@T Burns I don't have an ATMOX system, but from what I've seen they have one inside and one outside sensor input on their controls. One outdoor should be sufficient, but for a large crawlspace I'd prefer more than one just because humidity CAN be localized if there is bulk water such as a flood or plumbing leak. My home had mold and rot only in certain areas--generally the east (downwind) side. The ATMOX optional louvers don't appear air-tight but passively flap down over the opening when the fan isn't running, like on a dryer vent. It's probably no worse than a typical sliding crawlspace vent. Plotting temp and RH over time is a great idea. From there you can obtain dew point and get an idea how often an ATMOX system would be able to run with just fans to keep the RH below 60%. With tight clearance between floor framing and the ground, the joists will track ground temperature by radiant heat exchange unless you have lots of airflow. You can get an idea of what RH will be at the joist surfaces by looking at those temperatures and figure out what max average dew point should be allowed. From there you can look at historical dew points for your area and get an idea of what percentage of the time fans can actually dry the crawlspace. As the ATMOX folks point out in their literature, it takes an extended problem to elevate wood moisture content enough to cause mold. You may be able to get by with a dehumidifier for half the year or less. But I would definitely not install one of these systems without a dehumidifier as backup, integrated into the control logic. If nothing else, it will come in handy if you get a flood or a fan goes bad and you need brute force drying. There might be some aspects of encapsulation that could benefit your situation, but I'm leery about arbitrarily introducing spray foam, foam board, or plastic-wrapped batts, like the Youtube encapsulation guys do, without really thinking through the moisture transport situation. You could easily end up trapping moisture or hiding rot or termite activity in an old house that wasn't built to modern codes. For example, my home has poly flashing between the rim & band joists and the brick, lacks a brick ledge, and was not built with pressure treated sills. If the brick really gets soaked, the framing gets damp. This is a once-a-year event at most, but it has a way to dry. The last thing I'd want to do is to trap moisture in the lumber. Also, my home's crawlspace vents also admit air to the gap between the brick and sheathing, and blocking those gaps with foam board will reduce ventilation behind the brick. Retrofitting an older home has to be taken case-by-case. I wouldn't trust most one-size-fits-all encapsulation contractors to consider that. I would probably never be totally satisfied with an ATMOX system, since the control logic isn't arbitrarily customizable, but it's an incremental improvement over full-time passive ventilation that we know doesn't work in summer. Automating the ventilation and combining occasional dehumidifier use may be all you need to banish the mold if there are no drainage issues. Thanks for the tip about the upcoming revision. I'll have to get in touch with them to see if they're adding fan diagnostics.

Sigh....The "two A/C units" and "dehumidifier to the basement" tells me you do NOT have a whole-home A/C nor a whole home humidistat (dehumidifier and/or humidifier). So...as Sophie so eloquently points out (love Sophie's forthrightness) the house isn't ready for wood. Without the "whole home" systems, these humidity swings you are seeing will continue for the rest of the life of this home. The floors will get PUFFY in the summer (58% humidity is high for wood floors and high for every fixture in the home) and then SHRINK in winter (wood can handle about 10% humidity difference between summer/winter; anything more than that and you will get plenty of gapping in winter). Your GC is correct that the humidity is high for refinishing. Water based finishes still require indoor humidity to be around 45% to get them to work properly. Please, please, please discuss the UPGRADE for your home HVAC system to include the humidistat (change humidity at the touch of a button) with whole home A/C...or whatever system works best for your location. At this point...time is your best friend. If you rush this, you could be in for a horrible surprise that causes more delays than if you had just waited.

I would purchase a few hygrometers from home depot ($35 each) and place them around the house. I would also place one in the basement. I would then let them settle in for a day or two and then start taking DAILY readings for a week. I would write these down on a piece of paper or a spread sheet (documenting time of day and room location). You would also document the weather OUTSIDE to keep track of any correlation between indoor Relative Humidity and outdoor weather/humidity. Once you have a few points of data, you can then figure out what is going on inside the house. Hickory is dynamic when compared to oak. It likes to stretch it's legs in higher humidity and then shrink up with low humidity. Now for the dehumidifyer in the basement. You mention you are on a lake. Which means ground water is VERY high (the lake is just a large dip in the landscape where ground water has pooled). Add that to porous concrete and you have a very high chance of continuous water vapour (or liquid water) moving into the house through the basement slab. The AGE of the house/slab will tell us if you have a vapour barrier UNDERNEATH the concrete. If you do NOT have a vapour barrier (or it has been compromised = always a possibility) then you will have a concrete slab that is continuously moving vapour into the home. Every day. All day. Day and night. For the entirety of the home's existence. Whew! So much to know, right? First things first: go out and purchase 2-4 hygrometers and set them up around the home. While you are waiting for them to settle in, tell us a bit more about the age of the home and the type of basement situation you have (photos would be SUPER helpful). Tell us how you know there have been seepage issues in the past.

Not sure if this changes any of the advice you’d give but given the track record and the commentary here about the choice of material / lack of quality of the workmanship, No change. This is a minor cosmetic issue. And not an unexpected one if you understand how wood behaves with wide swings in humidity levels and other finer points of bowing, crowning, twisting, etc. when he took a look at the crack, he said it was probably a humidity issue... I'm assuming humidity is a common issue in basements and that lots of people have basements without cracked stairs so... Yes, humidity is a common issue. Wood is dynamic; it responds to changing humidity levels. It expands under high humidity levels (spring/ summer) and contracts when the level decreases (during the heating season). (Note the slight gap between the treads & risers--evidence of contraction during the heating season.) Decades of this cycle of expansion & contraction with the wood wiggling & pulling against the fasteners during the wet season and then contracting during the dry is how stairs get 'rickety'. In a basement, more so because the swing is wider--the basement being more humid than the rest of the house during the winter. how do I make sure contractor is addressing the root cause of this problem versus a symptom? I didn't see 'climate control' on the list of work performed. So that is outside the scope of his responsibility. Do you have a whole house humidification/ dehumidification system? Do you run a portable dehumidifier in the summer? Do you add humidity during the winter? resilient new stairs was the #1 requirement of this project What did you specify in the contract? What do you mean by 'resilient stairs'? Rubber, vinyl, cork?? In all probability what happened is that that tread has a slight crown and split under normal foot traffic. Crowning is more of a problem with solid wide boards like you have (vs a tread comprised of more narrow edge-glued boards.) More info here: https://www.stair-treads.com/faq/edge-glued-stair-treads.html The advise given above--to apply some stain to the crack now--is good advice. When the humidity increases, the split will close up. Alternately, you could replace the tread w/ no guarantee that it won't split. Knowing that the stain & finish on the new tread might not match the existing and that you will need to touch up paint. The paint job is a whole other issue. Obvious lack of prep; I would have specified new skirt boards...but this goes back to the original contract and what was specified. dusting the area so we could continue to use the laundry room that wasn’t in scope for renovation) weren’t held to — laundry room wasn’t tarped off and was unusable for a chunk of the renovation One of the facts of life is that no one cares about your stuff like you care about it. Water under the bridge now...but why didn't you call them out on it then? Or remove the machines? Or tarp it off yourself? Or drape some plastic over the machines? Block off HVAC vents? Personally, I would have taken care of it myself because I wouldn't want to pay skilled labor rates for simple housekeeping. Nor haul dirty laundry off to a laundromat just because the laundry room was too dusty...