Beams for flat roof

[old]

I am planning to extent the workshop and have to use a flat roof that needs to span 3meters . I have found tables to calculate conventional timber size on the net but i would like to investigate the engineered 'I' beams that are frequently used in new build i understand they are very strong but i cannot find any info on size required installation instructions, cost comparison etc can any one help please.

[engineerone]

why not make your own out of mdf?

you could make either hollow squares, or even i beams
using 10 foot boards.

paul

[paulchapman]

Flat roof; leaks; MDF

[engineerone]

well paul, engineered beams are only a form of strawboard or mdf, or similar from what i have seen, so the feeling is green mdf,
and then obviously paint properly.

of course the problem with all flats rooves is as you say, a pita
but i guess it depends on where you place the joints of the roofing felt.

paul

[paulchapman]

Paul, I've no experience of these engineered beams but I've had a lot of experience with flat roofs, both on my bungalow and on sheds. In my experience, roofing felt is a complete waste of time and will need lots of maintenance and frequent replacing. The thought of combining that with something like MDF (green or otherwise) to support a flat roof is asking for problems in my view. I had to have the flat roofs on my bungalow replaced a few years ago and went for a glass fibre type of covering which is seamless and doesn't give all the problems that you get with roofing felt and it wasn't a lot more expensive.

Leaking roofs cause so many problems I would think very carefully about the best sort of materials. You can often do a much better job for little more cost.

Cheers

Paul

[engineerone]

you are right, and i do agree, flat rooves seem to be the devil's spawn.

i was just suggesting another route. since in fact i have not seen much in this country about engineered beams.

paul

[dirtydeeds]

why dont people recognise the UTTER stupidity of flat roofs in this country

they are roofs designed for dry countries

this land isnt called green and pleasent for nothing

[engineerone]

i agree but tell it to the planners too

paul

[mel]

old .
to answer your question . you will need to look at the loading ratios, this will give you the centres of the the joist/beams and should give you the sizes of the beams
there was a lot of debate on byrons workshop build on the other forum
in my opinion its better to air on the cautious side and go for as heavy a beam as possible
"I" beams or bison beams are made of sterling board and are laminated top and bottom . i would'nt risk making your own
I read somewhere that factory made "I" beams can span up to 20 meters with no centre support

too continue the debate on flat roofs
if these are done properly they should give a lifetime of trouble free service {hard hat on and wait for the incomeing }
however, it is the roof of choice for the cowboy builder .
what a lot of people dont understand is that a flat roof is a built up felt system
there are other alternatives to the cap sheet being felt
this is best done by a professional roofer who has all the gear to do it properly , bitumen boilers and gas torch'es, etc, etc ,

hope this helps in some way
mel

[staffie]

Old,
Try a few of the selfbuild sites they have linkes to people like www.howarth-timber.co.uk, who manufacture the stuff. We use I beams when we did a self build 2 years ago for all the floors.
If memory serves it was a 10mm bord with 75x50 mm edges about 300mm wide and spans of 12 meters, they were placed at 400 mm centres. 18mm plywood screwed to tops as sub flooring, Insulation between beams.

I believe that you can also get a steel version which takes a polystyrene insert between the beams for insulation, this has to be borded with fireproof ceiling board.

Jock

[mrgrimsdale]

3M span I'd go for simple softwood joists - probably cheapest option.
Flat roofs need a fall - the more the better. Build it flat and add firrings, or build it with a fall.
Yes you need to build up a proper felt system with protection such as chippings.
Avoid all mdf, chipboard, but roofing ply should be OK.

cheers Jacob

[old]

Thanks for all your answers it seems to me that this is new tech. and there for used to solve specific long span etc problems so i will use conventional timber and keep it simple.

[dirtydeeds]

can anybody help me with a link to spans for timber, old mentioned he found them on the web

im not so good at googling, probably because i dont know what to "ask" for

[dom]

Try here DD

From another web site
What’s bizarre is that the span tables used to be embedded in the building regs, which are now in the public domain thanks to the internet. Get hold of a copy of the old Part A for England & Wales and there they are, in Appendix A, a 28-page blockbuster which covered every conceivable timber span you could ever think of, from humble floor joists to rafters and purlins.

[thallow]

dirtydeeds said:

im not so good at googling, probably because i dont know what to "ask" for

Not wishing to teach anybody about how to suck eggs but a great search tip which usually helps is to put a '+' sign in the search criteria; so if you were looking for 'engineered beams' then you may get return of
1.sites with 'engineered'
2.sites with 'beams' and finally
3.a list of sites with both,
the latter being the most relevant.

Putting in 'Engineered + Beams' tellls the search engine that the results must contain BOTH words and therefore your results are much more relevant and would only return number 3 from the above list! HTH ;D ;D ;D

[old]

Info.
www.planningportal.gov.uk/uploads/br/BR_PDF_AD_A_1992.pdf
Main page.
www.planningportal.gov.uk/england/professionals/en/4000000000067.html
then Part A archived version 1992 edition as above.
page 40 onwards

[nickw]

thallow said:

Putting in 'Engineered + Beams' tellls the search engine that the results must contain BOTH words ...

Strangely if you want to omit pages that contain certain words you need to put e.g. '-Columns' without a space between the - and the word. Inserting a space when using + seems to work though, as does leaving it out.

[jake]

thallow said:

Not wishing to teach anybody about how to suck eggs but a great search tip which usually helps is to put a '+' sign in the search criteria; so if you were looking for 'engineered beams' then you may get return of
1.sites with 'engineered'
2.sites with 'beams' and finally
3.a list of sites with both,
the latter being the most relevant.

Putting in 'Engineered + Beams' tellls the search engine that the results must contain BOTH words and therefore your results are much more relevant and would only return number 3 from the above list! HTH ;D ;D ;D

You don't need to do that with google, unless the second word is "and" "where" "how" or other linking words like that or a number or letter (which google ignores unless forced to look for them with a +). By default on Google, 'engineered beams' returns only results with both terms. For 'Engineered I beam', you would need to put a + in front of the I, or you will just get engineered beams again.

More useful on google are quote marks, so "engineered beams" gives you just pages which use that as a term or phrase, rather than pages which use both words somewhere (like "Walt Disney engineered the situation so that that Mickey Mouse beams at whatever the cat is called just as the plank falls on his head etc").

[thallow]

jake said:

thallow said:

Not wishing to teach anybody about how to suck eggs but a great search tip which usually helps is to put a '+' sign in the search criteria; so if you were looking for 'engineered beams' then you may get return of
1.sites with 'engineered'
2.sites with 'beams' and finally
3.a list of sites with both,
the latter being the most relevant.

Putting in 'Engineered + Beams' tellls the search engine that the results must contain BOTH words and therefore your results are much more relevant and would only return number 3 from the above list! HTH ;D ;D ;D

You don't need to do that with google, unless the second word is "and" "where" "how" or other linking words like that or a number or letter (which google ignores unless forced to look for them with a +). By default on Google, 'engineered beams' returns only results with both terms. For 'Engineered I beam', you would need to put a + in front of the I, or you will just get engineered beams again.

More useful on google are quote marks, so "engineered beams" gives you just pages which use that as a term or phrase, rather than pages which use both words somewhere (like "Walt Disney engineered the situation so that that Mickey Mouse beams at whatever the cat is called just as the plank falls on his head etc").

Whoa I stand corrected - I was taught to and I have been using that little bl**dy plus sign all these years and I dont need it!

Thanks Jake ;D