Basement Question for all you builders out there.

[winterulez]

Getting ready too do the rebar in my basement. Walkout basement 1850 sqft with step down footings. Icf walls. We are having the great debate now. On the front where there is no footing up top like the rest of the basement, should we hilti the rebar into walls or leave it so its like a floating slab. It's 50/50 right now on the decision. And how big of squares on the rebar 16" 18" or 24" I will be putting in infloor heating with 4" of concrete.

 

[Trashy]

I'm not a builder, but from what I have seen. I would fasten the rebar to the walls, and go 12" or 16" if your going with in floor heat.

 

[mach123]

No floating for me and I go 15mil 18 max depends on owner. Good luck

 

[Cyle]

No floating for me and I go 15mil 18 max depends on owner. Good luck

15mm rebar with heating lines in a 4" slab? That is not a good idea, 15mm rebar needs a minimum thickness of 5", not enough concrete coverage otherwise. Anything less then 1.5" above and below rebar or heating lines is asking for trouble. Also 4" won't even do with 10mm unless your heating lines go in the styrofoam.

Unless your parking some heavy vehicles in the basement, 10mm rebar is plenty on 16" centers. Most basement floors have nothing, most with infloor heating only use mesh. Could drill in, but with ICF, it's a gamble. Not a fan, you have no idea what kind of wall you got as you never see it. Shouldn't really need to though, unless the ground is very bad there. But if the foundation isn't on piles the ground is plenty good enough.

The most important thing about concrete standing up is preping and pouring it right, rebar, strength of concrete, etc are a small part, especially if it's not done right.

 

[byronkentgraham]

15mm rebar with heating lines in a 4" slab? That is not a good idea, 15mm rebar needs a minimum thickness of 5", not enough concrete coverage otherwise. Anything less then 1.5" above and below rebar or heating lines is asking for trouble. Also 4" won't even do with 10mm unless your heating lines go in the styrofoam.

Unless your parking some heavy vehicles in the basement, 10mm rebar is plenty on 16" centers. Most basement floors have nothing, most with infloor heating only use mesh. Could drill in, but with ICF, it's a gamble. Not a fan, you have no idea what kind of wall you got as you never see it. Shouldn't really need to though, unless the ground is very bad there. But if the foundation isn't on piles the ground is plenty good enough.

The most important thing about concrete standing up is preping and pouring it right, rebar, strength of concrete, etc are a small part, especially if it's not done right.

If you don't do it EXACTLY this way your basement will collapse on top of itself. No questions asked, no other way than this will work.

 

[Med1ogre]

I would drill and Hilti hit for piece of mind. If you hit a void which is highly unlikely, maybe some honeycomb, probably rebar haha.
Hilti hit will make that a non issue. It may not move if you don't pin it, but what about 30/40 years from now? Don't wanna be thinking about that floor when your doing your shingles lol.

 

[pipes]

PM the arbourist. he's an expert on concrete

 

[Uturn]

On mine we pinned all the way around the perimeter with 10mm rebar, including the walkout wall. Attached the rebar to wire mesh and the tubing to the mesh.

On the walkout end in this pic, we hilti'd the rebar into end walls and it ran all the way across(10' lengths). The rebar on the end walls was done after the tubing was installed. It was run on 18" centers. My slab is 5" thick. Strong enough to park a vehicle on!!

 

[imdoo'n]

On mine we pinned all the way around the perimeter with 10mm rebar, including the walkout wall. Attached the rebar to wire mesh and the tubing to the mesh.

On the walkout end in this pic, we hilti'd the rebar into end walls and it ran all the way across(10' lengths). The rebar on the end walls was done after the tubing was installed. It was run on 18" centers. My slab is 5" thick. Strong enough to park a vehicle on!!

yeah but did you get it cyle certified? otherwise like buck 50 ya will need to rip it out.

 

[bayman]

How thick are your walls, how high, how much load on your floor?

The stryofoam forms come with slot/clips for the rebar to attach to. Personally I would go with 15M@ 400mm horizontally and 15M @ 300mm vertically(overkill on the 300mm but it is your house after all.(just reread OP,walls are already done) The no footing comment concerns me, you will need extra rebar in that area. Yes on the dowels coming out of the footings into the slab.

As for your slab on grade, ensure that the ground is compacted really well and not frozen. Code says for any concrete cast against dirt, you need a concrete cover of 75mm to the rebar, so 100mm slab is close.

Again, depending on the load you plan on putting in your basement, I personally would go with WWM(welded wire mesh). There are three sizes of mesh to chose from,again personally, I would just go with the smaller size(6/6-10/10).That means the mesh has a grid 6"x6" and is 10 gauge.The stuff we use comes in 7'6"x20' sheets. The reinforcing is just for crack control. 1800 sq/ft, you will probably need to saw cut the slab for shinkage(with glycol lines this gets scary). If you have column supports in your basement, you should isolate them(build a box around and pour later, diamond shaped) and pour later.

When you pour the slab, make sure the ground and rebar/mesh is above 5 degrees. Properly cure and SEEL it. Use a laser to check the grade before and during the pour. Nothing worse than an uneven slab, makes forming partion walls a pain in the arse. 30 mpa concrete is again an overkill, but it is your house.
This is how I would doo it, but hey, what do I know. Hopefully the great builders don't redicule me.

 

[Cyle]

If you don't do it EXACTLY this way to do it. No questions asked, no other way than this will work.

Great job tuning in with your help! I will excuse your ignorance due to the fact that your illiterate and not able to read my post.

 

[Cyle]

How thick are your walls, how high, how much load on your floor?

