Screed guides over rfh moisture barrier?
I am pouring a new slab in my basement and have a few inches of gravel, an insultarp http://www.insulationsolutions.com/products/insultarp/information.html
moisture barrier, #3 rebar grid and pex tubing 12″ oc. The slab is 26′ by 43′ and I am having a professional come in and place and finish the concrete for me.
He has said he doesn’t find he can effectively screed wider than 11’3″ and suggested I divide the floor up into four sections 26′ by 10’9″. This will allow them to pull the screed board toward the daylight wall of the basement (the 43′ wall side).
He warned me that doing this will require me to drive some steel stakes through my insultarp moisture barrier to support the 2×4 guide boards. I assume this is unavoidable but am throwing the question out to see if there is a creative alternative to setting up mid slab guides without puncturing the insultarp.
The basement is on a slope and has good damproofing and drainage on the three underground walls with an underground drain to carry away whatever water does reach the exterior of the below grade walls. I don’t anticipate much standing water under the slab in the gravel bed so I am somewhat resigned to accepting around 20- 3/4″ holes penetrating my moisture barrier. I will try to see that the stakes are driven along the taped seams of the insultarp to ensure that they dont open up the interior of the insultarp to filling up with concrete.
Is there any merit in taking some three inch lengths of 3/4″ pipe and welding some sheet metal pads to the base of them, setting them on top of the insultarp and trying to drop removable steel pins into these pipes to support the hooks the screed guides rest in. My hunch is they wouldn’t be stable enough and would turn the concrete pour into a fiasco.
What do you guys do with a moisture barrier when you need to drive temporary stakes through it?
Thanks,
karl
Replies
From your link:
"Therefore, the foam insulation provides a consistent drain on the radiant system and the slab. Because of the innovative combination of insulation layers and aluminum,"
That is SO bogus.
First; the Foam insulation *never* "provides ... drain on the ... system."
Second; There is no such thing as a radiant barrior when the "radiant barrior" is in physical contact with the heat conducting material.
Third; Even if #2 was true, aluminum rapidly loses it's shineyness when in contact with cement or soil.
Check for yourself, bury a piece of aluminum foil in your garden for 24 hours and compare it to a new piece.
.
"What do you guys do with a moisture barrier when you need to drive temporary stakes through it?"
Stick 'em in. ~20 1/2" holes in 1100 sqft is nothing to worry about.
SamT
SamT is correct that the insulation in contact with the slab cannot provide a radiant barrier. IMO you are making a *MAJOR* mistake if you do not have at least R-10 XPS foam under your slab.
To answer your screed question, there is a product we call Combi-Form that you could use. It is a sheet metal V-shape that is installed in the form, with the "point" of the V pointing up and flush with top of slab. The point of the V has a thin strip of plastic about 1/8" wide by 1/2" deep along its length. It is installed on small piles of sack mix and brought to level (dryline across the slab forms). After the sack mix hardens the main pour is done and the finishers can pull their screeds along the tops of the V's. These also conveniently provide control joints as the slab shrinks. Very slick.
In the lower left of the attached photo you can see a piece of the material... it has a series of holes punched thru it. Sorry, could not find a web link, but a concrete supply house should know where to get it.
On this same pour I let them drive ~10 steel concrete stakes right thru the Stego Wrap and foam to set screed hooks, in some areas where the stemwalls are above slab.
Sam and Dave,
Thanks for the input. Anytime I research a project on the internet and then talk to my local suppliers I find the potential to get caught in a paradox of conflicting information. I used the insultarp on the suggestion of a neighbor and the well established local rfh supplier who sells mountains of the stuff.I realize you can never have too much insulation but I am in a moderate northern california coastal climate (Santa Cruz) where the temperature extremes are quite mild.Having installed it I am less than impressed with the "ease of insulation. I found myself frequently cutting open the "tarp" to straighten out the layers of foam that were bunched up on top of eachother. It was easy enough to duct tape the slits I had made but it was a big PITA.I am not especially inclined to defend insultarp but in regards to the shiny aluminum oxidizing in contact with concrete or soil: The aluminum surface is inside the "tarp" so it shouldn't ever have concrete or soil contact (unless I punch twenty stakes through it and create holes allowing concrete to seep inside the tarp).If anyone knows the Combi form "v channel" product Dave shows in his photo please pass along the name.
Karl,
Combiform is the name. Looks like it is available from WhiteCap and Muller Supply.
http://www.whitecapdirect.com/products/520C65
http://www.mullerconstructionsupply.com/pdf/MCS_110.pdf
Thanks for those links. Didn't know they had an adjusting system for it... but would be hesitant to use it over foam insulation, since we want the weight of the sack mix to keep the foam firmly on grade.
Also, looks like we use the 45 size. No need to thread the rebar, although I have seen that done on a few pours.
Panic, thanks for the link. Thank you Sam and Dave as well for the follow up posts.I shared Dave's concern about placing the combiform on top of insulation as it is a somewhat pliable surface.At this point I am leaning towards driving in some 3/4" pipe, taping the insulation around the pipe and dropping in short 3/4" pins to put the screed board hooks on. At least this way I won't be filling up the tarp sandwich with water and concrete through the stake holes.My "time saving" insultarp is becoming more and more of a disappointment.karl
"The aluminum surface is inside the "tarp" so it shouldn't ever have concrete or soil contact"OK, the aluminium will stay shiney, but that still isn't going to make that stuff a radient barrior.SamT