Metal shed leaks at concrete slab.

DuckyDave

Eight Pointer
Contributor
Metal shed gets wet on inside floor, takes 2 or 3 days to dry out afterwards (only if I leave doors open. If doors are closed because I am away then it takes even longer to dry out. Not good. In summer this creates a Temperature/Humidity Chamber).
What is best material to use for sealing around the outside perimeter? I am thinking either good quality silicone caulk or else "Great Stuff" foam. Or maybe use both Great Stuff from inside, silicone caulk from outside...
Thanks in advance for any inputs.
 

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ABBD

Ten Pointer
Contributor
Hard to see exactly from that photo. However, it looks like the bottom rail is sitting below concrete grade some. Also, is there adequate exterior grading away from slab? Does water pool in that area when it rains?
 

dubbeltap69

Eight Pointer
Contributor
I'll take a shot at it...

Whatever solution you go with, I'd suggest trying to find a way to get the water away from that area. If you have a pool of water just sitting there, it will find a way in. If you can shed most of the water away then most of your problem is solved.

I have moved away from silicone caulks. In my experience ALL caulks are going to fail eventually, so I try to go with the one that I can remove the easiest and reapply. Based on my experiences it's either a acrylic or polymer. For anthing that see's serious weather, I've pretty much switched over to OSI Quad Max which is a polymer. It requires mineral spirits to clean up. The good thing about acrylic or polymer caulks is when it comes time to repair or fix, a little heat and a putty knife and you can get it off fairly easily, not super easy though. Silicone I can never get off easy at all. Might be user error though.

Does it only collect at that location? You may want to try actually using a construction grout, and/or mortar to get the water away. Just mix a whole bunch up and build it up around either the galvanized base on an angle. You gotta somehow get that water away.
 

lasttombstone

Kinder, Gentler LTS
I don't know much about anything but it looks to me like that gray metal piece is just screwed to the concrete slab and the metal wall is behind that. There looks to be a gap on the right hand end. Is that what you are talking about or am I seeing something that is not there.
 

chevymec

Spike
I had the same problem with my shop and once I had gutters installed, the water almost stopping running back into my doors. Mine is off the ground more than yours though. A good sealer would help a lot.
 

Soilman

Old Mossy Horns
Contributor
First questions I'd ask is, "Is the concrete slab wider than the building?" or is it a "slope/water collecting problem".
If the first, I'd use either a tar type product or silicone to seal it from both the outside and inside.
If a slope/water collecting problem, the best permanent solution would be to build up around the concrete base with soil material to drain water away from the building.
Another solution would be to dig around the foundation, install 4" perforated drain tile and backfill with gravel. But, you will need to outlet the tile to the lowest natural slope of the land.

When I built my 20x20 shop building, I tacked together a square of 2x6's measuring 24x24 and hauled in enough soil material to fill in the square, raising my building foundation above the natural grade of the land.
 

ScottyB

Old Mossy Horns
Contributor
So many questions left to answer- is it coming in at the concrete level? Or is it coming in where the wall metal is setting on the galvanized rail? Personally wouldn’t won’t roof tar on it because I would step in it every possible chance and then it would be every where….. if it’s not coming in on the concrete, then you could flash the water away by removing a 1/2 inch at the bottom of the wall metal and tapering a piece of flashing into it. That should force it away and out to the concrete…. Or FlexSeal the crap out of it (askinda mentioned above)….. need to know the source so you don’t cause other issues in your repairs
 

HotSoup

Old Mossy Horns
So many questions left to answer- is it coming in at the concrete level? Or is it coming in where the wall metal is setting on the galvanized rail? Personally wouldn’t won’t roof tar on it because I would step in it every possible chance and then it would be every where….. if it’s not coming in on the concrete, then you could flash the water away by removing a 1/2 inch at the bottom of the wall metal and tapering a piece of flashing into it. That should force it away and out to the concrete…. Or FlexSeal the crap out of it (askinda mentioned above)….. need to know the source so you don’t cause other issues in your repairs

Roofing and flashing dries much like silicone
 

Dick

Twelve Pointer
Contributor
directing water away would be the best. if it gathers near the foundation it WILL get in. you could used hydraulic cement.
 

