View Full Version : Flowabl fill

02-21-2006, 09:40 AM
OK, I know everybody is tired of ep henry pushing flowable fill, but does anyone here actually use it? When I did my icpi class the instructors also recommended it and it sounds like a good idea to me. I will be building a raised patio at my own house soon and thought it would be a good place to try it out. Anyone had a bad experience with it?

D Felix
02-22-2006, 08:27 PM
I had always been interested to see what it would do and how it would work. We had a concrete sub do a pour with flowable around a pool for us late last fall on a project we just got back to today. Think it was 60-70 yards or so, areas of it are ~3' deep.

When you hear "flowable" and "self-leveling", you think that's exactly what it is. WRONG.:D

It's mostly sand and water, with VERY little portland mixed in. In fact, it's pretty easy to dig in, even once it's "set". "Self-leveling"? Forget it for fine leveling. It will flow, but it's essentially a really, really, really wet sand. If you need to screed it out, I think it would be harder than screeding out regular concrete, due to the fact that after it's off the truck and on the ground, all the water drains out/down. Especially when you have 2-3' of filling to do.

What we did was fill with the flowable to grade minus a foot for the most part. There were areas that were lower due to running out of fill, but that was OK with us. After it set for several days (or a couple of weeks, don't remember; this was in late November/early Dec), we then put down fabric and compacted gravel over the fill. I'm sure we will still have another lift to pack in before we screed sand and lay pavers, but the 4" or so thats on it now seem to be holding up just fine. I didn't notice any areas that looked like they had heaved at all, but then again, we haven't exactly had a lot of frost in the ground since before Christmas either...

I don't have any pictures at all of the site, let alone any of the fill going in. Sorry.:)



02-23-2006, 12:30 AM
Took the class but my instructors didn't go over it. Can someone give me an overview of what it is?

Dreams To Designs
02-23-2006, 07:57 AM
Vic, check out this site for a decent explanation.


It works great for backfilling against foundations and is recommended for the new Monumental wall blocks Techo has come out with. A couple of the contractors I work with have used it with great success.


02-23-2006, 01:02 PM
So you would build your walls then fill in with that. I guess you would still need the crushed to level it to exactly where you want it before you put the sand down? I usually use excavated dirt then the base material to fill my patios, I've never worked with wet products before so do you need to "Float" it like concrete?

Dreams To Designs
02-23-2006, 01:37 PM
Vic, actually you can use this in place of your crushed base. I don't know about filling hollow core blocks with flowable fill, that is an interesting idea. The big advantage is it is self leveling if specified to the right mix. In theory, it will find it's own level and should create a level base to build walls on, similar to a concrete footing, but no where near the strength of a concrete footing. You can use it to fill a raised patio area that can not, or should not be compacted. Many new homes, and lots of older homes are built with a foundation that should not be backfilled against with crushed stone and compacted to the proper density with plate or foot type compactors. I have not seen it, but have been told by SRW manufacturer reps that foundation damage has occurred due to compacting against foundations. The flowable fill acts as a monolithic material spreading out the forces that would normally be transferred to a foundation wall. If the correct level is attained with the fill, sand is screeded to 1" and pavers, slabs or wall stone can be built right on it. For the Techo Monumental block, it is used for the sole foundation material. These block are 1100 pounds each, and I'm not sticking my hands anywhere near them to screed sand or dust so they sit level. The flowable fill may have to poured into a form depending on the soil condition, but being a liquid product it will find it's own level across the entire distance of the pour or foundation. I have seen the surface smoothed with a trowel, but other than that the fill is ready when it dries.


D Felix
02-23-2006, 05:57 PM
You must be using a different mix than what we used. What we used did not find it's own level, especially a fine level. It did "flow" to some extent, but definately not like you'd think when someone says it's "self-leveling".

Put it this way though, 80 yards of flowable went in with 2 guys (after some forming) inside of 5 hours. To fill and compact that same amount with crushed limestone would have taken 3 guys at least 2-3 days. Gravel as a material would have been cheaper, for sure, but it was done MUCH faster.

I guess what I'm trying say is if you have a large area (and deep) that needs to be filled, use flowable. If you think you will use it to set a base for a wall, and it will level itself and you won't have to touch it, think again. From my limited experience with it, it is NOT truely "self-leveling".


Dirty Water
02-23-2006, 10:27 PM
From my limited experience with it, it is NOT truely "self-leveling".

Neither is concrete, but floating off a footing is super fast and easy.

I am ex-concrete guy, and flowable fill sounds like a great idea to me, as long as you don't expect it to be perfect.

