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Small Cabin Forum / Cabin Construction / Planning for 10x10 bunkie on rock shelf - Foundation?
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Fenny
Member
# Posted: 26 Sep 2022 16:32 - Edited by: Fenny
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Let the planning begin! So we picked up a couple of acres on a small island (square mile) in Northern Ontario this year and are looking to put a couple of small 10x10 bunkies on it next summer. It currently has as a very sketchy "cabin" built on it that we plan on eventually tearing down, but for now it it keeps the rain off and mosquitos out.

Anyways, to the point of this thread. My sister has picked out her spot and now we're looking at our own. The challenge is that we're looking at building on a rock shelf. I'll put up a couple of photos and you can see what I mean. So the slope is not bad and is pretty manageable for the first 10-15 feet before it drops off quickly. I'm thinking a 10x10 (to avoid permit requirements) with a 3 foot deck behind and to one side and a 4 foot deck out the front. So what I'm trying to decide on is what kind of foundation to build on. I was thinking I'd drill into the rock and using some rebar/concrete make some pads to mount the posts up. However, what I'm up in the air about is if I should basically just run two large beams the entire length (4-6 footings), and build on that. Or if I should skip the large beams and instead just pour more pads (12+) and build directly on them.

Right now I'm leaning towards two large beams going the length of the structure and then building the platfom on top of that. Although it would raise the structure higher it would give me more access under the floor if I ever need to get under it. It would also be easier to build as there would be a lot less drilling into the stone. With 2x10s I could probably get away with just 4 corners.

Here is an image coming into the spot. The arrow represents where I'd like to build.



From another angle:



From up on the rock shelf standing with my back to the water tank:



Very rough positioning of the 10x10.



I'm heading back this weekend and am planning on having a few 10 foot 2x4s in order to rough out where it would fit.

So what do you guys think?

Steve_S
Member
# Posted: 26 Sep 2022 17:19
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Just my thinking out loud here. It is most likely a wet spot whenever it rains and most certainly during spring thaw, the water will come down those rocks and it is obvious by seeing how much of it is exposed.

When there in a good Rain, watch what the water does. If Possible in spring during thaw time you will want to see what is happening on the land as well.

Next, I would NOT fight the rock !
I would suggest that using a jackhammer you could probably be able to make 8-9" Diameter holes about 10-12" deep where you could set 4 upright Steel I-Beams set into Concrete. For a 10x10 it would likely be best to have the beams @ 8-1/2 to 9' and about 3-4' in height so you have a bit of crawlspace access underneath, also to let whatever flows down to pass.

Frame the floor base with a double 2x8 perimeter and 2x8@16" oc. Attaching the 2x8 to the I-Beams could be done with Bolts, Plates & angle Brackets. 1/4" thick Marine Dock hardware is perfect for this sort of thing. Home Hardware, Rona & Homedepot carry a lot of those goodies.

The I-Beams you'd have to source, if possible get Galvanized. TIP: End Cuts which are pieces left over can be had pretty cheap, usually shorter pieces end up going to recycle and if you only need 3', 4' you could get luck with that but you'll have to look around. ** ALSO Look in Kijiji for used Steel I-Beams, you'd be surprised !

Gotcha in that... If you want to cut heavy I-Beams it's fastest with a plasma cutter, next Oxy-Acetylene, neither of which are for someone without experience!

Fenny
Member
# Posted: 26 Sep 2022 19:40
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Oh the property its self is VERY wet in the spring. It's like a big bowl. The idiots before built right on the water wash off. You can see years of shimming and shoring done under the cottage. It wouldn't be so bad if they'd build the whole thing on only a few footings, but it's all ad hoc and so there are a dozen different support points. It's a nightmare to try and level. Eventually I'm going to barge out the tractor and do some serious re-working, but that's years away.

As for the wash off on the rocks, I have no clue as the previous owner had thrown a large mound of debris right where you see in that photo. It was probably 10 years of branch and tree cut off. I've hauled it all out and next I'm going to clean it better to get an idea where I can easily work on the rock.

