Seeking Advice on New Construction Basement Shop

[ajt976]

Hello fellow garage junkies! Long time lurker/newbie here seeking advice for the initial planning of what will be my future 'basement shop' for our new construction home. We are currently finishing up the architecture phase so looking to get some input before we get the plans engineered. Please realize, my setup is far from ideal that presents some unique challenges and I understand that I will need to make compromises, just hoping you all who may have experience with this can help point out things for consideration before we begin building.

Essentially we are planning on utilizing a suspended slab (poured slab over steel decking) in our 850sqft garage that will provide around the same space underneath for a shop. We are doing 9' foundation walls so my guess is I will have somewhere around 8' ceiling height with the main support beam dropping down from there (height TBD). The current plan is to have that beam spec'd large enough to allow for a single post in hopes of keeping as much open floor space as possible. Our lot is a walkout, and while our final grade has yet to be determined the goal is to have access to the shop from the outside via overhead door as well as from inside the house with a 32" man door. Attached is a rough sketch of the space I'm working with and the adjacent basement areas, I've tried to add enough dimensions to give an idea without going overboard haha.

Overall this shop will need to be multi-use as well as some level of storage for outdoor equipment and a UTV (not sure if HOA will allow a shed). I like to dabble in a bit of everything so being able to keep the shop flexible to a degree is kind of what I'm after. Currently my interests are in woodworking and have started my collection of equipment (contractor table saw, router table, dust collector) with the hope of potentially getting into some automotive and welding projects if I have reasonable drive up exterior access to the rear of the shop.

My mind is all over the place trying to plan things out. I guess in general my question to you all would be what features would you recommend putting in this space this size and what all should I try to get added during construction? So far my thoughts are at minimum at least one floor drain, a utility sink, and a sub-panel. Anyone have thoughts on ventilation? Would you consider adding a second man door into the 'future bathroom' or opt instead for a dedicated urinal in the shop (probably the only place in the house where I could pull that off)? What else am I missing here?

Any insight is appreciated, I've come to learn and am keeping an open mind! This is our first build and my first dedicated shop, I'm sure that I will miss things but hoping to make sure I get the essentials covered.

Thanks in advance!

 

[larry4406]

Hope your budget is good.

Suspended slab on steel on decking is not cheap.

Steel has depth which affects head space below which might mean taller foundation walls and dropped footings so as to get acceptable height in the shop. This means lowered slab elevation in the shop. This can also mean the shop no longer gravity sewers and an ejector system is needed.

Pay attention to water stop seal of perimeter slab to foundation wall to preclude leakage into shop when washing garage above.

Weight of finished concrete might overload the steel unless the slab is poured at an incline to keep it at constant thickness. This requires steel to be pitched and beam pockets for same to be pitched.

I just went thru all of this for a customer.

 

[DBS5Window]

A friend of mine has a home with the same layout. Controlling condensation will be an issue if your garage above isn’t well insulated and climate controlled. Cold concrete garage floor on top and metal steel decking shop ceiling in warm moist air in the workshop dripping condensation in the workshop.

 

[ssdave]

I'd put in a separate mini-split for heat and cooling, to avoid odor and dust interchange into the living space. As part of that, put in an energy recovery ventilator to exchange fresh air into the space. Essentially, you want this to be sealed off from the house from an air exchange standpoint.

 

[matt_i]

Based on "UTV" and or other gasoline fueled items I'd place the floor of that basement space 1 step lower than the main floor where you will have furnace or water heater. Alternative would possibly be to raise those (assuming natural gas) appliances off the floor with steel stands or concrete blocks...

Just like a ground-level garage you don't want gasoline fumes creeping along the floor and then to be lit by open flames from the NG combustion.

Underground, moisture is always an issue. I'd make sure the poured (??) walls are exterior treated & tiled the same as if it were a high-end finished basement. High grade vapor barrier (10+ mil thickness) under the floor slab plus 6" minimum of washed, crushed limestone (iow increase the stone base to help break surface tension to the underside of the slab).

You will want to detail how garage door hardware, track-hangers, and openers, exterior trim (gaskets) are attached. Again I'm assuming poured concrete, its a little less forgiving than conventional wood framing.

