Roof timber queries

[garymcl]

Hi guys, looking for some help please.

Need to order my roof timber for the single storey extension, getting next to no help from my engineer.

He has specified 100x50 softwood for the wall plate.....does this need to be treated?

He has specified 150x50 C16 joists at 600c/c.....do these need treating.?

Finally, he hasn't specified anything for the rafters.....is there a standard timber I can use such as 150x50....would it be C16 like the joists? Also would the rafters need treating?

Can you also let me know what bolt I should use to bolt my wall plate onto my existing brickwork and at what centres should I bolt it at?

Really appreciate the help guys.

Gary

 

[catlad]

The normal rafter size is 3x2" if you do not intend to use it as living space treat all the roof timber and you want some wall plate straps, they look like long L shape with lots of holes in and spaced every 1.5 m if memory serves me.

 

[freddiemercurystwin]

The normal rafter size is 3x2"

WTF?

 

[garymcl]

The normal rafter size is 3x2"

WTF?

I don't know much about roofing but I thought that was a bit light myself?

I would have thought 6x2 minimum?

The loft space in the extension won't be "living space" so would I still have to get it all treated?

Cheers

 

[noseall]

Are we all just pulling timber section sizes out of a hat.

If so i say Four feet by six pills.

 

[noseall]

The normal rafter size is 3x2" if you do not intend to use it as living space treat all the roof timber and you want some wall plate straps, they look like long L shape with lots of holes in and spaced every 1.5 m if memory serves me.

Do you know anything about the building trade?

 

[^woody^]

You would be wise to use treated timber for any roof work. But you may be close to the home counties where treated timber is mandatory to protect against house longhorn beetle in any case.

You can use 3x2 timber (just like most of the houses around the UK have), but it depends on the spans between eaves/purlins/ridge

Wallplates normally strapped down with 30x5x1500 straps at max 2m spacing

 

[noseall]

Need to order my roof timber for the single storey extension, getting next to no help from my engineer.

He has specified 100x50 softwood for the wall plate.....does this need to be treated?

He has specified 150x50 C16 joists at 600c/c.....do these need treating.?

Finally, he hasn't specified anything for the rafters.....is there a standard timber I can use such as 150x50....would it be C16 like the joists? Also would the rafters need treating?

Some span sizes may give us a clue.

 

[^woody^]

3x2 will be fine .... for hitting your poxy engineer over the head with for his crap work.

Also how did these plans get approved? Is there a bit ripped off with the sizes on still on someone's desk at the council?

 

[freddiemercurystwin]

Its not essential that they're treated but would be beneficial especially given we're into autumn. You can just buy treated timber instead. The grade should be marked on the drawings but C16 is usually OK. The size of the rafters ought to be specified by the engineer but we can't help without knowing the span? Wall plate fixed with something like M12 bolts at 400 centres if good masonry or 200 cts if poor along the centre line of the wall plate but again your eng should have given you all this info.

 

[noseall]

You can use 3x2 timber (just like most of the houses around the UK have), but it depends on the spans between eaves/purlins/ridge

When was the last time you saw 3" x 2" specified for any structural aplication?

I'm not saying that it is not adequate but why would you? Why would you not use something as inexpensive as 4" x 2"?

 

[garymcl]

3x2 will be fine .... for hitting your poxy engineer over the head with for his crap work.

Also how did these plans get approved? Is there a bit ripped off with the sizes on still on someone's desk at the council?

Ha ha ha you guys crack me up, it doesn't seem to take much to get everyone on here having a pop....I love it!!

Firstly, yes, my engineer is crap, but you pay for crap you get crap...I've learned that the hard way.

Secondly, the extension is approx 40m2, 4m on the gable ends by 10m on the front elevation. Roof pitch approx 23 degree's.

The roof pitches on the 3 elevations, quite nice to look at but a bit of a pain in the ass to work things out. On plan, the rafters come in from the front elevation wall plate then when they hit the ridge rafter/beam (diagonal on plan) they'll turn 90 degrees and pitch back down to the gable end wall plate...this happens every 600c/c, until the central part of the roof where it is a simple pitch straight up from front elevation wall plate to the higher wall plate bolted into the existing facing brick.

So, longest span of rafter will be 4m (well...more if you use pythagorus's theorum!!!). All the ceiling joists will also therefore span 4m from front elevation wall plate to wall plate bolted onto existing facing brick.

Does that help....if not...maybe I'm the engineer for my own extension but I don't even know it!!

 

[freddiemercurystwin]

Span table only go up to a 150x50 and that'll span a max of about 3.2m without knowing loadings so really you need your eng to spec. Something like a 200x50 would prob be OK but only proceed if your BCO is happy with that size. If it were me I'd be going for 225X50s.

Prob 200x50 for ceiling joists aswell.

 

[noseall]

175mm X 50mm might scrape it at 400mm c/c.

 

[catlad]

most of the houses in Lancashire the rafters are cut from 3x2" and a lot are over a hundred years old and still going strong, but your roof is not the average roof, and on that respect its not going to matter what anybody on this site says its what your engineer specifies