Hardwood Floor Prep Moisture


  #1  
Old 07-08-15, 04:55 AM
S
Member
Thread Starter
Join Date: Jul 2015
Location: us
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hardwood Floor Prep Moisture

I am planning on installing hardwood floors in my single level home with basement. The hardwoods will be installed above the basement level. As part of my preparations I have been taking moisture readings. The moisture content of the 1/2" plywood subfloor is mostly 8%. However along a certain exterior wall I have had readings much higher 13-18%. The partcleboard I removed along these exterior walls was not wet. Just outside this specific wall a deck ties into the house. What could be causing this moisture. Please see pictures.

What would you put down over the plywood? 25/32 Advantech osb or 25/32 plywood?





Name:  DR.jpg
Views: 316
Size:  20.6 KBName:  under deck.jpg
Views: 274
Size:  35.8 KBName:  deck.jpg
Views: 285
Size:  13.3 KB
 
  #2  
Old 07-08-15, 05:38 AM
P
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,265
Upvotes: 0
Received 0 Upvotes on 0 Posts
I see two possibilities. It's really a combination. The moisture is coming through the foundation & the deck is causing water to collect on top of the outside wall. There is some discoloration, on the brick, itself. That could be from water.

Test the moisture, on the wall in the first pic. See how high off the floor, you get moisture. My guess is less than 2 feet.
 
  #3  
Old 07-08-15, 11:19 AM
czizzi's Avatar
Member
Join Date: Jul 2007
Location: USA
Posts: 6,541
Received 15 Upvotes on 13 Posts
Tell us a little more about the soffit material used under the decking. Even if it is vented vinyl soffit, it would hold a good bit of moisture in that cavity at all times. That moisture and high humidity would keep the rim joists and the house in a constant state of high humidity which may be migrating to the inside resulting in higher moisture content near the exterior wall. There area drainage systems designed for underneath decks to keep the area dry.

As far as the flooring underlayment, for nail down hardwood the specs are minimum 3/4" for OSB and minimum 5/8" for Plywood. Advantech is a great choice and is the industry standard for superior flooring.
 
  #4  
Old 07-14-15, 06:08 PM
S
Member
Thread Starter
Join Date: Jul 2015
Location: us
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
The under deck ceiling is constructed out of vinyl siding.

So I should remove all of the vinyl siding and put up something that will not hold moisture? Any suggestions?



Should I put down a layer of aquabar construction paper between the subfloor and underlayment? Or just on top of the underlayment?
 
  #5  
Old 07-14-15, 06:33 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 36,608
Upvotes: 0
Received 9 Upvotes on 8 Posts
Does the underdeck have a slope to it? For naildown hardwood, just use 15# roofing felt as an underlayment.
 
  #6  
Old 07-15-15, 03:50 AM
czizzi's Avatar
Member
Join Date: Jul 2007
Location: USA
Posts: 6,541
Received 15 Upvotes on 13 Posts
Vinyl soffet material is designed for air flow and ventilation, not water mitigation. While not cheap, there are under deck waterproofing systems designed to be sloped and channel the water to a gutter system that then drains it where you desire. Here is one that I have installed, but by no means is it the only one out there. DrySpace Under Deck Drainage - TimberTech

I think if you get rid of the moisture, your floor readings will normalize over time.
 
  #7  
Old 07-15-15, 03:57 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 36,608
Upvotes: 0
Received 9 Upvotes on 8 Posts
I have my local steel roofing company run the material upside down through their extruder at the prescribed length. Puts the color down, and the drainage in the proper orientation. All we need to do is provide slope.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: