Attaching furring strips to concrete block walls

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Old 10-16-12, 09:51 AM
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Attaching furring strips to concrete block walls

I need to attach some furring strips to concrete block walls and am running into several issues.

On one wall, the concrete exterior wall is not plumb. The top of the wall is over 1" inward from the bottom of the wall. The good news is that it seems to be uniformly over the entire length of that wall (12' long). I thought about ripping 12' long pieces of incrementally thicker strips and attach them horizontally to the wall first, then attach the vertical strips over that, but due to various copper pipes and electrical conduits I could not do that. So seems like I have to individually shim each vertical strip from bottom to top. Is there any issue with shimming so much? On top I would have to shim out a whole inch when the strip itself is only 3/4" (1" thick nominal)?

What is the best way to attach these strips to the wall? I am planning on using Tapcons. I don't have any powder actuated tools, and looking at some of the anchors most of them have a protruding head - I need something flushed with the strip to attach Durock or sheetrock over. Will using adhesives in addition to Tapcon result in a better connection?

When I do get to the point of attaching sheetrock, I am a bit confused as to the type of fasteners I should use. Most contractors I am getting bids from said to use standard drywall screws, they have been "doing it for 10, 20, 30, 40 years" and "never had problems". However, reading up on the subject I am seeing warning about using standard drywall screws on PT lumber as they will just "rot out in no time". OK since I am using all PT lumber for bottom plates (where it meets the concrete slab), and all furring strips over concrete walls, shouldn't I be using deck screws along the bottom of all interior walls, and over all exterior walls? I mentioned this to 4 drywall contractors I got bids from and ALL of them said "NONSENSE" this is not necessary and totally over the top.

Now, when I started on my remodeling, I have ripped out many existing sheetrock and they were attached to the PT furring strips using standard drywall screws thats over 40 years old. They don't show signs of corrosion. I then read that "OLD" PT lumber is not treated like they do now. Can someone shed some light on this subject? Do I or do I not need to worry about what screws to use depending on the type of lumber behind the wallboard?
 
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Old 10-16-12, 10:07 AM
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Have you considered just framing that wall in the traditional way with 2X3? Several advantages, it will save a lot of drilling for Tapcons and shimming, you will have depth for electrical boxes and other wiring and insulation. As far as rusting screws goes, if the area is that wet you will have bigger problems than rusting screws.
 
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Old 10-16-12, 10:07 AM
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Yep, new PT wood is treated differently and you need screws designed for contact with ACQ treated wood.

As to your first question, it's a little hard to tell by description but others may be able to discern, I would request pictures but guys like Chandler and XSleeper may not need them to help you.
 
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Old 10-16-12, 10:31 AM
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Toolmon, I wasn't referring to wetness from some plumbing leaks. The corrosion I refer to are from the chemicals in the PT lumber. One such article is here.

http://www.aces.edu/poultryventilati...5ACQLumber.pdf

I guess the problem is contractors in the field are either not aware of this or don't believe it? So I am doing a check here to make sure either I am over thinking this or they are being ignorant and haven't kept up.
 
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Old 10-16-12, 10:45 AM
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I was completely unaware of corrosion issues on new PT lumber. In fact, I didn't know the PT process had changed. You learn something every day.
 
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Old 10-16-12, 11:01 AM
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The fastener corrosion issue has been discussed here in various threads many times. Initially the recommendation was that only stainless screws be used in the new ACQ treated PT wood. That changed to allow use of galvanized fasteners. Probably as a reaction to the screams of contractors over the price of SS fasteners.
You can purchase 410 SS Tapcon screws. They are pricier than the steel version. However, I think the regular blue tapcon's are acceptable for use with ACQ treated lumber.

I am curious why you don't just frame the basement traditionally and not have to worry about the foundation walls being out of plumb.
 
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Old 10-16-12, 12:01 PM
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Wayne, this is not a basement. I am located in South Florida so no basement here. This is a bathroom with exterior walls on three sides. I don't want to use traditional framing there because I would lose too much room.

But the question is not restricted to the bathroom. As I stated, I used PT 2x4 or 2x6 for all bottom plates on interior walls since they have contact with the floor slab. That means the contractors would have to use special screws along the bottom of all new interior walls. When I asked the drywall contractors to give me a bid and I demanded special and appropriate fasteners to be used on bottom plates and all PT furrings, they all laughed and thought I was nuts...

I basically have four situations.

(1) Bottom plates - new PT lumber.
(2) Exterior wall furring strips - new PT lumber.
(3) Existing wall furring strips - old PT lumber that is OK to use normal drywall screws.
(4) Normal interior walls studs and top plates - non PT lumber.

Note that I am not asking what fasteners to use to connect the strips to the concrete as far as corrosion is concerned, I am asking what to use when connecting sheet rock to those wood later on. Sorry for the confusion.
 
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Old 10-16-12, 03:41 PM
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Unless your furring strips are at least 3/4 deep, your sheetrock screws will tend to bottom out. Your converging wall creates it's own problem as the thinnest you could use would be 3/4", and step up from there to bring it all into plumb. I am not a fan of poking holes in a perfectly good, otherwise non leaking wall, but I understand you are in Miami, and no basement. I would use PL Advanced adhesive on the furring strips with tapcons.
Use exterior grade screws to go into the pt lumber if you like to forestall possible corrosion issues, rather than sheetrock screws.
 
 

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