Sloped slab floor (garage alteration)

[Enrgxprt]

I have been seeing a bunch of existing attached garage alterations to habitable space..

Im wondering what you folks do/say or cite when it turns out the garage slab floor was poured on a slope (allowed) was simply tiled over or a laminate floor placed directly on without any attempt to level.

New codes require floor insulation, but if it was done 30 years ago and just being made legal now I have to apply the code in effect at the time of construction...

 

[steveray]

I have been seeing a bunch of existing attached garage alterations to habitable space..

Im wondering what you folks do/say or cite when it turns out the garage slab floor was poured on a slope (allowed) was simply tiled over or a laminate floor placed directly on without any attempt to level.

New codes require floor insulation, but if it was done 30 years ago and just being made legal now I have to apply the code in effect at the time of construction...

Level matters not as there is no IRC spec...If it is a newly conditioned space it generally meets new code...Wicked ugly to get through the IRC and honestly I am not sure if it really works, but here you go...

N1110.2​

Any unconditioned or low energy space that is altered to become conditioned space shall be required to be brought into full compliance with this chapter.

Exceptions:

1. 1.Where the simulated performance option in Section N1105 is used to comply with this section, the annual energy cost of the proposed design is permitted to be 110 percent of the annual energy cost otherwise allowed by Section N1105.3.
2. 2.Where the Total UA, as determined in Section N1102.1.5, of the existing building and the addition, and any alterations that are part of the project, is less than or equal to the Total UA generated for the existing building.
3. 3.Where complying in accordance with Section N1105 and the annual energy cost or energy use of the addition and the existing building, and any alterations that are part of the project, is less than or equal to the annual energy cost of the existing building. The addition and any alterations that are part of the project shall comply with Section N1105 in its entirety.

 

[bill1952]

Having just done this - with a permit and inspections - and now wonder if it complies? I laid and shimmed sleepers and put 1 1/2" rigid foam between sleepers, ply and hardwood floor over.

FWIW the walls and ceiling are way over minimum insulation requirements and the stem walls are ICF to footing.

 

[Sifu]

Encountered many times, nobody is ever pleased with the answer. When not a low energy space what I see most often is the floor raised to allow for adequate insulation, and to raise it to the floor level of the main house. I don't think there is a trade allowed for the slab insulation. Can't recall anyone actually digging up the foundation walls to install perimeter insulation.

There must also be a method to ventilate the new underfloor cavity space.

 

[Enrgxprt]

Yea, im well aware of what's required in today's code, its the 20-30 year old stuff thats a pita.. Anyone who tries to legalize something with a heavily pitched slab floor isn't gonna like me much. Poor workmanship is an exact fit. The definition states plumb, level and square. But those older codes.. ugh..

 

[Enrgxprt]

Having just done this - with a permit and inspections - and now wonder if it complies? I laid and shimmed sleepers and put 1 1/2" rigid foam between sleepers, ply and hardwood floor over.

FWIW the walls and ceiling are way over minimum insulation requirements and the stem walls are ICF to footing.

So with an addition meeting a passing Res-check or prescriptive R-values everywhere including slab edge R values compliance with the code is not achieved.

What you did sounds good, my concern would be.. sleepers and foam is not continous insulation. An accurate UA calculation (if provided) might let me state that the code was substantially met.

If you had continous slab insulation as shown in res-check web AND sleepers center in the field, you should be golden.

 

[bill1952]

So with an addition meeting a passing Res-check or prescriptive R-values everywhere including slab edge R values compliance with the code is not achieved.

What you did sounds good, my concern would be.. sleepers and foam is not continous insulation. An accurate UA calculation (if provided) might let me state that the code was substantially met.

If you had continous slab insulation as shown in res-check web AND sleepers center in the field, you should be golden.

I did think the ICF - 2" of foam both sides of concrete stem walls to 4' below slab - would cover slab edge. (Slab floats inside stem walls.)

 

[ICE]

A garage conversion isn’t exactly posh. The typical effort here in California is Red Guard over a cracked slab and an inexpensive composite floor.
It’s not to say that everyone is affected, but a slanted floor can make people quite uncomfortable. It is a subliminal irritation.