# Forum Home Renovation The Garden Shed  sealing around pre-existing shed

## CuriousChris

I have a large shed in our yard. Part of it is devoted to a two car garage the rest is rumpus room come sleep out. Sadly over xmas we received an unusually high (not seen in my 30 years here) level of water in the yard and it was above the shed floor by some 20 mm or so.  
When we lined the shed we did not even consider this event as a possibility (our yard was entirely under water and we live in an inner city Adelaide suburb). 
This totally ruined the flooring in the rumpus room which was laminate floating floor. Lesson learnt we are going to use vinyl planks.  
But I want to try and waterproof the shed so that in the future such a flood will not result in water ingressing into the shed by rising up between the metal and the concrete. The trouble is the shed walls are built, insulated and gyprocked and the cost of redoing the walls is just not worth it. Removing the external walls is a major task but not impossible. Still I want to try and avoid that if I can. 
Now I have around a 15mm gap under the gyprock and was trying to work out what I could do. What sprung to mind was that I could use an expanding foam  (such as the sika boom) and inject it into the gap so that it seals the concrete to the metal walls.  
I would try to clean out as much from under wall as is possible using the high pressure air gun and then pre spray it with water to give the sika maximum expansion and minimum secondary expansion (this stuff is water activate). 
Can anybody offer an alternative solution that does not include deskinning the walls? 
If you are curious as to why I am doing it now in April is we have just got our insurance payout, so now I can divert some funds to prevention.

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## Uncle Bob

I reckon you would be hard pressed to keep flood water out of a shed by attempting waterproofing.
It should be possible to keep it out by improving drainage though.

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## phild01

:Arrow Up:  Agree, can you trench around the shed.  You may need a pit that can be pumped out.

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## CuriousChris

> I reckon you would be hard pressed to keep flood water out of a shed by attempting waterproofing.
> It should be possible to keep it out by improving drainage though.

  My entire yard was flooded from the front fence to the back fence. There is no where to drain to.   

> Agree, can you trench around the shed.  You may need a pit that can be pumped out.

  As above where could I pump it to? 
This situation is courtesy of our council increasing properties many fold without increasing infrastructure. Where there was green, there is now concrete. The water flowed out of their houses,  down the road into our house. Ourselves and all the houses around us were flooded. In an area never flooded before.

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## phild01

Was the street also not draining?

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## Marc

The only thing you can do, short of a 100HP pump and a long pipe over the hill, is to build the shed on stilts.

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## CuriousChris

> Was the street also not draining?

  The street drained. But the inrush of water was so great it overflowed the storm water drainage. That's when the damage was done. 
We were alseep at the time so I cannot be exactly sure as to what happened. What we could surmise was there was a large rush of water down the street (it happens). the street drains were overrun and could not take the water (plus your usual vegetation blockages). The water banked up on the street and flowed over our driveway which is normally enough to prevent these occurrences and flowed into the yard. adding to our already overflowing gutters. 
The whole process only took a very short period of time. Our son woke us (he was in the sleepout). When we went outside the yard from front to rear was inundated and under water. 
As stated originally we got somewhere around 25mm of water in the shed. I can't protect the garage section (except sandbagging the double roller door). but I belatedly thought maybe I can make the rumpus room more resistant to water. 
The response I have received so far indicate this is not possible given my current situation but with no explanations as to why.  
Will the foam sealant adhere well enough to create an impermeable barrier? If not a short explanation why would be helpful.  
Apart from stilts or 100HP Pumps does any one have an alternate and sensible solution (in other words not taking the piss out of me).

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## Godzilla73

Could you build a raised floor in the sleep out section. Say 100mm high ?

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## MorganGT

I've got a similar situation in my garage. Slab was poured basically at ground level and one wall forms the property boundary, so I don't have the option of digging alongside that wall to add drainage.
In heavy rain water would seep up between the wall sheeting and the slab where they overlap.
Step one of my solution has been to set up formwork and pour a small 'kerb' against the wall sheeting on the inside using construction grout, which has penetrated all the voids and blocked most of the gaps where water penetrates.
Since this won't be a 100% solution against water penetration, plus the existing slab is uneven and a bit rough, I am currently preparing the floor to lay 40mm thick pavers on a mortar bed so that the floor level will be raised 5-6cm, bringing it above any likely flood level. Since the garage is pretty full, I have to do it in stages - currently I have the rear 2 metres of the garage kerbed and the slab thoroughly cleaned and waterproofed and am about to start laying pavers.

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## CuriousChris

> Could you build a raised floor in the sleep out section. Say 100mm high ?

  I had considered this but it would require removing the internal walls. a pretty major expense. 
I am currently looking at impermeable barriers to see if I can seal around the outside rather than the inside. The issue with those is the corrugations on the metal skin make it hard to seal in a permanent fashion. 
gripset makes a cemseal which is a water based "sealing slurry" I may be able to create formwork around the shed and poor the slurry into it creating a barrier.  It would be time consuming but could be done. sad part is I just got rid of spare sheets of corrugated tin which I could have used as the perfectly shaped form work.

