Learning curve


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Established Member
2 Dec 2013
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Waltham Cross
This is definitely a learning from past mistakes post.

So Last weekend I finally got around to build a new shed/storage unit in the back garden so the old one can come down (before it falls down). The new one is 8ft long and 4ft wide and about 3 1/2 ft deep and has about a 5 degree slope down to the front so the water can run off. I got the ply and felt order delivered Friday afternoon (that annoyed me enough as I was told I would get it in the morning so I had a day off to get a start on it, but that never happened). So I finally managed to get a start on it Sunday afternoon and I then proceeded to do some more Monday.

I learnt that I did not need to use 18mm ply for all of the design. I was going to have a lid that could open on the top and the doors at the front, but the 18mm ply was just to heavy in a 8ft length (who would have guessed :oops: )

After putting the sections together (rabbeted the bottom boards back and side to take the side panel and back panel and then screwed together, then just butted and screwed the back board to the sides and the top was then placed on top and screwed in place along the sides and back board) with much struggle I noticed the roof was sagging quite a bit so I had to cut some 9" x 2" I had lying around into a couple of 4" by 2" I placed one at the front and one at the back, it is not brilliant but it does the trick.

After all the frame was in place i put the felt on (paid the extra for some thicker nail on stuff and i def think it will be worth it) and then had to call it quits as the rain started.

So yesterday after work the weather was ok so i thought i would but the doors on. done a few rough measurements and had the general dimension and thought a bit of trimming and all would be good. Boy was i wrong sagging made it a nightmare. so currently there are two very tight fitting doors on the unit (well tight fitting at the top as there is a gap at the bottom that increases to the middle (to about 20mm) as it is raised on stilts to keep it from getting soaked and therefore the bottom board sages in the middle)

Plan of action tonight if the weather stays dry is take the doors off and trim them down from the top so they can open freely. Then make a better structure support for the bottom board to minimise the sag but keep the unit off the floor and to hopefully close that gap up at the bottom. When this is done i should have a nice sturdy dry storage shed, ok its not brilliant but I have learnt a lot from this and it does its job.

Lessons learned:
If making an 8 ft long shed with 18mm ply make a frame for it so it is supported.
Make the roof tilt go back and not forward so the doors could go in and have a tighter fit to the unit and not hit the overlapping felt.
Think about materials, can you get away with 12mm ply or maybe a mixture of 12 and 18mm ply.
If building a base to raise the unit up build it ahead to lay the base on and fix it to it and not as an afterthought.
Ensure everything is square by measuring diagonals throughout the build.

Well hopefully someone else can learn from my experience.


Established Member
26 Mar 2014
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No harm done just add the supports which are obviously missing and you'll be good to go. You don't want it to sag but even worse you don't want it to crack when a cat jumps down on it or someone inevitably sits/leans on it.