For the builders,

I have a span of 8m front to back of my bungalow, there is no supporting wall in the hallway that leads front to back of my house so no wall to rest a beam on, so whats the plan, ? surely you cannot get a timber to support an 8m run front to back ?

mark

 

i've seen them use laminated beams to get big lengths, metal/wood/metal/wood/metal sandwiched together and bolted through, but you are talking about 12" high beams for that sort of thing
the other alternative is to use an rsj, but again, you have to think about what sort of rsj you would need to use

in either case, you'd have to think about the load it was supporting and so, in any case, you'd have to get a proper architect to draw up plans etc with loadings and all that on it

i think mondeo man does this for a living althoguh there may be others

 

Ask chip he'll know.

 

Are you just curious what's there or do you want to add a beam for some reason?

.

 

Mark

If its a bungalow the chances are the roof trusses make up the ceiling joists and are engineered to span the 8m due to the construction of the roof.

The joists in my house are 7"x2" 13.5" c/c and span 4.8m ( this is ground floor ceiling/first floor floor ) they need support as they need to be a lot deeper to span that length.

It would help if you explained what your problem was?

J

 

you need a copy of the trada span tables, they used to be part of the building reg docs but now are seperate. The timber section sizes differ depending on whether they are to be used as floor joists or roof joists.

On my conversion we used 8.4m unsupported spans for the room in roof trusses and these were 220x45 timbers, but you can go much smaller if they dont need to be load supporting, the design of the w pattern transfers the load around the truss so that the bottom timber does not have to have a large section size

 

im going for a loft conversion, the current roof is the std purlin type not a trussed roof, so i need the support for an extra floor.

the last loft conversion had nothing like this span and had enough supporting walls through out the building to split up the lengths, might be a roof off job also to raise the angle.

 

what you can do if you want a cut roof rather than trusses and you dont want to strip the roof is to lift the lowest couple of layers of tiles and slide in the main new floor joists, then do the same with the roof joists under the tiles and build them up into trusses internally using nail plates to join the timbers, once built the original timbers are then redundant. Section wise for that span you need the same as mine 220x45

 

I had already decided that I was going to lift the lower section of slates and outer brick tope layers and slide in the joists so thats no worries, it was just the length I was bothered about for approx 3 joists, is it not 220 x 75 i need (not 45 ? )

cheers
Mark

 

is a question for a srtuctual engineer not a builder

 

I have an architect coming round in a couple of weeks to sort it but nothing worng with questioning what others have done mate, and i would of liked to think a builder would know what to do really, or else do they just follow instructions ?

 

im sure a good builder could come up with some ideas but unless your a qualified structual enginer / architec i dont think youd stand a chance against planning

 

Mark

For this type of work it will need building control so they'll want structural calcs.

 

yep, fully agree with that hence the architect/engineer coming round, nothing worse than just listening to one person though as how do you know if they are right or wrong

with the amount of alterations we are having done the council will be all over it anyway

 

more like youll pay 300 quid and theyll turn up once

 

Damn right...

I spoke to building control about my alterations and they advised on how and what to do to proceed...

Got a structural engineer to check what I was doing was ok, got the calcs, job done.

 

been down already and given me a price for full autocad design and plan and council submission plus fees and management option of Ł550, thats the only one of 4 that i called who actually bothered to turn up, seams like the whole building trade must be loaded as non of th fuckers want any work, ive been in contact with 5 builder since december the st for quotes and have had 2 back, one took 4 weeks, the other took 3 weeks, I gave them all the same project (not the loft conversion) with all the same dimensions etc one came back at Ł24,496, the other Ł8975

and from what i know i think the 24k didnt want the job by the sounds of it, either that or they are just a complete rip off !

 

Are you going to run a proper small building contract????

Or just pay as you go???

Got a QS on board?

 

i ment building control with that mate, i personaly think they are fucking useless but you cant do anything about that

them prices are all over the fucking place, the 8 grand one would of had the money and done the off im sure

 

I have not got anybody on board yet as the building trade seams to be the biggest bunch of lazy bastards ive ever tried to give money to!

of the two that gave me the quotes, both live within 1/2 mile of me and are both known in the area and have been working in this area and beyond for a known 20 years plus, so i dont see why they would want to leg it for 8k ?

 

you could get tgi beams but personally id put in a steel half way then joist into the web

 

just had a better read id personally go with a steel and minimum of 8x2's thing you have to think of is when your loft is done what are you having up there wieght wise? fitted wardrobes etc? best with 9x2's i think as gives you plenty of strength although 8x2 will do the job fine

 

Mark, on our loft we converted we spanned 7.2M in timber with no central support just from front to rear plate.

