Drilling Concrete Foundation for 3/16" Screws

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Old 10-08-15, 04:05 PM
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Drilling Concrete Foundation for 3/16" Screws

I am planning to install 2" rigid insulation on the inside of my crawl space against the 8" poured concrete foundation wall. If the surface was nice and flat I'd probably just glue the sheets on it but since it isn't I was thinking that screws with large washers would be a better approach. I ordered (200) 3/16" x 3 1/4" Tapco screws and (250) of the 1 3/4" plastic washers that are made for rigid insulation to get started. I expect the whole job will require 200-300 screws total.

Questions:

1) Am I crazy. Is drilling so many holes in concrete too much work for my purpose?

2) What type of hammer drill and bits should I buy to do the job reasonably well without spending too much?

3) Any other thoughts or comments on my project.
 
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Old 10-08-15, 04:50 PM
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For that many holes a rotary hammer might be worth the money. They (rotary hammers) are heavier than hammer drills so holding it up to drill so many holes in a wall won't be fun but the heavier hitting drill should make each hole go faster.
 
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Old 10-08-15, 05:38 PM
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How unflat is that walls? Hard to believe that it is so uneven you can't glue it. Just a few dollops (6-8 for a 4x8 sheet) of glue will hold the panel in place just fine.
 
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Old 10-08-15, 09:12 PM
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How unflat? Every 2' there are pieces of the snap ties from the forming system sticking out. I don't know if the insulation boards would press onto them and hold in place. Even if the snap ties aren't an issue there are also ribs where the wet concrete bulged through the gaps in the forms. There are also irregularities along the top of the strip footing that would make setting the boards level more of a challenge. I suppose I could elevate them a bit and fill the bottom gap with spray foam to mitigate that problem.

On the issue of drilling for the screws:
I stopped and grabbed a 5/32 masonry bit to try a few test holes with a regular drill. My 18v cordless was able to drill holes well enough that I don't think I need a very powerful hammer drill to do the job. I think I'll just start with the cordless and see how it goes.
 
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Old 10-09-15, 01:19 AM
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Hi meander,
I didn't connect the drilling to foundation insulation, until I had some time to kill, now 4 am.
Anyway, a couple of late thoughts.
1. Is the foam foil faced or exposed foam? If exposed, it may be required to have a thermal barrier over it, drywall or a special (expensive paint). Or a 1/2" layer of foil faced insulation, but all must be acceptable to your local authority.

2. From your description of the "flat" may not be that difficult. I just carried all of my foil faced foam downstairs and will be gluing it in place shortly. For those seams or any irregularities I will use a diamond cup on my grinder, although a regular grinding disc would probably do just fine. I will have the shop vac in place to catch as much dust as possible while I grind. But I placed a 4' 2x4 across the wall and it isn't that bad and as TI stated, it won't take a lot.

3. One of the objective when installing the foam against the concrete is to eliminate any air circulating behind the foam. Typically you would run a few horizontal beads of glue, bottom, middle, and top. If full wall height, then maybe a few more.

4. At the top, plan on detailing some pieces over the top edge and into the joist cavity which will be insulated in some manner.

5. Where the rim joist rests on the foundation it is a common location for lots of air leakage so be sure whatever you do it gets sealed.

I'll catch you later this morning for any follow up questions.

Bud
 
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Old 10-09-15, 01:45 AM
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bosch bulldog & sinosoidal anchoring pins are our go-to's - drill the hole & hammer 'em in but you already bought conc screws
 
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Old 10-09-15, 10:01 AM
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Bud:

1) I haven't decided for sure what type of insulation to use yet but I was leaning toward the blue board made by Dow which is unfaced XPS followed by some roll-on shiny stuff. I'm looking for a minimum of R10 and the foil faced EPS foam that the box stores sell is only rated R7.8 for 2" panels. I talked to locally owned suppliers but they wanted to treat me like I was bending over in a prison shower. I could special order from the big blue or orange box stores but the last time I did that they quoted 4 to 6 weeks and it took 11 weeks. Such is life in Alaska.

2) You might be right that grinding would be less work than drilling. I expected to do some of that anyway.

3) Good point on the air space behind the insulation. I'll try to press the boards against the wall as well as I can. I was hoping that using screws would allow me to avoid glue completely but I might want to reconsider. At least with screws I can remove the panels after they're installed and re-install them.

4&5) I concur. Sealing and insulating the rim joist is a top priority for this project.
 
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Old 10-09-15, 10:16 AM
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staydry:

I looked at the fasteners made by Rodenhouse that you hammer in. If I could get them at a good price I probably would have pulled the trigger but shipping to Alaska doubles the cost. They seem like they'd be easy to install after the hole is drilled but if I recall they require a 5/16 hole where the screws only require a 5/32 hole. If I had pro grade equipment to do the drilling it wouldn't be an issue but my homeowner grade tools seem like they might handle the 5/32 holes much better.
 