The stryofoam forms come with slot/clips for the rebar to attach to. Personally I would go with 15M@ 400mm horizontally and 15M @ 300mm vertically(overkill on the 300mm but it is your house after all.(just reread OP,walls are already done) The no footing comment concerns me, you will need extra rebar in that area. Yes on the dowels coming out of the footings into the slab.

As for your slab on grade, ensure that the ground is compacted really well and not frozen. Code says for any concrete cast against dirt, you need a concrete cover of 75mm to the rebar, so 100mm slab is close.

Again, depending on the load you plan on putting in your basement, I personally would go with WWM(welded wire mesh). There are three sizes of mesh to chose from,again personally, I would just go with the smaller size(6/6-10/10).That means the mesh has a grid 6"x6" and is 10 gauge.The stuff we use comes in 7'6"x20' sheets. The reinforcing is just for crack control. 1800 sq/ft, you will probably need to saw cut the slab for shinkage(with glycol lines this gets scary). If you have column supports in your basement, you should isolate them(build a box around and pour later, diamond shaped) and pour later.

When you pour the slab, make sure the ground and rebar/mesh is above 5 degrees. Properly cure and SEEL it. Use a laser to check the grade before and during the pour. Nothing worse than an uneven slab, makes forming partion walls a pain in the arse. 30 mpa concrete is again an overkill, but it is your house.
This is how I would doo it, but hey, what do I know. Hopefully the great builders don't redicule me.

Why would you seal a inside slab that will never be exposed to the elements? I have never seen that nor see the point. In fact a lot of cure and seals are way to hazardous to be using in a basement. Same with the sawcuts, you don't need control joints in a basement floor under any circumstances, it's a heated floor that is never exposed to freezing. It won't do anything for shrinkage anyways, control joints are so any minor cracking is done there hopefully. Also why would you space the rebar differently each way? It's always a evenly spaced grid both ways, to ensure it's equal strength both ways. Extra around large load areas, small corners, etc but otherwise go equal both ways.

 

[bayman]

Why would you seal a inside slab that will never be exposed to the elements? I have never seen that nor see the point. In fact a lot of cure and seals are way to hazardous to be using in a basement. Same with the sawcuts, you don't need control joints in a basement floor under any circumstances, it's a heated floor that is never exposed to freezing. It won't do anything for shrinkage anyways, control joints are so any minor cracking is done there hopefully. Also why would you space the rebar differently each way? It's always a evenly spaced grid both ways, to ensure it's equal strength both ways. Extra around large load areas, small corners, etc but otherwise go equal both ways.

You've never seen rebar spaced differently? That says alot.

 

[Cyle]

You've never seen rebar spaced differently? That says alot.

I did? Read it again. I said it's always done that way, big difference. Meaning people who don't know what they are doing won't space it in a equal grid.......Absolutely no reason in a basement floor to have it spaced differently each way.

 

[bayman]

I could show you hundreds of rebar drawings that have steel spaced differently but what would be the point, you've obviosly seen and done everything in constuction. Never said to place the slab at different spacing by the way.

 

[byronkentgraham]

Great job tuning in with your help! I will excuse your ignorance due to the fact that your illiterate and not able to read my post.

Who is my illiterate?

 

[Cyle]

I could show you hundreds of rebar drawings that have steel spaced differently but what would be the point, you've obviosly seen and done everything in constuction. Never said to place the slab at different spacing by the way.

Talking about residential, so would be good to see any of those, good luck! Who knows WTF your talking about, sounded like basement walls but he said they are done, so you obviously don't read to great. Also you seemed like you said to pour telepost pads after the basement floor? Last time I checked code said they had to be poured in so they can't be removed. And the pads have to be in before the place is framed (and it is obviously framed).

 

[Cyle]

Who is my illiterate?

So you can read????? Good! Trying doing it before you type next time and make yourself look like an idiot.

 

[byronkentgraham]

So you can read????? Good! Trying doing it before you type next time and make yourself look like an idiot.

I will try my best! Forgot who i was dealing with.

Rebar is an unnecessary expense. Don't put any in.

 

[plio7]

winterulze please listen to bayman......good info here, if you have a wall with out a fotting and the rest have footings, extra dowels should be used to maintian as equal of a conection to the foudation walls/footings as possible.......along with that if you follow what he said you shouldnt have any issues down the road.

How thick are your walls, how high, how much load on your floor?

The stryofoam forms come with slot/clips for the rebar to attach to. Personally I would go with 15M@ 400mm horizontally and 15M @ 300mm vertically(overkill on the 300mm but it is your house after all.(just reread OP,walls are already done) The no footing comment concerns me, you will need extra rebar in that area. Yes on the dowels coming out of the footings into the slab.

As for your slab on grade, ensure that the ground is compacted really well and not frozen. Code says for any concrete cast against dirt, you need a concrete cover of 75mm to the rebar, so 100mm slab is close.

Again, depending on the load you plan on putting in your basement, I personally would go with WWM(welded wire mesh). There are three sizes of mesh to chose from,again personally, I would just go with the smaller size(6/6-10/10).That means the mesh has a grid 6"x6" and is 10 gauge.The stuff we use comes in 7'6"x20' sheets. The reinforcing is just for crack control. 1800 sq/ft, you will probably need to saw cut the slab for shinkage(with glycol lines this gets scary). If you have column supports in your basement, you should isolate them(build a box around and pour later, diamond shaped) and pour later.

When you pour the slab, make sure the ground and rebar/mesh is above 5 degrees. Properly cure and SEEL it. Use a laser to check the grade before and during the pour. Nothing worse than an uneven slab, makes forming partion walls a pain in the arse. 30 mpa concrete is again an overkill, but it is your house.
This is how I would doo it, but hey, what do I know. Hopefully the great builders don't redicule me.