Old House floors

try2hard

Hi everyone. I'm in the process of buying an old home that will be gutted down to studs and re-modeled. I will be installing a new hydronic system, which I'm planning to be a mix of radiant floors and panel rads. Three floors including basement. I'm well-studied in hydronics and radiant starting with Dan's books and moving on from there. I also work with one of my friends, a heating contractor, with many of his system plans, heat loss calcs, control setup, etc.

The first floor will have radiant floors, but I'd like some input on the specific method. I was planning a staple up with plates because I have easy access to the joist bays from the basement, but have been considering over-the-floor options also. The subfloor is old planks, not plywood. It's very structurally sound and fairly level but I will be doing some major floor leveling for sure, and adding an additional bracing as needed. The final flooring will be ceramic tile and/or laminate wood -- depending on the living area.

Does anyone have experience using some above-the-floor radiant techniques in old homes that need floor work anyway? I've never worked with any thin-slab or above-floor systems. I'm just thinking it might be worth integrating the leveling and build-up of the floor with the tubing installation. Pouring a full pad makes me nervous because of weight. Further, if I proceed with staple-up/plates, any floor leveling materials above will add some thermal mass for sure.

Thanks, looking forward to your comments.

Jamie Hall

No comment directly on the heating system choice -- though I do sort of wonder what, if anything, was used before...

However. Old floors of that nature need to be approached with one caution in mind: they were not designed to modern structural standards with regard to deflection (the modern standard is a deflection of 1:360 at full load; the old -- if used at all -- frequently was twice that, and may not have been applied at all). Why is this relevant? Because it means that you should assess the deflection of each plank separately at full load. I have found that it is not uncommon for a given plank to deflect as much as an inch at mid span, particularly if the joist contact is uneven (as it frequently is). You may find that to obtain adequate stiffness for tile or any rigid floor leveling material that you have to add bracing to either the planks or the supporting joists.

This may also be a consideration for the type and installation of the radiant tubing.

STEVEusaPA

You may want to consider radiant ceilings and avoid alot of the pitfalls.
Staple up only with aluminum plates.
If you're doing ceramic, you could shore up the floor and do a wetbed, but you're looking at probably 1 1/4" minimum at the highest point and whatever thickness needed at the low point for a level floor. Shoring up is probably going to mean some beams (steel or engineered), a footer in the basement and posts-and an engineer.

Jamie Hall

@STEVEusaPA 's comment reminds me to add -- watch your dead load if you go ceramic. Again, older floors were designed for lower loads.

They are perfectly adequate for normal loads, and usually completely safe (although one can ask an engineer if one is concerned), but adding say 20 pounds per square foot for wetbed and tile may be a bit much, perhaps.

Gordy

First let's define "old home". then let's define what you actually have for floor joists their centers, and spans. I see you have planks for sub floor? Lastly is there bridging installed.

I use to live in a home built in the early 50's. The floor joists were sistered every other one. Bridging installed, joist size to spans were well with in the 360 deflecto rating.

Some would consider that an old home..

A 360 deflecto is the bare minimum for simple tile. Some other types require hire ratings. Depends on thickness of your tile, marble, or stone selection.

Jamie Hall

Good point, @Gordy -- I live in a bit of a bubble, and to me "old" doesn't start until about 1890... and more or less routinely contemplate the vagaries of buildings built around or before 1800!

Gordy

That's what I would call old, and a treasure.

My mom's previous home was circa 1910. Some real hacks back then on that one. 2x8 (full) spanning 14'-15'. 16 o.c. The floor had a roll as you walk feeling..........however it's still standing. Quality lumber back then old growth.

ChrisJ

Jamie Hall said:

Good point, @Gordy -- I live in a bit of a bubble, and to me "old" doesn't start until about 1890... and more or less routinely contemplate the vagaries of buildings built around or before 1800!

Mine didn't originally have a subfloor, just tongue and groove planks across the joists. No sheathing either, just clap board.

However, I've never noticed the floor boards deflect at all. The joists however, being 2x8's across a 15' or 16' span 24-26" on center, do deflect, a lot. I say 24-26 because whoever built the house clearly didn't measure much. They're "about right".

One day I may do something to beef it up. Maybe not, I don't know. It's only lasted 150 years so far.

Gordy

It was no different back then. You still had various levels of quality homes.

In my mom's home which was a one story someone either at the time of construction, or later used 1x4's sandwiched to make a 4x4 randomly installed mid span to basement floor to beef the spans up. I say randomly being maybe every 4 joist.

The old FA octopus coal furnace they just cut a foot out of the joist mid span for a diffuser, and then scabbed a 2x8 4' long next to to it. Lol.

Jamie Hall

It's sometimes amazing that the old places stand up... the old entry hall in the main place I care for is in the bit built right around 1790. Single 1 by 10 to 12 floorboards, on joists which are more or less 8 by 8, give or take an inch, on spacing more or less 24 inches, give or take an inch ... or two or three... spanning 16 feet -- and not all the floorboards touch all of the joists. There is a grandfather clock in that hall -- about 1810. I can't keep it running as the floor deflects too much!

And you have to love things like the cut out joist!

Gsmith

not much changes. I just had a plumber cut 4" diameter holes through seven consecutive 2x8 floor joists to run a new sewer drain on a bathroom renovation--he didn't appear to care if the remaining wood could support the floor-it probably could not. Building inspector caught it.

Gordy

Yes somethings never change. 1/3 the depth of a floor joist, and not closer than 2" from ends, top, or bottom. 2 3/8 would have been max for a 2x8. What was done to correct the issue?

Gsmith

steel straps added top and bottom to equal the strength of an uncut joist.

try2hard

Thanks for everyone's comments and good shout-outs about the floor load and deflection. I'm thinking the finish flooring is going to end up more on the laminate end, maybe just adding ceramic in the kitchen and bathrooms.

My general contractor and I were discussing further today and I'm thinking of having a structural engineer come in, if only for general thoughts. The home was built in 1930, so not super old but not mid-century either.

I'll post back later in the project.

JUGHNE

I have some old literature from the "Infloor" radiant heating company. That system simply stapled tubing to your existing wood floor and then covered it with lightweight concrete.
The pour is a minimum of 1 1/4" @ 12 lbs/sq ft.
It is self leveling which could correct some issues.
Gyp-crete can have ceramic tile laid over it or carpet.
Infloor is now defunct I believe but there is still the Gyp-crete product available. A company that deals in that could perhaps direct you concerning your structural situation. FWIW

Gordy

johnbridge.com

Brewbeer

+1 to johnbridge.com I have multiple tiling projects posted on that site and they were very helpful in one project where I needed to sister existing joists to reduce deflection enough to install tile.

Gordy

They are like the heating help.com of tile. Awesome site.