UBC & Block+Furring+Sheetrock?


Old 03-25-03, 01:27 PM
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UBC & Block+Furring+Sheetrock?

I'm planning to install 1x furring strips to the inside of my plaster-covered, cement block walls and on top of that mount a 3/4" sheet of rigid insulation and a 1/2" layer of sheetrock. Most of the walls in question are above crawlspace, so the subflooring is made of wood and the only code relevant to me is the '97 UBC. Also it should be noted that I am in the desert, where we get an average of 9.32" of rain, a year.

This is part of a major renovation and though I realize that I can ask at the town hall; Thus far, I haven't always gotten a "correct" answer from the person who answers the phone and because I'll be applying for a homeowner's electrical and plumbing license when I get my permit; I'd prefer to have as many bases covered and my plans most of the way, code-compliant before I walk in the door.

With that said, I have a few code(ish) questions, if you would be so kind... My list may appear daunting, I'm thinking that several of my questions may be easy to combine into a shorter response; Though, I'll welcome any answer in whatever form to any part of this query...

1) It appears from looking at an older copy of the code that I have the option of installing the furring strips, either 16" or 24" oc and because I will be mounting the sheetrock/foam with screws, my screw-spacing should be at least 16" if I go with the 16"oc studs, or 12" if I decide upon 24" oc; First of all, am I reading/understanding this correctly and because my 50+ year old walls are rock solid are there any opinions as to which spacing, I should choose?

2) I am a bit confused as to whether or not I should use pressure-treated or moisture-resistant wood; I can find in the code book that if I were actually framing a wall from scratch and if I was installing on cement floor, I would need to put pt along the bottom. But I'm primarily installing above a wooden floor and there would be no sill plate(?) because of my use of furring; Does anyone know, whether or not the national code calls for moisture-resistant furring or a vapor barrier between the furring and the plaster-covered block?

3) As I mentioned earlier, I have found spacing requirement for fastening the sheetrock to the furring, but I can find no code as to what kind of spacing might be required for the tapcons, I will use to fasten the furring to the walls; Is there any code on this, or does anybody have any suggestions as to what would give me the best hold? Minus code, I am thinking of putting them 24" oc; Any opinions? And are there any suggestions as to the length of tapcon, I should purchase for this project? I assume that the block in my plaster and stucco-covered wall is the same as was used to construct the wall which surrounds my property; Or at least, I see no reason not to assume as much... These hollow-core blocks have 1 1/2" of cement as the "frame" and once again, I will be using the tapcons to put a 1x (3/4) over them.

4) Also, I started sounding this project-out with the idea of using 1x2's, but as I got into the electrical stuff and sounded some of my other thoughts out in other forums; People kept assuming that I'll be using a 1x4; Is there any argument, other than having more room to work that I should consider when I'm selecting the strip size? What would you recommend or what is code?

4) And finally (for this post, anyway ); I am going to need to run emt conduit in the void between the foambard and the block on some of these walls; This was worked-out in the electrical forum, so it meets their code; But, if I wanted to run the conduit horizontally, it would be a lot easier, if I were to cut the furring so that there is an actual gap just large enough for the emt; Once again, because I didn't find a lot of relevant code on my last trip to the library; Does this sound like it might pass inspection and/or would it be up to the ahj whether or not he passes it? Or is there a specific thing in code that would forbid these 3/4" gaps for electrical?

I apologize for the length, but most anyone will tell you that I'm pretty intent on communicating as much about my situation/questions as I can in my initial posts on a subject and that my follow-ups do actually get shorter and shorter; But I guess, no one would ever accuse me of being a man of few words;

Thanks in Advance;

Last edited by magister; 03-25-03 at 02:35 PM.
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Old 03-25-03, 06:55 PM
awesomedell's Avatar
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Hello magister,

Like to type do ya?! LOL

If I was doing this, I'd attach my 1"x3"/4"s on 16" centers, using a hilti, or similiar masonry fastener. It's alot quicker than tapcon if you can get your hands on one.

Don't think there'd be any reason to use pressure treated furring, only place I ever use it is for sill plates.

Driest climate I've ever built in was central Colo along the front range back in the '80's, there we installed poly as a moisture barrier behind framed walls in basements, (split-levels really not a genuine basement.) Not sure how necessary it is in the desert. I'd check with some local builders for a more regional perspective.

Go ahead & run your conduit horizontal, the small gaps in the furring won't present any problem, just remember where they're at so you don't shoot a screw through that new wiring, that'll really tick ya off!

