Basement Remodeling question about subfloor
Hello everyone!
I have two questions i need answered about finishing my basement.
First a quick background: the house is 2006 and has above grade main drain pipe. The concrete floor has a vapor barrier under the concrete but the poared concrete walls dont look like they have anything on the outside, just the white rollout fiberglass with plastic shot to the inside for insulation.
Now for the questions
1. I want to use a dimpled membrane with 3/4 T&G plywood or osb as a screwed down dubfloor (i want to do real hardwood in most of the space thats why i want to go 3/4) and put my walls on top of that.
My question is how best to attach the wall baseplates to the subfloor?
Do i go into the conrete also or just attach them to the ply with 2″ screws?
2. I plan to do a sewage ejector pump to facilitate a full bathroom and i was wondering how beat to go about roughing it in. Should i complete the subfloor and framing first and then remove the areas of subfloor i will need to access the locations for breaking up the concrete for rough in or attempt to rouph in first and then make sure i frame the two walls that will have the venting and sink drain piping after the fact? (witch seems doable since ill have the pvc pipes stubbing up after i backfill the rough in)
How would you guys do it?
Thanks for your time its an irreplaceable gift.
P.S. i plan to not put the water heare or HVAC heater on the new subfloor so in the event of a leak it will be under the dimpled membrane. Would you recomend this?
Replies
Andy Engel's wrote a Fine Homebuilding article entitled "The No-Mold Finished Basement", where, on the floor, he used 1" of rigid foam (with all seams taped) covered with 2 layers of 1/2" plywood (attached with concrete screws). On the walls he used 2" rigid foam... Wall framing sits on the plywood subfloor...
I completed a basement bathroom for a client earlier this year, and used Saniflo pumps instead of a sewage ejection pump. I was planning to install a sewage ejection pump, but there was water about 16" beneath the basement floor. With the Saniflo pumps you don't need to trench the floors for the toilet, shower, and sink drains, but you do need to elevate the shower base by 4 to 6 inches. ( I cut a small hole for the shower p-trap in the concrete floor to minimize the step height.)
I would mount your hot water heater and HVAC equipment on top of the plywood subfloor, but in a waterproof pan with a drain tube and condensate pump, in the event of a leak. An electronic alarm for leaks would be worth the investment too...
I like the idea of the airflo under the ply that i wouldnt get with the foam board, especially since i know theres a vapor barrier under the concrete floor, itay be a better way to go on the walls though since theres fiberglass there now.
Its funny you mention the saniflow because thats whats there now in the bathroom the previous owner built and i hate the step up into the bathroom and then a step up again into the shower. I happen to know that the water table under the house is like 7 feet from when they dug for the pool so im sure a sewage pump pit is not going to be a problem.
What do you think about the framed walls? Should i go all the way to the concrete or just screw them to the subfloor?
I’m not a carpenter, so take this with a grain of salt. My framing terminology probably isn’t correct but hopefully you can pick up what I’m trying to throw down.
When framing a standard basement, they usually attach a treated 2x4 to the cement floor and then frame the wall with a standard 2x4 bottom plate on top of the treated 2x4. As far as I know, the new wall sitting on top of the treated bottom plate is nailed into the treated 2x4 and not through the treated 2x4 into the cement slab.
So using that logic, I would think you would secure the plywood to the cement and then secure the wall to the plywood.
The only difference would be an 1-1/2” of wood to secure to in the standard method versus 1” of wood to secure to in your plywood method. I’m not sure if 1” is enough to grab, but I would think it would be ok.
Matt Risinger’s youtube channel has tons of info. He did something similar to yours except he framed the walls first and did foam and plywood between the wall framing.
https://youtu.be/8SSG2AofIe8
Hope this helped
Thank you Mxnavy, i am thinking the same thing, if the ply is secured to the slab there shouldnt be a need to secure the bottom plate also.
Im Gonna go that route
Do what MrEd and Andy Engle recommend for the floor - 2 layers or 1/2" plywood, layers at 90* to each other. This is a very stable floating floor. We do it all the time. very flat and it doesn't call for penetrating the membrane below.
Perimeter lower bottom plate of the walls should be PT and fastened to the concrete floor with screws/ nails suitable for PT and concrete.
Perimeter upper bottom plate can be regular 2x material but you still need to use fasteners suitable for PT.
Intermediary wall baseplate can be screwed into the double layer plywood. 1" penetration is plenty. Typically subfloors are only 3/4".
Turn membrane up the wall a few inches.
Perimeter stud walls should be away from the foundation walls by an inch.. This makes it easy to pull cables behind the wall.
Do your demo of concrete before you start installing the subfloor.. Otherwise your doubling your work. I understand your hesitation, but laying out the Basement walls first will give you insights you wouldn't get until already well on your way. Yeah, then you have to do layout again, after you lay your subfloor, but it'll be quick - especially since you already made your mistakes.
Hope this helps,
Frankie
I haven't worked with dimpled membrane, but I don't think you need the airflow if the basement moisture is condensation from the air, and the rigid foam provides better structure for framing. The goal of the method that Andy Engel's uses is to seal the floor and walls totally, and the rigid foam on the floor gives you a nice cozy floor, unlike most basements. That is why the floor is done first (after rough plumbing), and the the walls framed on top.
Having said that, I just did a basement job where I framed directly on the basement floor, using PT lumber for the bottom plates with corrugated sill plate gasket underneath, so that is your choice. In this case, the rest of the basement was finished by others and I needed to match the level of the existing floors, but the floor is "stone cold" in the winter. (It's just luxury vinyl over a thin foam underlay.)
For the Sani-Flo pumps you don't need a step-up for anything but the shower. I wouldn't like a step for the bathroom and another step for the shower, but I didn't think a small step for the shower was a bad design trade-off. I framed a step in front of the shower to make the entry and exit from the shower easier, and the clients love the bathroom. (They told me they don't use the two upstairs bathrooms any more...)
I had intended to install a sewage ejection pump, so that is a good option, but the rough plumbing should be done first. To minimize the mess when trenching the concrete, I use a circular saw with a concrete-cutting blade, and I built a shroud using corrugated plastic and a wet-dry vac utility nozzle that is hot glued to the saw. This works great for minimizing the concrete dust...
Regards...MisterEd1957
As an owner of a sanibest/macerator I would recommend a proper sewage ejector pump if at all possible. This Sanibest needs cleaning every few years and the macerator blade needs replacing also. Today I spent almost 3 hours on it. Opening the top. spooning out crap and TP with a ladle before I could remove it to clean it properly. The tube with rubber gasket from the rear discharge toilet also leaks. Urine also crystalized, need acid wash to dissolve it.
This is the 3 or 4rth time I have to do this since installing it in 2008. It was the only solution I had but like I said.. If you can dig to install a proper sewage pump... do it.
Here's the article that I've referenced so you can peruse the whole article and the detailed pictures...
I just put a sewage pump in my basement. I cut up the concrete and got the rough plumbing stubbed out first, then I framed in the walls and finished well/vent plumbing. Next I put the floor in (dimple mat, two layers of OSB that overlap. I glued and screwed them together. I set the shower base on the concrete itself and put the floor up to it, as I have 7' ceiling.