Shed build - couple of questions!

[Hallsy]

Hi everyone,

I am part way through a DIY shed build, and have a few things that I would appreciate a second opinion on!!

First things first, the shed is going to be 3.6m x 3.0m, apex roof, with the apex along the long end (transverse apex??) as that suits the layout and door position of where it is in the garden.

The floor is 4x2 at 400mm centres, over boarded with 18mm ply. Framework will be 3x2 at 600mm centres, membrane then shiplap.

I have a couple of questions around the roof construction.

I wanted the eaves height to be around 2m, and the ridge to be 2.5m (which is maximum for a garden building on a boundary - correct?).

With a 1980mm eaves height (approx, whatever works out closest to 2m without ripping down a length of shiplap), that gives me a 16.1 degree pitch and 1873mm span.

I was planning on using a 3x2 ridge beam with 3x2 rafters (with birds mouth cuts), and then a length of 3x2 at the end of where the rafters overhang (sub fascia?), overboarded with 18mm ply, then either heavy duty felt, or possibly felt underlay and felt shingles.

Does this sound acceptable for the roof, or should I use a larger ridge beam and rafters?

The second question is also roof related. I would like to have an extended gable at the front, I have researched various ways to do this, but it looks like building ladder frames, and screwing them to the gable rafter is simplest. I was thinking of using 3x2 again here, with noggins at 450mm centres. How much of an overhang can this method support without sagging? I had read a maximum of 18", but that was using 4x2. Realistically I will want to go out by 18" max, maybe 12" if it doesn't look right.

Like this : http://www.howtospecialist.com/wp-content/uploads/2012/11/Installing-the-overhangs.jpg

Would I be better building this bit as suggested above, or would it be better to extend the ridge beam and sub-fascia timbers, then fix flying rafters on the end, and add noggins between gable rafters & flying rafters?

Any advice here would be much appreciated

Last thing, can anyone recommend a good manufacturer for the felt shingles? I have been told that Katepal shingles are good quality, any other suggestions?

Thanks again

 

[big-all]

first point
2.5m is from the ground not the floor
5x1 shiplap is cheaper per square m the coverage off 5" shiplap is around 108mm
here is my shed from 10 years ago looks the same[better] now
http://s21.photobucket.com/user/bigall2005/media/e1e47346.pbw.html?sort=3&o=15

 

[Hallsy]

Hi Big-All - thanks for your reply.

I will be aiming for 2.5m max height from the concrete base - that is what I'm taking as ground level.

Not really sure what is defined as ground level in the garden, as my garden has many levels!! But assuming some sensibility, 2.5m above the slab it sits on seems sensible!!

I have already bought the shiplap, it has been sat in my garage drying out for 10 days or so now as I had it pressure treated - it is 120 x 12 finished size.

I have seen your shed mentioned many times on the forums - it looks great!! I've gained plenty of good info from your previous comments!!

I just wanted to make sure that my proposed use of 3x2 for the roof will be ok, before I get to that point. If it isn't then I will size up as necessary, likewise - the method I plan to extend the gable.

This weekend I will be making the framework for side panels, so still have a little bit of work to do before I'll be at the roof stage!

 

[big-all]

so your shiplap is about 109 coverage coverage is the distance between 2 bits clipped together
give it at least 3 weeks preferably more to dry as it will shrink as it dries
the highest natural point the shed covers is the datum point so if the base is 2" thick but at one corner its sunk 1" below the natural ground level then its -1" above the base

if you look at the "A" frames on my shed they have no birds mouths they literally go to a point that finishes on the outside face there is 12mm ply on the inside then 3x2 planted on the face giving a further 2" bearing face so around 80% off the timber is supported
it was done that way to minimize the height but to give headroom
the wall frames are 6ft in height so giving about 5ft11" at the edge but about 6ft 2 under the center off the "A"
at a 30degree angle you dont really notice the low edge i am 6ft and have never banged my head its only the 16" to the side that are lower than 6ft 2"
3x2 is absolutely fine for the a frames i had planned on 2ft centers like walls and floors but miscalculated and only put timbers where the boards joined so up to 4ft apart with the thought off filling in the gaps but that never happened as there is zero noise even though there is often 150+kg off timber up there

 

[Hallsy]

Thanks again Big-All - I looked at some span tables but they tend to start at 4x2.

