The BIG shed project - Part 2 Roof

[GreenBoy]

Ok this may seem a dumb question for some of you here, but why do i need a ridge board?

I ask as i have been searching round the net for some plans for a shed to give me a head start on designing the shed, and have come across two types of roof construction.

The first requires a ridgeboard and generally also requires the rafters to have a bisrdsmouth (is this correct term?) cut into it so it notches over the ring beam, and the second is a system of trusses that are put in place and then have ply sheets nailed over them to give rigidity.

Is one easier to construct than the other and if you wanted some sort of dorma effect is it possible with both types of construction?

Sorry if these are particularly dumb questions but i honestly dont understand the pros and cons of both forms.

Many thanks
GreenBoy

 

[trousers]

I'm sure Mike will be along shortly but here's my 2p worth.
Pitched roofs are essentially a number of sets of timbers nailed together in the basic form of a triangle to give it inherent strength and rigidity.
In a "cut" roof, usually pairs of rafters are nailed to a ridge board at the high point, and to the wall plate (your ring beam) at the low (wall/birds mouth) end.
The pair of rafters are prevented from spreading apart under their own weight and the weight of the roof tiles/slates by an extra timber, called a collar, tie, ceiling joist (whatever is appropriate) which is nailed/bolted to each rafter, preferably at a low level.
Without the ridge board, fixing the rafter pairs would be tricky since each rafter would have to be (weakly) nailed to its opposite number only, and so each pair would be waving around in the wind until the roof battens were fixed at a later date, or additional braces were used.
The rafter/collar arrangement can also be made in a factory and delivered to site, which makes pitching the roof very quick, and although no ridge board is required, diagonal braces are a must to prevent racking and make the structure rigid.
Not sure exactly what you mean by trusses which have ply nailed over them, but there are many variations on the basic theme above, and that would be just one of them.
If you are building a shed, keep it simple. How big is it? What pitch the roof?

 

[GreenBoy]

The size of the shed is approx 12 feet by 24 feet. (3.6m x 8m approx)

I was thinking of making the roof approx 45 degrees to take the height up to the maximum 4m from a side wall of 2.2m. The idea being to give plenty of storage room above an open workshop area.

The idea of two rafters with a cross beam to make an A frame that its on the wall plate is strengthened with ply gussets at all joints and the the whole roof is boarded over and therefore not requiring diagonal bracing?

I am thinking of felt tiles as a roof covering and therefore should be ok on a pitch like this (?)

Thanks for your comments

GreenBoy

 

[Doug B]

The idea of two rafters with a cross beam to make an A frame that its on the wall plate is strengthened with ply gussets at all joints and the the whole roof is boarded over and therefore not requiring diagonal bracing?

That`s basically what i did, though it was done as a cut roof with a ridge board, for ease of erecting. Making an A truss on the floor then getting it up in place is hard work.

I only gusseted the top point of the A, & star washered & bolted the cross beam. The ply makes it very solid & the A shaped gives loads of internal head room.

I then fixed 2 x 2 battens on top of the ply running in line with the rafters, then felted & tile lathed so there was plenty of ventilation between the ply, felt & roof tiles.

 

[GreenBoy]

Doug

Thanks for the the reply - i think i am a bit confused - how did you use a gusset at the top od the A and a ridge board? Do you have any pictures you can post?

 

[Doug B]

Doug

Thanks for the the reply - i think i am a bit confused - how did you use a gusset at the top od the A and a ridge board? Do you have any pictures you can post?

I`ve no pictures, but all i did was cut a triangle out of ply matching the pitch of the roof, then cut a slot from the top point down the depth & width of the ridge board.
A framing nailer is a very handy tool, when doing roofs this way.

 

[GreenBoy]

Ahhh - I understand now

Thank you

 

[MikeG.]

Sorry, I have only just stumbled across this thread.

The question is what are you trying to achieve? If you want a vaulted ceiling, with no ceiling ties, then that needs proper designing.

Is this a building you have Planning Permission for? In other words, is the design set in stone? Sizes and spans are the important factors.

As Doug has ssaid, there are lots of approaches to building rooves, and the ridgeboard comes or goes depending on the system you choose. Lots of ancient rooves don't have them........some do. Almost all modern pre-fabricated truss rooves don't have them, but most site-constructed "cut rooves" do require them. Vaulted ceilings will sometimes mean having a structural ridge beam........a great big purlin that structurally spans the roof longitudinally.

So lots of options........now let me know what you are trying to achieve.

Mike

 

[EddieJ]

Mike has summed it up very well, and as an example of a very simple cut and pitch roof utilizing a purlin, this is what I tend to carry out 'budget jobs' where a client wants storage, but doesn't want anything too elaborate.
Interestingly, in local planning authority, planning and regs are only applied to storage, when the chosen flooring material is fixed down. Weird!

 

[Escudo]

I am interested in this subject.

