Garage Over Basement

[Renegade1LI]

Just curious if anyone has built a garage with a basement? Just bought a house we might retire at & want to add a second garage that would be attached to the house. The house came with a 1500 sq ft detached garage thats about 200 ft from the house, so I want to add an attached garage being that we're in snow country. We are thinking 900 sq ft with a apartment/guest suite above and I am thinking of building a basement below it to get some extra storage. I'm not looking for how to do it, just some ideas from anyone else that has, what type os access? Definitely would like at least a 4' wide access door from exterior, stairs from inside & a hoist maybe a 4 x 8 platform. It's a fairly level lot so I probably won't add vehicle access, but having a lift will be a big plus.

 

[readhead]

I have supplied steel structure and decking for quite a few garages with usable space below. Any structural engineer should be able to design what you need.

 

[jrsavoie]

I worked on one a decade or more ago, with no penetrations through the floor. You had to go out and around.

Ot was surprisingly economical. Made me wish I had done the same at my house.

Had to pour 12" walls with a brick ledge for the parking garage planks to sit on.

 

[CraigStu]

We once walked through a house under construction that had basement under the garage. As best as I could tell they used something like corrigated roofing panels as the form to pour the concrete onto for the garage floor. I know it would have been a lot stronger than standard roofing but that was it looked like when walking through the basement. We are in a hilly area so there are a lot of homes where the front is ground level and the back is ground level also.

 

[Renegade1LI]

We once walked through a house under construction that had basement under the garage. As best as I could tell they used something like corrigated roofing panels as the form to pour the concrete onto for the garage floor. I know it would have been a lot stronger than standard roofing but that was it looked like when walking through the basement. We are in a hilly area so there are a lot of homes where the front is ground level and the back is ground level also.

It's called Q deck, which is what I will probably use, the last bus garage we built had 8" concrete with # 5 rebar T & B 8" OC. I'll see what the arch recommends, but Q deck is a lot less labor than a formed arch.

 

[duneslider]

It is extremely common in my area, I was going to do it under my garage but after looking at it I just didn't really need more basement space than what I already had.

In my area it is done with precast slab. You just prep the foundation according to the precast engineers spec and once the foundation is in they bring out the slabs on a truck and drop them in place with a crane. I was surprised how affordable and easy to do when I got it quoted.

 

[HoosierMark]

Friend of mine built several houses using prestressed concrete beams to span his garage over basement space. He has passed away but I think he said they used them for building bridge decks. They were available for various length and thickness.

 

[Pontiac787]

This was covered recently. I think the thread was “Garage on a slope” or something similar. Yes, it can be done but it is expensive. The main issue, at least in my experience, is water from snow melt or rain dripping from the vehicles down to the lower level.

 

[firebirdparts]

. I'm not looking for how to do it,

He was just asking how big the door should be. On a flat lot.

and you’re talking elevator inside, right?

I think vehicle access is super important, but if it’s 8 feet below grade, maybe not. I would be happy with my machine shop down there, but getting it there is the problem.

 

[billconner]

I've been in construction for 40 years and never heard the name Q deck. Like Masonite is to hardboard, Q deck was one manufacture's name of or metal deck or form deck.

Thanks!

 

[Renegade1LI]

We use it a lot every school we build, parking garage they are all steel structures with Q deck poured floors. When I release the material I always say Q deck, never knew it by any other name, lol.

Q decking

“Q deck” was the common name for the HH Robertson Company's “Q-Lock Floor” composite floor deck, which was produced in 2” and 3” depths. ... The modern equivalents of 2”-QL-99 and 3”-QL-99 are 2” deep composite floor decks and 3” deep composite floor decks.

 

[Renegade1LI]

I'm not looking for vehicle access in the basement, just storage for materials, household stuff, thats why I will add a lift platform. Would be framed into the floor just like a stairway or duct shaft. As far as drainage I could put in floor drains or pitch the slab to the doors, I would prefer floor drains, could wash cars inside in winter & not have to open doors plus I will be adding radiant in the slab so it will dry quick. Now I just can't wait to start, but I have lots of time to think of how I want everything so thats a plus.

 

[jrsavoie]

This was covered recently. I think the thread was “Garage on a slope” or something similar. Yes, it can be done but it is expensive. The main issue, at least in my experience, is water from snow melt or rain dripping from the vehicles down to the lower level.

Not an issue if properly sealed. The one I worked on was grouted at install then had a sealer installed under a top coat. Hasn't leaked yet. Way over a decade has gone by. The top garage never got built and has been used for a patio instead

 

[73fxe]

Any opening in the floor will let exhaust into the lower level. You will need a vent fan in the lower area.

 

[Renegade1LI]

Any opening in the floor will let exhaust into the lower level. You will need a vent fan in the lower area.

Thats a great point, I do plan to have it professionally designed, everything meeting code or better with good ventilation.

