Building a shed

[Biddlesby]

Ok, so it's not very bushcrafty; but I thought you guys (and gals) might be able to help all the same. I'm building a 4x2.5m shed (or hope to!), and just getting the order for the wood all sorted and want to make sure I have planned it correctly. It is built on four telegraph poles (not full length obviously!) due to an uneven ground and prempting damp problems.

Basically the shed is built without any nails, but instead with timber joints I have made up and dowels through them. But it is also built cheaply, so hence thin wood, and so tricky joints. All the timber frame buildings I have seen on the net have huge pieces of wood; I am afraid my joints will not be strong enough due to their size. But I am not worrying too much about this as I can always stick a few screws in (thank god for metal).

More worringly, I am afraid the wood I am using may be too thin, as I don't really have any experience! The main joists for the floor are 2x4" and there are four of them spanning the length. Will they be strong enough?

The corner uprights are 2x2" but I am thinking of upgrading this: (a) the contents of the shed will be almost entirely on shelves and so rely on these uprights, and (b) I have tried to design the shed using diagonals that translate the forces into the corners. Do you think they should be bigger?

In terms of strength I am most worried about the roof, which will have to take the weight of two humans. It is constructed sparingly with 1x2" wood.

I hope somebody can help me out with this - I'm sure there will be, there's ALWAYS somebody on these forums :You_Rock_. Ooh, and here is a 3D model to help visualize what I mean.

I'll take photos along the build to record and display my bugger-ups, of course.

 

[g4ghb]

Oooooo I'n looking forward to watching this evolve - excelent, good on ya mate!

 

[Buckshot]

The walls should help stabalise everything so it shouldn't move too much, even if it does before you clad it.
It really depends on what you're planning to use for the pannels (floor, walls and roof)
I'd be worried about the roof with only one mid support and expecting it to hold two people. That's 2 metre gaps between each strut.
Similarly, the floor pehaps could do with the odd cross piece to stop the 2x4s from bowing and twisting out of position.

I'm no engineer though, so don't take my word for it.

Mark

 

[mr dazzler]

Can one of the mod's PLEEZE deal with that stupid pop up advert, why doesnt it have a X to get rid it if your not interested, if I was interested I'd look at it otherwise its a nuisance and besides its interfering with the post?

Biddlesby, I cant read all your post unfortunaetly because of that damned nuisance advert that gets in the way.
But I'd say keep the design simple. The "joints" on your diagram are neither nowt nor summat . For a shed say 10 foot by 8 foot I would be looking at 3x3, preferably 4x4 for corner post's and 8x4 jowl posts, 4x3's for stud's, 6x4 tying beam's. Sole plate 4x3 minimum, wall plate 4x4, principal rafter's 5x4, common rafters 5x2, ridege beam 6x3. Braces 4x3's. All tanalised and treated cut ends and insides of mortices. Use cleft ash or oak pegs to draw peg the tennons. Ypou shouldnt need any metal eaxcept to spike the common rafters to the wall (rafter) plate
2x1 isnt worth it (unless its a b&q osb roof job with 3 mm wall's, lean on it and it goes diamons shaped ) What weight does the structure have to support? You could be looking at 4x2 or 6x2 joist's at 450mm, 600 very minimum, centre's to take the weight. I would use half lap's for the sole plate corner's, mortice and tennons for all the sole to post and sole/stud connection's, english tying joint for post/tying beam/rafter plate conection, common birdsnouths for the other common rafters. Is the shed a office? workshop? Consider insulation and soundproofing. I would make the roof pitch steeper (about 50 degree) to create more roof storage. The braces need to be almost as fat as the posts, but dont need to be so long. Put your floor joists across the narrowest dimension not the length as in your pic, (less deflection) Or consider a concrete floor (more solid for working on)
Look at a few old frames, check out TFG site or carpenters fellowship. check out rupert newman's book

 

[Goose]

Can one of the mod's PLEEZE deal with that stupid pop up advert, why doesnt it have a X to get rid it if your not interested, if I was interested I'd look at it otherwise its a nuisance and besides its interfering with the post?