What roof design exists that does not have a "tie beam" I think that is the phrase to describe the piece of timber which is at the bottom of the truss . Say you wanted a roof that was completely open, a bit like a church?

Looked this up with that in mind;

http://buffaloah.com/a/DCTNRY/h/hammer.html

As another thought say you wanted a roof where one side could have the tie beams to say support storage above and the rest was open?

I understand that the tie beams are required to prevent the roof squashing the building. Presumably, if a suitably strong fixing is made at the ridge this is unlikely to happen?

Mike, I am still working and thinking about my own workshop plans and if possible I would like a roof design that was open to give a more airy space, perhaps with velux windows and the option for a serious overhead storage area over say half the building.

I must say the terminology when it comes to rooves is very confusing :? . I am reading a book from the library (well just looking at the pictures) by C N Mindham - "Roof construction and loft conversion" and it is going over my head (pun )

Cheers, Tony.

 

[GreenBoy]

Planning: I dont think i need planning although looking at the planning portal i am a little confused due to the recent changes...

this is the relevant section of the planning portal:

Planning Permission
Rules governing outbuildings apply to sheds, greenhouses and garages as well as other ancillary garden buildings such as swimming pools, ponds, sauna cabins, kennels, enclosures (including tennis courts) and many other kinds of structure for a purpose incidental to the enjoyment of the dwellinghouse.
Other rules relate to the installation of a satellite dish, the erection of a new dwelling or the erection or provision of fuel storage tanks.
Under new regulations that came into effect on 1 October 2008 outbuildings are considered to be permitted development, not needing planning permission, subject to the following limits and conditions:
• No outbuilding on land forward of a wall forming the principal elevation.
• Outbuildings and garages to be single storey with maximum eaves height of 2.5 metres and maximum overall height of four metres with a dual pitched roof or three metres for any other roof.
• Maximum height 2.5 metres within two metres of a boundary.
• No verandas, balconies or raised platforms.
• No more than half the area of land around the "original house"* would be covered by additions or other buildings.
• In National Parks, the Broads, Areas of Outstanding Natural Beauty and World Heritage Sites the maximum area to be covered by buildings, enclosures, containers and pools more than 20 metres from house to be limited to 10 square metres.
• On designated land* buildings, enclosures, containers and pools at the side of properties will require planning permission.
• Within the curtilage of listed buildings any outbuilding will require planning permission.
*The term "original house" means the house as it was first built or as it stood on 1 July 1948 (if it was built before that date). Although you may not have built an extension to the house, a previous owner may have done so.
*Designated land includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.
Building Regulations
If you want to put up small detached buildings such as a garden shed or summerhouse in your garden, building regulations will not normally apply if the floor area of the building is less than 15 square metres.
If the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval providing that the building is either at least one metre from any boundary or it is constructed of substantially non-combustible materials.
In both cases, building regulations do not apply ONLY if the building does not contain any sleeping accommodation.


the problems i see are the 2.5m height within 2m of the boundry - but moving the shed may maek this ok, although i am limited on space to move it to.

One thing i notice that there is no max height mentioned - i thought that there was a 4m height maximum for the ridge...

I will answer the other questions raised regarding the roof section later and i will try to post some pictures, as this will make things more clear.

thanks for the comments

GreenBoy

 

[EddieJ]

Planning: I dont think i need planning although looking at the planning portal i am a little confused due to the recent changes...

this is the relevant section of the planning portal:

Planning Permission
Rules governing outbuildings apply to sheds, greenhouses and garages as well as other ancillary garden buildings such as swimming pools, ponds, sauna cabins, kennels, enclosures (including tennis courts) and many other kinds of structure for a purpose incidental to the enjoyment of the dwellinghouse.
Other rules relate to the installation of a satellite dish, the erection of a new dwelling or the erection or provision of fuel storage tanks.
Under new regulations that came into effect on 1 October 2008 outbuildings are considered to be permitted development, not needing planning permission, subject to the following limits and conditions:
• No outbuilding on land forward of a wall forming the principal elevation.
• Outbuildings and garages to be single storey with maximum eaves height of 2.5 metres and maximum overall height of four metres with a dual pitched roof or three metres for any other roof.
• Maximum height 2.5 metres within two metres of a boundary.
• No verandas, balconies or raised platforms.
• No more than half the area of land around the "original house"* would be covered by additions or other buildings.
• In National Parks, the Broads, Areas of Outstanding Natural Beauty and World Heritage Sites the maximum area to be covered by buildings, enclosures, containers and pools more than 20 metres from house to be limited to 10 square metres.
• On designated land* buildings, enclosures, containers and pools at the side of properties will require planning permission.
• Within the curtilage of listed buildings any outbuilding will require planning permission.
*The term "original house" means the house as it was first built or as it stood on 1 July 1948 (if it was built before that date). Although you may not have built an extension to the house, a previous owner may have done so.
*Designated land includes national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.
Building Regulations
If you want to put up small detached buildings such as a garden shed or summerhouse in your garden, building regulations will not normally apply if the floor area of the building is less than 15 square metres.
If the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval providing that the building is either at least one metre from any boundary or it is constructed of substantially non-combustible materials.
In both cases, building regulations do not apply ONLY if the building does not contain any sleeping accommodation.


the problems i see are the 2.5m height within 2m of the boundry - but moving the shed may maek this ok, although i am limited on space to move it to.