 

[duneslider]

http://suspendyourgarage.com/

Here is a link to one of the companies that does it my area. There are tons and tons of these in my area. Usually, people are using the area for a theater room. It contains the loud sounds very well so you can really crank up the sound without shaking the whole house.
I haven't seen anyone add a lift into it and just use it for storage but why not. I see people put stairs in garages that go down to the basement so this wouldn't be much different. I would think you would just need a hatch that can seal and not let the "bad" air go down. Anyway, seems like your plan would be doable.

 

[Stuart in MN]

http://suspendyourgarage.com/ Here is a link to one of the companies that does it my area.

I noticed on their website in the homeowner question and answer section it specifically says do not spray out your garage with a hose...in any place that gets snowfall, there will be a bunch of melting snow on the floor from cars. Maybe it's not the same, but the floor will certainly get wet from time to time.

I know it can be done in the snow belt, a friend of mine has a house with a basement under the garage. They built it probably 20 years ago and it still doesn't leak as far as I know, but I'm sure there are waterproofing details that must be done carefully to keep it that way.

Sort of off topic, but the house they're working on this season in the This Old House TV show on PBS has a large section of lower level that will have an open patio on top. It's built with wood joists and I believe some type of Zip sheathing, but they haven't gone into much detail about how it will be waterproofed yet.

 

[duneslider]

We definitely get snow here but I wouldn't say it is really common for people to wash their cars in their garage here.

My brother in law has the suspended slab in his garage and I know they don't have any issues with water getting through but again, they don't wash their cars in the garage but they do pull the cars in covered in snow.

I have seen people do the B-deck and concrete also but that will require steel beams under the B-deck. I think you only want to span the b-deck 6-8 feetish between beams. I am guessing whoever mentioned Q-deck was thinking B-deck...

 

[Renegade1LI]

I noticed on their website in the homeowner question and answer section it specifically says do not spray out your garage with a hose...in any place that gets snowfall, there will be a bunch of melting snow on the floor from cars. Maybe it's not the same, but the floor will certainly get wet from time to time.

I know it can be done in the snow belt, a friend of mine has a house with a basement under the garage. They built it probably 20 years ago and it still doesn't leak as far as I know, but I'm sure there are waterproofing details that must be done carefully to keep it that way.

Sort of off topic, but the house they're working on this season in the This Old House TV show on PBS has a large section of lower level that will have an open patio on top. It's built with wood joists and I believe some type of Zip sheathing, but they haven't gone into much detail about how it will be waterproofed yet.

I will not be using precast planks, i plan on doing a poured arch and any openings will get a curb around it.

 

[Renegade1LI]

We definitely get snow here but I wouldn't say it is really common for people to wash their cars in their garage here.

My brother in law has the suspended slab in his garage and I know they don't have any issues with water getting through but again, they don't wash their cars in the garage but they do pull the cars in covered in snow.

I have seen people do the B-deck and concrete also but that will require steel beams under the B-deck. I think you only want to span the b-deck 6-8 feetish between beams. I am guessing whoever mentioned Q-deck was thinking B-deck...

No, it’s still referred to as Q deck, we still call it that

We definitely get snow here but I wouldn't say it is really common for people to wash their cars in their garage here.

My brother in law has the suspended slab in his garage and I know they don't have any issues with water getting through but again, they don't wash their cars in the garage but they do pull the cars in covered in snow.

I have seen people do the B-deck and concrete also but that will require steel beams under the B-deck. I think you only want to span the b-deck 6-8 feetish between beams. I am guessing whoever mentioned Q-deck was thinking B-deck...

No, we still refer to it as Q deck, most vendors still call it that, see link.

What Is a Q Deck and When Do I Use Q Decking? FAQ | D-MAC Industries

“Q deck” was the common name for the HH Robertson Company’s “Q-Lock Floor” composite floor deck. Learn more about Q decking types with D-MAC industries.

d-macindustries.com

 

[duneslider]

https://blog.metaldeck.com/q-decking-definition-types-alternates

Guess this explains why I haven't heard of it...I didn't get into construction until the 90's.

 

[firebirdparts]

This is a good example of what happens here when you give too much information. You'll notice that you've not had a single response that's on topic. But to be fair, how can any of us advise you? Surely, your planned use of the space is more clear to you than it is to us.

 

[rsanter]

a couple people on here have done this over the years.
you need to be very realistic on what will be in the garage as well as what and how you will get the stuff to the lower level.

a friend has a 5 car garage with 1/2 of one of the bays taken up by a long ramp leading to the basement that is the size of the whole house.
this setup allows him to roll anything don there that can be put on a rolling cart. even very heavy things he can use a winch on the truck or a tractor to enable him tp easily and slowly move heavy things up/down the ramp

for the floor structure, parking cars and having some storage is one thing, putting tons of equipment on that floor you better tell the engineer what the total weight and the floor loading PSF is going to be