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## CuriousChris

> I've got a similar situation in my garage. Slab was poured basically at ground level and one wall forms the property boundary, so I don't have the option of digging alongside that wall to add drainage.
> In heavy rain water would seep up between the wall sheeting and the slab where they overlap.
> Step one of my solution has been to set up formwork and pour a small 'kerb' against the wall sheeting on the inside using construction grout, which has penetrated all the voids and blocked most of the gaps where water penetrates.
> Since this won't be a 100% solution against water penetration, plus the existing slab is uneven and a bit rough, I am currently preparing the floor to lay 40mm thick pavers on a mortar bed so that the floor level will be raised 5-6cm, bringing it above any likely flood level. Since the garage is pretty full, I have to do it in stages - currently I have the rear 2 metres of the garage kerbed and the slab thoroughly cleaned and waterproofed and am about to start laying pavers.

  I am fortunate that I have access to all the exterior. The front is nicely formed with a path along the entire front of the shed. The rear though is pretty rough with the metal extending down over rough cast concrete. 
Your grout solution will help but you may want to consider using a rubber paint to seal it as well on the inside, this should protect against any hairline fractures and points where the grout does not adhere to the concrete. There are a few products which will do the job. unfortunately I do not have the access and therefore cannot apply such products (short of removing the gyprock off the walls).

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## r3nov8or

> ...unfortunately I do not have the access and therefore cannot apply such products (short of removing the gyprock off the walls).

  You don't have to remove all the gyprock, just cut along say 120 mm up all the way around the bottom.

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## cyclic

> I am fortunate that I have access to all the exterior. The front is nicely formed with a path along the entire front of the shed. The rear though is pretty rough with the metal extending down over rough cast concrete. 
> Your grout solution will help but you may want to consider using a rubber paint to seal it as well on the inside, this should protect against any hairline fractures and points where the grout does not adhere to the concrete. There are a few products which will do the job. unfortunately I do not have the access and therefore cannot apply such products (short of removing the gyprock off the walls).

  Marc summed it up, build the shed on stilts
i.e raise the bridge or lower the river.
My money is on lowering the river.
Find a way to cut the earth so water will run off before entering the shed. 
As to any other method, nothing, repeat, nothing will work.
Water will still enter via sheet joins and screws, not to mention seepage through the concrete.

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## r3nov8or

Since you have only seen it once in 30 years it's probably a "1 in 100 years" event and you can probably relax for at least another 30 or so  :Smilie:

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## phild01

Pics help, is it water entry only from the roller door reaching the habitable area that is the problem or is it also water getting in through the shed walls too?

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## CuriousChris

> Marc summed it up, build the shed on stilts
> i.e raise the bridge or lower the river.
> My money is on lowering the river.
> Find a way to cut the earth so water will run off before entering the shed. 
> As to any other method, nothing, repeat, nothing will work.
> Water will still enter via sheet joins and screws, not to mention seepage through the concrete.

  Geez whaddya know I never thought of the seams in the metal or the screw line. ain't I a dumb C. 
Your response is as condescending and unhelpful as was Marcs. If you had read my thread you would realise I am not trying to build an ark. Just raise the point of ingress to above its current level. If the water reaches the first line of screws then I have bigger problems, the water would then be well above the main house floor level.   

> Pics help, is it water entry only from the roller  door reaching the habitable area that is the problem or is it also  water getting in through the shed walls too?

  The main  entry of water is rising between the sheets and the concrete. I can  raise the door sill and I can seal the garage side from the habitable area  as I have access to the walls there, so its not my prime concern. As I only got a few mills into the  room I don't need to hold back much. and as r3nov8or said It most likely wont happen again which is why I don't want to spend much on it. 
Thanks for the help guys. It seems no one has much experience in this area and I'll have to continue winging it.

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## Marc

Condescending eh? Remind me to never reply to nincompoops from the welfare state.

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## cyclic

> ain't I a dumb C.

  Correct

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## MorganGT

> As to any other method, nothing, repeat, nothing will work.
> Water will still enter via sheet joins and screws, not to mention seepage through the concrete.

  Funnily enough the grout 'kerbs' I have poured so far in my garage have already stopped water ingress in heavy rain where they are installed, even before adding waterproofing over the top. 
Although I am still raising the floor level rather than relying solely on the kerbing.

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## Oldsaltoz

Hi all been away for time, flat out as usual. 
Re preventing water entering your shed. I have installed 50 x 50mm plastic angle, available at the green shed. Simply apply a bead of Sikaflex 11FC (fast cure) to the clean and dry concreate base and pop the angle on top with the upstanding edge on the inside. To seal the corners, just cut a short length off the angle and stick it over the corner joint with a bit more Sika. Just hope you don't get more than 50mm deep in the future.  :Smilie:

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## phild01

> Hi all been away for time, flat out as usual.

  Not lost at sea, good to hear ya back :Smilie:

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## CuriousChris

> Hi all been away for time, flat out as usual. 
> Re preventing water entering your shed. I have installed 50 x 50mm plastic angle, available at the green shed. Simply apply a bead of Sikaflex 11FC (fast cure) to the clean and dry concreate base and pop the angle on top with the upstanding edge on the inside. To seal the corners, just cut a short length off the angle and stick it over the corner joint with a bit more Sika. Just hope you don't get more than 50mm deep in the future.

  Thank you for your constructive comment. 
Unfortunately access is the problem which is why I was looking at the expanding foam solution. Its simply not worth the effort to remove gyprock walls (even just the lower sections) due to the rarity of such events. Climate change and poor council planning may make a mockery of that statement though. 
I think I'll go for the expanding foam (closed cell) internally with a further external spray or paint rubber seal. That should close off most areas where water is likely to ingress and reduce the effect of a flood in the future. 
I will also do a tester this weekend and build a dam outside a section of wall and check whether it adequately seals or not.

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