I'm not going to fight when I don't have to! My plan was anywhere I need to put a footing in I would drill a few inches into the rock and using some adhesive or concrete mix set the rebar "pegs" in. Maybe 4-6 per footing. Then using some Styrofoam just frame in around the rebar pegs and poor a concrete footing in that. So end up with something like this:



I would then make two primary support beams out of 3 2x10s and runs those under the main frame. Similar to what was done in this build:

https://www.small-cabin.com/forum/6_10475_0.html

I'll try and sketch it out and post it up here. I just thought the beams idea and having it lifted off the rocks more would be better for air circulation and primarily access for if I ever need/want to get under it.

DaveBell
Moderator
# Posted: 26 Sep 2022 23:24
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Agree with Steve. No Slab. Use piers so water flows under cabin. Make sure piers are attached in rock, masonry bit, rebar, epoxy in holes. Sonotube, rebar cage in tube, concrete.
Another Canadian in here built on a swale and totally fu%$ed up his concrete mix. Cabin collapse coming.

Not sure about Steve's idea about steel for a 10x10 but, it gave me an idea. Would be cool to cantilever a deck for more space. Then steel would be useful. Maybe build roof longer over deck for more useful space. I would pay engineer for review.

Houska
Member
# Posted: 27 Sep 2022 06:27
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Can't help on the construction technique (but watching this thread with interest), but ask around -- carefully -- locally regarding the permitting issues.

As you say, you should be able to build below 107 sq ft without a permit (if no plumbing) BUT if your local authority, whatever it is, is a stickler, the 3' and 4' decks might be included in the footprint if they're attached, or merely if they're less than 10' away. Or subject to permit and stringent railing requirements if the height fall-off the side is more than a certain amount. And you're still subject to whatever water setback rules and slope-steepness rules might apply for a larger structure that definitely would need a permit.

Finally, according to changes this past spring in Ontario, you can build a "shed" up to 160 sq ft without a permit, though it can't be residential and so a clear bunkie would not qualify.

While the core rules on building code are uniform in the Province, exactly how they're applied is very locally dependent. And enforcement may well be based on complaints, so a lot may depend on whether anybody else on your lake gets annoyed by what you're doing.

razmichael
Member
# Posted: 27 Sep 2022 08:40
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Second Houska! Although you do not fall into the "no permit for accessory building" mistake many make without having a main building as you have a main cabin (assuming it was permitted), there may be local rules applied to sheds, especially around waterfront, lot lines etc. In addition, the code includes more than a footprint limitation (recently increased as Houska noted) including single story, for storage only and other restrictions. Although unlikely, an inspector could check and if the inside looks like it is set up for living this could cause an issue.
Where we are (Quebec), despite the no permit rule, locally we do need one for even a shed - cheap but to make sure we are not located too close to the waterfront or property line.

By the way - lovely spot you have!!

Brettny
Member
# Posted: 27 Sep 2022 08:53
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Big box stores sell concrete anchor epoxy in a cawlk tube for $22. I would epoxy in some 5/8 galvanized threaded rod and bolt on a post base. If the rock is very un level I would have that threded rod stick way out of the rock and also epoxy in rebar. Then pour a small post size concrete base for it to sit on.

Grizzlyman
Member
# Posted: 27 Sep 2022 09:34
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Congrats!


Mine wasn’t near that sloped- but Canadian Shield none the less. How deep can you dig? Looks like a few inches at least?

I dug Down to bedrock, drilled in & rebar then poured a foundation- doesn’t need to be real thick(especially for a 10’ building)

If you can pour 4 level foundations then you can build beam right on the foundation without posts. That may be best for keeping it low -cardboard sonotube forms may be best for this.

I’ve built all my foundations (12 footing for cabin, 6 for deck, and 4 for sauna) with threaded rod bent inside the concrete foundation sticking up through it and then a post base bolted down to it.

