piece and cut up 2' into the old roof ???)
25. (How much sheathing should overhang the final facia piece?)
26. Cut and nail on, a plywood triangle to the vertical end of the soffit, cover with piece of siding
27. (What would this piece of siding be called? (It comes down the gable and stops with the original roof))
28. Nail on L-channel facia piece (will this cover the entire facia?)
29. Measure and nail on F-channel to wall, on or just beneath the nailer, horizontally level with the L-channel
30. Measure and cut soffit pieces, snap into place between L and F-channels
31. (Should I bother with a rubber-like ice shield at this point? (I don't have one on the original roof))
32. (I'm sure it's code in southeast MI for a new roof, but this project is just an extension)
33. Tack builders felt onto sheathing
34. Nail on drip edge and shingles
35. Nail up gutters
36. Cut and put in a ridge vent who's square area is equal to, or just less then that of the new soffits' sq. area
37. Drink a cold, cold beer

[mrcaptainbob]

I just came on for a few minutes tonight. I'll print this and 'digest' it. Most of it sounds good. Although, you went WAAAY over the estimate of 30 steps!! I was thinkin' about the rofing nails giving you grief, too....Will talk with you tomorrow....

[Umby]

Yes, it's a bit long winded, so take your time in replying.

I'm thinking about cutting back the existing sheathing to expose the older rafters to a depth, equal to that of, the new extensions' inside lengths. Understand?

This would solve several problems:
1. the dreaded old roofing nails hindering the inside rafter alignment
2. give me room to nail
3. I could work outside of the house instead of in a 160-degree attic
4. because I will be alone for most (if not all) of this project, I could see the rafter-tail alignment on the outside while nailing inside the attic
5. I could make a smaller bird mouth increasing the soffit sq. area and strengthing the overhang
6. and as a result, I would be cutting out and replacing the bad sheathing caused by the ice dams
(I love lists)
Regarding #5, this could cause a slightly different pitch where the two decks come together, but I don't think it would look unsightly or cause problems.
Some more for you to digest!