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!)...