You could run a 2x laminated beam right on the post base to span the 10’.

Also you could if needed brace the middle of the laminated beam with a post that doesn’t have a foundation- since you could just dig it down to bedrock and place on the rock.

I would keep the post/beam/joist buildup as small as possible as it will add up quickly on that slope and in that space.

gcrank1
Member
# Posted: 27 Sep 2022 09:44
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An inexpensive laser-level will be your friend

Fenny
Member
# Posted: 27 Sep 2022 15:22 - Edited by: Fenny
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Thanks guys, I think we're on the same page. I've been talking with the local building inspectors extensively over the past few months and here is what I've got for Ontario (for the French River area).
- 10x10 is largest I can go for human occupancy without a permit.
- 160 square feet is the largest I can go for a non-human occupancy structure. Ie. storage. without a permit.

I'm in the clear for the 100 square feet human occupancy structures because there is already a main cottage on the property. We will eventually have the cottage, that is around 400 square feet, re-designate as a "bunkie" because it's under 500 square feet and then put in permits to build the main cottage. Once the main cottage is done we'll tear down the "bunkie" that is in rough shape.

I'll post back again with more info after I head up this weekend. I'll get more photos and general layout stuff so you can better see what I'm thinking.

Thanks for the great replies!

[edit] the inspector I've been back and forth with seems pretty nonchalant about the building sizes and purposes, but we're not taking any chances as the property and structures are very obvious on the water. Now public health, regarding gray water options for the cottage has been a pain in the ass! More on that another day.

Fenny
Member
# Posted: 4 Oct 2022 15:47
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Update time. I slapped some 2x4s together to give me a visual to work with. See what you think. Below I've sketched out real quick what I'm thinking of.

Here you'd be looking at the front of the build.


Here is a shot from the rear. You get a good sense of the slope I'm building on here. Note that none of this is squared off or level. I just wanted a 10x10 visualization.


Another shot to see the slope I'm working with.


Here is the quick sketch up:
- BLUE is the support post that would be on a poured concrete anchored footing. Thinking maybe I can get away with just 4 supports if I do 3 2x10s beams? Probably more for the deck, once i get to it.
- RED is the 3X 2x10s for the two support beams. I'm thinking maybe if I go a little long on both sides then I can use that to support the deck that would have to wrap around 3 sides.
- GREEN is the main floor joists. I was thinking of 2x10s at 16". This way I could possibly do a 3' cantilever on the far side for a deck?


So basically the platform would be 13x10 but only 10x10 for the structure. With a 3' deck around the three sides. Thoughts? Being there looking at it my primary concern is that it's high on the rock. I consider this good for letting water flow under the structure but a challenge that it gets up pretty high on the far corner. I'm open to other suggestions.

Brettny
Member
# Posted: 4 Oct 2022 20:21
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Why not get a permit?

Fenny
Member
# Posted: 4 Oct 2022 22:54
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Why get one if I don't need one? We will eventually be building a full sized cottage on the main part of the property. This one, and another that my brother in law is putting in, will be to stay in for the meantime and eventually for guests to stay in.

DaveBell
Moderator
# Posted: 5 Oct 2022 06:11
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Now that I see the size of the natural stone deck, scrap the cantilever for a deck. Three feet deck? Not worth the trouble. Would the door be on the high side of the hill or lake side? Cut out that old pine on the high side of the hill and move dirt between the 2x4 and the hill to see if you would have a natural walkway to the stone deck. If not maybe move the temp frame downhill a little to see if a natural walkway is viable.

Grizzlyman
Member
# Posted: 5 Oct 2022 07:55 - Edited by: Grizzlyman
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Just built a 10’ x8 sauna at my place with more or less the same parameters on more or less the same ground. Slope was about 20” over 8’

One thing I DID anticipate but turned out to be a much bigger deal than I thought even is the height created by the post/beam/platform foundation. I intended to build just like you… but I ended up scrapping the platform on top of the beam and hanging joist like a deck between the beams to save 10”+ in height. Unfortunately I didn’t plan this and made the decision on the fly- it’s ok and fine but not perfect because of a few oversights on the fly…

I would consider building in this fashion.

