building a soffit


When our house was built, the contractor didn't install soffits. Each rafter "bay" (sorry, I don't know the terminology) under the eaves has 3 screened 1" diameter hole. I'm getting ready to build a soffit this summer, and I'd like to ask for some advice:
My house is 1700 sq ft. with a common attic. My roof has 9 large dinner plate-sized vents. What I'm wondering is whether I need to install a soffit vent on every single rafter bay (I know about continuous vents, but I'd like to stay away from them. I'm an idiot carpenter, the less cutting the better). Each side of the house has 30 rafter bays under the eaves, this would require installing 60 individual rectangular soffit vents. This sort of seems like overkill to me and I'm wondering if I can get by with fewer vents than that.
I'd appreciate any thoughts or advice.
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William_F wrote:

You can if you don't mind the attic being hotter than necessary and your shingles having a decreased life span.
If it were me, I would entirely knock out several of the bird blocks (the pieces of wood with the 3 holes) and put your rectangular vents there. I would decide how many to put in by following the rule of 1 square foot of ventilation for every 150 sf of attic space.
I would put in the continuous vents as they would better serve your need attic ventilation. If you don't like the addtional cutting, then go with Hardiesoffit which has vents built in the soffit material itself. Much less work than soffits and installation of vents.
See this site:
http://www.jameshardie.com/homeowner/prodhome/hardisoffit.php
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Robert Allison
Rimshot, Inc.
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You should provide as much venting as possible. This will lower your attic temperatures (thus helping to keep the house cooler), extend the life of your roof shingles, and minimize ice damming in the winter.

Be aware that the "bird blocks" also serve a structural purpose. They help prevent the rafters from twisting or tilting to the side. They're required by code here, regardless of how venting is accomplished.

I agree... I used aluminum "strip vents" I picked up at the local home center. I mounted mine at the outside edge of the soffit, against the fascia board. Then I cut the plywood to fit between the house and the soffit. It's no more complicated than just cutting the plywood to fit the soffit without the vent. Then I ran a bead of caulk along the edges where there were gaps or spaces that bugs could get in (Don't get caulk in the vents! :) ).
If the bird blocks have screens on them, I would probably remove those to allow maximum airflow. I would drill holes in the other bird blocks as well so EVERY rafter bay has air flow.
Anthony
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