Help with a floor in a portable garage

[Mustangous]

First question ( and I don't think this has been covered yet) is how long do you plan on having this portable garage there? Some of these things are guaranteed for 15 years. If you want it there for a long time, it's better to do it right. .

I honestly dont know how long I will have it there, at least 3 years. I would like to do it right, money permitting! meaning if it would be more cost effective to build a garage then I'd rather that. Lumber is down right now or i could order a prefabed unit. I am trying to keep cost a minimum because of future plans down the road. I am not ruling anythign out either. Eventually the land will be leveled, but I dont thing that will change anything for this. The base will be level anyway so I would just level around. I already have the frame work, just have to order a new cover and thats gonna cost $240 shipped.

For moisture control, you need venting and a vapor barrier (sold by Farmtek.com) to put underneath your flooring. I used compacted processed stone (maybe the same thing you're calling blue stone) and put the vapor barrier on top. I put 1/2 inch rubber matting on top of that. Its very durable and dry as a bone. I do keep the door rolled up most of the time in the Summer and close it only when I'm expecting a big thunder storm or a long, drenching rain. Short rainstorms don't seem to put any water at all inside the door.

I dont think blue stone is what you are refering too. What i was told was to just lay poly/plastic down over the dirt and put 4" of blue stone (1" rock that is pointy, not the round stuff) over that and that was it. But I am not sure if this is the best route. It may be an issue because I will be right up against a house (1' away).

Troy

 

[RedDirt]

Will the ridge of the portable garage be parallel or perpendicular to the brick wall?

If perpendicular grade the native soil to slope away from the building and plate compact it. Then lay down a plastic moisture barrier, the thicker the mil the better, and your blue stone, also sloped away from the house and compact the blue stone.

If parallel then you need some channel or trough between the garage and house to effectively carry away the garage roof runoff.

 

[Mustangous]

Will the ridge of the portable garage be parallel or perpendicular to the brick wall?

If perpendicular grade the native soil to slope away from the building and plate compact it. Then lay down a plastic moisture barrier, the thicker the mil the better, and your blue stone, also sloped away from the house and compact the blue stone.

If parallel then you need some channel or trough between the garage and house to effectively carry away the garage roof runoff.

The ridge will be parrallel, because of that tree.

 

[RedDirt]

See the sketch below.

First dig a trough along the brick wall that leads to daylight drain area at least 2% slope (1/4" per ft).

I'd place a 2x6 pressure treated board the length of the garage at the building side of the garage. You could use 2x4 pressure treated stakes 4ft on center to hold the board vertical. Next lay down the moisture barrier for the garage and at the brick building side lap the moisture barrier up the inside of the PT board. Then lay down your gravel base, 4" to 6" thick should do. Slope this gravel to the back of the portable garage at 1% (1/8" per ft). When you assemble your portable garage, run the fabric to the outside of the PT board.

This should keep all the garage roof rainwater outside the garage. If you have snow make sure the garage is far enough away from the brick wall so I can be shoveled out if needed. And try not to place the garage so close to the brick that rainwater does not sheet off the garage an hit the brick wall or you may have trouble inside the brick building.

 

[Mustangous]

Thanks Red for the reply...
For that trough, I am already digging 1.5' down along the garage for about 100ft to a lake for gutter drainage. So I was thinking, could i fill the trench along the garage up with rock and then surround the drainage pipe with rock all the way to the lake and then fill that(from the edge of the garage to the lake) the rest of the way with dirt? Would this act like a french drain?

Thanks again for the help!

 

[RedDirt]

Why are you going down 1.5ft next to the building? I'd be a bit concerned with undermining/weakening the foundation. Normally right next to a building I'd trench just deep enough for maybe 6" fill above the buried drains (at the uphill side then slope 2% down from there). Once away from the building edge you can deepen the trench for better pipe protection but make sure you have 2% or better grade to the lake.

You can put perf pipe in a drain rock filled trench next to the portable garage and it will be a french drain. This is a "ground gutter" application. BUT you do not want to tie in your brick building roof rain water leaders into the perf section (you'd flood the drain trench). Run your roof gutters underground in a separate solid pipe until they are downhill and beyond the portable garage ground gutters THEN you can join the pipes and take a single pipe to the lake.

The pipes leading from the roof gutters can be in the same drain rock trench as the perf (better above, not below the perf). At the downhill end of the drain rock ground gutter trench put a few foot section of solid onto the perf pipe then (downhill from there) join the roof and ground gutter pipes. The drain rock trench ends at the solid section that is attached to the perf. You can then earth fill the trench from there to the lake.

See Sketch. I've shown ground trenches on both sides of the portable garage. You may just want to do the one side between the buildings if natural drainage exists on the other side of the portable garage. I've also shown that you can attach other roof gutter drains too. I've shown the portable garage space a bit away from the other building just for drawing purpose. That spacing can be what you choose with the precautions previously stated about snow and splashing.

