Another frost wall vs. mono slab question...

[QuattroPower88]

Intro:
I recently purchased a new home in Connecticut and the only thing it is missing: A garage! This forum looks great... I aspire to one day build a garage like some members have.

Questions:
I have read a few of these threads but there is never a concrete answer.

1. Which is TRULY a better value for money for a 24x24 detached garage...mono slab or 4' Frost Wall foundation?
2. Does anybody remember what they paid for a similar project with either configuration?
3. Why does mono slab seem to be frowned upon in New England?

Current background info:

• Garage is a pre-built unit
• Pre-built company has me find my own foundation contractor, but highly recommends frost wall foundation for their garages to be placed on
• Town building inspector allows mono slab but also highly recommends frost wall
• Foundation contractor said he is happy to do a frost wall but says mono slab is sufficient
• Current mono slab quote is ~$8k. Frost wall ~$12k.

Thank you!

 

[kmacht]

In my town in Connecticut to have a mono-slab you had to be detached from the house and it has to have under a 600 square foot footprint. I went with a mono-slab but if I were to do it again I would go with frost walls. The reason being is that there isn't a good way to seal out water around a mono-slab building. The water will eventually **** under the wood sitting on the slab. With a frost wall the wood is up off ground level and you have a solid surface all around the garage to keep water out.

I also ended up going with a prefab garage from a place in Pennsylvania. Cost was about 25k with me doing all the concrete work and them dropping off a fully assembled and painted garage ready to use (less electrical). You can see my build here:

http://garagejournal.com/forum/showthread.php?t=70896&showall=1

Keith

 

[matt_i]

Imo best bang for the buck is a trenched-foundation monolithic pour.

You prep the flat ground by removing sod and topsoil. Can pour a pile of limestone in the center.

You rent a trencher or minihoe with trencher preferred. You excavate. You form & level the basic slab with 2x wood and stake it.

Spread and compact gravel with obvious care not to collapse the trenches.

Apply vapor barrier and reinforcement.

Pour concrete.

You get the benefit of a foundation below frost-line but nothing is actually done in the trench. The earthwork is the concrete form.

 

[QuattroPower88]

I also ended up going with a prefab garage from a place in Pennsylvania. Cost was about 25k with me doing all the concrete work and them dropping off a fully assembled and painted garage ready to use (less electrical). You can see my build here:

http://garagejournal.com/forum/showthread.php?t=70896&showall=1

Keith

Thank you Keith... yours was one of the posts I found when searching. It looks good. And sorry to hear you are getting water in, but appreciate your input. I am leaning toward frost wall despite the cost

 

[WickedMainer]

8k! For a slab and 12k for frost walls!!! Wow, sticker shock. could get 8 foot 24x24 foundation for less than that here. Not sure how much your concrete is there but I had 2k in materials in a 24x28 floor this year.

Think about future when you make the decision. If it won't have a second story or a finished second story at that monolithic should be fine, my fathers here in Maine has held up great. Our code is 400 sq ft and under detached you can do monolithic, he was told he can't build a second floor on it and he has been jumping through hoops to expand it... others may have different experience.

 

[WickedMainer]

I should mention it was required that the monolithic slab be insulated and vapor barrier when my father built his.

 

[Voi]

[*]Why does mono slab seem to be frowned upon in New England?

I should mention it was required that the monolithic slab be insulated and vapor barrier when my father built his.

WickedMainer,

Did your father's insulation requirements for a monolithic pour match the recommendations for a Frost Protected Shallow Foundation (FPSF)?

If that's the case for the OP I wonder if contractors just don't want to deal with the detail (hence being "frowned upon" as the OP wrote). Mono slabs don't require insulation or vapor barrier in my area so when you ask about FPSF's contractors really seem to get hesitant. And I've seen some very sloppy work with under slab/foundation rigid foam.

I have to do a mono pour (due to rock) this summer for a hopefully large shed. As I recall there is a square foot limit and as the building gets wider the edges need to be thicker.

 

[QuattroPower88]

8k! For a slab and 12k for frost walls!!! Wow, sticker shock. could get 8 foot 24x24 foundation for less than that here. Not sure how much your concrete is there but I had 2k in materials in a 24x28 floor this year.

