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Discussion Starter · #1 ·
I am starting the process of finishing the lower unfinished level of my house starting with furring out the cinderblock walls for insulation.

Below is my model of how I am thinking of building the wall based off of the RMAX specs.

RMax Install:



My design:


This is basically the same as the RMax install but with an additional stud wall and layer of RMax after the thermal break to hold plumbing and electrical.

I have a couple questions such as...

1. I don't really want to use Treated wood inside the house. Could I use something like Cedar instea for my furring strips if not also my stud wall.?

2. Does my electrical need to be in conduit inside RMax?

3. Should I connect the sections of my air gap between the cinderblock wall and the thermal break to assist air flow?

4. Do I need the secondary air gap I placed between the layers of RMax?

Any suggests or pointers on anything I am doing wrong or would be better off doing a different way are much appreciated.
 

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I don't really want to use Treated wood inside the house. Could I use something like Cedar instea for my furring strips if not also my stud wall.?

Just use doug fir and use sill insulation behind it. Actually works better. Since water will still wick through pressure treated lumber by capillary action

2. Does my electrical need to be in conduit inside RMax?
No


3. Should I connect the sections of my air gap between the cinderblock wall and the thermal break to assist air flow?
The air gap is to vent any moisture trapped behind the wall. It should be continuous from the floor to the ceiling joist bays

4. Do I need the secondary air gap I placed between the layers of RMax?

no

Any suggests or pointers on anything I am doing wrong or would be better off doing a different way are much appreciated.

The best way to frame a basement wall is to leave the framing 1" away from the wall. Now spray foam 2" closed cell foam behind and between the studs. Now you have a stronger wall that will not have a moisture problem internally.
 

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Fire-block the floor joist cavities above from the walls below and walls every 10', per minimum code; http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec002_par031.htm

You don't want any air to the concrete wall/foam board; http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

Foam board directly attached to the block, no air gap, or gap at insulations for c.l.'s; http://joneakes.com/jons-fixit-database/743

Don't use a poly-faced or foil-faced board as R-max; http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements?full_view=1

Air-seal/canned foam the rims first; http://www.buildingscience.com/documents/information-sheets/critical-seal-spray-foam-at-rim-joist/

Air-seal the drywall; http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/

Where are you located for thickness of foam?

Gary
 

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I have done a number of basements using XPS(extruded polystryene) foam, glued to the walls, then furring strips over the foam, with tapcons into the block. That holds the foam tight and provides for hanging drywall. 2" XPS=R-10. Moisture won't penetrate the XPS, and since the wood does not touch the block, no need for PT.
 

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Discussion Starter · #6 ·
@Gary for all that info!

Thanks for the replies I had a couple more questions:

1. Is Foamular 150 a suitable XPS rigid foam to use for this application? Is there any issue with double layering it, say two sheets of 2" giving me R-20?

2. What material do I use for a capillary break under my framed wall?

3. Is this wall paint an issue?


4. My rim joist are non typical / non existent? (The cinder block turns into some type of decorative block that goes all the way up:


5.Can I continue the rigid foam all the way to the subfloor? How do I fire block this correctly?


Thanks for all the help!
 

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The Foamular 150 is fine.

A poly sill sealer will act as a thermal/capillary/air break under a cedar sill plate. The warmed wall (with a sealer) won’t cause the slab (touching earth) to act as a “heat sink”. It will stop any moisture coming up to wet your wall studs; http://www.greenbuildingadvisor.com...ressure-treated-sill-plates-and-building-code And it will seal the gap under the wall from basement air reaching/condensing on the colder concrete block wall behind the foamboard (if not 100% sealed). Tape the board seams, canned foam the bottom and joints abutting the fire-stopping studs/material every 10’ lineally. Two layers of board are fine. The top plates of the wall (and the foam board) need to stop any wall cavity fire from reaching the floor cavities above. Best: http://www.diychatroom.com/f98/how-fireblock-framing-37190/

The paint may not be an issue, be sure all outside drainage is proper. Earth sloped away from house, down-spouts extended, etc.
http://www.lowes.com/pd_13280-46086-108942_4294858107__?productId=3363030&Ns=p_product_prd_lis_ord_nbr|0||p_product_qty_sales_dollar|1&pl=1&currentURL=%2Fpl_Insulation%2BAccessories_4294858107__%3FNs%3Dp_product_prd_lis_ord_nbr|0||p_product_qty_sales_dollar|1&facetInfo=

Cedar will substitute, check with your local building department, need the permit for H.O. Insurance paper trail, anyway. “Naturally durable wood”: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec017.htm

Cedar fits: “NATURALLY DURABLE WOOD. The heartwood of the following species with the exception that an occasional piece with corner sapwood is permitted if 90 percent or more of the width of each side on which it occurs is heartwood.
Decay resistant. Redwood, cedar, black locust and black walnut.
“ from: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_2_sec002.htm

On top the foamboard: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec002_par032.htm


Gary
 

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Discussion Starter · #8 ·
Gary thanks for all the help.