I think that about covers it, let me know if I missed anything or if you run into any more ??'s Good luck.
Old 03-25-03, 11:36 PM
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1) You, also are recommending that I step-up at least to a 1x3 furring strip at a 78% increase in cost? And, because I'd be going with a wider strip and probably wouldn't be able to get by with just a single line of fasteners; Do you recommend that I stagger the fasteners or install them in parallel?

2) You also suggest that I install the strips, 16"oc and fasten my sheetrock with screws spaced equal to or less than 16", apart? (Table 25-G)

3) When you recommend a Hilti; I interpret that to mean the "Hilti Powder Activated Fastening System" which understandably would be easier than pre-drilling holes; Unfortunately, according to their website, it's more than three hours in the wrong direction to an authorized rental center and the lowest-priced unit that I can find, offhand to purchase is around $200.

To be honest, back when I was thinking Tapcon, I was torn between buying a hammerdrill or renting one (1/2" @ $27/day or $45/day for the larger one); So, I'm not married to it, either. Are there any other manufacturers who make a powder-accentuated nailer, or something similar that might be lower-priced for a homeowner who is simply going to furr-out one part of the house, then furr-out the remainder next year and who has a remote possibility that he'd be able to use it a third time, when he is working on the slab in the "other" part of the house?

4) If I can find an affordable powder-nailer that I'll be able to justify in my own head or possibly, if the closest rental yard (50 miles up the road) has an off-brand; How far apart do you recommend, I put the nails that will secure the furring to the wall? And, if I go back to pre-drilling and using tapcons or another screw, you or someone might suggest; How far apart do you think I may be able to get by and still have a secure fasten that I'll never have to think about, again?

Thanks Again;
Old 03-26-03, 04:40 AM
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Just never seen anyone use 1"x2"'s for furring, but I suppose they would work. Either way you go I'd stagger my fastners.

Yeah remington, and a few others make powder charged nailers. $200 is about right for a hilti new. I bought my many moons ago at a pawn shop for about $75-$80. Actually I find a lot of good buys on tools at pawn shops, especially in the winter.

I'm assuming you're planning on puttin up regular 1/2" sheetrock, which is why I recommended the 16" centers. Now if you're going with either 5/8" rock or 1/2" Class C fireguard rock go for the 24" centers, that stuff is alot stiffer than the regular 1/2" Actually I've seen folks put up 1/2" regular rock over 24" centers, but there's alot of flex between nailers IMO

I've drilled for tapcons with my 18v cordless drill, just need to have a good quality masonry bit in it. The better the bit, the easier the drillin. Good ones are gonna run ya like $12-$20, but that is cheaper than buying a new drill.

Ok gotta get myself dressed and headed for work, 2 coffin ceilings and a 20 ft vault on the agenda today, so gotta have time for my wheaties.
Old 03-26-03, 11:52 AM
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i've read a lot of awesome dells answers and i can tell you he puts out a lot of really good advice and is well worth listening to. and you gotta like a guy who enjoys a beer after he's done. i don't know anything about hilti's. but 10 years ago i bought a hammerdrill because renting one would have cost me half as much as buying one. thought that if i ever used it again i would break even on cost and have a hammerdrill to show for it. came in so handy on so many projects that it's almost worn out now. all the basement work my friends and i have done for each other we buy 2x4's and split them. figure out where the wiring goes, drill hole twice as big as the conduit dead center in the 2x4 and run it through the table saw. we use 2x2's because a normal electrical box will fit flush to the new wall then. also gives us more insulation which is welcome here in minnesota. we attached them with 5 tapcons per stud, 16" oc. none of us has ever had a problem. i position the stud, drill a hole through it and the concrete and my buddy puts the screw in. reasonably fast and simple.
as for the rest of your questions, sounds like you are getting a permit to do the work. to me that means an inspection when you're done. since building codes vary so much from city to city and state to state, i would tell you to go find your local building inspector and get the answers from him before you even start. the word on our local building inspector is if you have to deal with him get him involved early. pretty decent to work with then. a real terror otherwise. know of one guy that had to tear down his deck because it was 6" too long for instance.
hope this helps.
good luck!
Old 03-26-03, 03:42 PM
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Dick; I also have read a lot of Awesome's advice and that's why I'm seeking it out; But, I apppreciate your input and the advice of any others, because as you imply, the view of a DIYer might not be the same as a professional (who I'm sure couldn't imagine drilling lotsa little holes, day-in and day-out, he'd never get done...)