Think about future when you make the decision. If it won't have a second story or a finished second story at that monolithic should be fine, my fathers here in Maine has held up great. Our code is 400 sq ft and under detached you can do monolithic, he was told he can't build a second floor on it and he has been jumping through hoops to expand it... others may have different experience.

I also had sticker shock as this is NOT what I had budgeted! But 3 separate quotes were all similar.

WickedMainer,

If that's the case for the OP I wonder if contractors just don't want to deal with the detail (hence being "frowned upon" as the OP wrote). Mono slabs don't require insulation or vapor barrier in my area so when you ask about FPSF's contractors really seem to get hesitant. And I've seen some very sloppy work with under slab/foundation rigid foam.

Good point. My contractor said it would include vapor barrier, etc if we took that route. In general, a piece of advice from multiple people was "just do it right" (referring to building a frost wall). But if it CAN be done right, why pay an extra $4k?

 

[readhead]

I presume that you guys understand that even a mono pour has to be below frost for the trenches.

 

[Kaizen]

More details are needed. how thick? fiber mesh or metal mesh? thickend edge 2feet deep? how much rebar in that?
Also you're going to need excavation and stone brought in and compacted either way you go. is that included?
In NE the better choice is with footers and walls at least a foot above grade then pour floor after. However for my 30x36 I was looking at 20 k including excavation and new stone brought in. So I went with the cheaper option which was still over 10k all included. 6inch thick w/mesh 4k psi

 

[Kaizen]

I presume that you guys understand that even a mono pour has to be below frost for the trenches.

Nope. Our frost line is 4 feet. If we had to be below it then that's a normal foundation with footers

 

[readhead]

Why can't you dig a four foot trench and pour concrete in it? Is there a code restriction where you are?

 

[WickedMainer]

Nope. Our frost line is 4 feet. If we had to be below it then that's a normal foundation with footers

second that.

 

[readhead]

Second what? Does your building department not allow mono pours at that depth? Or are you assuming they don't.

 

[forAK]

Second what? Does your building department not allow mono pours at that depth? Or are you assuming they don't.

Mono's poured here are typically 2x2. No one goes down past frost for a mono. A lot of the frost is sitting 4 to 5 feet.

 

[WickedMainer]

Second what? Does your building department not allow mono pours at that depth? Or are you assuming they don't.

I second that if code requires us to go to frost depth, which is 4' in our case, it requires a footer and then stem wall. pouring a 4' deep 2' wide footer doesn't sound very economical or logical

 

[Radix2]

Why can't you dig a four foot trench and pour concrete in it? Is there a code restriction where you are?

I imagine there is no restriction.

I think the issue becomes practicality and process. Sure, on a small job where you can do it all with one truck and crew it makes sense. Otherwise I question the savings vs footing,stem walls and slab where you get a simpler job doing it step by step. Same thing considering separate footers and stem walls or poured vs block. Additionally local soil conditions make working on top of 3-4 foot trenches difficult or impossible. Number of guys on the crew, what their routine is, etc etc. what makes the most sense is to get enough contractors in to see what the choices actually are in that time and place.

 

[WickedMainer]

I imagine there is no restriction.

I think the issue becomes practicality and process. Sure, on a small job where you can do it all with one truck and crew it makes sense. Otherwise I question the savings vs footing,stem walls and slab where you get a simpler job doing it step by step. Same thing considering separate footers and stem walls or poured vs block. Additionally local soil conditions make working on top of 3-4 foot trenches difficult or impossible. Number of guys on the crew, what their routine is, etc etc. what makes the most sense is to get enough contractors in to see what the choices actually are in that time and place.

not to mention no trench will be 2' wide round here by the time you dig the rocks and boulders out. New England farms rocks

 

[walrus]

Not sure where wickedmainer is but most small towns in Maine you can do whatever you want.. No one told me I needed anything but Ive poured lots of flat concrete and seen even more done and know what works here.
Well drained soil/gravel, compacted, rebar, insulation and monoslabs work here no problem

 

[saabman]

I added another bay on my freestanding garage/shop. The original 32x28 structure was sitting on a 4 inch slab with block footings. I got similar advice from the town inspector about a frost wall on the new structure. So my new 20x36 addition has a frost wall and 8 inch floor.