Regarding height it definitely make a few things more complicated in a small space on a slope. Aside from the structure itself being taller on the shoreline there is a challenge of getting into the building when the floor gets too high ON a slope… Its not necessarily obvious how this really complicates things unless you can be there and see it. More stairs are necessary since the ground is running away from you… and that means more space for those stairs since they’re longer… and in a tight space that can be less than ideal. There will also be an uncomfortable slope around the stairs… and you may have to go “out of the way” to get to the stairs.

I’d just make sure to plan for it. You want it to flow with surrounding.

Also- keep in mind you HAVE TO get on top of the structure for the roof and up high on the sides to do siding /sheathing. Not necessarily easy when the slope is running away from you… taller buildings complicate this. Think about even a ladder… where do you put a ladder if trying to get up on the high side if the slope is running away? What angle does it end up being? The reality is probably a very steep angle How do you put a ladder up when your on the “slope” side If the two legs are 6” different in height?

Not saying it’s not doable and you’ll have these challenges either way …. But The taller the building the more this complicates it.

Just a few things to keep in mind for size. Hope this helps
69173E92DF0746BE8.jpeg
69173E92DF0746BE8.jpeg


Fenny
Member
# Posted: 5 Oct 2022 20:19
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Quoting: DaveBell
Now that I see the size of the natural stone deck, scrap the cantilever for a deck. Three feet deck? Not worth the trouble. Would the door be on the high side of the hill or lake side? Cut out that old pine on the high side of the hill and move dirt between the 2x4 and the hill to see if you would have a natural walkway to the stone deck. If not maybe move the temp frame downhill a little to see if a natural walkway is viable.


I didn't really consider that options. The pine is a pretty awesome visual and it never occured to me to remove it, as odd as that sounds. With that said, I don't remember there being a simple walk around with the 10x10 in place. The plan is a double door up front, facing the water, to take advantage of the view, which is the whole point of the build location. The cantilever deck was primarily to the access to the front. The idea I had was a larger overhang off the rear with a 3 foot deck there for outdoor storage. Then the 3 foot walk around deck in order to access the front door and natural stone platform. The front would have a 2 foot deck under the 2 foot loft overhang. Not yet mentioned is that we also have foot traffic through this location in order to access our fishing hole, so the deck around the build would also serve as a safer way of getting there.

Quoting: Grizzlyman
I ended up scrapping the platform on top of the beam and hanging joist like a deck between the beams to save 10”+ in height. Unfortunately I didn’t plan this and made the decision on the fly- it’s ok and fine but not perfect because of a few oversights on the fly…

I would consider building in this fashion.

Regarding height it definitely make a few things more complicated in a small space on a slope. Aside from the structure itself being taller on the shoreline there is a challenge of getting into the building when the floor gets too high ON a slope… Its not necessarily obvious how this really complicates things unless you can be there and see it. More stairs are necessary since the ground is running away from you… and that means more space for those stairs since they’re longer… and in a tight space that can be less than ideal. There will also be an uncomfortable slope around the stairs… and you may have to go “out of the way” to get to the stairs.

I’d just make sure to plan for it. You want it to flow with surrounding.

Also- keep in mind you HAVE TO get on top of the structure for the roof and up high on the sides to do siding /sheathing. Not necessarily easy when the slope is running away from you… taller buildings complicate this. Think about even a ladder… where do you put a ladder if trying to get up on the high side if the slope is running away? What angle does it end up being? The reality is probably a very steep angle How do you put a ladder up when your on the “slope” side If the two legs are 6” different in height?

Not saying it’s not doable and you’ll have these challenges either way …. But The taller the building the more this complicates it.