What advert?

 

[Biddlesby]

Cheers everybody! I have been speaking to a local builder. He says unless you are using 6x6 oak, you can't really do the whole timber joint thing. He reckons lap joints weaken the wood so that effectively it is half the cross section, but I think that if the forces are compressional it doesn't matter. I was also going to use dovetails in the bars that provide tension to prevent spread (1x2"). Are lap and dovetail joints a bad idea?

Mr Dazzler, you are very helpful, but I don't understand some of the phrases you use! Jowl post? Sole plate? Timber buildings are a different language, I need to buy the book.

As for upgrading the sizes of wood, I am thinking 3x2 for the upright pieces, 2x2 for the diagonal pieces, 3x2 for all the roof pieces except the tensioning bars that prevent spread which will be 1x2. The joists in the floor now go the other way, with a crosspiece as Buckshot suggests across the middle, and also two extra posts halfway along.

Are these good changes?

 

[mr dazzler]

Hi biddlesby
Your builder has his opinion, but I disagree . You can assemble a frame from any size timber (within reason of course, 2x1 is just not up to it!!), thats the beautyof Mortice and tennon construction. I mean most "shed's" are stapled together from 2x1, (2x2 if your lucky ), and 12 mm boards. I would still go with the sort of sizes i mentioned before though! !/2 laps are absolutely FINE on sole plate corners and simple scarf's (the sole plate was a great innovation when someone realised if you set the frame post's on a horizontal timber on the ground or a low wall, instead of buried in the ground they wouldnt rot as fast; the sole plate is the square base that the rest of the frame sit's on) I was recently inside a black snith shop about 250 years old and the largest timbers were only about 5x4 (oak) and its still here despite a bad fire in about 1860, its supported a tile roof quite well. Long timbers for plates were made up from simple half lap scarf joints they are still there they have taken the load for about 250 years Theres a sort of snob prejudice against 1/2 laps weird really because its time tested and proven method. They still use it in France even for repair work's. And your right compression works ok with them, try to posiotion the 1/2 lap (scarf) at or near a post (scarfing is just joining 2 short timbers to create a longer one) Dovetails are good BUT you gotta cut them real snug, they lose a lot of efficiency if they are slack (not as forgiving as a M&T) and they can tend to also lose efficiency as they timber's dry out. The tying joint makes use of a dovetail between the rafter plate and the tying beamto prevent spreading but there is ALSO another tennon as well on the wider part at the top of the jowl post (in the photo the main vertical post) A jowl post supports a tying beam and the wall (rafter) plate, AND a principle rafter as well! Thats why they need to be meaty especially at the top. A tying beam runs across the building and prevents the walls splaying apart. A 3 bay frame will have 3 tying beams as well as intermediate floor joists. The rafter plate runs lengthwise of the building and prevents the gable ends tipping away, an under surface for braces to fit up into and provides a surface for the rafters to sit seciurely on. Here they all come together in an classic english tying joint, superb technical efficiency and technological developement based on over a thousand years of insight and experience.
http://www.bespokeoakwrights.co.uk/jowl.jpg
http://www.bespokeoakwrights.co.uk/design.html
Look how the brace's are short, if you want doors/windows etc the short ones wont get in the way, long ones will. What cladding are you proposing. Clapboard's look good, but you could use industrial steel sheets like they use on b&q warehouses etc.
Hope this helps, cheers Jonathan

 

[JonnyP]

Being a builder I have knocked up one or two sheds before, but most are shop bought as they work out cheaper in the long run, but, if you have the time and knowledge, go for it, but I think the materials alone will not be that much cheaper than a shop bought shed.... From your drawings I would say, use more supports underneath, as just one on each corner on a 4 meter long shed is not enough...Personally I would use nails, especially for the cladding, but would screw the rest...I would use 2" x 2" timbers for the frame work and 18mm ply for the floor and roof. I reckon it would take me 5 days to put it all up too...

