New foundation for existing garage

[J Boogie]

Hey everyone - I own a duplex built in 1890 in St Paul, MN.

It has a big old carriage house/garage - foundation half crumbling, half wood plank.

Enough room for 2 cars AND a decent sized workshop.

Not sure what to do about the foundation though.  I have thought of tearing out the wood planks, jack hammering away the crumbling concrete half of the foundation, and putting gravel in there for now.

The long-term plan would be to convert the duplex to SFH (it's in a neighborhood where it'll be worth more as a SFH) and at that point I'll probably tear the old garage down and build a new garage with a studio/1 bedroom accessory dwelling unit above it.  That's probably 8 years out.

In the meantime, should I try and jack the structure up to pour a new slab & footers (and be able to use that slab later when I demolish the structure?) or go the DIY gravel route?

[Jack]

A wooden foundation? You Northerners sure have some funny ideas about building stuff! Around here, such a thing wouldn't last five minutes before the termites ate it and the humidity rotted it into dust...

Beyond expressing my incredulity, I have little to add. However, I do think that if you decide to pour new concrete now, it's important to think carefully about the eventual plans for the upstairs apartment (and be sure you're not going to change your mind about them later) because I assume the footers will have to be larger than they'd need to be without the second story.

[J Boogie]

Well, the house itself has a very thick limestone foundation.  You are right though, us northerners don't really worry about termites much.

The foundation of the garage is concrete for the first 10 feet or so, then wood planks.  No degree of levelness on the floor at all.  Our inspection report initially said we should tear it down and just pour a parking pad, but he thought we were buying it as a rental, not to live there. 

(Inspector said renters like to leave sh*t in garages and you can't toss it out until 90 days after they leave by MN law, and you don't get significantly higher rents, and people will complain to you if someone steals their sh*t, etc.  Sorry for the tangent.)

When I told him, he said we could just re-do the foundation because the structure is solid.  But he said we shouldn't even park in there because the wood planks might have nothing but eroded soil beneath them and they could collapse.

[ShoulderThingThatGoesUp]

Are you talking about the foundation, or the floor? Is the floor just wooden planks with dirt beneath them? What are the walls themselves sitting on?

[jda1984]

I think some photos would be helpful here. 

I'm just across the river, J Welterweight!  Have a 1900 duplex as well (that used to be SFH).

[Fishindude]

Tear out the floor, install shoring to hold walls in place, remove and replace foundation, then pour a new floor.
Tough job.   Probably not a job for an amateur do it yourself-er, and could be pretty expensive to hire out.

Try to find a foundation repair company and have them take a look at it for starters.
Without photos, we can't provide much more info.

[CatamaranSailor]

I'll echo the fact it's probably a pretty big job...not impossible for a DIY'er...just lots and lots of hassle. However, there definitely ARE permanent wood foundations that are used everyday, in every geographical location, and meet all building codes.

http://www.hillspg.com/pdfs/Perm%20Wood%20Foundation.pdf

http://woodfoundations.com/

In fact, for this instance, it might make sense. The nice thing about engineered wood foundations is they are built using traditional framing techniques rather than having to pour footings and place concrete forms.

That being said, if it were me, I'd carefully run the numbers. I'd be awfully tempted just to rip everything out and start from scratch. Good Luck!

[paddedhat]

A wooden foundation? You Northerners sure have some funny ideas about building stuff! Around here, such a thing wouldn't last five minutes before the termites ate it and the humidity rotted it into dust...

Seriously? Not only does the previous post provide accurate information on durable treated wood foundations, but there are thousands of them, with decades of proven history right in your city. I was working with Habitat for Humanity Atlanta in the early 90s, when they were doing hundreds of them a year. At that time, at least one big builder in the area was using them as a selling feature.

[Drifterrider]

Hey everyone - I own a duplex built in 1890 in St Paul, MN.

It has a big old carriage house/garage - foundation half crumbling, half wood plank.

Enough room for 2 cars AND a decent sized workshop.
Not sure what to do about the foundation though.  I have thought of tearing out the wood planks, jack hammering away the crumbling concrete half of the foundation, and putting gravel in there for now.

I just watched an episode of Rehab Addict.  They lifted an old very large garage, removed the concrete, poured a new floor and set the garage back down.  They can lift a house, they can lift a garage.  BUT.... on TV they never really tell you what it cost.

[lthenderson]

Hey everyone - I own a duplex built in 1890 in St Paul, MN.

It has a big old carriage house/garage - foundation half crumbling, half wood plank.

Enough room for 2 cars AND a decent sized workshop.

Not sure what to do about the foundation though.  I have thought of tearing out the wood planks, jack hammering away the crumbling concrete half of the foundation, and putting gravel in there for now.

