I'm currently living in a new build in Ottawa Ontario for which I took possession in February 2020 ( I've been here for about 5 months ). The humidity levels in my basement have gone gangbusters in the past couple of months. I currently have 2 dehumidifiers running full throttle 24/7 to keep the RH at around 50%.

Without these machines running I've seen the RH climb up to the mid 70s.

I thought I had it under control, until I saw water inside the vapour barrier.

The builder told me it was because the cement isn't completely cured yet... Is this true? My understanding was that cement took around 30 days to cure.

Note that the landscaping isn't done yet, so the grading isn't right and we don't have any eavestroughing as of yet.

Should I be concerned about mold? I feel like they are pulling on fast one on me... I had plans to finish the basement ( Seal the floors, put up drywall etc). Any advice?


Water droplets behind the vapour barrier

  • 1
    Yes, new homes emit a ton of moisture. Just about everything that goes into a home is wet. If the outdoor humidity is low, run your HVAC fan and open everything up. Turn off the dehumes, of course.
    – isherwood
    Jul 15, 2020 at 14:25
  • Is the water inside or outside the vapor barrier? Is there hydrostatic pressure in your slab? (Is a sump pump running regularly?)
    – isherwood
    Jul 15, 2020 at 14:27
  • What is "eavestroughing"? That's a term I've never heard before. Are those what we here in the States call "rain gutters" (a trough at the eve for catching rain water off the roof)?
    – FreeMan
    Jul 15, 2020 at 14:28
  • The water is inside the vapour barrier. I don't have a sump, as for the hydrostatic pressure , this is below grade so I'm assuming that is what is happening. The walls are all insulated and covered with vapour barrier. Note that not all of the walls have these water droplets, only some.
    – Flujee
    Jul 15, 2020 at 14:30
  • "eavestroughing" is indeed a rain gutter! :)
    – Flujee
    Jul 15, 2020 at 14:31

3 Answers 3


Your home has been in this state for 6 months. There should not be any extra moisture that needs removing after this length of time. And 6 months is more than long enough to start getting lots of mold and water damage behind that vapor barrier.

The purpose of that vapour barrier is to prevent moisture from inside the home getting into the insulation. There should not be water on the outside portion of it!

I don't know your local building codes, but in our area of the country (SK), they require sealant on the exterior walls, weeping tile and sump, proper grading. I don't believe that eavestrough are required.

  • Contact your city's building inspector. Let them know you have a new build, that you can see water inside the moisture barrier in the basement, and the builder says its normal. Request that they come look at your new build home, request what the builder planned for sealing the basement.
  • Document what you are seeing and doing about the moisture. You want lots of pictures, dates. Record the approximate amount of water you get out of your dehumidifiers.
  • Contact your insurance company. They may be willing to go after the builder as well, because they will be the ones on the hook for damages if your are covered.

I don't want to sound negative, but you are probably going to end up fighting your builder over this. They are either incompetent, or malicious. A newly built home should have proper drainage and sealing on the outside of the basement walls to prevent this. Your new home warranty only lasts for a certain amount of time. Get the ball rolling ASAP.

  • Thanks!!! I've started documenting anything and got a hold of an inspector!
    – Flujee
    Jul 16, 2020 at 17:44
  1. Did it often rain in the last days/weeks?
  2. Do the neighbours (new buildings) have the same problem?
  3. Are all doors/windows in the basement closed during daytime?

As stated before, a new building needs to get rid of all the water in the concrete and other material. This can take many months, even if concrete may reach its final strength after 1 month.

A basement should be vented only during night time. The statistically dryer air can get in, will be heated a little bit during daytime (closed doors/windows), and thus conveys water out of the building, when this air will be replaced with dryer air from outdoor the next night. This is also valid when using dehumidifiers. Windows/doors closed during daytime, open during night time.

All material which is to be dryed should not be covered with anything. The water must find a way to diffuse out of the material.

Incorrect drying of buildings is the most often mistake that causes huge damages to buildings - in the long run.

  • 1) There has been rain! 2) The neighbours had the builder close up their walls before possession. They have no idea what is happening behind their drywall 3) They are indeed closed!!
    – Flujee
    Jul 15, 2020 at 18:23
  • If your esteem, should I contact the builder and raise this as an issue?
    – Flujee
    Jul 15, 2020 at 18:29
  • Could be a mistake to not seal the exterior underground walls. Especially in rainy areas with stopping ground like clad layers the exterior walls need to be waterproof. Photos, documentation, water color, consulting experts etc. may help to convince the responsible company to fulfill the contract to build a dry basement and not a facility to grow champignons.
    – xeeka
    Jul 15, 2020 at 18:36

If you have water this is a giant red flag that they did not properly drain your footings.

Especially true if you have a descent slope. I would be requiring them to dig out install proper drains. Yes the concrete is cured. they would not build on uncured foundation walls ? Don’t let them play that game. Yes it is cured enough but even well cured concrete will pass water when it is not properly drained. Keep after them because it is really impossible to seal from the inside proper drainage and you will have a dry basement that can be finished.

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