Loft Conversion floor advice

Discussion in 'Builders' Talk' started by craigb2120, Mar 8, 2012.

  1. craigb2120

    craigb2120 New Member


    I am in the process of doing a loft conversion

    I have installed a velux and now want to do the floor.

    I have a 3 bed semi and want to add a useable room.

    The house is a 1950's build.

    I want to strengthen the floor and board it.

    The length of the loft is around 18ft.

    I can see there are two main wooden joists (i think they are 8x2)

    What i want to know is can i run additional wood along side these to double up and then build the floor off these ?

    (or even one each side i.e. treble the wood).

    Can i screw/bolt onto these or do i need to cut them into the wall at each end ?

    I am not adding a dorma or bathroom,.

    I will be getting a permanent staircase fitted in due course.

    Many thanks
  2. Your doing a loft conversion and you should be following plans and be getting it checked for building regs by building control. But any how, sounds like the 8 x 2 ' s that your talking about are probably binders which are not really anything to do with a new floor. You need to use the right sized timbers based on your length using the trada tables, using any supporting walls should your span be too far. These can eithr rest on the existing wall plate or hang off a new fixed wall plate off a suitable wall. You could have them going ino the brickwork buts thats a hard way of doing it. As soon as you put in a fixed staircase your pretty much calling it a loft conversion making it need building regs
  3. craigb2120

    craigb2120 New Member


    Many thanks for the reply.

    I will look into building regs tomorrow.

    I am trying to do it a cheaply as possible but don't want to do anything unsafe.

    The wood i refer to runs the full length of the loft (i.e. 18ft) and there are two of them.

    They run on top of the wood that runs width ways.(which i believe are the trusses)

    I was thinking of running the wood next to these lenghth ways (are you saying to run width ways - not sure what i would attach to ?)

    I can hang the wood off of a wall plate as you advise.

    I really wanted to get an idea if it was feasible ?

    I will have to look up trada tables but am not very technical....

    Any further advice is very much appreciated.

    Thanks again Craig.

    Attached Files:

  4. big all

    big all Screwfix Select

    a lot off homework on you part i am afraid and to get it up to habitable standard 7k as a starting point :(
  5. Hammerman99

    Hammerman99 New Member

    As Leicester says, these timbers are probably binders.  Effectively the ceiling joists "hang" from these. It is likely that these timbers will be removed and larger floor sized joists will sit next to the ceiling joists and be fixed to them.

    However best advise is to spend a bit of money now on getting someone round to produce a plan showing constructional detail. This will save you money in the long run as there are many factors to consider. Construction, insulation, finish, access as the hardest thing to achieve in loft conversions is the staircase. It must have minimum headrooms and often this means positioning a staircase where it takes space away from the loft conversion or the room from where it starts.

    Get professional help now. Fail to prepare is to prepare to fail

    A member of The Stanley Tool Jury. Hammeran99. Follow me on Twitter
  6. craigb2120

    craigb2120 New Member

    Hi many thanks for the replies.

    I have dug around a bit and can confirm the following about my roof space.

    It is a 'cut roof' and has the joists running width ways with purlins and binders X2 the full length. There are two struts coming off the purlins centrally that meet in the middle (at a small block in the floor) there are also a few hangers.

    I now know that the long pieces of wood as advised are binders.


    What i want to do is remove the two struts and add strengthening to the floor maybe by :

    1) doubling up the binders and running additional hangers

    2) sistering the joists or hanging new joists (across the width).

    I know i need to take additional advice etc (fully understand) but i would like to get on a do as much a possible myself (under a tight budget).

    I am really after an idea from anyone that has done similar if this sounds feasible and also what sort of size wood i should use.

    I have already added 14 braces cut from 4x2 on each rafter (to brace them)  just below the apex - (like a ridge collar i suppose ?).

    As before all comments and advice is greatfully received.

    Thanks again..


    (I have also moved the header tank above the water tank and now need to get the big metal water tank that supported the header/expansion tank out of the loft opening)
  7. Hammerman99

    Hammerman99 New Member

    Get an architect of structural engineer round first. DO NOT UNDER ANY CICUMSTANCES remove the two struts. These are supporting the purlins and in turn oppose each other. Where they meet will be a structural wall which transfers the weight and support down to the ground. The purlins need to be supported in another way, probably by a purlin wall (vertical stud wall down from the purlins). The problem is that these walls need proper support. DO NOT BE TEMPTED to build a wall down to either the binders or the current ceiling joists. This would transfer the weight of the roof onto your ceiling! you will either need a steel beam under the purlin walls or a series of timbers bolted together. This is why you need a structural calculation. The engineer will start with this aspect of the buid.  I have asked an engineer to calculate a lower purlin wall, to create a larger room with the walls at either side only 900mm high. The existing roof timbers could probably span greater than current span.  ( the purlin is probably mid way but could go lower). I would build the new purlin walls then remove the current purlin.  Result is a larger room.

    As a professional builder I would not even attempt this work without structural drawings and specifications. The work is notifiable so you need to use Building Control.

    Stop any further work and get professional help.

    A member of The Stanley Tool Jury. Hammerman99. Follow me on Twitter
  8. Astramax

    Astramax Super Member

    Hammerman99 is correct this, work is notifiable so you need to use Building Control. 3 bed semi, anything you do to your roof may or could affect your neighbours property so hope your insurance policy covers this work !!!!!!!!!!!!!!!
  9. craigb2120

    craigb2120 New Member

    Hi Hammerman99 - Thanks for the reply.

    Just as an update to your points..

    I am not going to remove the struts now. As you have rightly said i would need to put steel or in my case build a wall down to the timbers bolted together and supported by the walls each end of the loft.

    I will look into how much a structural engineers would charge and get one round. That way i can be sure that whatever i do has the correct configuration.

    Many thanks for the advice.........

  10. Hammerman99

    Hammerman99 New Member

    I would get quotes ans also think about architects or architectural technologists. I deal with a man who works from home, uses cad and has a structural engineers package on his computer. Plans and calls for £300 all in. A structural engineer has quoted me £400 for on calc in the past.

    Hammerman99. A member of The Stanley Tool Jury.  Follow me on Twitter
  11. craigb2120

    craigb2120 New Member

    That sound like exactly what i need.....
  12. craigb2120

    craigb2120 New Member


    I can confirm all the measurements.

    3 bed semi

    Pitched roof with red concrete tiles

    Perlins x 2

    7x2 16.5 ft long (cut into wall at one end not attached at the other.

    Struts x 3 (each side)

    4x2 meeting in the middle at a block on the loft floor

    Rafters x 14 (each side)


    Binders x 2 (1 each side)

    4x2 length just under 16.5 ft (not attached to the wall)


    4x2 spaced about every 14 inches

    23ft total length (width of loft) but laid as two lengths that cross over supporting wall in the middle of the loft. (approx 11ft each length)

    Cross members x2 (one at each end)

    2x4 11ft approx attached to rafters ( was 3 but i removed the middle one)

    Strengtheners x14 (span the top of each rafter) - I fitted these recently

    2x4 (approx 25 inches cut)

    There joists rest in the middle of most of the loft on a structural wall and onto the wall plate (i.e. on top of).

    no dorma or bathroom being fitted


    Attached Files:

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