Detailing Wine Cellar Beneath Front Porch
I’ve designed wine cellars, conditioned and unconditioned, in basements and main floors, in a cave, etc., but I’ve never designed one in a basement, under the front porch. What is unique for me is that, it is under the front Porch of the house, so the concrete floor of the front porch is the ceiling of the wine cellar, and will serve as a FEMA room too.
The house is near St. Louis, MO, CZ4. The exterior dimensions for the Porch are 12’x12’. The Porch is elevated about 4’ from the ground level, so it will have 7 steps going up, and three exposed sides, probably with cultured stone.
I’m also planning on using capillary break on the footing, 3/4 gravel rock with draintile on the outside and inside of the footings. I don’t know what type of water-proof and thermal material to use between the conc. Porch floor and the top of the foundation wall, maybe a concrete silicone sealant (Dap, Quikrete, etc.); but I’m still looking for more specific ideas for that Porch/floor ceiling and top of foundation wall joint.
On the inside, I was planning on installing 2” R13 polyiso min., around the conc. walls and ceiling, then 2×4 flat wall, before we clad with T&G wood. The owner doesn’t know yet if it should be conditioned or not, but he knows for sure, that where his wife’s “office” will be… ;-))
I’ve read a couple of BSC articles, some at GBA, FHB, and JLC, more on the BS of the argument, for basements, but not on a wine cellar argument. Any thoughts or ideas are welcome. Thanks.
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Replies
Armando,
Is the porch fully covered? In a previous house, I had a basement room like this and keeping water out was a challenge. It is important to ensure that the pan membrane is integrated correctly with whatever you are doing on the exterior. And as I just noted in another discussion, you want to have a drip edge groove in porch slab.
Yes, a full membrane "roof" on the porch floor is critical, with the waterproofing wrapping down and over that joint between the slab and the foundation walls to join with the waterproofing on the walls. If you use liquid waterproofing on the walls, it can go over/around brick ties used to keep the stone veneer in place. Once you've got a 100% water barrier on the outside of roof and walls, you can use any foam insulation on the interior. I'd aim somewhat higher on the R value, with half the wall and all of the ceiling exposed to the exterior. R-19 minimum, but more wouldn't hurt. No floor insulation - you want the ground to temper the air inside the wine cellar.
For a wine cellar there are two ways to go. One is to essentially build a walk-in fridge, which is an insulated room with a heat pump. The other is to have a room that stays at underground temperatures. I'm going to talk about the second.
As a rule of thumb, once you get to 12 feet below the surface the soil temperature is constant year-round, and it's equal to the year-round average air temperature. You can get a good idea of the average temperature by getting the average monthly high and low temperatures for a place and averaging those 24 numbers, for St. Louis it works out to 58F. Another rule of thumb is that earth provides about R4 of insulation per foot, so that 12' of soil provides about R48 of insulation. If you want a room that is going to stay at soil temperature year-round, and it's less than 12' below the surface, it has to have R48 between it and the surface.
This room is going to have 100% humidity almost all of the time. There will be some air exchange with the outside, and when the outside dew point is above 58F there will be condensation. There won't really be any way for the moisture to escape. Wine itself won't be affected by the humidity, it will actually help the corks maintain their seal, but the labels may get moldy and the glue on the labels may soften causing them to fall off. You definitely want the interior to be made of impervious and waterproof materials.
Such a wine cellar would not be part of the conditioned part of the house, and the border between the wine cellar and the house should be treated like an exterior wall.
My wife's sister has a very similar room to this in their home outside Toronto. It's basically a poured foundation and concrete ceiling. It acts like a natural root cellar, but without the dirt floor. You may find you don't need to condition it to be a wine cellar, it might end up maintaining the right temperature (or at least pretty close) on it's own. That might be something to think about, but I know the wine people are pretty particular so it might be worth monitoring things for a little while before you trust it completely.
I have a smaller version of this in my own house, with a wood framed "ceiling" that supports a brick porch above. The wood isn't in the best of shape. I'd consider using a steel structure here or prestressed concrete pad "ceiling". Basically build with materials that won't have a problem if they get wet periodically. You're building an underground vault, and underground stuff tends to be damp. I would make sure to use moisture proof materials regardless of the type of sealing work you do trying to keep moisture out. Belt and suspenders here is going to help you down the road I think.
Bill
I built a similar space, a basement extension that serves as the front porch and underneath is part of the conditioned basement space (a bathroom).