Last edited by Meanderthal; 10-09-15 at 10:49 AM.
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Old 10-09-15, 11:01 AM
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The foil on the EPS may not be heavy duty enough to meet your local codes, where as the Dow Tuff-R uses a heavier foil. Still needs the approval of local code authority. (don't I hate to keep having to say that, but all local authorities have that ability) Anyway, the 1.5" Tuff-R is about R-10 and may eliminate the need for other thermal barrier. PLUS, although they don't consider it, if you leave the foil surface exposed to the basement you add between 1 or 2 R to the value. I've seen Dow state that ?somewhere?

I opted to go with just 1" of Tuff-R at R-6.5. I believe the foil plus detailing over the top will give me a little extra, and I ran the heat loss calculations for 1" vs 1.5" and it fell way short of justifying the added cost. Foundations are so terrible for heat loss that adding anything improves it. But once you add R-7, adding another R-3 to it doesn't gain a lot. It is like a 30% reduction of an already much lower number. Not sure what your energy codes require or whether you are just looking for a reasonable job.

I intend to brace my foam against the wall with glue and "hope" it sets up in a reasonable time. I'll test the first sheet to be sure that approach is solid.

Bud
 
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Old 10-09-15, 11:31 AM
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Thanks for the input on other insulation options Bud. I'll check into them. I probably should have started another thread about the insulation because I can't seem to get good information about the types that I find here in Anchorage. I even called R-Tech to get clarification on their products but the guy on the phone who was nice and tried to be helpful just wasn't. He kept pointing me toward using their 25psi product which isn't available at home-owner friendly sellers instead of discussing the specs for their 15psi product that I see on the shelves here.

The 2" R-10 recommendation came from a nerdy energy auditor who did what appears to be a pretty thorough analysis. The same guy will be scoring my work for a State energy rebate program that could reimburse a fair chunk of the cost so I'm hesitant to deviate too far from his recommendations.
 
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Old 10-09-15, 02:36 PM
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Very familiar with the carrot approach. Down in the lower states the audit approach with a promise of savings to pay for the improvements has gotten a bad rep with over promising and the drop in energy prices. I believe AK is rather strict on who can provide an audit so what you got was probably worth it. Do your improvements have to show a specific reduction from what he projected for energy costs?

I'm surprised that your auditor recommended R-10 in AK, which is all zone 7 or 8 and IECC 2009 requires R-15 minimum. (IECC, International Energy Conservation Code) "nerdy energy auditor" we do tend to be .
https://energycode.pnl.gov/EnergyCodeReqs/?state=Alaska

Air sealing will be one area his testing will see improvements, so do as much as you can. How old is your house? What do you heat with and cost. I use oil here and currently about $2 a gallon, but hit almost $6 back when I started doing audits. I ran into people paying over $10,000 a winter for heat and others who kept their homes barely above freezing. I specialized in helping the elderly and ran into many sad situations, heat or eat??

If you want advice on other aspects of that audit I can review it.

Bud
 
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Old 10-09-15, 05:14 PM
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Thanks for the offer to review my audit Bud. If you PM me your email address I'll send it to you. It will answer several of your questions.

My house is 25 years old. I bought it in a foreclosure sale about 14 months ago. It needs some work but overall it is sound. It was built with a vented crawl space then at some point the vents were covered and a half-assed job of insulating was done which I hope to improve on.

The State of Alaska claims that their energy rebate program is a huge success, or at least they did in 2012. They say that on average participants spend about $11k and get back about $6.5k in rebates and that the break even point on the cost of those expenses is about 4 years. You can read about it here if you are interested:

Publications | the Cold Climate Housing Research Center

We have folks here who have to choose between heat or eat too, especially out of town where natural gas isn't available and they rely on heating oil. We have a whole separate program for those folks though. They can get their energy upgrade stuff for free if they have less than 60% of the median income or 100% of median income if they are elderly or have children or handicapped dependents in the home.

I didn't mean to imply that all energy auditors are nerds, just my guy. It's good though, I'm learning the things about building science that more of us should know.
 
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Old 10-09-15, 06:07 PM
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No Problem on the nerd reference, energy auditors have to be a bit nerdy to do the job.

Photo #5 in this link is a nice crawl space.
New Light in Crawlspaces | Building Science Corporation

That's a huge rebate potential. I don't even try to follow what Maine is doing as the state controls all of those funds and they have their preferred contractors. I refused to give up my independent status to work under their thumb. Besides, I'm supposed to be retired.

I'll take a look at the audit, should be interesting as AK has to do some things differently.

I glanced at that publication and added it to my reading list, thanks.

