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Floor Joists

Postby davedvd4 » Tue Apr 21, 2009 5:32 pm


I want to create a bit more space in my loft. I dont want to go down a full conversion route with a staircase etc as i dont have the space to put 1 in. All i want to do was create some floor space for storage.

Currently i have 8 vertical joists going from the floor joists up to the pitch of the roof. I have been informed that these are to stop the ceiling sagging and dont have any stuctual purpose. I have been told that if i wanted to remove them so i can create some floor space all i would need to do would be to make my floor joists stiffer. As they are 3inch now i was told to screw another 3inch piece of timber to them to stiffen them up.

Has anybody else done this or have any advice on doing this?

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Postby stoneyboy » Thu Apr 23, 2009 11:10 pm

You really must get a structural surveyor regarding the removal of the braces.
I would doubt that doubling up the 3 inch joists will provide sufficient strength for a useable floor, again talk to the surveyor.
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Postby plumbbob » Fri Apr 24, 2009 11:47 am

I'll agree with Stoneboy here. You can't just cut away braces without careful consideration. I cannot entirely agree (although it is difficult as I can't see it) that the brace is simply there to give additional support to the ceiling.

Roof trusses do not rely on the timber bulk to take the weight. Instead they use a carefully calculated set of triangles to spread the load. Removing part of the structure could seriously weaken the whole roof.
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Postby davedvd4 » Fri Apr 24, 2009 5:05 pm

Thanks for the advice, I have already removed a couple of braces but will definately seek some advice before i go any further!!
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Postby Perry525 » Sun Apr 26, 2009 5:27 pm

With a normal pointed roof, the joists are there to hold it together, the roof load of timber and slates/tiles, would push the walls out and cause the building to collapse, the joists are there to stop this from happening. This means that the joists are held in tension and can support a surprising load, indeed the braces are there to help support the rafters and the load of the tiles/slates whatever and stop the roof from sagging.
You should not remove any brace, as they are there to do a job.
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Postby davedvd4 » Tue Apr 28, 2009 1:54 pm

The vertical pieces of timber are not actually part of the main joist. They are just nailed on every other joist. The actual triangle of the joist is 3 seperate pieces that looks like it has been assembled in situ. The floor joist is also supported in the eves by 2 furlings that run into the walls at either end.

I have been in contact with a "Loft conversion specialist" who is going to call round and have a look for me. I did get a joiner from work to have a quick look and he said it looked ok to him
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Postby bd3cc » Mon May 25, 2009 9:37 pm

I have never known a "chippy, builder, roofer " use more materials than he has to. So if it is there, it is there for a purpose, and should not be removed.
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Postby the specialist » Wed Jun 03, 2009 7:45 pm


In my experience I have never seen a roof supported on 3" joists. The timbers you describe sound like "strings" put in during construction to hold the joists in place and stop sag.
The roof usually sits on a wall plate on the inner leaf. To stop roof spread there are usually purlins built into the gables or horizontal timbers tying the rafters together known as collar ties. The construction you describe doesn't sound like trusses.

If you want to remove these timbers then yes you do need to strengthen the loft floor. I suggest fixing additional timbers at right angles to the existing (cross battening) and screwing boards down to them. This will help spread the weight.

Don't forget this new floor will still have limitations as to load bearing capacity.
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