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Engineered Timber I Beams or Hollow core

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  • 08-10-2011 9:18pm
    #1
    Registered Users Posts: 22


    In the process of a starting a new building and deciding whether to go with hollowcore or engineered timber i beams ( BCI Joists) for first floor. The BCI joist look a good alternative with knockouts for services, no movement or shrinkage.
    The hollow core has the advantages of sound proofing. Would be interested in hearing your thoughts on both options or anyone who has used the BCI joists.


Comments

  • Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    In the process of a starting a new building and deciding whether to go with hollowcore or engineered timber i beams ( BCI Joists) for first floor. The BCI joist look a good alternative with knockouts for services, no movement or shrinkage.
    The hollow core has the advantages of sound proofing. Would be interested in hearing your thoughts on both options or anyone who has used the BCI joists.
    ive specified and worked with the I joists. i guess that apart from the low Co2 of the I joist the rest comes down to detailing-out the movement sound.. have already decide on whether your going block or timber frame?


  • Registered Users Posts: 22 Redfowler11


    Already decided to go with block construction. 150mm cavity.


  • Registered Users Posts: 458 ✭✭kboc


    I used conrete prestressed slabs. If i was doing it again I would give far more consideration to the beams you mention. I had to drill through slabs for various reasons, a bloody night mare, as regards sound proofing I still can hear my wife walking around upstairs


  • Registered Users Posts: 120 ✭✭dfader


    In the process of a starting a new building and deciding whether to go with hollowcore or engineered timber i beams ( BCI Joists) for first floor. The BCI joist look a good alternative with knockouts for services, no movement or shrinkage.
    The hollow core has the advantages of sound proofing. Would be interested in hearing your thoughts on both options or anyone who has used the BCI joists.

    Hi all,
    Sorry for dragging up an old post but I want to do a comparison of using timber I beams versus precast concrete for upper floor of our proposed two story build.

    Relevant details of proposed build;
    2400sqft two story.
    MHRV.
    Thinking rads not underfloor heating.
    Cavity wall construction; 250mm pumped cavity.

    Info I am looking for;
    Suppliers in Ireland (Northwest even)
    Cost.
    Making soundproof - can it be made nearly as sound proof as precast and whats the best and most economical way of doing this.
    pros/cons
    Experiences of those seasoned pros out there that have used them in this situation.

    I have read the technical briefing for the Denby dale passive house and am swayed by this so I know about airtightness details and other obvious advantages relating to ducts.
    http://www.greenbuildingstore.co.uk/page--denby-dale-passivhaus-technical-film.html

    Have been quoted €3800 for precast flooring so I really want to fully cost both to help make decision. With the precast I will need a suspended ceiling that i have not yet costed.
    This may need to be moved to prices/cost forum or should I have two seperate posts for cost and general info.

    regards,
    dfader


  • Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Your quantity surveyor and architect Will do this cost comparison and offer you acoustic options. What's more difficult to cost is the potential extra knock-on factors of Mvhr ductwork etc that are particular to your layout.


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  • Registered Users Posts: 120 ✭✭dfader


    BryanF wrote: »
    Your quantity surveyor and architect Will do this cost comparison and offer you acoustic options. What's more difficult to cost is the potential extra knock-on factors of Mvhr ductwork etc that are particular to your layout.

    Brian,
    Thanks for your advice, what acoustic options would you suggest?

    Also when you say whats more difficult to cost is the potential knock-on factors of MHRV ductwork, I am not sure what you a getting at here. The main reason I am considering the I beams is for the ease of housing the ducting in the joists as opposed to having the extra expence of fitting a suspended ceiling to the hollowcore slabs and also saving on overall depth. The knock on factors that I see related to MHRV and precast is boring holes for services, suspended ceiling, supporting ducting. Please advise on other potential knock on factors you refer to, obviously will discuss with Architect also.
    Thanks again,
    dfader


  • Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    dfader wrote: »
    Brian,
    Thanks for your advice,
    1. what acoustic options would you suggest?
    2. Also when you say whats more difficult to cost is the potential knock-on factors of MHRV ductwork, I am not sure what you a getting at here. The main reason I am considering the I beams is for the ease of housing the ducting in the joists as opposed to having the extra expence of fitting a suspended ceiling to the hollowcore slabs and also saving on overall depth.
    3. The knock on factors that I see related to MHRV and precast is boring holes for services, suspended ceiling, supporting ducting. Please advise on other potential knock on factors you refer to, obviously will discuss with Architect also.
    Thanks again,
    dfader
    1. there are several systems on the market, your architect will go through them with you, they will not be as expensive as the price of a sus ceiling. there is also little things like gluing and screwing first floor/ attention to detail etc
    2. exactly + this potential overall increase is a knock-on around every wall in the house
    3. i didn't design your house - ask your architect

    http://www.woodspec.ie/sectionbdetaileddrawings/b9flooring/

    http://www.boards.ie/vbulletin/showthread.php?t=2056504253

    there are others, but i don't want to add products on here - your arch will advise


  • Registered Users Posts: 1,282 ✭✭✭sas


    dfader wrote: »
    The main reason I am considering the I beams is for the ease of housing the ducting in the joists as opposed to having the extra expence of fitting a suspended ceiling to the hollowcore slabs and also saving on overall depth.