Bud
 
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Old 10-14-15, 01:53 PM
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Hi meander,
Still reading, but wanted to update with new information.
I started grinding my basement walls using a 4" diamond cup. Works great, but had to immediately STOP. Wow, way too much dust. So, I'm in the process of putting together a hood of sorts where I can attach my shop vac and run the grinder underneath. The actual grinding is easy, but I couldn't see the wall in front of me.

I'll post again once I have this working. I will also be adding an exhaust fan to the nearby basement window and running an air filter I use when cutting wood.

Bud
 
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Old 10-14-15, 07:50 PM
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Hey.. Every foam board I have seen except for Dow Thermax says that a fire rated barrier is required between the foam and the living space. Where I live that includes crawlspaces. Basically any foam on the interior of the house needs to be behind drywall or some other approved material.. I believe they require a 20 or 30 min fire rated material.

Beyond 1/2" drywall or thick enough wood I don't know what else qualifies? If something else does qualify that would be easier to install than a wall, it would help me too cause I have to do the same thing you are.
 

Last edited by flapjack56; 10-14-15 at 08:45 PM.
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Old 10-15-15, 08:01 AM
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The enforcement of fire protection requirements seems to vary quite a bit from place to place so it's probably best to ask someone with local knowledge. My understanding is that intumescent paint or a durable radiant barrier are enough fire protection for crawlspaces up here. That doesn't stop building officials from telling folks to use drywall though, after all it isn't their time or money.

I'm leaning toward using reflectix radiant barrier initially but I might upgrade it at some point.
 
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Old 10-15-15, 09:55 AM
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Just from a pure practical standpoint, if it were my house, I would install a thermal barrier. Rigid foam insulation produces toxic gasses when it burns, which will kill you.
 
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Old 10-15-15, 04:09 PM
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Regarding fire protection; there certainly doesn't seem to be a consensus as to what should be done. If it was a basement or a crawl space connected to a basement then at least an ignition barrier is in order. When it comes to stand-alone crawl spaces like mine you will find that even contractors who specialize in them routinely use rigid insulation without thermal barrier, and often without ignition barrier, radiant barrier or any facing at all. Search "crawl space encapsulation" to see what I mean.

https://www.google.com/search?q=craw...FYpbjgodtNoIyQ

Also, according to Owens Corning their Foamular products do not require any covering when used on the interior of foundation walls under certain circumstances.

From their website:

"In certain foundation applications, such as crawl spaces, the model building codes only require that foam insulation is covered with an ignition barrier. Typical ignition barriers include: mineral fiber insulation, plywood or sheet metal. These applications do not require a thermal barrier. Where a crawl space is not connected with a basement or half basement, FOAMULAR; insulation may be installed on crawl space walls without a cover material. Contact Owens Corning for model building code evaluation reports."

What I propose to do far exceeds the fire protection of some of the professional jobs shown online or the listed requirements of the XPS manufacturers.
 

Last edited by Meanderthal; 10-15-15 at 04:27 PM.
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Old 10-19-15, 01:55 PM
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A few thoughts now that I'm about 20% done:

At this point I'm glad I chose to use the screws and large washers instead of glue. I've been putting 4 screws per large piece but only one is necessary to hold a piece in place while I add the other three. Time spent drilling pilot holes is negligible in the bigger picture and there is no mess or dry time to cope with. Although I don't get the air sealing that glue would provide the screws force the insulation up tight to the wall.

The most time consuming part is the rim joist. I caulked all seams then added 4" of batting to the cavities followed by pieces of 2" rigid cut to fit tightly within each joist bay. I still need to follow up with more caulk and/or spray foam and tape.

Bud wasn't kidding when he said that grinding concrete clouds the air quickly. It works well but you can't do much of it without aggressive measures to vacuum and/or exhaust the dust.

I'm using the Owens Corning Foamular 250 insulation. Other than the fact that it is pink and costs too much I like the stuff. With my cordless jig-saw I can cut 1/4" strips of it that don't break apart easily. I suspect that the expanded foam products would just break apart if I tried to do that but I could be wrong. I pounded several pieces into place with a rubber mallet and they take the beating with minimal damage. The blue Dow stuff is probably just as good or better but it was more expensive so I went pink.
 
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Old 10-19-15, 03:09 PM
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LOL. I have tried my dust collector hood and even with that I will need the window open with an exhaust fan. Otherwise it works. My hose connection from my shop vac to the dust hood ended up with a hole half the size of the hose. I will have to change that as I need ALL of the air flow I can get.

My insulation is the 1" foil faced (both sides) polyiso and I'm trying to be careful not to puncture the foil on the concrete side. It is one inch and eventually I will add furring strips and drywall. The r-6.5 increases to R-9.3 (their numbers) with the air gap and foil surface. For now the foil will sure brighten up the place.

Bud
 
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