new construction to old,leveling out floor

[angrymime666]

Greetings All,

Im not new to the forums, just new to being a member. I have found alot of useful info on here, and thank you.

my current project involves a house built in 1947 and attaching a new addition to the existing structure. as with old houses its not quite square and level and attaching the new does present some interesting issues. not major, but just require some opinions.

I need to mate up a new construction floor to old construction. since the new will be level I need to level out the old to it. basically the old is higher in the centre and drops about 1/4" over 11 ft to the outside wall. I thought about using self leveling then a 1/2 ply on top for a nice new surface for a smooth transition from old to new.

I really dont feel like lowering the centre of the house since I think this will throw off the dynamics of the rest of the house.

your thoughts?

G

[tjbnwi]

Being only 1/4", deal with it after the shell is up and you getting ready to finish. Your method should work well, just keep the added thickness in mind as you're framing.

Tom

[dlhunter]

1/4" isn't that bad. I've seen new houses worse. Like to said, let it go until finish. What type of flooring?

[m beezo]

despite the fact that I might be called a hack but I do not know if I would be too bothered by 1/4 inch in 11 ft. For much of construction I would think that could be accepted without too much problem. I know lots of folks like self leveling but I am not a big fan of the stuff. Have seen it crack many times under stress and when placed on top of flooring, especially when you start to get to the really thin portions.

Like Tom said, keep it in mind once most of it is built and figure out if you can live with it.

This is a good question and I am waiting for other answers. I have struggled with how you build it, level or to match what is there.

[tjbnwi]

Beez,

If you have issues with SLC cracking, use plastic lath. Mapie is the brand I use.

Tom

[davenorthup]

3/16" variance in 8' is the standard tolerance for many flooring types. I'm with Mark if the 1/"4 is gradual over that 10'...

I never had issues with SLC cracking unless the subfloor was not stable..

[angrymime666]

thanks All for the replies.

I will be installing ditra and tiles on the new/old construction. I may be incorrect with how much its is out. possibly 1/4 - 1/2" over 11 feet. I see no issue with the SLC and then adding the ply on top, then ditra and tiles. I just wanted to see if there are alternatives to the solution I had in mind. Im always looking for a better solutions.

I just want to get a near seamless transition.

G

[tjbnwi]

You have to prime the sub floor with laytex primer and use lath (I use the plastic lath from Mapie) if you are using SLC over a wood base. I set my tile on the SLC, I would be concerned about the fasteners for the added layer of ply fracturing the SLC. Stiffen the floor pour your SLC, set your Ditra, set your tile.

Don't forget the in floor heat, pour your SLC over it.

Check the primer bottle, wood floor 50/50 mix for ply, used straight for concrete. The brand I use anyway.

Use low expansion foam at the wall plates and check the floor for possible "leaks". Protect lower floors with plastic to collect "drips".

Use a bow rake with the tines up to massage the SLC. Mix as much as you can at on time. I use the large storage totes or a 30 gallon plastic garage can to mix in. A single pour is always the best way to get this to work.

Measure water exactly.

Tom

[Graacc1]

When you get to the sub-floor sheathing it would be a good idea
to weave the panels across the seam where the two buildings meet,
this will help to strengthen the transition area. In other words,
don't let any sheets land too close to the building seam.

Geoff

[angrymime666]

You have to prime the sub floor with laytex primer and use lath (I use the plastic lath from Mapie) if you are using SLC over a wood base. I set my tile on the SLC, I would be concerned about the fasteners for the added layer of ply fracturing the SLC. Stiffen the floor pour your SLC, set your Ditra, set your tile.

Don't forget the in floor heat, pour your SLC over it.

Check the primer bottle, wood floor 50/50 mix for ply, used straight for concrete. The brand I use anyway.

Use low expansion foam at the wall plates and check the floor for possible "leaks". Protect lower floors with plastic to collect "drips".

Use a bow rake with the tines up to massage the SLC. Mix as much as you can at on time. I use the large storage totes or a 30 gallon plastic garage can to mix in. A single pour is always the best way to get this to work.

Measure water exactly.

Tom

Hmmm... good thinking about the fastners breaking up the SLC. perhaps I could predrill the fastner holes?

the only reason Im using the 1/2 ply is to transition between the new and old construction. the floor is pretty stiff already with 1.5 t&g subfloor on old and 3/4 on new. it just made better sense to me to get a nice level floor by placing the 1/2 ply after the SLC. perhaps Im wrong. wouldnt be the first time :)

does this make sense (SLC, ply, predrill fastners, ditra, tile)or am I better off with ply, SLC, ditra, tile. which would give me a nice seamless floor?

thanks

G

[tjbnwi]

Check the Mapie SLC for thickness allowed. Also check Ditra XL.

I would not put ply over the SLC.

Tom

[dlhunter]

I don't think I would sandwich the leveler between two plywoods. I might build up some of the lowest spots with 1/4" ply before the second layer of ply. How big of an area are we talking about that needs to be leveled?

[tjbnwi]

Forgot to mention, I have put down Ditra in low areas (to decrease the amount of SLC needed), poured SLC over it, placed Ditra over the SLC, then set tile.

Tom

[angrymime666]

I don't think I would sandwich the leveler between two plywoods. I might build up some of the lowest spots with 1/4" ply before the second layer of ply. How big of an area are we talking about that needs to be leveled?

Thanks for the advice. I will not sandwich the leveler with ply. The area is approximately 240 sq feet.

[BThomas]

1947 house
Post war - scarce materials - you say 1.5 subfloor - what are the joists? Tile is heavy. You don't want deflection.
What size tile are you placing? The larger the tile the more important it is for the floor to be level.
I just did a similar ( dip in the floor ) Used SLC than thinset cement board to that before tile. Large 20 X 20 tiles worked out well
Just my 2cents
Bill T