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Raising high the roof beams, checking rafters to see if it's time for a new roof


There comes a time in every rehab when the roof just has to be done. The old drywall buckets that have been collecting rain while other work gets done have got to go.

There are reasons why a bad roof isn't always the first item on the rehab agenda. In a big project there are lots of pipes and vents that run through the roof. You don't really want a plumber sawing away on a brand-new roof surface; if he makes a hole, you'll have to call the roofer back to repair it, or risk losing your guarantee.

A typical flat, hot-tar built-up roof, like those on most row houses, is guaranteed for 10 years -- if the original roofer comes back every three years to recoat with hot tar (at the owner's expense), and if he is called back to repair it every time work is done that affects the roof (such as new plumbing or having a deck installed). So careful staging of roof work is important.

The house we're working on is a three-story, four-level brick town house with two expanses of flat roof. The third-floor roof is in pretty good shape, but the second-floor roof has real problems.

We think the second-floor roof was never flashed (protected with sheet metal) where it meets the back wall of the third floor. Water getting in there over many years before we bought the house had destroyed the beam that supported the third-floor wall and had damaged the second- and first-floor walls and the staircase the two walls supported.

The beam had to be replaced, the third-floor back wall had to be rebuilt (not in brick, but framed, to accommodate large windows), and rain had to be kept out, so the walls beneath could dry out. That was the first thing in the house we fixed.

But because so much of the new plumbing had to run through that second-floor roof, we waited to replace it until all the "systems" work was done. (Plumbers cover pipes with rubberized "boots" that are nailed and cemented to the roof. This treatment keeps the roof from leaking around the pipe, but the original roofer still has to come back and seal around the boot for the roof guarantee to be in effect.)

While we were working on installing plumbing, heating and air-conditioning, we patched the roof -- several times, in fact-- and still occasionally needed to stick a bucket under a drip.

Now the time has come to fix the roof. We are frequently asked how to decide when a roof needs to be stripped of old roofing and when the sheeting underneath needs to be replaced.

With a flat built-up roof, the answer depends of what's underneath. In our case, the ceilings were long gone to water damage, so we could look up and evaluate the rafters and sheeting. If you can't see the underside of the roof, you should be able to tell by walking on it whether the underside has "soft" spots. A lot of "bounce" means problems -- it could be a broken rafter, a rafter slipped out of its pocket in the wall, or breaks or rotten spots in the sheeting. The only way to identify the problem is to strip the roof to the original sheeting.

We could see broken and slipped rafters as well as soft spots in the sheeting. And the surface was rippled like a washboard from old patches and recoatings. Applying a new surface over this old one could allow water to pond in the ripples. A persistent pond will eventually become a leak. So for us, the answer is:

It all has to go.

First, we fixed the rafters and built "headers," doubled rafters, around the chimney (another item left off the list 120 years ago).

The next step, if the weather will allow, is to schedule a weekend to strip the roof down to the original sheeting. The old sheeting will be repaired in places where it's especially bad, then new sheeting -- 5/8 -inch thick CDX (roof-grade) plywood -- will be glued and nailed over the entire surface. Then the flashing is installed -- the wide metal strips that seal the surfaces to intersecting walls. The edges of the roof get metal "drip-edges" to seal them where they meet the gutter.

There are different kinds of guttering systems; the one we plan to use has a flange that's nailed into the sheeting, so gutters and downspouts will be installed next.

Then the entire roof gets a "base sheet" of heavy tar paper.

That's the end of the weekend. The tar paper will be covered with plastic to keep water off until the next nice weekend -- or until the roofer arrives.

It's a good idea to schedule the roofer to arrive right away. (Check with the roofer before you put down the base sheet; he may want to do this himself.) Installing the top surface of a roof is a job best left to a professional -- because you get that guarantee. The best roof for this situation is a hot-tar built-up roof -- and few homeowners have access to 400-degree hot tar.

Next: Finding old house parts.

Mr. Johnson is construction manager for Neighborhood Housing Services of Baltimore. Ms. Menzie is a home writer for The Sun.

If you have questions, tips or experiences to share about working on houses, write to us c/o HOME WORK, The Sun, 501 N. Calvert St., Baltimore 21278. Questions of general interest will be answered in the column; comments, tips and experiences will be reported in occasional columns.

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