I'm also kinda with you on the hammerdrill, it's a tough choice; I did call the "local" rental yard and they have a strip-loading Ramset brand for $25 a day, so I'm looking into that aspect of the awesome advice (opinions?). But, because I'm apparently going to need a drill to repair the block wall which surrounds my property, plus punch a couple of holes in it; I'm thinking that it might not hurt to upgrade from my corded 1/3 hp handheld. She's been good to me and there's nothing wrong with her, but I'm also just learning about the different tools and such...

As for the inspection; Yes, I'm getting a permit and an inspection; Basically, I'm doing a multi-year, top to bottom upgrade to the fixer-upper we bought and I'm not only trying to plan-out as much as I can do under a single permit to save money, but I'm also going to take advantage of those 10%-off coupons from the box stores, so I'm trying to put together a couple of lists in hopes that I can buy 95% of everything on two receipts.

I am putting together a list of questions for the building department, but so far, because they don't build much of anything around here and for a few other "special" reasons; Half the time when I call with a quick inquiry, I've gotten an answer that was later contradicted, one time within the same phone call. So my master plan is that because there aren't any relevant additions to the national code which I can find, I figure I'll put everything to code as much as I can tell or gather, submit my plans for the plancheck and then make any changes, they may require.

And, if I weren't putting wiring in the void between the foam and the block, I probably wouldn't worry about doing the wall to code; But since the all-purpose inspector will be coming-out and looking at the switches, I need the furring to meet his requirements.

As to the electrical; It appears from my calcs and according to the advice that I got in the appropriate forum which caused me to do those calcs; A 4x metal box, screwed flat to the block has a depth of 2" which is what I should end-up with, when all is said and done.

Several folks have also pointed-out the electrical aspect and that's why we worked pretty hard to come-up with a fix in the electrical forum; Basically, I'd prefer not to lose the extra 3/4" on some walls because my home is comprised of numerous offsets and some rooms have three block walls (including the kitchen), so if you add-up all of those 3/4", they wouldn't add-up to much in some rooms, but in others it just seems like a lot...

So, now with all that said; Is there any Awesome advice or input from others, as I weigh my alternatives and keep researching the uses of these tolls and my various options. (BTW: I am really almost finished with this "master plan"; WhoooWhoo; I got a couple of odds and ends to finalize, but I"m primarily down to trying to figure-out questions like, how far apart I can space the screws and a few logistical questions about how something might be easier or preferred by future homeowners)

BTW: After thinking about it and weighing the advice I have received in this thread; I figure that I could probably stagger the screws/nails, sixteen inches apart, so that I'll end-up with three fasteners on each side of a 1x3 and hold them in place for fastening with glue; Of course, I'd love to reduce my costs by going back to a 1x2, but a few people whom I put stock in their opinions have either, suggested bumping-up the size or during a search, I discovered a post I found where they say they used to use 1x2, but they don't any longer.

I guess a 1x3 would be more "fixed" and it would be easier to hit the mark, but being so cheap that I squeak; I'd really love to reduce the price of my "studs" and go with a single line of fasteners; But I also want the thing to never move and though my walls are rock solid, I'm the newbie to the field.

Any opinions, suggestions or experiences about any of this from anyone? Any additional Awesome advice?

Old 03-27-03, 08:56 PM
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Since you're working on a permit, best thing to do is not call their office, go there, first thing 7:30 am & meet the inspector. Get his insights on common mistakes for this sort of project for a DIYer, & make your plans accordingly. Getting on the right side of those folks is crucial to how your long term project will play out. I've been in construction alot of yrs, trust me on this one.

You're right, I couldn't imagine charging a customer $50 an hour to drill a 1000 little holes. That being said, if you decide to go the rental route, I'd opt for the ramset over the hammerdrill for this particular project, but from the description of your drill, I'd say it's time for an upgrade anyway, especially since you're on the beginning end of a rather long term project. If you go with the ramjet, be sure to ask in advance how many fastners (if any) come with a day's rental. Don't want any nasty surprises at the check out.
Old 03-27-03, 09:07 PM
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Try this thought and bear in mind this is designed for much colder climate but check with your local inspectors as to what they do in yoru area...

"I guess this is the best and most economical way to construct walls that would be placed on the exterior. I prefer to see 2x4 but as mentioned by others they can get 2x3's. You still need that W/T plate. Doing the framing 16" O.C. provides a solid base for your 1/2" drywall. If using traditional framing method, frame your new wall 1" from the vertical block/masonry surface if using R-13. The reason to keep the wood out from the walls is the moisture that could damage them. If using insulation like R-19 and only 2x4 studs, the insulation would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I have recommended hanging a vapor barrier between the back of the wall and masonry surface. This doesn't allow for the insulation to touch the wall and air movement is not restricted but at least you won't create damage to the insulation or wood. If you do want to increase the R value, move the wall out further or use the R-13 and then apply a rigid insulation over the studs (warm side) then drywall (not paneling) *Code advises a 15 minute fire rated material over any rigid insulation - 1/2" Drywall*..