Just a few things to keep in mind for size. Hope this helps


Thanks! Yup, that's been on my mind. The access to the build comes in from behind. It's pretty easy and a manageable slope/trail to the rear. However, once the 10x10 is built getting around it to the front, without a deck, will be challenging. Either I wipe out the big pine next to it, that will open a path higher up ( I think), or I do a deck around the slope side, which would be more build, but ultimately safer and also easer for erecting the walls and accessing the roof.

I do like the idea of having it 10" lower by skipping the dual beams, it just means more footings I think. So many decisions. I appreciate the feedback guys, thanks!

FishHog
Member
# Posted: 7 Oct 2022 08:13
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So in your other post you said you are south of Sudbury. I’m also south of Sudbury and my township is unorganized. Obviously it depends exactly where you are but have you verified that you do need building permits where you are?

silverwaterlady
Member
# Posted: 7 Oct 2022 09:57
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WARNING: The rules are changing in unorganized townships in Northern Ontario.
Since Covid and the arrival of a lot of new people escaping the cities in Southern Ontario.

The changes do not sit well with anyone I know.
There is a reason we want to be in a unorganized township.
Not all of it has to do with building.

Fenny
Member
# Posted: 9 Oct 2022 10:01 - Edited by: Fenny
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Unfortunately we are not unorganized and are stuck paying property taxes annually to the township of french river.....and getting no services in return.

I've been in contact with the municipality as well as public health regarding our build. 10x10 is no permit and 10x16 is no permit (if no human occupancy). Both these builds are considered accessory buildings as we already have a cottage on the property. We do have the option of building a bunkie as well, up to 500 square feet, but that would require a permit and we're jus not ready for that yet. This 10x10 is basically sleeping quarters only. For now it will serve as the primary living quarters when we start building the main cottage (the existing cottage will eventually be torn down and is in rough shape).

In a nut shell, I'm setting something that is simple that we can stay in as I learn more about off grid living and start planning the full size cottage. This structure will be a long term sleeping quarters for our kids and their families even after the cottage is built.

So far everyone we've talked to about the build (government officials) has been pretty laid back about it, as long as we stay far enough back from the water line and aren't running and black or gray water. Once I put their minds at ease with that information they don't seem to care what I'm doing on the property (surrounded by crown land, no land linked neighbours within a km, at the other end of the island)

gwindhurst
Member
# Posted: 9 Oct 2022 14:34
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Quoting: Grizzlyman
The reality is probably a very steep angle How do you put a ladder up when your on the “slope” side If the two legs are 6” different in height?


Build your walls on the deck/subfloor, stand them up then use wall scaffolding brackets and create a temporary platform all around the outside of the structure. I've even used cantilevered 2x6's secured on the outside of a structure at each end (and supported underneath as necessary for long spans) and laid planks across for staging. Or you can search for "wall scaffolding brackets" likes these https://www.amazon.com/Qualcraft-Carpenters-Staging-Bracket-2300/dp/B0009H5P9K

Erik
Member
# Posted: 11 Oct 2022 10:58
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Beautiful location, excited to see how it comes out!

Fenny
Member
# Posted: 11 Oct 2022 14:11
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Quoting: gwindhurst
Build your walls on the deck/subfloor, stand them up then use wall scaffolding brackets and create a temporary platform all around the outside of the structure. I've even used cantilevered 2x6's secured on the outside of a structure at each end (and supported underneath as necessary for long spans) and laid planks across for staging. Or you can search for "wall scaffolding brackets" likes these https://www.amazon.com/Qualcraft-Carpenters-Staging-Bracket-2300/dp/B0009H5P9K


Fantastic, thanks!

Fenny
Member
# Posted: 9 Feb 2023 20:06
Reply 


Time for an update. I've changed our plans to a 10x15 build instead of a 10x10. However, this means I'll have to go through the permit process as although I don't need a permit for a 10x15 shed, I do if there is human occupancy.