 

[ajt976]

Hope your budget is good.

Suspended slab on steel on decking is not cheap.

Steel has depth which affects head space below which might mean taller foundation walls and dropped footings so as to get acceptable height in the shop. This means lowered slab elevation in the shop. This can also mean the shop no longer gravity sewers and an ejector system is needed.

Pay attention to water stop seal of perimeter slab to foundation wall to preclude leakage into shop when washing garage above.

Weight of finished concrete might overload the steel unless the slab is poured at an incline to keep it at constant thickness. This requires steel to be pitched and beam pockets for same to be pitched.

I just went thru all of this for a customer.

Larry, noted, it's definitely not cheap but in our area this seems to be the normal process for a suspended slab. I will ask about the incline/pitch, good insights. The perimeter seal is definitely a concern of mine as I would like to be able to utilize the upper garage to wash a car in the winter if necessary.

A friend of mine has a home with the same layout. Controlling condensation will be an issue if your garage above isn’t well insulated and climate controlled. Cold concrete garage floor on top and metal steel decking shop ceiling in warm moist air in the workshop dripping condensation in the workshop.

Absolutely, the upper garage will be insulated, however not sure on how 'conditioned' it will be. As I'm sure is typical in your area, I imagine I'll be lucky to get a single register and return in the entire garage. I was wondering if it would be worth looking into a LNG heater for the upper (and possibly lower) garage(s) to help with this.

I'd put in a separate mini-split for heat and cooling, to avoid odor and dust interchange into the living space. As part of that, put in an energy recovery ventilator to exchange fresh air into the space. Essentially, you want this to be sealed off from the house from an air exchange standpoint.

Dave, this is good input. Honestly I went back and forth about tying this lower shop in with the rest, specifically if I decide to vent the dust collector outside I was concerned about drawing in fumes from the LNG furnace in the adjacent basement. I will bring this up with the builder in our meeting this week to see if he has any suggestions. I like the mini-split idea in general, just not sure how we would implement it.

Based on "UTV" and or other gasoline fueled items I'd place the floor of that basement space 1 step lower than the main floor where you will have furnace or water heater. Alternative would possibly be to raise those (assuming natural gas) appliances off the floor with steel stands or concrete blocks...

Just like a ground-level garage you don't want gasoline fumes creeping along the floor and then to be lit by open flames from the NG combustion.

Underground, moisture is always an issue. I'd make sure the poured (??) walls are exterior treated & tiled the same as if it were a high-end finished basement. High grade vapor barrier (10+ mil thickness) under the floor slab plus 6" minimum of washed, crushed limestone (iow increase the stone base to help break surface tension to the underside of the slab).

You will want to detail how garage door hardware, track-hangers, and openers, exterior trim (gaskets) are attached. Again I'm assuming poured concrete, its a little less forgiving than conventional wood framing.

Thanks Matt, I do believe we are already required by code to have these appliances off the ground but I will check. If it makes any difference this lower shop is separated from the rest of the basement by 8" poured concrete foundation walls, sorry that's probably not real apparent from the sketch. Per the moisture, yes, definitely concerned. When I asked our builder about this, he explained that they use a dual tile system for drainage. I'll ask about the prep for the slab, I wonder if it would be worth insulating underneath as well? And yes, I am weary of the garage door framed into the concrete foundation walls. I tried to do some research on this and how it would work. I won't know for sure until the plans are engineered but he gave the impression that they would likely want a piece of steel to serve as a header at the top of the foundation wall? Depending on where that sets, I imagine that would make it kind of goofy for framing in the top of the garage door opening. Anyone have any examples of how this is done?

Thanks for the responses!

 

[matt_i]

Its sort of non-traditional, and might be slightly more expensive, but might be better if you could header with a heavy-wall box tube. There are still radiused corners to deal with instead of sharp edges but at least it could be set planar to the outside of the poured wall (and presumably by ordering proper size, achieve same on the inside of the wall as well.

 

[spudley]

Have you considered precast concrete panels such as Spancrete? I have those under my home 24' x 34' garage topped by 3" of concrete. I access this strictly recreational room under the garage through the basement or an outside "Bilco" (Wizard of Oz type) door leading outside.

