Footer Slab Question - Page 2 - Contractor Talk - Professional Construction and Remodeling Forum

mics_54 · 07-11-2009, 12:05 PM

When in nonexpansive soils (NFS) an insulated slab on grade might be legal. It depends on local codes (if applicable) However if the existing house in on a block foundation one may assume a similar foundation on an addition might be recommended.

DJ9222 · 07-11-2009, 05:32 PM

In my part of the world if you are building space to be used as LIVING space it must have footings snd stem wall below frost line (36").... good luck and check with building inspector........

WarriorWithWood · 07-11-2009, 05:53 PM

Quote:

Originally Posted by mics_54

When in nonexpansive soils (NFS) an insulated slab on grade might be legal. It depends on local codes (if applicable) However if the existing house in on a block foundation one may assume a similar foundation on an addition might be recommended.

It'll never fly around here, I don't care how deep the original is. You need to go 36" deep minimum.

mics_54 · 07-11-2009, 07:15 PM

I checked the pittsburgh website and didnt see any ammendments addressing the issue. If pittsburgh uses the 2006 irc and didnt adopt any local ammendments then I have to assume that the irc code R403.3 for frost protected foundations may apply. There are stipulations that the structure is a heated space. Frost protected insulated foundations may not be used on outbuildings, garages, car port or attached to buildings with crawlspaces or basements. The OP will have to determine if the code applies to his circumstances. The pittsburgh website http://www.city.pittsburgh.pa.us/BBI/ indicates the area has an Air Freezing index of 1500 which is the least value of the air freezing indexes listed on the irc chart R403.3

Oh and for New York... it is the same.

http://www.dos.state.ny.us/code/rcfaq.htm#footings

Q.Does the residential code require footings to frost for all buildings?
A. No. Section R403.3 entitled “Frost protected shallow foundations” provides that for buildings where the monthly mean temperature of the building is maintained at a minimum of 64ºF (18ºC), footings are not required to extend below the frost line when protected from frost by insulation in accordance with Figure R403.3(1) and Table R403.3.
EXCEPTIONS:
1. No foundation not so protected may be attached to frost-protected shallow foundations.
2. Unheated garages, porches, utility rooms and carports shall not be permitted to be attached to dwelling units with a frost-protected shallow foundation.
Materials used below grade for the purpose of insulating footings against frost shall be labeled as complying with ASTM C 578.

JDC Owner · 07-12-2009, 12:08 AM

Thanks for digging some info mics, I was heavily researching FPSF systems for awhile now. I don't know if one will qualify though, the addition is going to be attached to a heated basement and unheated garage. Plus the soil seems very susceptible ( alot of silt ), but I'll make some calls and see if it checks out.

mics_54 · 07-12-2009, 12:28 AM

If it's attached to a basement and unheated garage it must be on a footer below frost line. (36" in Pittsburgh)

rino1494 · 07-12-2009, 05:12 AM

PA building code requires a foundation wall of no less than 40". Using block, that is 5 courses, plus a 8" footer. Also, the footer must be at least 20" wide.

Also, you must be at least 3' in the ground. So, if your wall is sticking out of the ground pretty good, you may need to add extra courses. For approval, just submit plans for 5 courses.

WarriorWithWood · 07-12-2009, 07:15 AM

Quote:

Originally Posted by mics_54

Q.Does the residential code require footings to frost for all buildings?
A. No. Section R403.3 entitled “Frost protected shallow foundations” provides that for buildings where the monthly mean temperature of the building is maintained at a minimum of 64ºF (18ºC), footings are not required to extend below the frost line when protected from frost by insulation in accordance with Figure R403.3(1) and Table R403.3.
EXCEPTIONS:
1. No foundation not so protected may be attached to frost-protected shallow foundations.
2. Unheated garages, porches, utility rooms and carports shall not be permitted to be attached to dwelling units with a frost-protected shallow foundation.
Materials used below grade for the purpose of insulating footings against frost shall be labeled as complying with ASTM C 578.

Here's what I found in the 2006 IBC

Quote:

1805.2.1 Frost protection. Except where otherwise protected
from frost, foundation walls, piers and other permanent
supports of buildings and structures shall be protected
by one or more of the following methods:
1. Extending below the frost line of the locality;
2. Constructing in accordance with ASCE 32; or
3. Erecting on solid rock.
Exception: Free-standing buildings meeting all of the
following conditions shall not be required to be protected:
1. Classified in Occupancy Category I, in accordance
with Section1604.5;
2. Area of 600 square feet (56 m2) or less for
light-frame construction or 400 square feet (37m2)
or less for other than light-frame construction; and
3. Eave height of 10 feet (3048 mm) or less.
Footings shall not bear on frozen soil unless such frozen
condition is of a permanent character

jkfox624 · 07-12-2009, 07:31 AM

Slabs dont fly around here no matter how you do it. We always shoot for 40" minimum to top of footer minimum 2' wide 8" deep with 2 rows rebar. Your gonna need 2" foundation foam on inside of stem wall we usually use a poly foil double bubble insulation under the slab.

WarriorWithWood · 07-12-2009, 07:38 AM

Yup, same here. It's been a while so I was stuck on the 36" but it is 40" here now.

EDIT: I'm assuming you mean a slab with no footings.

rbsremodeling · 07-12-2009, 07:50 AM

Quote:

Originally Posted by WarriorWithWood

Yup, same here. It's been a while so I was stuck on the 36" but it is 40" here now.

Do you guys get a lot of snow up there Dennis?

mics_54 · 07-12-2009, 08:57 AM

Quote:

Slabs dont fly around here no matter how you do it.

WarriorWithWood · 07-12-2009, 09:19 AM

Quote:

Originally Posted by rbsremodeling

Do you guys get a lot of snow up there Dennis?

Not as much here in SE Pa. but the NE gets several feet a year.

jkfox624 · 07-12-2009, 05:03 PM

We usually get 6+ feet a year depending on how the lake effect falls. To the NW a bit just into NY state they get hammered, one place got like 23' last year. And yeah sorry shouldnt have said any slab meant slab on grade or frost protected slabs are a no go, it has to have footings below frost line.

cdkyle · 07-12-2009, 06:54 PM

Old school rule of thumb: Footings should be twice as wide as wall and minimum of 6" below frost line. Shouldn't have a problem if you conform to this rule, but I would check with local AHJ.

mics_54 · 07-12-2009, 08:39 PM

forget it.