 

[WickedMainer]

Not sure where wickedmainer is but most small towns in Maine you can do whatever you want.. No one told me I needed anything but Ive poured lots of flat concrete and seen even more done and know what works here.
Well drained soil/gravel, compacted, rebar, insulation and monoslabs work here no problem

Your in Maine I'm in the unofficial state of northern Massachusetts

 

[walrus]

Your in Maine I'm in the unofficial state of northern Massachusetts

That would be a problem

 

[WickedMainer]

I added another bay on my freestanding garage/shop. The original 32x28 structure was sitting on a 4 inch slab with block footings. I got similar advice from the town inspector about a frost wall on the new structure. So my new 20x36 addition has a frost wall and 8 inch floor.

Did you need expansion joints or anything special?

 

[readhead]

I can see rocks being a problem for a clean trench. We have that issue in places around here also.

By the time you over excavate, form, pour and strip the footings then form, pour and strip the walls then backfill and compact and form, prep, and pour the slab you cannot convince me that pouring some extra concrete in a mono pour won't be less expensive. And save several days in the process. One pour, one inspection not three.

 

[WickedMainer]

I can see rocks being a problem for a clean trench. We have that issue in places around here also.

By the time you over excavate, form, pour and strip the footings then form, pour and strip the walls then backfill and compact and form, prep, and pour the slab you cannot convince me that pouring some extra concrete in a mono pour won't be less expensive. And save several days in the process. One pour, one inspection not three.

Timewise definately makes it seem like a logical idea. Just adds so much extra concrete I think it might be almost as much as just paying someone to do it the form way. At least the joint along the perimeter would be stronger like a a normal monolithic. My opinion really is based on no one does it that way around here and there has to be a reason. A couple of the concrete owners also hold patents for several tools and equipment so i can't say they aren't opposed to change or innovation.

 

[WickedMainer]

That would be a problem

At least it's not Portland. They don't ask what do we regulate they ask what don't we regulate again

i will be moving at some point. Been pretty rapid shadow conversion. Not sure why people even are given a leg to stand on when they build a house right on the boarder of a farm field then raise hell about the noise from haying, the smell from spreading manure and so on. Saving grace is maines agriculture laws that trump ordinances to a degree. Might have to look into some yaks...

 

[walrus]

At least it's not Portland. They don't ask what do we regulate they ask what don't we regulate again

i will be moving at some point. Been pretty rapid shadow conversion. Not sure why people even are given a leg to stand on when they build a house right on the boarder of a farm field then raise hell about the noise from haying, the smell from spreading manure and so on. Saving grace is maines agriculture laws that trump ordinances to a degree. Might have to look into some yaks...

Move to a fishing community and whine about the lobster boats. We used to lease a field for hay. Chicken manure pisses people off

 

[WickedMainer]

I can see rocks being a problem for a clean trench. We have that issue in places around here also.

By the time you over excavate, form, pour and strip the footings then form, pour and strip the walls then backfill and compact and form, prep, and pour the slab you cannot convince me that pouring some extra concrete in a mono pour won't be less expensive. And save several days in the process. One pour, one inspection not three.

Just thought about something. Couldn't do it on my land. Still need to backfill. 3' down hit clay, and even 11 ft down it's still clay. Well draining soils might still work you wouldn't be able to step near the trench to work the concrete in anyway or rebar. I was 8 feet back from a foundation hole carrying a panel last summer and the slope collapsed in front of me. I didn't go in luckily because the form ties may have made it quite painful or lethal

 

[readhead]

I understand that a mono pour doesn't work every time everywhere but we do it whenever we can.

 

[WickedMainer]

Move to a fishing community and whine about the lobster boats. We used to lease a field for hay. Chicken manure pisses people off

They won't have to worry about lobster boats if they keep making anywhere near water unaffordable to anyone except out of state


Chicken manure is a public emergency in southern Maine every year. Enjoy a good laugh
http://www.pressherald.com/2015/10/14/smell-like-manure-permeates-york-county-communities/

 

[Kaizen]

I can see rocks being a problem for a clean trench. We have that issue in places around here also.

By the time you over excavate, form, pour and strip the footings then form, pour and strip the walls then backfill and compact and form, prep, and pour the slab you cannot convince me that pouring some extra concrete in a mono pour won't be less expensive. And save several days in the process. One pour, one inspection not three.