I have an 8' ceiling with no posts or beams. If I used the area as a shop, I'd want a higher ceiling. I heat the area (when needed) with a 8' electric baseboard easily, and run a dehumidifier in the summer.

Above the 4' Bilco opening, we used an 8" steel beam as the header.

 

[ajt976]

Its sort of non-traditional, and might be slightly more expensive, but might be better if you could header with a heavy-wall box tube. There are still radiused corners to deal with instead of sharp edges but at least it could be set planar to the outside of the poured wall (and presumably by ordering proper size, achieve same on the inside of the wall as well.

Can't hurt to ask. I assume the objective here is to make it easier to deal with than a typical I beam as far as framing in the door? Again, I was a bit confused on how high in the wall the steel would be placed and if there would be space between it and the rough opening of the door.

Have you considered precast concrete panels such as Spancrete? I have those under my home 24' x 34' garage topped by 3" of concrete. I access this strictly recreational room under the garage through the basement or an outside "Bilco" (Wizard of Oz type) door leading outside.

I have an 8' ceiling with no posts or beams. If I used the area as a shop, I'd want a higher ceiling. I heat the area (when needed) with a 8' electric baseboard easily, and run a dehumidifier in the summer.

Above the 4' Bilco opening, we used an 8" steel beam as the header.

I did do some research on that and I didn't find many in my area that opted for the precast slab, I was wondering if it had to do with the proximity to the manufacturers and transit costs? I will inquire with the builder to see if he has any insight on this. Good to know on the height. 8' is definitely not ideal, however my last "shop" was the 2 car garage (and only a portion at that) in our split level that was just under 8'. I'll see what he says about potentially digging this space down, I know he said the sewer is plenty deep on this lot, however ultimately it will come down to cost.

 

[rsanter]

You need to better define what you will be doing in the shop. That can lead to more recommendations.

If it was me I would try for an additional foot of height.

Also I would look to see if the install of an I beam that would both help support the ceiling as well as give you something to lift things could be a great benefit.

Yes adding the man door into the bathroom can be very worth it. You can then you it also as a sort of mud room that you can wash off in or shower ....etc before going into the house

Compressed air? Where is the compressor going to be? If it was me I would install it on piping that would connect the main garage, the lower shop, and a couple places on the side and back of the house. This would mean you can use just one compressor and have access to air in several locations. How about airing up tires for the main garage? Blowing things off or inflating things in the back yard.....etc

How about including a little room on the outside of the house to store yard tools or misc. if the HOA does not allow a shed and you do not want to clutter your shop space....including a exterior axess closet on the house can solve this. You could even set it up to be a compressor room as well

 

[firebirdparts]

if you do woodworking, then I would say spare no expense on sawdust control. I had a boss who did that in his basement, and it was spotless, so it is possible. That is a big issue with wood. You could consider having some equipment that rolls outside. You could consider how you're going to compress storage of items used for various types or work while you do other work. That is a big problem for me; I grew up poor, and all my equipment is free/cheap/stolen, so I don't get to pick the perfect fit for my space. If you paint anything, then you want fume exhaust for that as well. The building style will be pretty airtight, and that'll have advantages and disadvantages.

 

[atch]

I have two recommendations.

1. (touched on above): Do NOT use house AC/heat in this shop. No matter how much dust control you have you'll still get super-fine sawdust particles in the rest of the house. You won't need A/C unless you consistently leave the outside door(s) open during hot weather. You won't need much heating either. Install some kind of electric baseboard or similar for the winter if it becomes necessary. I'm 2 hours straight east of you so have the very same climate.

2. Insulate the OUTSIDE of your concrete walls. 2" of rigid foam works wonders.

The advice above comes from personal experience. I built a house in 1987 with my shop in the basement. I lived there 13 years.

1a. I turned off the registers in the shop shortly after moving in and kept the door closed. We still got fine sawdust in the house on occasion. I never opened the heat/AC registers again and never needed heating or AC.