 

[demographic]

If it was me making the shed I would have the head and sole plates of each wall made out of at least 3x2 and more likely 4x2 and the uprights going between them at nailed 16 inch centres.

If you make the shed with 8 feet high walls you don't even have to cut the plywood or orentated strand board to height.
The boards will give it the strength that you are trying to get from your diagonals.
I would staple something like tyvek onto the ply or orentated strand board walls then put horizontal shiplap or TG&V boards over it.
Maybe even put insulation between the 4x2 and board the inside, if you use 3x2 you cant fit as much insulation in so its your choice.

Put the boards so they stand upright cos of they are layed on their sides they lose something like 40% of the strength.

Can't say I would bother with mortice and tennons, half laps or any other old style timber joints as it just takes time and isn't needed.
I have as near as dammit just finished doing 6 half million pound houses all with "traditional" roofs, the only mortice and tennon joints in all of them are in the staircases.
Your floor will need something like 6x2 at 16 inch centres also, you could get away with less but I wouldn't.
Also its better to have the floor joists running across the short span (width) instead of the length of the shed.

That should give you enough to be going on with.
Regards Scott.

 

[JonnyP]

If it was me making the shed I would have the head and sole plates of each wall made out of at least 3x2 and more likely 4x2 and the uprights going between them at nailed 16 inch centres.

If you make the shed with 8 feet high walls you don't even have to cut the plywood or orentated strand board to height.
The boards will give it the strength that you are trying to get from your diagonals.
I would staple something like tyvek onto the ply or orentated strand board walls then put horizontal shiplap or TG&V boards over it.
Maybe even put insulation between the 4x2 and board the inside, if you use 3x2 you cant fit as much insulation in so its your choice.

Put the boards so they stand upright cos of they are layed on their sides they lose something like 40% of the strength.

Can't say I would bother with mortice and tennons, half laps or any other old style timber joints as it just takes time and isn't needed.
I have as near as dammit just finished doing 6 half million pound houses all with "traditional" roofs, the only mortice and tennon joints in all of them are in the staircases.
Your floor will need something like 6x2 at 16 inch centres also, you could get away with less but I wouldn't.
Also its better to have the floor joists running across the short span (width) instead of the length of the shed.

That should give you enough to be going on with.
Regards Scott.

S'orry mate, but thats overkill...I am sitting in an 8 x 16 shed right now made from a framework of 1.5" x 1.5" and it is a solid shed and has been up for many years.... Using 4" x 2"s and 6" x 2"s will cost him a fortune and are not necessary...In my view..

 

[mr dazzler]

If it was me making the shed I would have the head and sole plates of each wall made out of at least 3x2 and more likely 4x2 and the uprights going between them at nailed 16 inch centres.

If you make the shed with 8 feet high walls you don't even have to cut the plywood or orentated strand board to height.
The boards will give it the strength that you are trying to get from your diagonals.
I would staple something like tyvek onto the ply or orentated strand board walls then put horizontal shiplap or TG&V boards over it.
Maybe even put insulation between the 4x2 and board the inside, if you use 3x2 you cant fit as much insulation in so its your choice.

Put the boards so they stand upright cos of they are layed on their sides they lose something like 40% of the strength.

Can't say I would bother with mortice and tennons, half laps or any other old style timber joints as it just takes time and isn't needed.
I have as near as dammit just finished doing 6 half million pound houses all with "traditional" roofs, the only mortice and tennon joints in all of them are in the staircases.
Your floor will need something like 6x2 at 16 inch centres also, you could get away with less but I wouldn't.
Also its better to have the floor joists running across the short span (width) instead of the length of the shed.

That should give you enough to be going on with.
Regards Scott.