It will be at least another week before I am ready to use the shiplap, so should be nice and dry by then. It had been drying for a few days before it was delivered, and measured around 124mm iirc, they measure 120/121mm now so about nominal.

What is the recomended expansion gap for shiplap? 2mm or so?

 

[big-all]

still about 2mm too big
minimum coverage around 107mm when fully shrunk so fitted at around 109-110mm
what is the measurement from the shoulder to the base on the back??[exclude the tongue]
i dried mine for several weeks and it still wasn't dry enough

 

[Hallsy]

I'll have to measure it, I only checked overall height and cover height, on the driest boards that was 120mm with 110mm cover.

I'm still mulling the roof over, what is a stronger design, 3x2 A frames with 18mm ply gussets, or a ridge beam & rafter roof with collar & rafter ties? I'm thinking I'd need a larger ridge beam than 3x2 - many designs I have seen would seem to use at least a 6x2 ridge beam.

With approx 2m eaves height, either method will give me enough head room (i'm only 5'9"!!) - I'd just prefer to build the strongest design with what I have (3x2 & 18mm ply), and buying say a length of 6x2 for the ridge if necessary.

 

[big-all]

i used 12mm ply as that turns the end frames into 3" matching the wall underneath
also added strips to the outside face for the txg shiplap to screw into
if its 110mm then as tight as you can to the plank below as 109-110 allows shrinkage in the summer and expansion in the winter
also only one fixing per plank per area in the lower 20-25% off the board
on my shed the bottom plank covers the floor and a further 25mm beyond so any water running down the walls is shed onto the ground
i dont have a ridge i have 18mm ply and 4 layers off torch on felt [base/under/2 top coats]with everything at the ridge doubled so the ply rests on itself and cant go anywhere
i prefered to draw the trusses on the floor cut the ply and all the timbers to the "rod"and this kept the roof within about 6-8mm over its length
the ply on each side was cut to 6ft giving a 6-8" overhang all round and a 30 degrees angle
the 2ft offcuts where added to the floor to give a 10ft wide floor and a 12ft length
9 sheets in all for floor and roof

 

[Hallsy]

Thanks again Big-all, I think I'll go with the a-frame method then - at the end of the day it will still be far stronger than many 'off the shelf' sheds.

I'll make a temporary jig on the floor to keep them uniform as you suggest.

 

[big-all]

you dont actually need a jig just a full sized drawing to follow
make all the components fairly accurately but about 3mm short as this allows a bit off adjustment if timbers are a fraction different
once you have made the first one you can use this as a template on a bench but the fact its 3m long it may be difficult
just lay the components on the template screw on the ply plates flip and do the other side this will prove 2 things {A}you havent screwed it to the floor and {B}the drawing is symmetrical

 

[chris_o]

You might this useful if you do cut and pitch, almost makes it too easy! In the process of making a small shed for myself at the moment

http://www.blocklayer.com/roof/rafter.aspx

 

[Hallsy]

Cheers Chris - will take a look

 

[Hallsy]

I have a quick question over defined ground level for the 2.5m max height.

As I understand the regs, this is 2.5m above adjacent natural ground level, and when the ground is uneven - the highest point.

Does adjacent mean adjoining in this instance, or rather, next to?

The concrete slab I put in sits an inch or so higher than surrounding ground on three sides, but on one side I have a lawn, retained by sleepers that sits four inches higher than the concrete base at it's highest adjacent point (sleepers & lawn run off). I have left a gap of a few inches between the sleepers and lower concrete base, that I will fill with gravel to aid drainage and prevent water from running to the slab.

Question is, can I use this as ground level? It is adjacent and natural, I did level the lawn off last year as it ran off to nothing, but the original highest point has not been exceeded.

At my proposed eaves height and 2.5m ridge from concrete base, that will give me a 15' pitch, which is on the limit for shingles, so if I can keep eaves at same point above floor level ( suits a door I want to use), but gain 100mm or so on ridge (against higher adjacent ground) that will give me a slightly steeper pitch - which would suit the shingles and my eye better.

This shed will be adjacent to a pavement behind a 6ft perimeter wall, so shouldn't bother neighbours anyway - but the way I interpret the regs, it would be fine?

 

[big-all]

its from the highest natural point on the ground it"covers"

 

[Hallsy]

Fair enough