D Felix
02-23-2006, 11:15 PM
Floating off a footing of concrete would be MUCH easier, IMHO, than trying to screed and "float" off a footing of flowable. The water just doesn't hang in the flowable like it does mud, due to there being a very, very, very small amount of portland in the mix.

Remember, essentially all flowable is, is really, really, really wet sand. Basically what you find at waters edge at the beach. Take that out of the truck (a contained unit where the water HAS to stay mixed with the sand), and put it on the ground, and boom, the water drains out. Wet sand doesn't move very easily.

Not trying to discurage anyone from using flowable, just trying to make sure everyone knows what they are getting.


02-24-2006, 09:45 PM
If I can find a supplier in my area I'll use it for my patio, but will leave room for 4" of qp (3/4-) and 1" of sand. This is the way I was told to do it since it can't be pitched due to the self leveling properties.

Bigvic, have you ever had a settling issue using the excavated dirt to fill a raised patio?

02-24-2006, 11:03 PM
when you call in the load to the concrete plant tell them to send it out at about a 4 inch slump and then let the driver of the mixer wet it up to your aproval when he gets to the the site .

02-26-2006, 12:36 AM
Not yet and hopefully never, the soil here is mostly sandy so it compacts very well.

02-26-2006, 12:49 AM
Bigvic, have you ever had a settling issue using the excavated dirt to fill a raised patio?

That is a no-no. Unless you are excavating sandy/gravel soil, always replace it with modifed (2a) stone.


02-26-2006, 12:46 PM
the soil here is mostly sandy so it compacts very well.

I use the dirt from the trenches, and fill the rest with modified. Of course the dirt from the trenches doesn't amount to much.

Grn Mtn
03-20-2007, 12:05 PM
not sure if this link was around last year: http://www.flowablefill.org/

I called around here and only one cement company is mixing it and they use the ash type, 4-8yd min $55 per yard.

What I found interesting in the link is how you can specify different psi and how over 150 psi you cannot shovel it.

03-23-2007, 11:26 AM
Is anyone planning on using this stuff on a job anytime soon? If so would you mind taking pictures of the process like prep, pouring, screeding etc. I'm gonna ask the guys at my ICPI class next week in PA about it and see what their thoughts are.I am very interested in this stuff because I have a large raised patio scheduled this summer. Thanks.

03-26-2007, 12:58 PM
Here are some pics from MAHTS. i have posted pics before of a job we did with flow fill.

03-26-2007, 01:32 PM
Hey Chris , I saw that pic 2 years ago at MAHTS. I think the contractor had to dig some 9' of soil out because it was unsuitable !

03-27-2007, 02:25 AM
McKee or others,
If you don't mind I have a couple questions because some of you guys have used this stuff in past jobs.

1). Like in the last pic where the crew is pulling it around, I see the walls are backfilled with aggregate like they normally would be and I'm assuming that drainage is behind that wall, so I guess my question is, say you were to just build a wall and not backfill, and bury the drainage pipe while filling up the remainder of the raised patio area with the flowable fill. Can this be done or do the walls have to be backfilled say at least 18" because this stuff does not drain like aggregate does and then behind the aggregate just fill the area up like a swiming pool with water??

2). How long would it take for this stuff to dry say it being poured a foot in depth? And I've pulled concrete around before and I would have to imagine flowbale fill to be heavier because of the higher sand content therefore what kinda time in comparison to concrete do you have to pull it around to level it before it dries. I would think it to be longer since sand holds moisture well.

Thanks for your help.

D Felix
03-27-2007, 07:51 AM
It'll drain; remember that it's only sand and portland, mixed very lean, and with a LOT of water. I think I'd still use free-draining aggregate behind a wall with this stuff used as fill though.

It actually has less working time than regular mud. Concrete has a much higher portland concentration than this flowable fill, and will hold the water in longer. Once flowable hits the ground, the water starts to immediately drain out (which is what's supposed to make it "self-leveling"--the water "pulls" the sand/portland down to a level state). Towards the bottom of the dump, it stays workable for some time, but the top gets dry rather quickly. At that point you can't "pull" it around like regular mud, but you can scrape it around if needed.

03-27-2007, 10:12 PM
i asked that specific question at mahts this year in regard to the drain column, because i have not gotten a straight answer. they all seemed to agree that a drain column was not necessary, this was ep henry and a engineering firm that designs SRWs. that is what i thought because the flow fill does not allow nearly as much water though as a crushed stone. you can put the drain column if you like i don't feel its necessary.

and as d felix said you do not have as much time to work flow fill like regular concrete. we have poured 20" of the stuff and could walk on top of it a in hour or two.