2a. I insulated the entire outside of all concrete basement walls with 2" of rigid foam. Because the concrete was always at room temperature (never cold) warm humid air NEVER condensed on the walls. There was never any need for dehumidification and there was never the musty smell typical of basements. The foam went all the way to the top of the concrete. Obviously some of this was above ground level. I had the gutter folks make up flashing using the same metal as the gutters and covered the foam with this flashing. Therefore none of the foam was exposed to sunlight or other outside elements. I framed the house such that the underneath of the siding (outside of the sheeting) was in the same plane as the outside of the flashing.

 

[ajt976]

if you do woodworking, then I would say spare no expense on sawdust control. I had a boss who did that in his basement, and it was spotless, so it is possible. That is a big issue with wood. You could consider having some equipment that rolls outside. You could consider how you're going to compress storage of items used for various types or work while you do other work. That is a big problem for me; I grew up poor, and all my equipment is free/cheap/stolen, so I don't get to pick the perfect fit for my space. If you paint anything, then you want fume exhaust for that as well. The building style will be pretty airtight, and that'll have advantages and disadvantages.

Yea, I know that in my previous garage I had a hard time containing dust so I'm really hoping to implement some legit DC in this shop. The idea is that it should be easier now with a dedicated space that won't be housing our daily drivers. And yes, I really like the idea of mobile bases for everything. I guess I must have a fear of commitment because I'm very hesitant to make anything permanently fixed! Kind of why I'm having a hard time finalizing these plans, specifically regarding poured foundation walls, haha.

I have two recommendations.

1. (touched on above): Do NOT use house AC/heat in this shop. No matter how much dust control you have you'll still get super-fine sawdust particles in the rest of the house. You won't need A/C unless you consistently leave the outside door(s) open during hot weather. You won't need much heating either. Install some kind of electric baseboard or similar for the winter if it becomes necessary. I'm 2 hours straight east of you so have the very same climate.

2. Insulate the OUTSIDE of your concrete walls. 2" of rigid foam works wonders.

The advice above comes from personal experience. I built a house in 1987 with my shop in the basement. I lived there 13 years.

1a. I turned off the registers in the shop shortly after moving in and kept the door closed. We still got fine sawdust in the house on occasion. I never opened the heat/AC registers again and never needed heating or AC.

2a. I insulated the entire outside of all concrete basement walls with 2" of rigid foam. Because the concrete was always at room temperature (never cold) warm humid air NEVER condensed on the walls. There was never any need for dehumidification and there was never the musty smell typical of basements. The foam went all the way to the top of the concrete. Obviously some of this was above ground level. I had the gutter folks make up flashing using the same metal as the gutters and covered the foam with this flashing. Therefore none of the foam was exposed to sunlight or other outside elements. I framed the house such that the underneath of the siding (outside of the sheeting) was in the same plane as the outside of the flashing.

Thanks for the input Mike. I started research on the best way to accomplish this and wondering if a small ERV would work for this (anyone have experience with the Panasonic FV-04VE1 and comment on if it's sufficiently sized for this space?) to exhaust anything from the shop and bring in some fresh air.

I'm glad you brought up the bit about insulation the foundation and then perhaps not needing any A/C. I feel like a hole in the ground would be reasonably comfortable in the summer time and you'd only need a little help with heat during the winter.

PS - Go Tigers!

 

[Brconley]

I’m currently working on HOA approval for a 36x36 detached shop with a suspended slab on a walk out lot. Looks like we’re in the same area. Lots of good info here. Thanks for the thread. I’m planning cars and metal work on the upper and woodwork on the lower.

When I was researching, a mini split was a little more expensive (before operating costs) thank the various heating options. But seemed like a reasonable investment to be able to run heat in both garages and have a/c if needed was pretty attractive. I think the difference was between 1,000 and 1,500 in my case.

Also, separating the wood work from other projects helps a ton with dust control even before you add other methods.

Lastly, not sure if you do auto work, but if you want a lift in the garage portion it can be done, but it takes some figuring from a structural engineer. Just had them stamp my plans. Happy to share a contact local if it’s helpful.

Subscribing to your thread. Looking forward to updates.