The deck of the front porch is actually a roof and I treated it as such. I ended up using steel corrugated decking that slopes towards the front foundation. it allows serves as the pitch for the concrete when it got poured. I used poly sealant at all the seams and transitions of the steel decking to make it watertight from moisture content of the concrete slab. The concrete on top sheds bulk water, it's open to the elements. The underside I primed with an etch primer and sprayed CC spray foam which meets the poly sheeting at the walls. The Wall poly goes down to the subslab gravel layer. All this in hopes that if the roof or the foundation walls develop a leak, I have a redundant interior system and it also keeps moisture out so it can be better controlled in the conditioned space. The foundation is ICF with a roll on waterproofing (not very good but we had amazing constraints) and also two layers of dimple sheeting and gravel backfill for good drainage.
Hope that helps with some ideation.
Jamie
It sounds like it will be a “cold room / root cellar” When it is -10° outside and the cement roof gets cold even with a few inches of foam the roof will be colder than the floor. With little air circulation from the home being a concrete box left to its self it will want to be 55 and almost 100% humidity. That makes it a good wine cave but when it is cold outside the roof will condense water and it will drip like rain.
Consider building some slope into the ceiling so the condensation will run off to one side and down the wall to a floor drain. The other option is to plan on dehumidifying enough the keep the dew point below the ceilings temp but you will still want a drain.
Walta
Great information, thank y'all. I wish this wine cellar was inside the house foundation, but being under an open front porch, and 4' of the ground, presents different challenges. You guys gave me some good ideas to follow through. I appreciate it. 👍
I have storage in the crawl space under my porch. The 2x8 walls are insulated and covered with plain old t&g cedar on the interior. The exterior is redwood over asphalt paper. The concrete slopes outward to pin hole drains, so any moisture can drain. My AcuRite sensor shows 42f it is 9f outside.
Looks like similar approach. Thanks.
Hi Armando! I think others have touched on the fact that the biggest worry is bulk water/rain water penetrating from the ceiling/porch above. Just how many thousands of dollars will the wine collection cost... not to mention the interior finishes? A water leak from above could cause a lot of damage quickly. The most bombproof option would be an inverted roof with drainage mat--per Figure 1-3 in this column:
BSI-052: Seeing Red Over Green Roofs
https://www.buildingscience.com/documents/insights/bsi-052-seeing-red-over-green-roofs
Once you have dealt with that aspect, you want to insulate the above-grade (and slightly buried) portions of the walls, and the porch ceiling. Those are the portions of the basement wall that will see seasonal temperature extremes--check out the infrared shots below. Once you're maybe a foot or two below grade, the temperatures have a lot less variation. The first set of shots was taken in winter, the second in summer... with expected patterns.
Hi Kohta – Thanks for the guidance and info. As I was suspecting, this is much more than a simple wine cellar. I think I don’t have a problem with the inside detailing, my problem is with the outside, and the cold joint between the Porch floor and the top of the foundation wall. Making it worse is that half of the foundation walls are exposed, and half are under ground. I’m going to do a detail and post it here for review, based on Fig. 3. I’m thinking of a cold cellar under a porch kind of thing, common up north.
Armando, you might condsider using some EPDM roofing membrane as a sort of waterproof liner between the top of the wine cellar and the bottom of the porch. You'd need to be sure the top of the wine cellar was pitched and didn't have any depressions that would allow water to pool up on top of the membrane though.
It's amazing how something so seemingly simple can become so complex when you want to do it right! :-)
Bill
Up north, the ground is a lot colder and the summers aren't as hot.
In St. Louis, average high temperature in June is 86F, July is 90F and August is 88F. Read my response #3, I believe you're going to need significant insulation to keep this space in the safe storage range for wine during the heat of summer.
Thanks Guys. I'm working on a detail using sealed 4'x8' PVC Sheet Panels to form the Porch floor, as opposed to a suspended OSB, but leaving the PVC there. Then I'll cover it with EPDM, a drainage mat, and then the slopped concrete slab, plus required flashings.
The exterior of the walls, I'm thinking of using a waterproofing coating or membrane, followed by cladding (Stucco, Cultured Stone, etc.) above ground, and a drainage panel below ground.
The interior of the walls, I’m thinking 2”-4” polyiso against the walls and ceiling, 2x4 flat framed wall, and T&G Cedar.
I’ll post the details for review when I’m done with them.
Hi Armando,
I read a contractor's blog several years ago where he used a piece of right-angle stainless to cover the gap between the wall and "floor." The floor edge had an additional bend that he epoxied into a kerf cut in the patio slab. It looked a lot more robust than anything else I could find. Keeping the rubber roofing membrane under the slab (and tying it into the wall) would give you redundancy.
In the best of all worlds, this whole assembly will be located under a deep overhang or porch.
Here is a quick detail for the Porch Floor and the Foundation Wall joint, as described above. Any comments?