Home Improvement : After You Find Leak, Roof Repair Can Be Easy : Home Maintenance: Conduct an inspection to determine the extent of the damage. Patching wet spots and replacing tiles and shingles can be done by a novice.

If you are plagued by the prospect of having to spend a small fortune to re-roof all or part of your house because of an isolated leak or two, you may want to invest an hour or so to attempt the repair yourself before committing to a major expense.

Most roofs that leak in only one or two places usually do so at locations that are easily repaired by the novice.

The first step is to determine the proper roof area to focus on in relation to the drip marks or stains on the ceiling or walls. Normally this is self-evident but with some roof slopes and floor plans, the water source can be hard to locate.

If you have doubts, taking measurements from the walls, windows, doorways or other points of reference to the damage area and extrapolating these dimensions on the roof may help.

If you have a large enough attic to climb into, inspect the underside of the roof above the ceiling damage and look for tell-tale water marks.

Sometimes water will “roll” down sloped beams and rafters and drip down to a point on the ceiling some distance from its true entry point. If you find a hole or spot of daylight coming through the roof, push a straight wire through it so you can easily spot it from the roof.

When you know roughly where the leak is coming from, do a visual inspection of the suspected roof area. If you have a flat roof, use a putty knife, trowel or thin piece of strong wood to apply a product called “wet surface” roofing cement to any cracks, holes or open seams you find in the roof surface. This cement is available at most paint and hardware stores in one- and five-gallon containers.

Pay very close attention to any sheet metal flourishing around vent pipes or chimneys as these areas are very prone to corrosion and joint separation.

Apply the same roof cement generously to any openings you find. This material is very pasty and will actually fill a substantial gap without sagging. The defective surface must be swept dust-free before application.

If you do not find a definite defect in the roof surface above the leak, spread a thin layer of cement over a 10- to 15-square-foot section in the suspected area. Chances are you will cover the leak point and possibly preserve the surrounding surface in the process.

For sloped roofs with asphalt or fiberglass (not wood) shingles, follow the same repair procedures described for flat roofs, but pay extra close attention to the “valleys,” the diagonal joint where two roof surfaces come together.

These are very common leak points for sloped roof systems, as the valleys carry the rain water from the roof surface above.

The cure for leaky Spanish or concrete-tile roofs is essentially the same as for a flat roof, but obviously, the tiles have to be removed to expose the waterproof membrane below. Wear very soft rubber sole shoes and step gingerly, never contacting less than two tiles at the same time to avoid breakage.

Carefully lift the upper and lower tiles in the suspect area and pull the long nail holding each one down with a pair of pliers.

Set the tiles carefully aside as you patch the surface below. Replace the tiles exactly as they came out and be sure the long hold-down nails are secure.

Problems with wood-shingle or shake roofs (shakes are cut thicker and less uniform than shingles) require the same visual inspection and patching as other roof types do, but cracked or broken shingles should be taken out and replaced instead of patched.

Lift the overlapping shingle(s) above those in question to expose the retaining nails. Carefully pull the nails with long nose pliers or cut them with wire cutters to remove the damaged wood.

Buy a full bundle of wood shingles (the extra ones will come in handy someday) from almost any lumber yard and push a new shingle up under the overlapping pieces as far as possible, or until they align with the adjacent shingles.

Make sure that there are no gaps showing on the side of the new shingles before you nail them down. Use two 2-inch galvanized nails per shingle, but cut the tips off with wire cutters before driving them in, to prevent splitting the wood. A temporary repair can be made by using a rectangle of galvanized sheet metal instead of a shingle.

As with asphalt or fiberglass roofs, pay very close attention to the valleys when inspecting a wood roof, not only because they carry water from above, but because they are formed of sheet metal which often rusts through. Patch any worn areas with roofing cement.

Now that the leak has been patched, it’s time to put your work to the test. Draw a pencil line around the ceiling or wall stain or any plaster damage as a reference point. Allow the patch to go through three major rain storms and check the size of the stain two days after each rainfall. If it has not expanded at all beyond the pencil lines and the plaster feels dry to the touch, you can pat yourself on the back for having successfully fixed it yourself!

Remember that your roof requires periodic inspection and maintenance to avoid problems before they occur. At least twice a year, check it for cracks and holes, loose shingles or tiles and missing vent caps or open seams.

DR, Use roof cement to seal around cracks on vent pipes and flashing.