Roof driving me mad!

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Im in the process of self building a double garage which measures 22 feet (length) x 17 feet wide approx.

The plans state I have to use 220x75 C16 joists at 400 mm gaps.

Everyone I know (who knows a little about building today) thinks this is major overkill and I would be able to use 180mm x 50 and at 600mm gaps.

Please can anyone offer advice on what would be a sensible (safe) level as 220x75 at 400mm gaps seems to be very expensive!

Also can anyone tell me what the recommended run off would be for a 17 feet flat roof. Thanks.
 
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Everyone I know (who knows a little about building today) thinks this is major overkill and I would be able to use 180mm x 50 and at 600mm gaps.

who are these people you know and what qualifies them to advise?

180mm x 50mm over 17 feet, don't make me larf!

at only 50mm thick your joists would need to be 240mm deep.

if you had a furring or diminishing strip going from 3" to nowt you would be ok.

it begs the question why did you not use roof trusses and form a pitched roof?
 
so your relying on a little knowledge to back up your argument to save a few quid on some timber. good job we have bcos really
 
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Thanks to both replies so far although making a judgement that im trying to scrimp on costs by cutting back is a little uncalled for I think?

"so your relying on a little knowledge to back up your argument to save a few quid on some timber. good job we have bcos really"

I think if you read my origional post back you will see that I am actually looking for advice and at no point state this is a cost cutting exercise. I simply state the fact that there is a cost difference and I dont call £300 pounds of a difference a few quid?

The whole point of posting was to find out what indeed is correct and had I been looking to scrimp a few quid surley I would have then just goine ahead and ordered, doesnt take a genius to work that one out?

With regards where the info came from it was two seperate people, one a joiner who builds kit house for a living and they obvously pass building control. The other was from a guy I know who worked for a roofing company granted in an office :) but did deal with all the quotations.
 
the only way to lessen the timber depth is to halve the span with a steel beam. ££££££.
 
Noseall, thanks for the info about the 3" and sorry didnt mean to ignore your question:
"it begs the question why did you not use roof trusses and form a pitched roof"?

Basically there are 4 of my neighbours who have similar style and I thought the best idea was to keep it inkeeping with everyone else around me.
 
Thanks to both replies so far although making a judgement that im trying to scrimp on costs by cutting back is a little uncalled for I think?

"so your relying on a little knowledge to back up your argument to save a few quid on some timber. good job we have bcos really"

I think if you read my origional post back you will see that I am actually looking for advice and at no point state this is a cost cutting exercise. I simply state the fact that there is a cost difference and I dont call £300 pounds of a difference a few quid?

The whole point of posting was to find out what indeed is correct and had I been looking to scrimp a few quid surley I would have then just goine ahead and ordered, doesnt take a genius to work that one out?

With regards where the info came from it was two seperate people, one a joiner who builds kit house for a living and they obvously pass building control. The other was from a guy I know who worked for a roofing company granted in an office :) but did deal with all the quotations.

well i apologise for any offence caused, but you seemed to refer to people with a little knowledge and the fact that it was over the top and therefore expensive.
 
I'm certainly no expert and also thought that the 75 x 225 joists specified for my planned double garage (5.9m wide) were over the top until I checked on the web for the correct loadings etc. I discovered that these are, in fact, the correct spec.
BTW had BC out on Friday who told me my strip foundation 1.9m away from an oak tree will have to be 2.83m deep. He suggested a raft foundation instead. Just as well I'd only dug a short strip down 800mm!

Dave
 

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