Possible warped plywood due to lack of ventilation in the roof?

Question

We are in the process of buying a house that doesn't have any ventiliation in the roof. The roof is basically flat and after walking around on the roof we have found a couple of spongy spot. The roof is approx. 3200 square feet and we are wondering how much it would cost to reinstall new plywood, add ventilation and then refoof the entire house. We are going to be asking for a deduct on the purchase price, but I don't even know where to begin in figuring this cost.

The roof is a EPDM rubber roofing system and it is slightly pitched to the center of the house from the front and the back of the house and then there are roof drains in the center. The pitch looks kind of like a wide V.

Answer 1

By basically flat, do you mean there is some pitch to it?

Is it a dual pitch or gable roof or single sloped?

Is it shingled or have a built up roof system?

If it is gable pitched, we had the same problem, it was built in the 70's and the contractors only put small gable vents on two ends of the home. This was VERY insufficient for a 2/12 pitch roof. We ended up re roofing the house and having to replace MANY MANY of the sheathing panels (what you're referring to as plywood) and also installing a RIDGE VENT.

Ridge vents are VERY efficient way to ventilate a shallow pitched roof. You can cover the entire attic space where as w/ louvers (square turtle looking things on homes) only cover a small area and usually only have openings on a few sides. Ridge vents/caps run right along the peak of your roof and also have blocking (meshy foamy strip) to keep insects and water spray out of your attic space. You place your cap shingles right over the top of your ridge vent and if you weren't looking for it, the avg. passer by would not notice your ridge vent.

As far as the roof sheathing (ply wood) figure a cost of anywhere from $15-25 per 4'x8' board ( that's your major cost )
Ridge vent, we bought ours for $30/ 30'. Check your local lumber yard or Menards or something like that. They'll have better deals than buying online (in my opinion).

One more thing, you only need ventilation over parts of the structure that HEATED! So, for example, ventilation is NOT necessary over the garage.

Hope this helps!

Mena
Architectural Building Technologist

Answer 2

is the the rest of the plywood solid and not warped == if it is there is a way to save the spongie areas with out replaceing then and in the way you do it you will never have to touch it again can you get to the back side and if you can so much the better ===yes get the cost of repair for the roof and then fix it your self its not that bad to repair soft spots in roof ===when you take a trailer in to fix soft spots on the floors from water leaks they pull up the floor covering then push up from the back side with a pice of plywood cut to the size between the braces or joist then they go inside and if the wood is 3/4 thick they take a 1/8 to 1/4 and drill 1/2 way through the plywood in a patteren like a grid spaced 1/2 apart now that the floor is level and make sure it is dry go to the store and buy 1 gal fiberglass reisn and mix enough for area needed (make sure to mix a little more than neede as the wood is going to soak up 1/3 of the fiber glass use a puddy knife to move it around then put a heat light on it the kind they use on cows and chickens ( not the red one) leave it 4 ft away and this will set up level , will kill all the mold , and never flex again no mater what happens any little bumps or high spots can be sanded level so they dont show through flooring ps if you cant get to the back side of the plywood you can level it with the fiberglass ---- this is the best fix ever in bathrooms where the floor has gotten soft around wet areas that where left go the key to this is make sure you dry the wood with the heat lamp or heater it has to be 100% dry JFB PS THEN VENT THE ROOF

Answer 3

I would call a professional to give you an estimate. It can easily go into the thousands$$. Better to be safe than sorry.

My Mom had a porch roof addition redone with the rubber roofing. It was 9'X 26' and in 1990 it cost her $1,200. The shingles were removed but no wood replaced.