I don't know the type of rainfall you have to recommend a pipe size. Calculate your combined roof sqft that will be running through the solid pipe then ask a local plumber/roofer what size pipe you should use to carry that volume of rainwater in your area.

For the drain rock trench use 3/4 minus rounded, smooth, clean, drain rock, like you'd use in a septic leach field. Don't use your blue stone, it is a different animal, made to compact, not drain. Keep the drain rock at the top of the trench exposed. You may want to place a 2x4 PT curb, slightly elevated above grade, to keep the drain rock separated from the adjoining earth or blue stone.

For best performance place a "U" of woven filter fabric at the bottom and sides of the drain rock trench. Woven fabric is better here than the felt type as the felt is more prone to clogging in certain soils.

If you can afford the minor added expense use perforated PVC or SDR pipe not corrugated pipe. If you use corrugated, perf or solid, pay close attention to grading the bottom of your trenched flat, no dips. Water will collect in dips, velocity will slow, and sediment will collect there and eventually could lead to a clog.

At least one clean out to grade would be a good idea to add. Place as far upstream as you can. Bring the vertical pipe to grade and connect to the drain line with 45 degree fittings and a bit of straight between the pairs (a sweeping turn), a "TY" fitting, or "Sanitary T", so that a snake can be easily led into the drain pipe.

 

[Mustangous]

Thanks for the help Red!

The reason for goind 1.5' deep at the back corner of the garage is because that would give me roughly 1' above the pipe for fill. Originally there was a pipe, i think made out of clay, it looked black, that was about 2" - 3" below grade that i crushed with a truck. So i wanted to go deeper to avoid that and I may have a lot heavier equipment in the future going across it. And i have to drive up close to the house because of other obsticals.

Here is a pic of what it looked like and the type of grade i aleady have...

 

[Mustangous]

I am planning on using 4" drain pipe, not the corregated stuff. I didnt think that was a good idea to use. Originally i was planning on using rock as a drainage channel under gound as what you recommended the preforated pipe. See below for that. Your design sounds better, but my concern originally was that the ground water entering the gutter pipes may cause an issue somehow. But if i connect far enough down stream than there should never be an issue, correct? I figured I could always use either of the gutter pipe for snaking if ever need be.

I should get the sock for the prefforated pipe in the trough section, right?

I assume I can use the same glue for drainage pvc pipe as the sewer scd40 pvc?

Thanks again for your help....I think this is gonna work out good.

 

[RedDirt]

Mustangous,
You are on the right track now. But you don't need drain rock in the trench once you have joined your pipes into the single solid leading to the lake. If you connect a solid pipe to the perforated pipe then join this to the separate solid (that carries your roof gutters) down stream and beyond the end of your rock trench you'll be fine. The rock backfill ends at the solid section added to the perf. I use a board in the trench and backfill with gravel on one side and earth on the other and pull the board up as backfill raises. Think of all those holes in the bottom of the perf pipe as the drain in the bottom of the kitchen sink. Once attached to the solid main drain pipe there is no longer any need for drain rock.

You could use a sock on the perf pipe but I'd rather see you use the filter "U" in the bottom/sides of the trench. A sock covers the small perforations and sometimes these can clog with silt and prevent water from entering the holes. Better to have a decent grade (2% or better) for water velocity to scrub the pipe and provide an upstream clean out for a bad clog. We've installed thousands of feet of drainage, always added cleanouts (because they are required by code), but I don't recall the clean outs ever being needed. None-the-less a cleanout is good insurance for a few bucks investment. If the end of the gutter will work for snake access this will work. Avoid sharp 90 degree connections. Use at least long sweeps or two 45's separated by a short length of straight: much easier to snake.

By the way, the perforations are placed down. You should place a two inch layer of drain rock in the bottom of the trench, then lay your perf pipe, then back fill with drain rock.

Also, your building downspouts should not be tight plumbed to the underground drainage pipes. They should dump into a drain sink with 4" to 6" of air gap between the downspout and the drain grate top. Leaves and debris from you gutter will end up on top of the drain grate and not in your pipe line. Plumbing, hardware, and big box stores should normally carry the drain boxes and grates. The plastic boxes and grates are fairly reasonable.


The same glue will work on PVC, SD (thinwall) pipe. It will not work for ABS (the black waste and vent pipe). They do make thinwall SD perforated pipe also and that would work for your system instead of sked40 perforated. If you mix the two types be sure to get the bushing needed to make up the diameter difference.

Good luck.

 

[Mustangous]

Hey Red, I just want to say thanks for taking the time to help me through this project. I am very confident to tackle this....

Today i bought most of the material, now i have to get the rock. I talked to one place and he recommended QP(quary process) for the garage/tent area and trap rock for the trench/trough area. Thats what they sell for compacting and drainage rock. So i just have to check around for prices, but i will probably go with the the first place because he took the time to help educate me as well.

Thanks again. Ill take some pics and post them...