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The Marko Files: The Case of the Wet Floor

November 27, 2015

Vinyl siding needs a drainage plane—just like all other siding types do. You must drain the rain—you must have Plan B

This mystery tale comes from Marko Vovk, an engineer, inspector, and indoor environment specialist. The specified repair is a patch, but an affordable option that will work until the siding needs to be replaced. At that point, not only should a continuous drainage plane be established, but extra insulation should be added to the walls to further bring this house into the 21st century.


In this video were going to show you how to find a water leak in a new home that has vinyl siding and no drainage plane such as Tyvek plastic sheathing.

During this investigation I was accompanied by the a local piano celebrity that goes by the name of T. Theodore Edward Dylewski from the famous “T and Rich Dueling Pianos Show” purchased a new home built in 1997 in the city of Avon Lake located in Ohio.

Soon after moving into the home, Theodore noticed a slightly moist floor corner in the first floor dining room.

  • He knew it wasn’t a winter problem because it leaked on and off all summer.
  • He knew it was not a plumbing problem, became the second floor bathroom was not located above this moist floor area.
  • He knew it wasn’t a gutter problem because his gutters were cleaned and did not appear to overflow.

T was not sure if the dinning room leak was from:
  • His Anderson Window not having end dams at the bottom sills,
  • The house missing the Tyvek drainage plane
  • A possible condensation problem
  • or if it was the exterior wall penetrations that were not 100 % caulk sealed.

During the water leak investigation, T and I perfumed initial moisture testing, took photos of old moisture stains of the dining room floor and of the basement band joist pockets that existed below this moist floor area.

This was done to create a base line to see if anything would change after water testing.

We tested the wall surface temperatures and indoor humidity to determine if wall condensation conditions might be occurring. They were not.

Soon after, we started to water test the back of the house vinyl siding and all mechanical penetrations such as

  • AC suction line
  • Electrical service
  • Cable TV

Holes in the wall leaked, but that wasn't the problem

We did find that the water leaked at mechanical wall penetrations; however, these were below the dining room floor moist area. T knew that his first repair was going to be easy. He will remove all basement band joist insulation and caulk all holes, penetrations, and joints.

Even though 'All Windows Leak,' these ones didn't

We then water tested the windows and window frames. Water did not appear to be leaking at the windows. T’s second repair was going to be easy also.

He was going to caulk all Anderson sill end dams that were exposed.

Rain gets past siding, so houses need a backup plan

We continued to water test the back of the home’s upper siding, lower siding, and even underneath the vinyl siding.

It wasn’t until we water-tested the corner that we realized some water intrusion. The dining room floor stain became larger and the floor moisture content increased. Below the dinning room, the band joist pockets also became visually moist.

This repair was not going to be difficult, either. T would have to install a drainage plane like Tyvek behind the vinyl siding at this dining room exterior corner location. It was determined that the dinning room floor leak was largely contributed by the lack of a drainage plane such as Tyvek.

Moisture encounter appeared to be form the unprotected sheathing at corner, at sheathing butt joints and at box band joists.

In this case, T was lucky that leaks were not occurring at other areas of the home. Some of his neighbors may not be so lucky.

During this building era, many cities such as Avon Lake, Ohio permitted building homes without drainage planes. Yes, you must drain the rain. You must have Plan B. What was the city of Avon Lake thinking back in 1997?

Marko Vovk has inspected over 15,000 homes and buildings. He is a civil engineer and is state licensed in lead, radon, and termite damage. Marko is certified in HVAC diagnostics, HVAC balancing, carbon monoxide, Certified Indoor Environmentalist, and is a ICC B1 International Code Consul Building inspector.

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