 

[ajt976]

I’m currently working on HOA approval for a 36x36 detached shop with a suspended slab on a walk out lot. Looks like we’re in the same area. Lots of good info here. Thanks for the thread. I’m planning cars and metal work on the upper and woodwork on the lower.

When I was researching, a mini split was a little more expensive (before operating costs) thank the various heating options. But seemed like a reasonable investment to be able to run heat in both garages and have a/c if needed was pretty attractive. I think the difference was between 1,000 and 1,500 in my case.

Also, separating the wood work from other projects helps a ton with dust control even before you add other methods.

Lastly, not sure if you do auto work, but if you want a lift in the garage portion it can be done, but it takes some figuring from a structural engineer. Just had them stamp my plans. Happy to share a contact local if it’s helpful.

Subscribing to your thread. Looking forward to updates.

Nice to see another local! I'm happy you are in an area that will allow a detached shop (fingers crossed you get approval). Unfortunately the lots in our chosen neighborhood just aren't big enough at 1/3ac to accommodate this, not to mention we are going to be fighting a faster dropping grade than anticipated.

I like the mini-split for the upper garage, however I'm just not sold yet on if it will be needed down below. Due to the current grade on the lot, we will be dropping the house down pretty close to street level and that will put the lower 'shop' area pretty well underground. Are you planning on using one mini-split unit to serve both spaces? Just curious how you will do this. I'd really like to be able to have some kind of access from below (thinking air compressor lines) however I'm not sure I want to put a penetration in the slab itself and wondering if going out and up would be better.

I plan on inquiring about having the engineer take the 'future lift' plans into account, however I believe I will unfortunately be limited on height in the upper garage as well. Definitely worth asking about though. A nice 4 post lift would be great for storage and allow for some work as well.

 

[ScottsGT]

Go higher.

That's about all I got.

 

[Stuart in MN]

Yea, I know that in my previous garage I had a hard time containing dust so I'm really hoping to implement some legit DC in this shop. The idea is that it should be easier now with a dedicated space that won't be housing our daily drivers. And yes, I really like the idea of mobile bases for everything. I guess I must have a fear of commitment because I'm very hesitant to make anything permanently fixed! Kind of why I'm having a hard time finalizing these plans, specifically regarding poured foundation walls, haha.

I've recently been watching videos from Blake Weber, a woodworker in California. He works out of a one car garage, and has some pretty clever ideas for dust control, as well as ways to fit all his machines into the space. He may be worth checking out for ideas and inspiration. https://www.youtube.com/c/BlakeWeber/videos

 

[Brconley]

I like the mini-split for the upper garage, however I'm just not sold yet on if it will be needed down below. Due to the current grade on the lot, we will be dropping the house down pretty close to street level and that will put the lower 'shop' area pretty well underground. Are you planning on using one mini-split unit to serve both spaces? Just curious how you will do this.

You can get mini splits with one outside unit and multiple, in this case 2, interior units. Depending on heating cooling requirements prices vary but multi zone not much more than single zone.

 

[ajt976]

I've recently been watching videos from Blake Weber, a woodworker in California. He works out of a one car garage, and has some pretty clever ideas for dust control, as well as ways to fit all his machines into the space. He may be worth checking out for ideas and inspiration. https://www.youtube.com/c/BlakeWeber/videos

Yes! I've seen is videos before and was interested in his latest workshop build. I will definitely be looking to guys like him with the 'one car shop' type setups for something to go off of.

You can get mini splits with one outside unit and multiple, in this case 2, interior units. Depending on heating cooling requirements prices vary but multi zone not much more than single zone.

That makes sense actually. We talked with our builder today and are making sure I have provisions to add a mini split and/or ERV/alternate ventilation for both the upper and lower garages. He also said that some electric baseboard heating would be standard procedure for this type of build to help keep both slabs warm.

It does sound like I'm gonna be stuck on height down below unless we are willing to drop some serious cash to dig it out. I realize this isn't ideal for many here but I see it as one of the compromises made to have dedicated shop space. I will have 10' in the upper garage, and likely I'll be keeping the third bay there for more automotive work where the height could be more helpful.

Everyone keep their fingers crossed for me as we wait on our plans to be finalized and engineered!