Kraft Faced insulation is fine to use in the above scenario. No need for the poly and you can do everything easily. You may find this easier and I would do this versus unfaced and vapor barrier because I don't like to play with it any more than I have to.

Let me add one other thing, rigid insulation used on a concrete/masonry surface is fine. Considerations to make in using this is;

1. If you are just using 1 1/2" rigid and furring strips - A. You need W/T strips to protect the wood. B. The strips can be adhesively applied but they must be solid - mechanical anchors may have to be used to insure that if shelving is installed it will hold. Problem with this is, the penetration into a sealed concrete/masonry surface is damaged and subject to leaking. C. Any electrical boxes will have to be shallow - sometimes makes it hard to wire. D. You must use a fire retardant material over this as per Code.

(Most books, articles about rigid and furring strips fail to say anything about the use of W/T and this will get destroyed and be a good source for mold/mildew with the slightest hint of moisture)

2. Alternative which does add cost is to apply full rigid sheets to the concrete/masonry walls, adhesively applied, then place frame wall against the rigid, then insulate between studs and cover with drywall. The Rigid insulation does then act as a the vapor barrier. Do not tape/seal the seams. This allows it to breath and dry up any condensation that may form.

So here is some more stuff....

1. Vapor barrier should be placed directly under the drywall. The warm inside air containing water vapor can get past the wall finish and insulation and condense inside the colder wall cavity. If enough of this happens, and the water cannot escape, wood rot, mold, and other moisture-related problems are likely to occur. For this reason, building codes often require installing a vapor diffusion retarder on the warmest side of the wall cavity. This is what is required in Minnesota;

"A 4 mill poly vapor barrier must be placed against all concrete or block exterior foundation walls prior to applying furring strips for full height of the wall. Another 4 mill poly vapor barrier must be placed over furring strips and insulation prior to covering with finish materials. (State Energy Code Requirement)" - MINNESOTA CODE


2. W/T is wood treated. International Residential Building Code says "it must be used whenever wood is in contact with concrete and/or masonry". Check it out with your local inspector. This would also include furring strips applied directly to a vertical block wall unless you use the vapor barrier behind it.

3. If you are considering using 2x2's as furring strips I can only give you my 2 cents worth and you decide.
A. Are you going to have electrical in the walls? Short depth boxes make it difficult to wire. 2x4's would be better. B. Are you planning or foresee hanging shelves or cabinets on the exterior walls? Not alot of strength and may be subject to splitting easier than 2x4's.
C. I personally can't seen how 2" will make a difference in conserving space when you consider the hassle of doing electrical or other carpentry issues.
D. Depending on what you are talking about when it comes to the pre-cut polystyrene, the white foam board, which is the molded expanded polystyrene (MEPS) only is available in R-2 - 3/4" thick, it only costs about $5 per 32 SF. The better quality with R-7.5 is the pink foam - extruded expanded polystyrene (XEPS). This is great stuff but costs more.

Just a note, when you use NON-W/T stock as the 2x2's or 1x3's as furring strips, you have to place a vapor barrier between that and the block wall - you have to attached the furring strips to wall somehow, right? You can't adhesively apply them, you have to use a ramset - this obviously has drawbacks...you just put a hole through the poly making it useless which in turn starts the problem with moisture touching the wood. Second, is if you used W/T or Non-W/T stock and have a waterproofing sealer on your block walls, you just penetrated the block, puncturing the seal coating that was suppose to stop water/moisture...creating possibly a worse problem....water that fills the concrete block cores starts to drain out or will leak in heavy rains. Just thought I'd bring this up. I would do 2x4 walls with R-11 or R-13, insulation would cost about $.02-$.03 more per square foot than the white foam and be better all around. Leave the walls out 1" from the block when framing, apply your poly over the studs apply the drywall and be done. You'll have no problems then.

Food for thought....
Old 03-27-03, 09:58 PM
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Thanks for all your help, dude(s)! I'm going up to the rental yard this weekend (50 miles, each way) and I'll take a look at what they've got; The ramset certainly seems a lot easier...

Thanks Again;

Archive Info
The various threads which helped develop my plan of action are all linked from
the following discussion which also contains climatic data specific to my locality;

Last edited by magister; 03-28-03 at 12:04 AM.
Old 03-29-03, 09:18 PM
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Good luck.

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