I have read over pretty much all of that and understand the how and why. I am currently test gluing a piece of Foamular to my painted wall. The glue says it is not recommended for walls with paint but it seems to be holding ok.

The only think I am not exactly clear on is the fireblocking method.

I have read through the very good post on here and made another diagram..

Which of these ways do I need to install to properly fireblock? (I also posted this is the fireblocking thread)

Do I need to block the top of the foam board as I have done on the left?

 

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The left side is correct, blocking the wall cavities from the above floor/ceiling cavities in case an outlet shorts/sparks to start a fire. This would limit it to the 10' wide section of wall only.

I would slip some Grace I&W shield behind the joist ends, if not tight to the block for a capillary break there, bigger gap-use sill sealer. You need a stud with Grace on the edge, every 10', sistered next to a layout stud for wall fire-stop. Use sill sealer between the studs for thermal break as the f.s. one is touching cold blocks-through the membrane (heat-sink). Foam board installs between the vertical sistered studs. Notch longer studs or add small wood pieces with Grace at the plate areas to fire-stop.

Gary
 

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Discussion Starter · #10 · (Edited)
Thanks again Gary,

The left side is correct, blocking the wall cavities from the above floor/ceiling cavities in case an outlet shorts/sparks to start a fire. This would limit it to the 10' wide section of wall only.
Does this mean I only have to fireblock once every 10'? Wouldn't it be best to put a fireblock in every joist space?


I would slip some Grace I&W shield behind the joist ends, if not tight to the block for a capillary break there, bigger gap-use sill sealer.
What is Grace I&W? I don't think I can access the joist ends. But I will take a look at it.

You need a stud with Grace on the edge, every 10', sistered next to a layout stud for wall fire-stop. Use sill sealer between the studs for thermal break as the f.s. one is touching cold blocks-through the membrane (heat-sink).
If I am reading this correctly. I want a double stud every 10' horizontally to act as a horizontal fire stop incase a potential fire moved horizontally between studs? Or are you referring to the top plate area?

Foam board installs between the vertical sistered studs.
This would be a sandwich of my Foamular and two studs then?

Notch longer studs or add small wood pieces with Grace at the plate areas to fire-stop.
 

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Fire-block top continuously.

F.b. studs every 10' apart. Foam board between them. The stud f.b.(from wall stud to CBU - no foam for a sandwitch) has to stop fire between cavities. F.b. is not fire-block, only: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec002_par032.htm

http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec002_par033.htm

http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec002_par034.htm

I don't recommend putting fiberglass or mineral wool directly on wet blocks for fire-stopping, hence the extra stud every 10' across the length of the wall.

If I am reading this correctly. I want a double stud every 10' horizontally to act as a horizontal fire stop incase a potential fire moved horizontally between studs?---- correct.

You cannot have foamboard between the f.s. stud and the CMU. It could melt and lose the integrity of the 10' section of wall.

Grace I&W is a stick poly/bitumen coated weather seal material, any window/door sticky wrap will work.

Gary
 

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Discussion Starter · #13 ·
You cannot have foamboard between the f.s. stud and the CMU. It could melt and lose the integrity of the 10' section of wall.
So I need to interrupt my Foamular thermal barrier every 10' with a horizontal fireblock stud? Won't this create a thermal bridge to my framed wall?
 

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Correct. The 1-1/2" wide stud edge with the sticky wrap will create a thermal break. To offset it from acting as a heat sink (warming the studs with conditioned air transferring by conduction to the CMU), by sill sealer between the fire-stop stud side and the regular stud side. The 1-1/2" will be a thermal short in the foamboard, ask your Inspector if it can be installed continuously, as Formular with sleeper wood at the 2' joints.

Gary
 

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Discussion Starter · #15 ·
Alright,

Thanks for all the help I will talk to the city now that I know how it should be done and see exactly what they require!

Thanks again.
 
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