The plan is to build on the same location as above, but I'd like to extend it another 5 feet. I'm building it robust and secure for human use for now, once we build a cottage it will either be a storage shed or overflow sleeping for extra company.

The goal at this stage is to finish the planning and submit the permit request. Then start building here at the house to bring it up in pieces. I figure it will cost a bit more and take more time to build it here but being a boat in build I'd rather spend the time here at home rather than out on the island.

More to come in a couple of months.

Fenny
Member
# Posted: 2 Apr 2023 14:52
Reply 


Ok guys, looking for affirmation or suggestions. I think I have the footing plans figured out but I want to run it by some other minds for feedback as this is my first build. The plan in a nutshell (for some background) is 6 concrete footings, a 2x6 double rim joist base, 2x4 walls and tin roof. I'm hoping to get up the first weekend of May for stage 1: setting the concrete footings. So that's what I want feedback on, here is tentatively what I'm thinking:

- 6 Footings are planned around the perimeter of the base to catch the rim joists: the 4 corners and then one more at the middle of each of the 16 foot runs. On the high side the double rim joists would sit directly on the concrete footings and on the low side I'd have 6x6 posts spanning from the footing to the underside of the rim joists.

Here are the questions:

1) This build is basically on bedrock so I was planning on doing 8x8 concrete footing by drilling 4 holes in each spot and then dropping 6" rebars into the holes. 3" of the rebar would be set in the bedrock with and adhesive and the other 3" would be above grade to strengthen the concrete to form the footing. I'd use something for a form and then pour the concrete around the 4 rebar spikes. On the high side it would be a flat surface for the PT 2x6 joists to rest on but on the low side I'd use a 6x6 standoff post base for a PT 6x6 post that would span the 2 feet or so up to catch the rim joists of the pad. So some questions:

- Is 3 inches into the rock enough? Would you go deeper?
- Should I put a standoff post base for the high side under the rim joists? I didn't think it was really necessary as the concrete pad should be 3" above grade and provide clearance from the ground and water.

Anything you guys see wrong with this plan? Or suggestions?

Grizzlyman
Member
# Posted: 2 Apr 2023 20:49
Reply 


How deep is the soil there? Is there any? When I did it on my Canadian Shield shoreline, I had 6-12” of soil in SOME spots.

If there’s enough soil, you can skip the form and pour right into the hole. Dig it out of course, clean it up, drill your holes and pour on the bedrock in the hole. I had a few where I didn’t have to drill since the bedrock was fractured and was able to pound rebar down in the fissure- that may be an option too… just depends.

Also- I poured my footings a lot bigger- like 20x20 or something similar. I figured the bigger surface area, the better for conforming to the bedrock shape, and adhesion.

If you have to use forms, you can use small rock to fill in around and inside the form because the bedrock certainly isn’t level.

Hope this helps

KelVarnsen
Member
# Posted: 3 Apr 2023 10:58 - Edited by: KelVarnsen
Reply 


I had a contractor replace the piers for my cabin a few years back. He used a rock saw to cut a flat and level spot in the granite for each footing and then used square pier blocks.

Fenny
Member
# Posted: 4 Apr 2023 14:21
Reply 


Thank
Quoting: Grizzlyman
How deep is the soil there? Is there any? When I did it on my Canadian Shield shoreline, I had 6-12” of soil in SOME spots.


No significant soil to speak of. Maybe an inch or two.

Quoting: Grizzlyman
Also- I poured my footings a lot bigger- like 20x20 or something similar. I figured the bigger surface area, the better for conforming to the bedrock shape, and adhesion.


I'll keep that in mind, can't hurt to make them larger.

Quoting: KelVarnsen
I had a contractor replace the piers for my cabin a few years back. He used a rock saw to cut a flat and level spot in the granite for each footing and then used square pier blocks.


I'll keep that in mind, didn't even think of that.

socceronly
Member
# Posted: 25 Apr 2023 17:29 - Edited by: socceronly
Reply 


Ah,.... nvm... I read more.



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