DuckyDave

Eight Pointer
Contributor
Wow! Thanks folks for all the input! There is definitely some more troubleshooting required on my behalf before I jump in and implement a solution which may not be the most effective one. For example, I THINK there is no significant puddling occurring on one of the 4 sides, but I am not 100% sure. So I need to observe the problem closely during our next rainstorm (shed is located at a cottage in Central/Eastern Virginia--about an hour from my house). No rain in forecast next 10 days, if we get any precip at all it will likely be snow.
However I have concluded one thing from your inputs thus far--whoever built this shed (I am guessing 20 years ago maybe?) would have created a much drier interior had they not poured the slab (that shed sits on) completely flat. Had they sloped the concrete even slightly away from the walls of the shed then the water would have drained away better. Now with that flat slab there is no help from gravity getting the water away.
I will do some more troubleshooting and update this thread. Thanks again.
 

Johnnie

Ten Pointer
Just a thought, just below the center screw appears to be either rust/debris at the base of the rib. Compare to the rib on the right. Are you certain you aren't getting water inside of that rib somewhere further up? Water could be falling from height and splashing over the base flashing. Most common issue I've seen is what others stated here, water pooling on the outside and flowing under/through the wall to the inside. If so, dig a trench/drainage to get the water away from the building.

Johnnie
 

DuckyDave

Eight Pointer
Contributor
Couple new/additional photos attached, will add text/descriptions later today.
 

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DuckyDave

Eight Pointer
Contributor
Some additional details:
1) Facing the doors the shed is approximately 10 feet wide by 8 feet deep.
2) the concrete slab was poured flat with no appreciable slope in the slab. The shed was built/set on top of the slab with no sealant material between the metal base and the concrete. On the front of the shed the slab extends approximately 27 inches and (using a Carpenter's Level) the slab at the front is either level or possibly has a slight inward (wrong way) slope. The soil/grade at front is lower than the slab (good). On the left side slab is 10 inches wide and flat, possibly slight slope away (good). On left side the slab is above grade (good). On the rear slab is 22 inches wide, flat and above grade. On right side slab is 12 inches wide and flat, basically even with or slightly below grade/soil (next to carport--see #3) .
3) Facing the doors on the righthand side the grade is even with or slightly higher with a carport on that righthand side. There are no rain gutters on the carport . So in a heavy rain there is not only water from the shed that needs to drain away but also rain coming off the carport that must be drained away. It seems feasible to install a shallow French Drain to carry that water away to rear/back or shed where grade is low enough to keep water out of the shed.
4) adding gutters (95 inches long) and downspouts that drain to rear of shed should help a lot. Also adding a gutter to the portion of the carport ( longer than shed is deep plus front and rear slab dimensions = 95 + 27+ 22 = 144 inches minimum ) similarly draining to rear of shed should help a lot.
5) a previous owner of the property applied some type of sealant/caulking at the base of shed on the righthand side and at the rear. However the caulking is degraded and has separated from the metal base. This needs to be removed/redone.
6) If I do all of the above and leaking persists then I could add some flashing sloped around the base. This may or may not be necessary. A special challenge exists at the sliding doors where flashing would interfere with doors which slide inside (not outside) the fixed metal front walls. I might just lay a length of PT decking in front of the doors when doors are closed.

'Sound like a plan? Did I overlook anything? Thanks again for all the inputs.
 

bigten

Old Mossy Horns
Contributor
I totally misunderstood what you had, as I was thinking this was a larger building, so had no input. I now see my mistake and will make one suggestion. I'm sure it is anchored to the concrete in some manner although most of those are tied down with cables that go through the structure. If it is bolted, I would loosen or remove bolts (or nuts if studded), raise building slightly and install a gasket between base and concrete. 1/4" pliable rubber would be my choice of material.
 

DuckyDave

Eight Pointer
Contributor
I totally misunderstood what you had, as I was thinking this was a larger building, so had no input. I now see my mistake and will make one suggestion. I'm sure it is anchored to the concrete in some manner although most of those are tied down with cables that go through the structure. If it is bolted, I would loosen or remove bolts (or nuts if studded), raise building slightly and install a gasket between base and concrete. 1/4" pliable rubber would be my choice of material.
BigTen, I was wondering about a gasket also. Next time I am at the property I will clear enough junk out of the shed to see how shed is anchored and whether lifting would be feasible. Coupled with some gutters on the shed and on that section of carport I think a rubber gasket would be very effective. Thanks.
 

DuckyDave

Eight Pointer
Contributor
I was at the property yesterday, discovered the shed is anchored by screws going into (I am guessing--can't see this) lead slugs (or similar) pressed into holes in the concrete slab. The most important feature I saw is that there IS a spongy gasket material under the metal base. The material is badly decomposed. So I SHOULD be able to pry up the shed base (1 side at a time--using a pry bar and wooden wedges) to reinstall new gasket material. But I will also install rain gutters on the shed and adjacent portion of the carport to get the water away as much as possible. I might also put caulking or similar along the outside of base to protect the gasket material from sunlight segregation. If the solution lasts for 30 or even 20 years that is good enough-- I will probably be gone from this earth by then lol.
So question is...what is the best gasket material? Something this shed's manufacturer (name unknown) recommends/sells? Boat hatch or automotive door material? Garage door seal? Thanks for any input...
 

