Raising/Levelling a floor on cement


C

charlesg

I am planning on raising a floor a floor on a current cement floor in a
small room (100 sq.ft). This was a porch at some point and the cement
floor has a pitch away from the house, so I plan on leveling the floor
at the same time.

Assuming my plan makes sense, I would run the furring strips away from
the house, one end would be about 1/2" thick and the other end, thick
enought to achieve a level floor (I predict no more than about 1" 1/2.
Each strip would be gun nailed in the cement every 16" or so and
plywood (1/2" thick) would be screwed on top to receive whatever finish
is decided (carpet or laminate).

My plan is to start by snapping a line around the room showing the
height of the level floor and measuring the thickness of each strip
from there.

I'm looking for general opinions on the project and tips to get it done
right? How wide a piece of wood should be used to support the plywood
floor? What's the best way to cut each piece on a angle on the full
length of the piece (about 8')?

Any other gotchas or specifics I should be worried/concerned/carfull
with?
 
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C

Chris Lewis

According to charlesg said:
I am planning on raising a floor a floor on a current cement floor in a
small room (100 sq.ft). This was a porch at some point and the cement
floor has a pitch away from the house, so I plan on leveling the floor
at the same time.

Assuming my plan makes sense, I would run the furring strips away from
the house, one end would be about 1/2" thick and the other end, thick
enought to achieve a level floor (I predict no more than about 1" 1/2.
Each strip would be gun nailed in the cement every 16" or so and
plywood (1/2" thick) would be screwed on top to receive whatever finish
is decided (carpet or laminate).
1/2" ply isn't good enough for 16" OC, and probably not good enough for 12".
Think 5/8" or better still, 3/4".
My plan is to start by snapping a line around the room showing the
height of the level floor and measuring the thickness of each strip
from there.
This is a good time to rent a laser level.
I'm looking for general opinions on the project and tips to get it done
right? How wide a piece of wood should be used to support the plywood
floor? What's the best way to cut each piece on a angle on the full
length of the piece (about 8')?
You'd need to make a taper jig for a table saw to come close to
getting reasonable tapers. Tapering jigs 8' long are a PITA to handle.
Besides, assuming the floor isn't uniformly sloped, it'll "telegraph" the
unevenness.

Scribing, then jig or bandsawing each sleeper to make dead certain
it was level would be a serious PITA.

You should consider a self-levelling flooring compound. At 1 1/2" at
one end, that could mean a heck of a lot of it. But, if it's feasible,
it's by far the easiest.
Any other gotchas or specifics I should be worried/concerned/carfull
with?
You're going to have to assess the need for vapor barrier.
 
L

louie

Chris said:
1/2" ply isn't good enough for 16" OC, and probably not good enough for 12".
Think 5/8" or better still, 3/4".
Or tongue & groove OSB subfloor?
My plan is to start by snapping a line around the room showing the
height of the level floor and measuring the thickness of each strip
from there.
Use a string level to mark your corners, then snap the line (or use a
laser level as suggested by Chris Lewis)

What's the best way to cut each piece on a angle on the full
length of the piece (about 8')?
You could cut the pieces straight and use shims to make it level,
however you'll need a lot of shim material and it'll have to be placed
under every nail/fastener.

Ditto the comment about a possible need for vapor barrier. In
addition, depending on climate, what about insulating?
 
D

DT

...
I'm looking for general opinions on the project and tips to get it done
right? How wide a piece of wood should be used to support the plywood
floor? What's the best way to cut each piece on a angle on the full
length of the piece (about 8')?
I trim pieces like this fairly often using just a circular saw. Cut the pieces
from 2x4's or even 2x3's. Lay the boards across two saw horses and measure each
end, snap a chalk line. It helps to C clamp one end of the board to the saw
horse to keep it steady, move the clamp when you get to it. Use a nice coarse
blade for the saw, I recommend an 18 or even 16 tooth Dewalt framing blade,
it's what I use.

Now, if you plan your cut line well, you may be able to cut each board into two
equal pieces that fit, especially if you use 2x3's.

If you aren't comfortable sawing straight in a narrow 2x4, start out with a
2x10 or something. Layout the first taper and cut it, then swap ends to layout
the next one, this will keep the remaining board fairly even in width as you
go.

Dennis
 
S

SQLit

charlesg said:
I am planning on raising a floor a floor on a current cement floor in a
small room (100 sq.ft). This was a porch at some point and the cement
floor has a pitch away from the house, so I plan on leveling the floor
at the same time.

Assuming my plan makes sense, I would run the furring strips away from
the house, one end would be about 1/2" thick and the other end, thick
enought to achieve a level floor (I predict no more than about 1" 1/2.
Each strip would be gun nailed in the cement every 16" or so and
plywood (1/2" thick) would be screwed on top to receive whatever finish
is decided (carpet or laminate).

My plan is to start by snapping a line around the room showing the
height of the level floor and measuring the thickness of each strip
from there.

I'm looking for general opinions on the project and tips to get it done
right? How wide a piece of wood should be used to support the plywood
floor? What's the best way to cut each piece on a angle on the full
length of the piece (about 8')?

Any other gotchas or specifics I should be worried/concerned/carfull
with?
I believe you will experience difficulty in "shooting" than many nails in
something that is not much more than a furring strip.

I just removed a floor that was 3/4 ply with 16" OC structure. It was way to
springy for the tile I am installing.

Why does an exterior floor have to be level?
 
J

James \Cubby\ Culbertson

charlesg said:
I am planning on raising a floor a floor on a current cement floor in a
small room (100 sq.ft). This was a porch at some point and the cement
floor has a pitch away from the house, so I plan on leveling the floor
at the same time.

Assuming my plan makes sense, I would run the furring strips away from
the house, one end would be about 1/2" thick and the other end, thick
enought to achieve a level floor (I predict no more than about 1" 1/2.
Each strip would be gun nailed in the cement every 16" or so and
plywood (1/2" thick) would be screwed on top to receive whatever finish
is decided (carpet or laminate).

My plan is to start by snapping a line around the room showing the
height of the level floor and measuring the thickness of each strip
from there.

I'm looking for general opinions on the project and tips to get it done
right? How wide a piece of wood should be used to support the plywood
floor? What's the best way to cut each piece on a angle on the full
length of the piece (about 8')?

Any other gotchas or specifics I should be worried/concerned/carfull
with?
Is the floor exterior? If so, you may want to retain the slope. If not,
I'd consider using a levelling compound. Otherwise, I'd probably bandsaw
them into the taper.
Cheers,
cc
 
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R

rider89

I would guess that this slab was once open to the weather, but is now
enclosed.

bill
 

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