I'm by no means a concrete expert but I've never seen that around here. Not sure why but anyone that goes 4 feet down does footers. Our concrete up here is I think way more expensive then other areas as well. I used previous posts on here to get a rough idea of what I was going to be paying and found it wasn't even close. With fiber I think I was at 140 something per yard. On the last pour the plant had to add hot water and bumped me another ten per yard for freaking water. i'm loving my simple man's slab so far.

 

[WickedMainer]

I understand that a mono pour doesn't work every time everywhere but we do it whenever we can.

How far down have you gone again? You must have a similar frost

 

[WickedMainer]

I'm by no means a concrete expert but I've never seen that around here. Not sure why but anyone that goes 4 feet down does footers. Our concrete up here is I think way more expensive then other areas as well. I used previous posts on here to get a rough idea of what I was going to be paying and found it wasn't even close. With fiber I think I was at 140 something per yard. On the last pour the plant had to add hot water and bumped me another ten per yard for freaking water. i'm loving my simple man's slab so far.

Somewhere between 95-125 a yard last time I checked as a reference for anyone reading this

 

[readhead]

I can go from 32"-48" in twenty miles. Altitude varies between 6K-12K.

 

[WickedMainer]

I can go from 32"-48" in twenty miles.

I will talk to the neighboring town's CEO who is at least knowledgeable and reasonable for his input

 

[saabman]

Did you need expansion joints or anything special?

Nope, they just tied the wall in to the block stub wall. I live in an area we're 2 ft below the topsoil is glacial push aka sand. So my slab does not float in the winter.


Sent from my iPhone using Tapatalk

 

[Homebody]

The reason being is that there isn't a good way to seal out water around a mono-slab building. The water will eventually **** under the wood sitting on the slab. With a frost wall the wood is up off ground level and you have a solid surface all around the garage to keep water out.
Keith

A single layer of 8x16 concrete blocks around the perimeter will solve that. We put a garage on a slab in 75 doing that and no water issues where the wood meets the blocks to this day.

 

[joes169]

We do a number of "floating slabs" every year, and after probably close to a hundred since I've been in business, I haven't seen a problem with them yet, at least not for a samll 24' by 24' detched garage. Perhaps they heave an inch or two in winter, but who would even know if all of the surrounding ground heaves with them? The most important detail with them is to ensure the grade beam around the outside perimeter is sufficient and contains adequate rebar.

As for "trench footings", they're not common here, and for good reason. Our building code requires a footing (8" thick minimum) that extends a minimum of 4" each way of the frost wall on each side. Also, they can't be dug to perfection, so they leave hundreds of areas or frost to "pick" at the sides of them and lift them. Pretty much the same reason son-tubes are required, because they promote a smooth finish that isn't susceptabel to frost "picking".........

 

[saabman]

Here is a pic of the frost wall on mine after pouring (with the forms removed).

 

[WickedMainer]

mono pours were very common before the codes required going below the frost line. I don't recall any that have issues even 30 years later.....water shouldnt be an issue. As mentioned, blocks can be used but just having proper grading away from building and having gutters solves most issues. there are probably methods to meet code without going below the frost line that im not aware of, but its unlikely they are cost effective if you still see everyone doing the tried and true method of footers and walls.



No one has mentioned it but where you have to go below the frost line, ledge at shallow depths can be advantageous. pin it and mono pour it. With proper drainage this is probably the cheapest option and far more stable and less prone to settling then one with 4 foot frost walls in clay soils...Not to mention there is a big benefit with load bearing capacities and future expansion options. If you need to have a septic system or desire a green lawn around it the cost can become a different story.... Much of maine and new England has bedrock within 3' of the surface.

I wish appraisers didn't wack values around here so much for not having a full basement. Unless its daylight I would rather build on bedrock and take the savings and use it toward a bigger attached garage. Basements that aren't daylight are costly, more prone to water and mold issues later, waste space in the form of stairs and have less utility value then attaching unfinished utility/storage space above grade. Except small lots with dimension restrictions, areas prone to tornados, people using it as a root cellar as was the intended purpose, I don't understand why we hold full basements to such a high level. I certainly don't understand when faced with the option of having to build a raised ranch due to water table issue.....