furring strip over rigid insulation

[River Runner]

Looking to install a significant amount of furring strips over 2" rigid insulation. I'll probably use 2x4's on flat. Insulation is attached to CMU block that is filled every 2'. I admit I should have probably attached furring strips first then filled between with 1.5" insulation but the 2" is already up and this way I get continuous insulation. Furring strips will support the attachment of natural wood siding.

I've been looking at fastening options and its a little more costly than I expected. I can use 5" Tapcons and it will give me a 1.5" penetration into the block. Tapcons are freaking expensive.

Other option, countersink each screw hole 3/4" and use 4" screws for a 1 1/4" penetration to save some money.

Last option, use an undersize bit and hammer in a 40D nail for a 1 1/2" penetration. Concerned about strength and pullout.

Thoughts?

 

[alwaysFlOoReD]

I would use 3/4" plywood ripped to 3" and drill some holes with a 6" long concrete drill bit. Iirc 3/16" works with a double dipped 3.5" nail. If the hole is too big stuff one or two lengths of bailing wire in the hole before the nail is hammered in. Done right the nail cannot be pulled out without pulling concrete with it.

 

[PCustoms]

Somewhere there is a This Old House video that does you exact scenario.

I think they used wedge pins, but I could be butchering the name.

EDIT:

Spring spike




Fast forward to 7:15

 

[mike93lx]

Somewhere there is a This Old House video that does you exact scenario.

I think they used wedge pins, but I could be butchering the name.

EDIT:

Spring spike




Fast forward to 7:15

This is exactly what I did in my basement. Worked great

 

[River Runner]

Interesting, I’ve never heard of a spring spike. Thanks

 

[lilredex]

I used metal strips (studs) that were almost flat, but with a slightly raised "V" center section to push down between the insulation panels. Attached the drywall to these.

These:

https://www.bmp-group.com/docs/default-source/default-document-library/retainer-tee-stud.pdf?sfvrsn=2

 

[mike93lx]

I used metal strips (studs) that were almost flat, but with a slightly raised "V" center section to push down between the insulation panels. Attached the drywall to these.

These:

https://www.bmp-group.com/docs/default-source/default-document-library/retainer-tee-stud.pdf?sfvrsn=2

But you still have to attach those to the wall, which was the OP's main concern

 

[lilredex]

Didn't touch on that, because the solution is already there.....spring spikes. I would have used them too if available forty years ago. I drilled the blocks and installed inserts.

 

[Northislander]

I did 3/4 pressure treated rainscreen strips on icf foundation. Drilled hole thru strip and foam into concrete with a 6" concrete bit then pushed a piece of weedwacker line in then screwed with 5" deck screws.

 

[nadogail]

I often shoot nails with my Ram Set to attach wood to concrete walls and blocks.

 

[The Cobbler]

I question the need for 2X. can you not use 1X or even plywood ripped?

 

[billconner]

I often shoot nails with my Ram Set to attach wood to concrete walls and blocks.

Was my first thought but couldn't find 4 1/2 - 5" powder actuated fasteners. Do they exist?

 

[mike93lx]

I often shoot nails with my Ram Set to attach wood to concrete walls and blocks.

Through 2" of foam?

 

[CraigStu]

Is the rigid foam glued to the block? If so, could you glue the strips to the foam. Or even glue the siding to the foam?

 

[yeldogt]

Looking to install a significant amount of furring strips over 2" rigid insulation. I'll probably use 2x4's on flat. Insulation is attached to CMU block that is filled every 2'. I admit I should have probably attached furring strips first then filled between with 1.5" insulation but the 2" is already up and this way I get continuous insulation. Furring strips will support the attachment of natural wood siding.

I've been looking at fastening options and its a little more costly than I expected. I can use 5" Tapcons and it will give me a 1.5" penetration into the block. Tapcons are freaking expensive.

Other option, countersink each screw hole 3/4" and use 4" screws for a 1 1/4" penetration to save some money.

Last option, use an undersize bit and hammer in a 40D nail for a 1 1/2" penetration. Concerned about strength and pullout.

Thoughts?

Is this inside or out ?

How rigid is the siding?

 

[billconner]

Interesting problem. If I were doing it, I think it would be all about time. Furring would seem to have to be wood, so powder actuated fasteners and galvanized Z furring is not practical. Drilling and a fastener seem slow. Makes me think tapcons are fastest and 2x2 probably get away with 3 - maybe 4 - certainly fewer than ply or one by. Star drive 4".

 

[River Runner]

This is on the outside. I did this the non conventional way. I wanted block on the inside and to cover the block with insulation and siding on the outside. My reasons for this were that I wanted a block interior with a nice glossy paint for ease of cleaning and durability. But, I also wanted insulation and it to not look like a block building on the outside.

The siding will be 1x12 pine board and batten with a metal wainscoting on the bottom 3'. Its rough sawn from a mill (was way less money than LP or Hardi, which has also been hard to get here.) Its going to be cut a true 1"x12" and will be green so it will shrink down a bit.

This style does present some issues as its vertical siding and not lap. I know I should have an air gap so that the siding can breath.

I thought I could use powder actuated fasteners but they don't make them long enough to go through a 2x and 2" foam.

I'd like to use more than just 2" foam for insulation but adding more seems to create some challenges. My initial thought was horizontal 2x over the foam and then filling the space between the furring strips with 1.5" foam so I'd have a flat wall of foam and furring strips. This method however doesn't leave a gap behind the siding. This was going to work but I changed from a composite siding to natural wood and didn't think about the issue of not having an air gap.

I already have the 1.5" foam but I can use it for another project if needed. If I used 1" foam between the furring strips I'd have a 1/2" gap but the problem would be no vertical drainage with the horizontal furring strips. I think I might be stuck doing a grid pattern to retain drainage and be able to attach vertical siding.

I'm really good at complicating what should have been simple!

Some may say just put it on and the air gap isn't absolutely necessary. I'm not worried about my block building rotting, especially with 2 layers of foam, just that the natural wood siding would prematurely fail as moisture will get trapped between it and the foam its directly in contact with.

 

[River Runner]

The best approach I can think of is to install vertical 2x furring strips over the 2" foam every 24". My walls are filled at 24" intervals with concrete and rebar so I'd have a good anchor for the furring strips.

Then fill the space between the 2x furring strips with 1" foam leaving the 2x's protruding 1/2" past the 1" foam. Then screw 1x4 furring horizontal on the 2x furring strips so that I can attach vertical siding. This provides a 1/2" air gap and will allow drainage. Freaking ton of work but I may have designed myself into a corner.

 

[billconner]

just on board and batten - I'm using 1x10 and 1x2, and plan to install 1x10 tight together and apply preservative/sealer and let dry for at least 2-3 months. I coat all sides of battens at same time and sticker to dry.

Just a thought.

Can you ramset metal Z furring through foam and slip your second layer of foam in the Z? Maybe some glue too. Might have to screw board and batten, or use minimum Z and then screw one by furring. Vertical Z, horizontal furring, and vertical board and batten. Decent rain screen. Furring behind horizontal metal wainscoat could even be vertical.