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bigten

Old Mossy Horns
Contributor
Concrete was probably drilled and lead anchors installed for bolts to thread into. Remove bolts, lift one side at a time, reseal and replace bolts. I think I would look for a rubber seal to place back instead of a foam type. I would also run a bead of sealer along the outside prior to tightening anchor bolts.
 

DuckyDave

Eight Pointer
Contributor
I agree that is probably how the shed is anchored. The shed is packed full of tools and stuff so I couldn't inspect for all of the fasteners, I found only 1. I am hoping all the fasteners are accessible and not covered over through the assembly configuration. Time will tell... meanwhile yes I do think having a gasket along with additional sealant is a good idea. Next week I hope to do some shed clean out and further inspection. Thanks.
 

pattersonj11

Old Mossy Horns
Contributor
I would suggest to clean it up around the edges with a pressure washer or best water pressure you can. Try to get down to bare concretes. Then silicon to your hearts desire. The ground around it and the shelter roof are not helping you one bit at all. That’s all based on if it’s leaking between the building and concrete. If it’s coming in between the metal......more silicone. It will seal anything, but you will hate the day to take it apart or fix something.
 

ABBD

Ten Pointer
Contributor
It looks like poor grading around a good portion of the slab. If you don’t fix that you are wasting your time and your money.
 

DuckyDave

Eight Pointer
Contributor
Yep, all good points made here...install gutters to keep water from getting near shed base in the first place, fix grading so whatever water does get there drains away efficiently, install a new/better gasket protected by silicone caulking applied on pressure-washed concrete. Pretty certain that if I do all this the shed will stay dry for 20-30 years (max) that I will be around. Thanks All .
 

Dick

Twelve Pointer
Contributor
personally, I'd just either grade better or install cheap gutter and caulk.

I think once you start messing with replacing gaskets and such, you'll just open up a can of worms. I've learned, still learning, the KISS method fits most situations.

And just to prove my ignorance of all matters, come visit my home and property renovations...🤣🤣🤣
 

DuckyDave

Eight Pointer
Contributor
Quick update: over the past couple months I found brand new elbows, hangers etc at flea market. Bought only gutters 16 foot piece I cut into 2 lengths 8 foot each. Completed project for $60-70. Shed has been bone dry inside for at least a month despite several hard rains. Did not have to caulk around base but might still do as a precaution. I recommend gutters to any owners of these inexpensive sheds manufactured by Arrow. Thanks to all for the advice.
 

Longrifle

Old Mossy Horns
Contributor
If you use a double row of 1" wide butyl tape to replace that foam seal you'll likely never have to worry about it again. Caulk is a last resort for me but in situations that require it I'll always use Lexel brand caulk, it doesn't deteriorate like the others. I've been on metal roofs that I did 10-12 years ago, both are still doing the job.
 

DuckyDave

Eight Pointer
Contributor
If you use a double row of 1" wide butyl tape to replace that foam seal you'll likely never have to worry about it again. Caulk is a last resort for me but in situations that require it I'll always use Lexel brand caulk, it doesn't deteriorate like the others. I've been on metal roofs that I did 10-12 years ago, both are still doing the job.
Longrifle, thanks for the tip. I should have clarified that upon further examination it appears there never was a foam seal--there was only some caulking (which has separated over time) around the outside perimeter base.
Where would you place the double row of butyl tape? Would that be 1 row along the outside perimeter/base and the other row around inside perimeter base? Or lift up the shed from the concrete and place the 2 tape rows beneath the metal sides and above the concrete (this would be a royal PITA, if even do-able at all)?
I will keep your suggestion in mind as I continue to monitor for rain seepage. But for now I am very surprised at how much of an improvement was gained by simply adding gutters.
 

Longrifle

Old Mossy Horns
Contributor
Yeah I'm sure it would be a chore but if you could put them side by side between the concrete and the steel frame you'd likely never have to worry about water getting past it. That stuff is like chewing gum that never really completely dries....
But you're right, keeping the water from getting to it with gutters is the best solution. The problem is that during a driving rain with wind the gutters don't come into play. I'd run a bead of Lexel around where the sides meet the rail for the same reason.
 
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