New Roof On An Old House

knucklehead

A freind of mine needs a new roof on his lake house. I has a single layer of regular 3-tab asphalt shingle. My question is, do the old ones need to be torn off or can we leave them on and go over them with the new? We are getting different opinions up at the coffee shop. I told him I would check into it.

shanekw1

I suppose you can go over the old ones, but I don't know why anyone would.

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RandyB1986

I hate when people overlay houses...it dont really save that much but can cost you a lot down the road.

Slyfox

No matter where you ask this question your going to receive many different opinions.

No matter if it's a new construction, re-roof or lay-over, if the roof is installed properly it will look good and last.
If it's installed improperly it will not.

Don't re-use existing flashing's, drip edges, vents, etc.
Make sure there are no deck or facial issue's that need attention.
Follow the manufacturers recommendation for lay-overs.

Lay-overs are a time tested procedure proven to work,
re-roofs were commonly excepted until manufacturers and insurance companies realized it was more feasible to push for re-roofs.

Contractors example, more work = more money.

Insurance example, they pay less to replace a roof in a storm damage situation if there's only one layer.

Manufacturers example, they increase their potential sales by the added need for underlayment materials.

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PA woodbutcher

I do an occasional layover if the original roof isn't too bad. Watch for heavy curled shingles and the dry brittle ones.

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'The trouble with our liberal friends is not that they're ignorant; it's just that they know so much that isn't so.' - Ronald Reagan

Red Adobe

I do metal roofs over shingles, I have an ins co that preffers i dont tear off and won't pay for it they will pay higher for the metal to offset the difference. Adjuster says the shinlges make for less noise and hail damage.......I like it becuase i dont have to worry about a sudden rain storm cuasing my insurance to skyrocket

where im at
My material cost for propanel w/ trim comes out to $1.10 a sq ft (I use a gutter/facia trim i designed that hides the ridges on the end and will handle the flow of the heaviest turd floater rains and it stops the avalances of snow as well)

cheap tamcos are around $0.72 decent shingles are around $0.99

food for thought

as for overlaying shingles if done propper it looks fine I would check the truss framing and make sure they are in good shape and will hold the extra weight (99% will) but i have seen a sagging roof after overlay due to no triangulations in the truss

Darwin

Here in Michigan, code allows 2 layers of shingles on an existing roof. However first layer should be in decent condition.

I would just do a complete tear-off if I could. It's hard to tell the condition of the sheathing underneath.

If the customer is on a tight budget, though, you should be able to get away with it.

Good luck.

J-Peffer

I honestly feel (in my opinion) regardless of the condition of the old shingles, not taking them off will decrease the life of the new shingles over the top.

I think if water does get through, between layers of shingles, you run into a worse rot issue too. They hold the moisture between 2 water proof membranes that get hot in on the sunny days and the moisture just festers.

You just can't get the same quality of work, going over some old shingles as you can over clean decking with new underlay.

DavidC

I'm on the side that says your new roof won't last as long if you lay over. (We call it reroof in these parts) However, if it's my house we're talking about and I don't expect to out live the roof, I'd lay over. (or reroof, which ever is most efficient) If it's likely that I'll have to do it again it's a strip job.

I've done it for plenty of customers on a tight budget and it has worked out fine. Of course I'm careful to follow the manufacturer's recommendations for doing so.

Good Luck
Dave

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Framer53

My roof on my house was 3 layers. First was cedar shingles and lasted for a long time. My house was built in the 1880's. Then 2 laywers of asphault shingles. The last layer was in excess of 30 yrs. old.
When I was selling shingles, I used the example of carpet. Carpet without pad doesn't lasty as long as carpet with pad. I can tell you that, in my mind, if there is only one layer, one more won't hurt.

Slyfox

The second layer on my house is 20 years old this year, which is a decent life span for a 25 yr oc 3-tab and there still not leaking, blowing off or curling yet. They are staining pretty bad tho.

I always recommend re-roofing also, but I assure people I can install lay-overs to last if that better fits their budget.

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747

How many square is the roof? You say lake house. How much to get a dumpster out there. Or do you have a dump truck. How much to dump it? I say if its not a lot of square and you can get a dumpster out there or dump truck i would rip it off. You can reroof. Your just adding cost next time it needs a new roof. 2 layer tearoff is more then one.

Slyfox

I believe that's his reason for asking.
A lay-over will cost less than a one layer re-roof.
spend less now, more later.

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