One thing i notice that there is no max height mentioned - i thought that there was a 4m height maximum for the ridge...

I will answer the other questions raised regarding the roof section later and i will try to post some pictures, as this will make things more clear.

thanks for the comments

GreenBoy

I highlighted the 4m clue for you! :wink: :lol:
What it does fail to mention though, is that the measurement is taken from the highest point around the building. So use any banks, retaining walls etc to your advantage!

I'll try and sort out some info and advice for you later. Dealing with issues of planning for outbuildings and garages, is pretty much a daily part of my job.

 

[GreenBoy]

Doh! ](*,)

Shows you should always read these things slowly (knew I shouldn't have given up on the old method of following the words with my finger and letting my lips move as i read)

Thanks for the guidance!

 

[Deejay]

Hello Greenboy

A useful site for roofing , and more.

http://www.blocklayer.com/

Cheers

Dave

 

[GreenBoy]

Wow great site - thanks deejay

 

[CWatters]

The size of the shed is approx 12 feet by 24 feet. (3.6m x 8m approx)

The other issue is Building Control Approval.

I make the area 29sqm which is >15 but < 30sqm. Building Control Approval would be required if any part of the building was within 1 meter of the site boundary.

Best avoid that because I believe a workshop is classed as a habitable room and you get into issues about insulating and heating to meet the regs.

 

[GreenBoy]

Hi Guys

Sorry for the delay in coming back to you but my PC has just died on me - something to do with the graphics card dying and taking the motherboard with it - i am therefore using my wifes laptop - under very strict instruction NOT to fill it up with rubbish and lots of 'geeky' internet web sites !!! As if?

So - first EddieJ -what a great looking structure. Rather more than i am looking for.

The reason for the BIG shed project is currently i have a brick built shed (APPROX 7x 7) on the back of my house which i want to empty so i can extend the bathroom (which is also 7x7) -- which is in the old coal shed! and also combine the storage with a 6x8 wooden shed i have at the end of the garden - approx 150 feet from the house and is used for the lawnmower and junk.

I also want to make some room for a workshop as my current situation requires me to dig out a black and decker work mate onto the lawn ad work between rain showers and periods of lets say less than good health (check out crohns on the interweb if you can be pineappled (pun intended)) where i can 'fiddle' and hopefully learn something useful to do with my hands as i am a 'cubicle rat' that sits in front of a PC all dy at works and need something to do in the evenings and weekends)

Mike - My garden is very long and thin, and the new planning laws worry me - to obey the 2.5m tall within 2m of the boundry i would need to place a shed of any size right in the middle of the garden - my garden being approx 25 feet wide. i ma therefore rethinking things - may be TWO sheds - one for storage and one for a workshop - would you get away with building one and then building the second next to it (read attached?) - as my site slopes the entire length of the garden one shed would be lower than the other and therefore they would look like two sheds ...

Sorry i cant post some google sketchup pics at the moment as stated before i am using my wifes laptop and it cant handle it... will post as soon as my new pc components arrive...

CWatters - by going to two shed - i might be able to build within 1m ... need to do some thinking on this,,,


Thanks for all the replies - much appreciated.

GreenBoy.

 

[MikeG.]

Greenboy,

don't get things confused.......the planning requirements you mention are describing what you can build, and where, without planning permission.. There is absolutely no reason to have anything other than the shed you want...........it is just that if it falls outside the criteria mentioned you will have to get permission. Big deal!

So, you decided where you want your shed, and how big you would like it. Then toddle along to the planning department with a sketch or 2 and some photos, and discuss it with a planning officer...........then if necessary get some drawings done and sbmit. £150 fee, 8 weeks later you get your permission.

Don't worry about all those criteria at all. You aren't being restricted by them......all they are doing is taking a whole lot of uncontentious applications out of the system.

Mike

 

[Tom K]

Could the Hon Mr Garnham clarify "Floor area" does this mean floor ie inside or does it mean footprint?

 

[EddieJ]

Could the Hon Mr Garnham clarify "Floor area" does this mean floor ie inside or does it mean footprint?

Here you go Tom, this may help answer that question.. http://www.oaksales.co.uk/planningguide.html The measurement for my standard two bay frames is 5486mm x 5971mm (32.75m sq). But by the time that you have deducted the brickwork to the three sides and the pads, the measurement is reduced to 29.72m sq