How to find a roof leak

The best way to find a roof leak is to follow the signs. However, this is not always a reliable way. There are many things that can divert water for hundreds of feet (or even thousands). Thankfully, in most cases leaks are able to be found or a general area can be isolated and repaired in order to fix the problem.

It is important to know some things about the construction of the building and take the information into consideration as you begin to locate the leak.

Fast Tip: For a flat roof with seams that are exposed simply walk on the seams and feel around where 2 or more seams meet together, watch and listen to see if there is water or bubbles escaping from the leak. This method is sort of like submersing a bicycle tire under water to find a leak but, your foot provides the pressure, go slow, don’t make a lot of waves 🙂 Also, works best with ponding areas and moderately wet areas. 

Different Types of Leaks:

Leaks caused by decay:
These are simply difficult or near impossible to fix without some major overhaul. If the leak is on a small section of roof, consider replacing the entire section. In situations where multiple layers of roofing exist it may be impossible to find a smooth junction on the roof to do a field-tie-in (meaning the repair can not be properly attached/shingled/waterproofed to the existing roofing materials) in this situation it is necessary to find an ending point such as a ridge/parapet wall/eve to terminate the repair area. This is for a larger repair area where leaks are impossible to specifically locate due to a rotted or decayed roof.

Leaks caused by improper installation
These can typically be fixed by following the proper Shingling technique for water shedding outlined in a good DIY Manual or here

Often, improper installation can be seen and pinpointed from the surface of the roof, look for inconsistencies in shingles, are they lifting, missing? Examine the sheet metals, any punctures, missing pieces, pieces that are reversed? A “reverse lap” means trouble and is pretty easy to fix. Typically reverse laps are not detected from peripheral viewing but, require opening the roof and further examining how things were put together. These type of repairs can be quickly remedied by an experienced roof repairman or Savvy DIY’er! Old pipe boots (rubber) can be replaced or repaired using a new jack for a few dollars or some special tapes/caulking.

Look over the HVAC units and pipes carefully, notice that water can enter a pipe with an incomplete or broken boot seal.

Leaks caused by blunt force
Tree limbs and other environmental hazards typically leave obvious gashes in the roof and prove easy to isolate.

Leaks caused by sharp force
Was this an accident, manufacturing defect, or did something intentionally cut this? Good luck finding these, if you’re working on a Rubber Roof EPDM and it is ballasted with rock and the slice is somewhere in the field, plan on uncovering all the seams first, clean and check thoroughly, make repairs and water test.

If you shovel rock on a roof do not, do not, do not stack all the rock in one pile unless you want the building to cave in from too much weight. Instead shovel corn rows and check the roof in three foot swaths with some slight shifting it is only 1/2 the work (only move the rock one time my friend, except 1 row by default).

Other sharp force leaks might be easier to find but it is a matter of stretching the roof and searching by eye sight and by hand. These can be tedious to find but repair should be simple.

Leaks caused by wind
Normally these are easy to find if, a section of roof is leaking, wind drives water into places it would never go otherwise. Check the weather when the leak occurred and see if the winds were coming from an unusual direction. Sometimes these things never reoccur.


Did the leak happen just once or, is it reoccurring?

What is the roof deck constructed of? Concrete, wood, metal?

Can the leak be traced by following signs in the attic and examining the signs of water?

If repairing: Is the proper material being used for the repairs? (some materials don’t mix and will decay one another).

Locating a leak can be tricky, moisture detectors are available for purchase.

Many professional roof mechanics and contractors are excellent at finding leaks quickly and making the needed repairs for potentially lower cost than investing in expensive equipment or learning a new trade. It is helpful if homeowners are able to provide an access to he attic. Also, sometimes contractors will not carry a ladder that is small enough to bring into a home so, this is something you might consider providing if you already own one or a flashlight if the attic space is not sufficiently lighted.

Things to consider when leak finding:

Wood roof decks are usually 4’x8′ plywood or 1″ wood, these are typically easiest to locate leaks on because there are so many ways the water can enter the attic. Usually wood tells a good story about leaks and you can read these signs.

Metal roof decks can allow water to run on a low slope for hundreds of feet in any direction and in multiple directions. One leak on a roof with this type of deck can show up in many places, follow the signs carefully, don’t jump, hopefully the roofing material will tell you a better story if this leak is stubborn to locate.

Twin T concrete roof decks look a lot like the underneath side of a new bridge or interstate flyover. The Twin T is pretty amazing and simplified construction for some decades. Water can really run on these decks but you can measure the spans and see the cracks and have a heyday searching. Again, it is most probable to find the leak from the top side. However, don’t miss any clues because they are valuable.

Standing Seam Metal roofs don’t have a roof deck in many applications. under the roof is C-channel and I-Beams separated by large spans of up to several feet (6’… 10′ etc.) as there is not a specific code for how close the spans should be and the architects/engineers work those things out for each project. Insulation catches water and gets awful messy. Open the acoustic ceiling, check out the insulation and start digging into the fiberglass until an entry point is located if desired. Standing seam roofs that are properly maintained leak a whole lot less. And, standing seam roofs on stand-alone construction leak less (as I’ve observed). Building junctions, tie in’s, HVAC Penetrations, Seams, Screws and Sealants are the keys to success here. Think Waterproof.. not watershed.

OR just hire me