Yeah the cynic and pragmatist in me says your probably right, why persist in trying to maintain old tradtions, why try and rsist the onward march of "progress" (whatever that is)?? But then not everyone thinks of carpentry as revolving round chopsaw/router/nail gun/UPVC type stuff 1st fix 2nd fix airfix (to put all the plastic on ) And what are new style timber joints, the old style traditional ones are just as relevant today as they ever were, and it was biddleby who first mentioned wanting to make use of joints to begin with. Your solution may well be fastest and cheapest, because it suits convenient industry material size's and use of power tools etc, but will almost certainly lack character No insult intended scott, its just how it is

PS Bidlesby if you use a standing brace like you have in your drawing, reverse it so that it joins to the sole plate near the centre, and the corner posts at their tops. This will be structurally more sound supporting the 4 corner's well, which in turn support the rafter plates etc etc, its also traditional. And theres no reason why you couldnt combine some traditional frame joint element's and also make use of nailed elements also, that approach was common in farm buildings eg spiking in wall studs and rafters or using bolted knee bracket's instead of tennoned braces. As in everything (for whatever reason which I dont really understand) time is money and they did such to try to keep costs reasonable.
When alls said and done you might just be better off buying a eady made timber building
cheers Jonathan

 

[demographic]

S'orry mate, but thats overkill...I am sitting in an 8 x 16 shed right now made from a framework of 1.5" x 1.5" and it is a solid shed and has been up for many years.... Using 4" x 2"s and 6" x 2"s will cost him a fortune and are not necessary...In my view..

Well, its about standard for flooring over a 2.5 metre span, if its sitting on a flat concrete base then it's supported a lot better.
I wouldn't put less in a house so I wouldn't put less in the floor of a shed either.
Also for me if its getting covered with ply I would make the sizes in multiples of the board sizes so the width would be 2440 mm (8 foot) instead of 2500mm cos cutting that 60mm ripping would get on my nerves for the sake of not much space

If the floors made of 2x2 at 36 inch centres (as is the diagram )and it isn't supported by something thats flat underneath its going to be as waffey as fook.

The walls are thicker cos that allows him to put some insulation in it at a later date.

Most garden sheds sold these days wouldn't withstand the Three little pigs versus the wolf test in my opinion

If he isn't going to use plywood then he is better to put the TG&V or shiplap boards on at 45 dergrees from the horizontal like the old balloon constructed american barns, that way is far more rigid than using the boards horizontally as it triangulates the structure effectivley without needing extra struts.

He wants a strong but cheap shed, thats strong but still fairly cheap.

<shrugs>

 

[mr dazzler]

its going to be as waffey as fook.

sealy Posturepedic style floors

I dont se the need to do those american tube style footing's in the diagram. If a concrete floor is inpractical then I would use a series of brick piers or a low wall to support the sole plates and floor joists, you get a level working surface to go off. Also youd get good ventilation under the shed, but harder to keep warm. I just built another deck with just them sort of pier supports, I used 6x2 joist's for it (10 foot run). I agree with demographic about the joist arrangement. Like I said earlier 450 mm spaced 4x2 or 6x2, maybe at 600 space's at a push, but then the floor will flex if theres a lot of load. Thats simple structural reality. If your onto a solid concrete floor it doesnt matter wether the joist is 1 1/2 inch, 4 inch, 8 inch or whatever, its only basically a packing piece between concrtete and floor deck. However, if the joists are in mid air, on piers etc then their structural strength is critical. Big timber seems like overkill but it means that the structure will more likely last a long time, more than 15, or 25 years (with good maintenance of course, clean gutters etc)

 

[Biddlesby]

The wood sizes will be larger than a B&Q shed but not quite as big as some people have suggested! Here is the design as it stands at the moment:

I need help with how to fit the crossbeam that goes perpendicular to the joists - at the moment it is floating in the air! Is it necessary? I am thinking of putting two more joists in, making them 24" centres and 2x4" cross sections. The shed will continue to be raised on 6 telegraph poles.

I also need help as how to fit the central tensioning beam (1x3"), as ideally it should be raised and so have to fit into the two sloped peices on the roof - sorry I don't know the technical terms!

 

[demographic]

What are you going to clad the shed with?

 

[Biddlesby]

Shiplap - horizontal - for the walls, ply for the floor, ply and roofing felt for the roof.

 

[weaver]

Here's mine.