    1 HRV company I spoke to claimed this was a very misleading point.

    If your ducting runs parallel to the beams then your fine.

    If you need to run perpendicular and are using rigid ducting, it's not easy at all to actually get the lenghts of ducting in one the beams are all in place.

    If you have beams at 600 centres and 8ft ducting lenghts, it would be virtually impossible to install them between through the web of the beams.

    They said in that case they typically run the flat square pvc ducting beneath the IBeams in a service void (much like that created beneath hollowcore by suspended ceiling).

    In my house I have hollowcore. In the utility we had to run HRV ducting beneath the hollow core. Everywere else we had the design take account of wardrobes (walk ins etc) upstairs and drop the pipe directly from the attic to where it would appear in the ceiling downstairs i.e. no section of it needs to travel horizontally once it passes through the hollowcore to downstairs. Am I making this clear?


  • Registered Users Posts: 120 ✭✭dfader


    Perfectly clear sas. Should be lots of scope in my design to do likewise with vertical ducts only to ground floor. They dont say that in the brochure alright.
    Brian. Thanks for woodspec link.


  • Registered Users Posts: 5 SimmentalT


    Hi, we are currently deciding between I-beams joists or hollow core precast.

    Does anybody have any feedback on whether I-beams are creaky after a few years?

    Thanks


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  • Registered Users Posts: 12,346 ✭✭✭✭Calahonda52


    SimmentalT wrote: »
    Hi, we are currently deciding between I-beams joists or hollow core precast.

    Does anybody have any feedback on whether I-beams are creaky after a few years?

    Thanks
    HC is a much better option if you can make it work.
    I-beams properly [specced, stored on site and fixed] are also a very good job and wont creak but acoustically the HC is king

    “I can’t pay my staff or mortgage with instagram likes”.



  • Moderators, Society & Culture Moderators Posts: 38,904 Mod ✭✭✭✭Gumbo


    Just be mindful of the increased fire safety requirements in the timber beams or open web timber joists.

    Your arch/Eng should advise.


  • Registered Users Posts: 509 ✭✭✭divillybit


    Have a 2015 built 2 storey detached house in an estate that I've owned from new. It has timber joists, but not the engineered I beam type. The timbers have bowed a little now over time and as the house settled some tiles have cracked and you can know when there is someone walking around upstairs. There is a good 5mm gap now in spots where the skirting board was nailed to the wall upstairs and the timber flooring has dropped. I'd love to have the hollow core beams but Im not complaining too much, the house has doubles in value since I bought it based on what my neighbouring house has recently sold for so I bought at a good time.


    My question is, would taking down the existing ceiling and putting in 1 or 2 lengths of steel rsj's the width of the room but perpendicular to the existing joists to put under the joists to 'prop' them and raise them to remove the sagging. The rsj's would be bolted to the eternal block walls and internal block wall. The existing ceiling level is quite high so there would be space put in support beams and more insulation and a new lower ceiling level below the support beams. Hope that makes sense!



  • Registered Users Posts: 39,188 ✭✭✭✭Mellor


    the house has doubles in value since I bought it based on what my neighbouring house has recently sold for so I bought at a good time.

    House prices going up, has a great free good factor. But unless you are selling, you haven’t actually made anything. Plus, if you do sell and realise the gain. If the next house has gone up too, there’s no actual gain.


    The existing ceiling level is quite high so there would be space put in support beams and more insulation and a new lower ceiling level

    How high is the existing ceiling?



  • Registered Users Posts: 509 ✭✭✭divillybit


    Ceiling level is 2.85m high which I suppose isint quite high, it's just a painter remarked that it was quite high when he was doing some painting for me.



  • Registered Users Posts: 39,188 ✭✭✭✭Mellor


    Ok He probably only priced it as 2.4 and was angling for more money. 😉

    2.85 would be enough to fit beams in. But I think you’d be mad to lose the high ceilings for a minor issue upstairs



  • Registered Users Posts: 509 ✭✭✭divillybit


    Have you ever seen additional support beams like what I'm thinking retrofitted into a house @Mellor, I've a good few cracked tiles and the upstairs does creak alot in spots. All due to the joists bowing a little



  • Registered Users Posts: 39,188 ✭✭✭✭Mellor


    Only in the case where a support wall was being removed. Repairing the tiles is an option also.

    but maybe I’m underestimating the extent.



  • Registered Users Posts: 3,663 ✭✭✭chooseusername


    Even though the house is only 7 years old I'd say an engineer would still have to spec a support beam.

    Depending on whether it's timber frame or block built a competent builder could do it easy enough.

    If you want a flush ceiling with a recessed beam, bear in mind partition walls upstairs, plumbing and wiring etc.



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