In terms of fastening sill plates to a 4" slab with 1/2" pex running through it (PEX is stapled to XPS, so it should be on the bottom of the slab)- Most of the walls are partition walls, although some are build in line with existing support posts (thus they may be assisting with some load bearing....?) My plan was to use a sill gasket between my PT sill plates and the slab. As far as fastening them, I have been advised on one hand to use concrete fasteners (such as tap-con screws 1" deep), as the PEX is still theoretically another 2 inches below. Others suggest avoiding the risk and simply using construction adhesive, and assuming tying in the top plates to joists above are good enough. (now would you glue the sill plate down, then glue the sill onto that???) - also what adhesive may work best for this application. I figured I may go by general consensus and respect the experience and thoughts of the individuals on this forum. Thanks in advance.

you will want some sheer even if minimal to prevent bottom plate movement.
I have used successfully used products like red head 1/4 in. x 2-1/2 in. Split Anchor combined with liquid nails.
Minimal depth in slab but sheer, the glue will do the rest.
This will lock the plates in place while glue drys, then come back and finish framing.
Dan

I would be surprised if a building inspector passes you without some form of mechanical shear, particularly if the wall is load bearing. The issue with glue and concrete is guaranteeing the longevity of the glue bond when it may be exposed to moisture passing thru the concrete from below. I do not think there is any way to glue something to the concrete with a sill gasket sandwiched in there anyway, as the gasket will be the weak link in the middle of the union. What exactly is the building type? Is this a basement? Slab on grade main floor? If it is a SOG and these are load walls, there may be some uplift restraint required also? Those anchors should have been embedded in the pour though.

Well if the slab has not been poured yet, you could carefully layout the tubing to avoid the areas where the walls need to be anchored. But as a caution, flowing concrete has a lot of energy, there is no guarantee that the tubes stayed where they were stapled to the foam...

If the slab has already been poured, you could put some heat into the tubing with a water heater and a circ pump and try and determine the tube locations. There are two basic ways to do this. The first is with an IR thermometer moving across the surface looking for the warmer areas, which should correlate to tube locations. The second basic way is to spray a thin mist of water onto the concrete, then turn on the heated water flow thru the tubing. The water should evaporate first from the warmest areas of concrete which should be over the top of the tubes giving you a short lived visual representation of the tube layout until the rest of the water evaporates.

The high tech way is to get someone in there with a thermograph to visually look for the warm areas over the tubes to see the tube layout... At any rate mark the warm lines and don't drill there for your Tapcons or Titen anchors

Project:
Finishing a walk out basement in an existing structure, current basement is dirt - slab on grade to be poured.

I have yet to lay our the tubing on the foam, so I can take a picture and make markings to locate loops, although some of the walls by the perimeter where the coils are making their turns back will not have much spacing near the pex.

I can do your recommended 'locator' strategies to assist with avoiding the pex as well - as I have an IR thermometer.

I figure tapcons seem to require the least amount of depth, and was leaning towards them, in addition to adhesive. (4" slab, I think the plan was 2.75" tapcons which would mean 1.25" depth of the screws and a drill hole depth of 1.75" - so they would be fairly shallow if the pex depth is 3.25" down ideally). Although I guess 2.5" split anchors would work as well.... looks like they rely on expansion versus threads.

Figure 2 anchors per 8' sill?

Hilti powder actuated fasteners or 1/4" Tap-Cons (blue concrete screws) ~2-3/4" long (gives 1-1/4" penetration into the concrete) along with F26 or PL Premium construction adhesive would be my recommendation. The Hilti is faster, but there would likely be more upfront costs to buy the tool if you don't already have one (might be able to pick one up cheap on ebay). This assumes that you already have a drill for concrete and an impact driver for the screws.

I would think that even a $200 Seek thermal camera would show a heated tube that had popped up closer to the surface.

Well if you havn't poured yet, that is easier. Layout the wall locations on the foam and don't route tube there... You can add small spikes/stakes between wall locations and adjacent pex runs to insure the tube dosn't migrate while the concrete is flowing and being raked smooth. They can be pulled after the concrete is poured before finishing.

If you do have to run under a wall location, note these locations from above pour structure/walls very carefully. One way is to pull a tape between two marked spots on the existing basement walls Write the distances from the wall on the foam adjacent to the tube, or leave the pulled tape measure in place then take pics(leave marks on the wall so you know where to measure from after the pour). You can also add small spikes on either side of the tubes to keep them at the marked location untill the concrete stops flowing. Doing this, the only way the tube at the spike locations should move, if at all, is up.

As for anchor spacing, 6 FT O.C. Should be fine with anchors placed within a few inches of the end of each individual piece. For the 8' exmple you mentioned above, I would use 3 anchors at 6", 4' and 7'6". Three has the advantage of alowing you to tru up the pressure treated sill/footer to your chalk lines. That middle anchor also helps hold them their as the PT wood tends to change shape as it's moisture content stableizes. For short wall sections 3'-4' and less, I would probably only use the 2 anchors 6" from each end, and only use a third if I need to pull the board straight...

Thanks for the very detailed specifics, ronmar. As far as trying to modify my tubing to avoid where the walls will be, I just don't know how feasible that will be (maybe for some walls, but not all). Its a 25x25 square with partition walls, and my pex layout was not going to zone individual rooms, but just keep it simple. However, it will be very easy to calculate where my fasteners will be, and assure tubing avoids those areas.