The long-term plan would be to convert the duplex to SFH (it's in a neighborhood where it'll be worth more as a SFH) and at that point I'll probably tear the old garage down and build a new garage with a studio/1 bedroom accessory dwelling unit above it.  That's probably 8 years out.

In the meantime, should I try and jack the structure up to pour a new slab & footers (and be able to use that slab later when I demolish the structure?) or go the DIY gravel route?

Without pictures it is hard to give great advice but I'm guessing the crumbling concrete foundation is much better than removing it and adding gravel. Without jacking or moving the structure out of the way, it would be impossible to pack the gravel into place tight enough that when the last piece of foundation was removed the entire thing wouldn't settle down and possibly cause other issues. If you are going to the expense of jacking it up anyway, then I would just pour the foundation properly at the time. Since it sounds like you have big plans for the structure within eight years, my advice would be to just preserve what you have until that time. Patch up the crumbling foundation and call it good. When you have solid plans in the future, then you jack up the structure and pour the foundation right.

On a side note, jacking up structures to repour foundations or basements is not as expensive as you might think. In my area, you can get an entire house jacked up to repour the basement for less than a couple thousand.

[Fishindude]

I've jacked up and raised a few structures to make repairs just like what you are wanting to do.  It's not that difficult if you know what you are doing. 
If you don't know what you are doing it can be very dangerous, and severely damage or ruin the existing structure you are trying to save.   Get somebody with some experience involved.

[J Boogie]

Hey everyone - I own a duplex built in 1890 in St Paul, MN.

It has a big old carriage house/garage - foundation half crumbling, half wood plank.

Enough room for 2 cars AND a decent sized workshop.

Not sure what to do about the foundation though.  I have thought of tearing out the wood planks, jack hammering away the crumbling concrete half of the foundation, and putting gravel in there for now.

The long-term plan would be to convert the duplex to SFH (it's in a neighborhood where it'll be worth more as a SFH) and at that point I'll probably tear the old garage down and build a new garage with a studio/1 bedroom accessory dwelling unit above it.  That's probably 8 years out.

In the meantime, should I try and jack the structure up to pour a new slab & footers (and be able to use that slab later when I demolish the structure?) or go the DIY gravel route?

Without pictures it is hard to give great advice but I'm guessing the crumbling concrete foundation is much better than removing it and adding gravel. Without jacking or moving the structure out of the way, it would be impossible to pack the gravel into place tight enough that when the last piece of foundation was removed the entire thing wouldn't settle down and possibly cause other issues. If you are going to the expense of jacking it up anyway, then I would just pour the foundation properly at the time. Since it sounds like you have big plans for the structure within eight years, my advice would be to just preserve what you have until that time. Patch up the crumbling foundation and call it good. When you have solid plans in the future, then you jack up the structure and pour the foundation right.

On a side note, jacking up structures to repour foundations or basements is not as expensive as you might think. In my area, you can get an entire house jacked up to repour the basement for less than a couple thousand.

That's basically what I'm looking for.  In 5-8 years I'll probably tear the whole thing down and pour a new one, so for now I'm looking to patch it up and call it good.

I just need to make sure it's safe and solid enough to park cars on.  The front half is a jagged, uneven concrete slab.  IMO solid enough to park on for now, with or without patching.  The back half is even more jagged, even more uneven wood planks that I fear might not be well supported underneath. 

I should mention that this is a true carriage house - it's original purpose was to house a horse drawn carriage.  I believe half of the floor is wood because that half was used more or less as a stable and wood flooring is more comfortable for horses.

So maybe I should just pull up all the planks, fill in any gaps with gravel, and then look into what I can do to have a smoother surface as I hope to do plenty of woodworking there and I don't want to drag my festool vac across gravel.

Thanks for all the replies everyone.  With all this engagement I think I'll go ahead and take some pics after work today.

[J Boogie]

So here are some pictures.  As you can see it's in rough shape.  You can kind of see where the concrete foundation ends and the wood floor begins.

The last pic shows how things might have become hollowed out underneath the wood planks due to critters burrowing or what have you.

So the plan (to be able to park there safely for the next 5-10 years before I demolish the whole thing) is to pull up all the wood planks and fill in all the openings with gravel.  Solid plan or no? Is there a better route for me?

[J Boogie]

Close up of the foundation/footer from the inside, close up of cavity where animals probably burrowed underneath wood planks

[lthenderson]

[quote author=J So the plan (to be able to park there safely for the next 5-10 years before I demolish the whole thing) is to pull up all the wood planks and fill in all the openings with gravel.  Solid plan or no? Is there a better route for me?[/quote]

I think this is the plan I would go with until you figure out what you want to do with the rest of the structure. Gravel is pretty cheap and can be removed or added too as you change your mind.