I’m having 2 slabs poured in the next 2 weeks. The first is my shop slab 26×48. The foundation guy put in Foamular 150 over 6 mil plastic, 6×6 wire mesh and I’m putting in the radiant tubing. My question- can Foamular 150 be used under a slab? He claims it can but I believe the compressive strenght is 15psi vs 25 psi for the Foamular 250. The foam hasn’t been put in the house slab yet but a load of it is sitting waiting to be installed. Is it critical enough to remove the 150 from the shop slab? If it should be removed- who pays?
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
There are a number of ways to achieve a level foundation and mudsill.
Featured Video
Builder’s Advocate: An Interview With ViewrailHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
Are you going to be parking earth movers on the slab?
Question? How many lbs/sq ft does 15 PSI repressent.
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The shop will be for woodworking-no cars. The heaviest items will be a planer, lathe, stacked wood. Also another question. We've had some heavy rain in the last 2-3 days-water is puddled under the foam and on top of the 6 mil plastic-is this an issue? The pour is scheduled for Friday. Also the foundation guy says he's using a 5 sack mix- how does that translate to strength? When I ask him questions it's like pulling teeth. He just says its strong enough.
I don't know enough about placing concrete or the strenght of a 5 bag mix.But for some that does. How much water are you talking about that is puddled?.
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Greetings from nearby.
I assume since you are doing tubing that you are doing a 4" slab, and that you don't have a forklift in your shop. The Foamular 150 is fine for both slabs, the limiting factors are really the thickness and the lack of rebar anyway. 5-sack concrete is the bare minimum for slabs IMO, I use 6-sack... it's a stronger mix and it's easier to finish. I also use rebar in slabs and think it gives better results than mesh.
You could ask for 6-sack and all he has to do is order it, but equally if not more important is the slump he pours (i.e how much water in the mix) and whether you keep it adequately covered right after the pour to prevent immediate cracking. We pour a 3" slump with a water reducer and cover slabs with plastic and keep them wet. If the weather gets hot and sunny next week, and you pour a slab and leave it out in the sun, you will likely be sorry.
Also, what is the fill and how was it prepped?
It is a 4 inch slab. He is probably going to use a pump truck. Every pour I see in this area uses a pump. I think its just an easier way for them to do it and the cost is just passed on. Does using a pumper generally mean the concrete is wetter(greater slump)? Since there is radiant tubing- when is the best time to put in control joints? Contractor wants to cut them in when dry. Makes me very nervous. Should I insist having them tooled in when they pour?
Contraction joints should be cut within 24 hours.
Protection is easy - figure out where the joints will be cut and mark the locations on the foundation wall. Purchase steel 1" x 1" angle - cut the angle into pieces 4" or so long and tie with electrical tape over the top of the tubing in the area where the joints will be cut.
This detail can also be used where radiant tubing passes under a wall plate that might be nailed to the slab - the steel angle will deflect nails to the side.
Jeff
That's a great idea, especially to protect from plate fastening because I bet you could locate those chunks of angle with a magnet.
A boom pump is the way it's done here. It makes getting the mud in the right place a lot easier. On my job now we could barely get a chute onto the house, so it's moot. You could specify 6-sack pea-gravel mix batched for a 3" slump, with water reducer added to work as a 7" slump. The mud will flow well and then harden up for finishing about like usual. They should use minimal calcium, 1% or less. My guy does not use it, there are chemical alternatives that work fine if you want an accelerator. Probably not necessary this time of year with a morning pour.
Water reducer makes the water "wetter" for a short period. It is the alternative to adding a bunch of water to get mud that flows out. Polyheed 997 is the usual around here.
You didn't mention what the fill was and how it was installed. This is critical.
There is an 8x15inch footing and a 24 inch high 8 inch thick wall. The slab will be poured inside this -level with the top of the wall. The fill was 5/8" minus about 6 inch thick. It has been sitting for about 2 months.
Was the topsoil removed from under the 5/8"? Was the 5/8" compacted with a vibrating plate or some other mechanical means?
The topsoil was removed. The 5/8 minus was not compacted other than the bobcat running around on it. It did sit for abouit 2 months and to me seemed solid as a rock.I appreciate the advice on how to order the concrete-slump, additives etc I hope the foundation guy will be open to more questions and suggestions. As a novice I don't want to offend but I still want it done right.
Cost passed on?Yes, but using a pumper can mean one less man on the job, two less on some jobs. That balances cost.But also, not only is it easier to use a pumper most of the time, it makes for a better job because of less separation of aggregate, IMO.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
What thickness of Foamular 150 are you using? I am evaluating installing a similar system in a below grade slab but have heard mixed ideas on how thick the layer of foam should be.