From what I remember the timbers were 9x3 inches and they had to be 300mm centres instead of 400mm. We had to use 27 of them across the whole roof which cost a packet.

All calculated up and building control approved.

 

Agreed, judging by the builders on here I asked, none of them actually have any sort of detailed knowledge of the calcs involved, crude guesses at best, definately worth talking to a structural engineer instead.

 

Sounds like it can be done, though i may price it in steel as well if the timber is that dear, reclaimed stel can be had for a good price

cheers guys

 

out of all the builders ive dealt with it seams they like to follow an instruction book and cannot decide whats right for themselves when it comes to something like this.

 

10% more span will need more than 10% more support, as obviously its an exponential relationship, so the difference between 8M and 7.2M may be significant, definately a good question to ask a structural engineer who knows for certain.

Not the sort of job you want to do and then have to redo!

 

Exactly the experience I had with them on here when I tried to ask some serious questions in my thread where everyone was taking the piss over a few untidy blocks etc, not one of the builders involved was able to to demonstrate any significant depth of knowledge on the subject.

 

by putting the RSJ in half way then joisting into the web of it it will reduce the cost alot reason being 8.0m length are rare and have to be bigger like said 9x3 or alike so but using the steel u could get away with 8x2 (personally 9x2 and theyre much cheaper in 4m lengths

 

That sounds like your ceiling will be lowered in the rooms below. If so, Building Regulations stipulate a minimum height so you need to make sure you comply with that too,

 

he is right i design and build timber frame and traditional build homes for a living. Cutting down your span will a better idea, a beam is the trick as said timber over 7.3m is nearly impossible to get and you will be running about 200mm ctrs for the run which is a lot of timber and will dramatically increase loading on the supporting walls below. I did a quick calc and that is not knowing your dead and live loads from your design. Also you can go for TJI engineerd beams which will span longer but they are expensive but are VERY good again you will be at close CTRS.

4.3m is a standard joist size so get these and web them into a beam and keep a decent strength. the longer the span the more chance of it "dipping" in the middle or as I see time and time again a spring in the floor when you walk over it which is really annoying and will do ur head in with hair line cracks! what is the span like if you run the joists the other way? Also will you be building any walls off the floor, they willl all have to be stud at that length and some might fail a load calc at 8m.

for a span that size, you will need to get a structural engineers report and clacs.Rest the beam on pad stones to ensure a better job but you will probably be asked to show calcs that the origional foundation will be able to take the additional loading by building control as well as floor loading calcs and beam size calcs.

 

the joists couls go the opposite way i sippose as the span that way is considerably less and has a full supporting wall running front to back of the house?

great to chat with some professional people at last, the rsj across is another feasable idea

cheers guys.

at least when teh guys come back next week i can quiz them on what they say

 

not a prob mate, other thing whichever way you joist, make sure you put the camber up to help avoid bowing in the wood lol

 

As said above we bought 7.3 M lengths and they were not easy to get hold of. I think the 27 odd lengths we bought cost around Ł1500. They were also VERY heavy and a pain to manoeuvre up into position!!!

I cant remember exactly but being all timber meant building regs had to allow for 30mm of deflection (I think) so they had to sit 30mm above our ceilings. Once they were all noggined (SPELLING) together and the floor boards were glued and screwed (which again I am sure was part of the strength) we dont really get any movement at all.

We also had to have a double strength A frame kinda thing in the centre to support the roof as no steel was used. I think all the roof beams outside of that were doubled up too!

All I remember was there was lots and lots of wood used!!!!!!!

 

its not cheap sadly but if you can gat away with a steel the thats my advice ad once ceiling is up and floor down you wouldnt know its there and done right will be solid

 

with 9x3's that size you must have the biggest trees in the rain forest lol, poor animals lost the penthouse lol

 

Have you not got timber yards in chingford ? a 7 m length of 7,8 x2 is no harder to buy than a 2.4 4x2

 

Also I recommend using structural ply rather than smart ply or chipboard for the flooring..

 

most place will only have upto 5.2 plus if he goes 7m span he'll be needing say 9x3 and straight tree that length im sure you'll find are rarer withought without shakes and splits etc so not many people will stock them and often special order.

 

some places will laminate 2 bits of wood together to give you the length, at least that's what they used to show on "this old house" with steve and norm