How Many Dormers Do I Need?


I’m getting bids from roofers in my area of Los Angeles to do some maintenance repairs to my pipe flashings. The roof was redone in 2012 and I bought the house in early 2015. I had a leak last winter repaired at the base of the single turbine vent on the roof of my 1700 sq ft, single story home. I’ve had 2 roofers out who have given me 180 degree advice and bids so I’m throwing it out here while I wait for a third company to come over.

Roofer 1 can replace all of my flashings, but he is recommending replacing the turbine with a dormer and adding 5 additional dormers for ventilation. I have probably 20 16"x4" soffit vents running around the perimeter of the house. Are this many dormers necessary??

Roofer 2 is taking a minimalist approach and suggest not tearing things out and replacing the flashings because he feels the cutting an replacing may risk water intrusion. He is suggesting a good quality sealing pass around all of the flashing that he claims will last 10 years. Is less better than more when it comes to roofs??

Both roofers have 40 years of experience in the area and are well reviewed and regarded. What are the thoughts of the pros on this forum??


I don’t know since I’ve never seen the job or even know what type of roof you have. However when roofers say “sealing” it usually means going up there with a huge bucket of tar and smearing it all over the place and hope they are lucky enough to stop the leak. That is never the proper way to fix a leak and I would only do that to a roof that was completely shot just to hold someone over until I get a chance to replace the roof.


I would be in the middle, I would replace pipe flashing that’s easy. As far as dormer vents I would only convert to them if doing whole roof.


Thanks. I agree with your philosophy. In the 2 years we’ve owned the home, the leaking has always been around the flashings. For some reason the original roofer shingled completely around all four sides and did not leave the bottom metal lip exposed to assist in run off.

What’s your opinion on the dormers???


If you don’t have a hip roof you could put ridge vent on and do away with the turbine. That would include removing existing ridge and cutting a vent space in decking 1and half inches from peek on both sides put on ridge vent and nail ridge shingles over that


If venting is truly an issue, I would look into less intrusive options such as ridge vent or hip vent before Retrofitting dormer vents into the field of the roof.


I discussed Ridge venting with the roofer, he explained that my southern california 50’s roof doesn’t actually have a very long ridge, so dormers are the only option.

I had a third roofer out and now I’m really confused. He told me that hardly anything on my roof was done correctly by the previous owner’s roofer, and he thinks the best bet is to reshingle the whole single layer roof over the first and add dormers. He explained that the 3 tab singles weren’t laid out properly and that because of the CA heat he’ll have a hard time pulling up just the ones he needs to to repair the flashings. The cutouts aren’t aligned properly between some of the rows. the top of the cutout slots are not covered by the next row of shingles by about 1/4", and our valley flashings are about 2-3" short just above the gutters.

So, I’ve got one guy who wants $600 (his minimum) to seal everything, one roofer who will replace flashings and add dormers for $2k, and one guy who will redo the 6 year old roof for $10k.

So now this rookie homeowner is more confused than when I started.


You can post pictures of your roof using


The length of your ridge is not as important as the net free open space. 1 pc of shingle over ridge vent can replace two box vents. Continuous soffit to continuous ridge vent is optimal.


The workmanship would have to be atrocious
For me to suggest to a homeowner to do a nail-over on a 6 year old roof.
Yes, i need to see some pics.
Nothing you have described by your potential roofer
has me convinced to do a nail-over.

Just the fact he suggested a nail-over
Would have me kicking him to the curb.


I thought it was a 1:1 ratio.

Here’s the science. Hope that helps. Certainteed also has a calculator for figuring correct amount of ventilation.


Back a few posts…do you have a venting issue?. If the current turbine is adequate leave it it place and change venting the next time the roof is replaced. Upload some pictures so we can give you better advice. You may only need some minor repairs to get another 10 years out of the roof unless there is a real problem with the install other than the ascetic issues of 3 tab shingles not properly aligned.


I don’t think I have any venting issues. My biggest concern is leaks around flashings. This dormer thing arose from the roofer who came to take a look. Here are a couple of pics I took from the top of. Step ladder. I didn’t walk the roof.


And another pic


And one last one. Sorry the system will only allow me one upload per post.


For some new reason it looks like they did not replace the pipe collars/boots when replacing the roof for some reason. They cost less than 20$ and take more time to reuse than they do to replace while replacing a roof. I would just have them replaced and re look at the roof and venting in 10 years.

Replace the boots then install the perma boot…never mess with your pipes again.:+1: