Building Homes or Extensions/Loft Conversion

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Expert: - 3/8/2009


Question

Second Half - Study
Hi, I live in Northern Ireland and I have 2 questions. Firstly I'm coinverting one half of my 'L' shaped loft into a bedroom and bathroom. This half has been prepared (ie. it has the correct steel beams installed BUT the floor joists are only 120mm high. Is it true that they need to be 150mm thick to meet building regulations? If so can I just add 3mm onto the top of them or what should I do?
Secondaly, I want to make the second half into a study for myself but it has verticle supports nailed onto the standered trusses and the steel beams. Can I revove them or replace them with what? You can see what I mean in the attached photo? Please contact me if more info is needed.
Thanks

Answer
Hi Aaron, the thickness of your joists is more related to the span of the joist than anything else.  Right now your 120 mm joists are only good for maybe 1.25 meter span..a 150mm joist will span maybe 2-2.5 meters..Adding a strip of wood to the bottom will not suffice.  You need to add a new joist with the proper sizing.  You won't need to remove the old joist though, you can add the new joist alongside the old one.  This will involve removing the floor sheathing, adding the new joists and then replacing the sheathing.  From your photo it appears that the verticle supports are holding up your ridge.  To remove them you will need to use a beam to replace them.  The size of the beam will be determined by the length required.  You might be able to forego the beam if you add collar ties to the rafters.  These are horizontal ties that connect the two opposing rafters to keep them from spreading apart where they attach to the walls.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com
    Questioner's Rating
    Rating(1-10)Knowledgeability = 10Clarity of Response = 10Politeness = 10
    CommentVery qucik response. Excellent advice. I would definatly nominate Bruce E. Johnson for Volunteer of the Month.


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Bruce E. Johnson

Expertise

I can answer any construction related question in regards to carpentry, concrete, drywall, masonry, structural elements of any type of building, residential or commercial. Interior or exterior.

Experience

Custom Commercial and residential buildings. Churches, theaters, schools and auditoriums. Most recently I am working with the Catholic Church on several design build committees. I have a website related to scheduling and project supervision. Although my expertise is more related to multimillion dollar commercial, educational and theatrical projects my generous credentials in residential and remodelling construction make me a viable source of information regarding all forms of building questions.

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