As I will be stapling the pex to the foam, would it be just as stable to use extra staples near walls to assure the PEX is not moving? Granted, perhaps there could be some slight movement laterally if the entire foam panel moves, however since it is wall to wall, it would be a matter of an inch or two. I know ronmar mentions tubes may move

There are existing loadbearing posts, which the partition walls will be aligned, that will make it very easy to calculate and measure the locations of walls, staples, and where fasteners will be.

My only conflict I can think of abstractly, is at the perimeter walls. Concrete will run out against the perimeter insulation. I was going to form up my stud walls and leave a 1/2" (or perhaps 1"?) gap to allow for air flow behind the wall. (perhaps I should run the stud walls flush against the perimeter insulation?). I have not yet created my pex layout (plan is Blueridgecompany), however I would think that my turns/apexes (apices?) would be near these walls and I would have to take quite a bit of care.

Perhaps my concept of spacing of the pex (that it wont actually run that close to the perimeter of the slab) is skewing my thoughts.

As far as fasteners, Im leaning to the tapcons, sill gasket, and Loctite PL (which Im using anyhow) - does the adhesive go between the gasket and concrete, the wood and gasket, or both?


Again, even with tubing movement, poor measurements.... there theoretically should be an 1.5-2 inches of concrete between the drill bit and the PEX (4" slab, pex being at 3.5", pre-drill tapcon screw going to 1.5-1.75").

I would not use a sill gasket if you are using construction adhesive under the plate.

if a sill gasket is used, one would then not use the adhesive?

I may just do the gasket then, as I need some to wrap my rough plumbing.

So,
You have a heated slab, Dry
6 Mil moisture barrier under insulation, yes?
Sill gasket is for what?
Adhesive is for attachment to slab and Adhesive (liquid nails) will also smear out to create a gasket.
It is reasonable to spray paint the wall systems on the foam, hold off pipe 6" from all walls,
Document on blue print where you breach walls if you are really worried about hitting pipe.
In the past when I use to install we often would do that.
Dan

Dan -

Sill gasket is just additional barrier I guess. Given that I have to buy some to wrap my rough plumbing, I don't know what to do with the other 100' I have on the roll

I have yet again waffled back to ' OK, Ill just use the adhesive' and put the gasket to the used construction store.

As far as "spray pain the wall systems" - I am thinking you are talking about spray painting the PEX layout on the foam? Yes, that's the plan. 6" off the walls was the number I was not sure about, but was going to get to when I ordered the product (from you kind folk). I think given my layout, it will be easy to track where my pipe is running, as I have lots of landmarks to take measurements off of..... as long as during the pour no large movements of PEX occur ( I could always double the staples holding down the PEX).

Again, as long as that PEX stays on the bottom, one shouldn't be too close to hitting anything anyhow. Im more worried about the concrete finisher being shallow and careful with the control joints. I suppose I could spray paint those out as well, so he is only crossing a minimal number of loops, however is there any advise or input on how to assure his proper work as well - regarding depth, tooling rather than cutting, etc? The concrete contractor does many slabs in my development (new constructions) that are hydronically heated, so I assume he is well versed, but you know what you get for making assumptions.

Control joints;
If this is not a finished slab and joint appearance is not an issue you can have the concrete finish worker use his edging trowel on extension (this is a 1/2 radius with a 2 or 3 inch flat) . this will separate the aggregate in the slab, The concrete will then crack along this line, it will leave a jagged hairline crack.
Alternately you can place rebar on top of pipe exactly where cutes will be, this provides insurance that pipe is cooperating in that it cannot rise up above rebar, if sparks fly shorten depth of cut.
Spray paint; for clarification spray paint on the foam the wall system of the basement, doors, closets, so on. Bring pipe in and out of rooms through door ways. If you do cross a wall document location on blueprints.
Dan

OR the CC folks can use something like "zip-strip"(google it) pushed into place as it is poured. This provides a weak spot along which the shrinking CC can split with no post pour cutting necessary...

Ron - I mentioned the zip-strips to the CC, however he kinda poo-poo'd the idea. I may have to revisit it and push the envelope. I would think its just something he is not used to doing as his 'standard'. He may be trying to cut costs just by cutting afterwards, but I don't mind paying more for resting easier at night. If not, Ill follow Dan's idea of the rebar.... it would be easy to place this along where the joints would be and warn the CC.

Dan - I understand now... spray where the walls are placed on the foam, not where the PEX is going. I could do this, however visually its pretty easy to eyeball without the paint, as there are about 8 support posts currently, and all of the walls basically are formed by the posts. I will probably just do all of the above mentioned.... route pex elsewhere whenever possible, cover with rebar, take precise measurements where I know cuts and holes will be drilled, use extra staples.

The slab will be finished, as I am then going to grind/polish/stain/seal and leave it as is - (Although Ill have to jump to a different forum for specifics on that, as that is its own set of 'which way is best' - if anyone wants to be super helpful or insightful, Id be happy to private message you).

As far as the whole project goes again, I cant thank the members enough. I went from uninformed to feeling very comfortable with multiple aspects of this project. - side note from previous posts - open system is out, small closed system with boiler panel is in. Permitting was not being very willing.... Dan, sent a PM to you regarding your company and a promo email I recently received.

As Dan suggests, the slab will be dry so no sill gasket is needed. A premium construction adhesive will do the trick with no nails.
If you are really concerned about either moisture or shear, glue and shoot down steel stud track (as used in commercial drywall construction) and stand the stud wall inside. The pins to hold the steel track are only 1/2" at most.

If you are going to finish the concrete for your final floor, consider putting wall angles (1' x 1") under the walls on top of the foam with the legs down. This will provide a crack inducer which will cause any shrink cracks to occur under the walls and not in the middle of your nice new floor.