Thanks,
learner
Here at least the code is R10 (2") with a thermal break around the perimeter.
Yeah I typically here 1" minimum. I read somewhere that you should really have 4" to ensure the best thermal break from the soil. In terms of a thermal break b/t the slab and the foundation walls how does that typically work especially in terms of using a radon barrier? Would you lay the floor foam over a vapour barrier sealed to the walls with acoustic caulking, then have a foam wall as high as the slab is thick to provide the wall/floor thermal break?Thanks,learner
I am getting ready to start construction on my 3000 sf super-insulated home outside of Philadelphia. I will be spraying 2 inches of Soy based urethane foam directly to the stone after the Superior Wall foundation has been installed. Foam will be sprayed up the footers of the basement wall therefore not requiring and extra vapor barrier. Have seen several homes and a auto service center done this way. Wire is laid directly on foam and pex attached.
Radiant installers love it because the foam dries very hard and they don't have to worry about breaking the blueboard normally used.
John
I worry about cutting the tubing when the control joints are cut in.
4" slab = 1" deep kerfs. Ideal placement for crack control reinforcement (WWM) is in the top third of the slab, ~ 1 3/8" deep, but in the middle is acceptable, 2" deep. Hah! you'll never see the ideal. However, you're putting the tubing on top of the WWM, 1 3/8" - 1/2" tubing = 7/8". And 1" deep joints???
Typically WWM is layed on the substrate and pulled up into the wet mud some uncontrolled distance. Who knows how far from the surface your tubing will end up.
The saw used to cut the control joints won't even notice any tube protecting angle iron you put in.
Any water on the plastic or foam is unacceptable, because, when, if ever, it evaporates, it will leave large voids under the slab, and that garuntees unsightly cracks and dips or it will substantially reduce the strength of the slab. Most likely both.
I reccommend:
The WWM goes away. The water goes away. Lines are snapped on the foam to show the layout of #4 rebar, 2' OC, the control joints, and any walls going up. The tubing gets stapled to the foam staying 6" away from any parallel rebar, joints or walls. An accurate dimensioned drawing is made of the location of any tubing crossing a wall or next to and parallel to a joint. Then, I would set the rebar on 2" chairs and pour.
SamT
Sam, we have slightly different methods. I'm using #3 bars 18 OC and I'm going to try to get 1" dobies for them on this job. Might have to bust up pieces of cap block or something. The tubing is wired to the top of the mat. The goal, which is debated by many, is to get the tubing to mid-slab rather than stapled to the foam. I am persuaded by the mid-slab argument, and do not like the uncontrolled nature of WWM at all, never use it. Control joints that are tooled in during finish are safer than cutting, although I can work it out to score parallel to the tubing, and well between.
Woodscreek, the 5/8" sounds OK but we run a Bomag vibrating plate compactor over it. I would do nothing to yours, you will be fine.
My suggestion, which can be hard for me to implement even after 20+ years in the biz, is to stop being afraid of the concrete guy. Take the concrete supplier out of his contract, tell him you will order and pay for the mud. Then order whatever it is you want. If he can't get with that program, let him go and hire other finishers. Based on the very minimal info here my sense of your guy is that he is doing the minimum spec. There's an excellent outfit over there called Emil's Concrete Construction that can finish your slabs. They have a website.
Got any photos of your job to post?
The debate is close enough, that I'm of the opinion that your method is as valid as mine.But, I'll still recccomend mine in re the tubing placement(|:>)SamT
I don't have any photos but will try in the next day. I spoke to him today to try to put it off til next week. I may have trouble being there the day of the pour. He said it wasn't necessary that I be there. I said I wanted to monitor for leaks with the system pressurized( is it necessary?). He said if there was a leak(which he says he's never had) that a barbed fitting with hose clamps is the fix. I insisted it wasn't the way its fixed. Getting that rock and a hard place feeling.
Tubing in the slab should be on air test from the time it's installed all thru construction. That way if you hit a tube you will know it immediately. The concrete guy has nothing to do with fixing tubing, don't even ask his opinion. Since you installed the tubing you need to get the lines tied together into one big loop, cap one end, put a test gauge on the other and use a compressor to put it under test. 30 PSI should be enough. I have also been required to put tubing under a 100 PSI hydrostatic test.
edit--you could install the manifolds to facilitate the test. My sub has some that he uses just for this purpose.
Edited 7/23/2007 10:14 pm by davidmeiland