Steven L. Smith, Bellingham, WA Home Inspector (King of the House)


Skylight Inspections (Concealed components, visual limitations)


        It is not good news, but to be truthful, it is iffy as to whether or not a home inspector will be able to reliably detect subtle seepage around skylights. Many factors and variables are involved and sometimes you can, sometimes you cannot.

        Flashings and seals around the glazing at corners of skylights are vulnerable to leaks. The watertightness of any given skylight is dependent on the quality of the skylight itself (manufacturers’ responsibility) and proper installation of flashings-seals and the placement of underlayments at the top side (responsibility of in-the-field installers).                  


                           Velux manufacturer specifications, various means of waterproofing

        Once the roof surface is in place, shingles or other roofing materials obstruct the view of the flashings and underlayments.


                             Roofing materials obstruct the view of flashings and roof felts

        Usually, even when attic access is possible, the view will be restricted. The light shaft, at a properly installed skylight, will be fully wrapped with thick insulation. The photo below, for illustrative purposes, is an example of a skylight that is partially wrapped.


                   Attic photo, insulation is wrapped around light shafts

Sometimes seepage, moisture intrusion or damage might be detected at the bottom side of a skylight when looking up from inside a building.


                                  Obvious water intrusion below skylight

Unfortunately, to complicate matters, some degree of staining below a skylight does not necessarily mean that the skylight is leaking. Stains are frequently caused by drips as warm interior air rises and condenses on the cool surface of the skylight glazing.

Since skylights can be problematic, watertightness reliant on a number of concealed components, any homeowner should closely monitor skylights. On a regular basis, clean moss and roof debris from around skylights.


                        Qualified roofer to clean around skylights

Monitor skylights from interior space and, if any indications of seepage become apparent, promptly contact a roofing contractor. Identifying leaks, sooner rather than later, reduces the odds of, at a later date, requiring costly repairs.

Steven L. Smith

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Comment balloon 6 commentsSteven L. Smith • August 23 2014 04:56PM


Have never seen a skykight that doesn't leak. Not a question of if but when. Really a maintenance issue that you just can't reach out and see. 

Posted by Bill Reddington, Destin Florida Real Estate (Re/max Southern Realty) over 4 years ago

Bill, I have seen many of them that do not leak. Or at least they were not leaking at the time of the inspection. Now, many of them will probably leak at some point in the future but I cannot go too far ahead with my crystal ball so I provide general maintenance guidelines and warnings.

Posted by Steven L. Smith, Bellingham WA Home Inspector (King of the House Home Inspection, Inc.) over 4 years ago

Hello there ,

hawk eyes. Yo are really doing a good maintenance.

keep it up!


Have a great SUnday...

Posted by Christopher Lotte, Central Ohio Realtor, 614-390-9243 (Red 1 Realty) over 4 years ago

Excellent discussion Steve.  We have two skylights that were installed properly.  My roofer friend who did a roof tune up for me last year (replaced plumbing boots and repaired the ridge vent) looked at our skylights carefully and proclaimed them still sound.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 4 years ago

Considering the percentage that do or eventually will leak, not something I want. 

BTW, what's the use of a skylight in any attic????

Posted by Lenn Harley, Real Estate Broker - Virginia & Maryland (Lenn Harley,, MD & VA Homes and Real Estate) over 4 years ago

Christopher, doing the best I can with what I got.

Jay, Thanks. I appreciate your comments. No question they can leak but as inspectors we cannot tell every client their skylight will leak. Like you infer, maybe it will and maybe in won't or maybe it will leak 20 years down the road. There are many other components at a house that are more likely to wear out like those rubber boots at stacks.

Lenn, it is not that anyone puts them in the attic but,  unless there is a cathedral ceiling or some unusual situation, to get the light from the roof level to the ceiling below, the skylight light shaft has to pass through the attic. Attic is between roof and ceiling, so there it goes. That shaft should be insulated so, the situation is, the inspector cannot see the underside of the skylight. I have seen an attic skylight -- a roofer made a mistake and it went nowhere. From above you could see loose fill insulation below.

Posted by Steven L. Smith, Bellingham WA Home Inspector (King of the House Home Inspection, Inc.) over 4 years ago