LOFT FLOOR SISTERJOISTS

[Nicetoseeyoutoseeyounice]

Ok so we'll forget the Wickes decking idea. I have read I can strengthen the existing loft joists by sister joisting, how do I bolt these to the existing joists and also do they need to then be independently supported by hangers at either end, only small room, 10 x 6 feet, and I have a wall on either side, one outside wall and one is bathroom (dormer house). I would have thought by sistering the joists this only put more pressure on the ceiling below, or would it? when I look at the bathroom floor which is the room next to loft space it would like this method has been used there and that was done by house builders in the 60's. Or must the new floor be totally indendent and not even touch ceiling joists. I am reading lots of different methods and dont know which one is best to follow. Any help greatly appreciated.

 

[Nicetoseeyoutoseeyounice]

So I take it then, no one know the answer?

 

[masona]

It's best to put bigger joists in, are you making a room up there?

 

[Nicetoseeyoutoseeyounice]

We are sort of making a room. At the moment it will just be for storage but would like to do as best possible just in case. I have read all articles on this forum and also on 'Loftshop', I know I must strengthen the existing joists and if I use sisterjoists these must be secured to the existing. But what I cant seem to find is that once the new are fixed to the old does each new joist then have to sit in a hanger on each walled side of proposed new room. It is possible for this to be done as this is the direction of the joists but is it a must or would just attaching new deeper joists to old be suffice.

 

[marshman]

if it was mine I would be putting them on hangers

 

[Nicetoseeyoutoseeyounice]

Thanks marshman. I am going to try and draw diagram and upload as its a bit hard trying explain fully, but any other thoughts welcome.

 

[Nicetoseeyoutoseeyounice]

Here is diagram hope this has worked.

 

[Nicetoseeyoutoseeyounice]

Well it didnt work, how can I do this, have spent ages drawing diagram. Thanks.

 

[MasterAbacus]

type the full link to your picture, im sure someone will fix it

 

[Deluks]

Hangers aren't necessary, the existing joists are just probably resting on the supporting walls, and nailed into wallplates. If the existing joists aren't going anywhere then sistering alone will be adequate. What you must make sure of though, is that the new joists have an adequate bearing at each end.

Just think of the new joists as 'replacements' for the current ones. Imagine that the existing ones aren't there and fix the new ones using the same lengths, and on the same load bearing walls.

 

[Nicetoseeyoutoseeyounice]

Thanks Deluks, I understand and found that quite helpful. I have emailed my diagram to this site and hope they will put it my post for me, dont know any other way of posting it and I spend ages doing it.

Right the thing is now, these joists of which there are about 11 running across the whole area into eaves, and of which I will only boarding about 7 off and doing the sisterjoints to, well, there are two other joists running right across and nailed to the 11 joists, which I understand are binders and stop the joists from spreading, how do I get my new sisterjoists to cross these, would I have to make notches all the way along each sisterjoist to sit over the 2 binders, or, as I have been told, can the binders be cut. They wont be totally removed as the bits in the eaves would stay and so would the start of the binders as they wouldn't affect the first sisterjoist. Then I bolt new joists to old and have been told that the new boards once fixed in place would then act as binders stopping any spreading.

This really is hard to explain, just wish I could upload my diagram. If someone knows what I mean can you help. Please.

 

[Deluks]

Tricky to give full advice without knowing what goes where in your roof.

Cutting the binders seems inevitable, but you should be cautious about cutting them until you fully understand what they do and how to make sure the ends are supported.
The binders need to be cut where the first of the new joists meet them, then you should fix the cut end onto the new joist, possible with a metal joist hanger. This means that this new joist will not only be supporting the new floor, but also the rest of the ceiling joists which are attached to the binder. With this in mind it should be at least doubled up, or a bigger section of timber used.

I'm being a bit worst case scenario here, maybe a little over cautious, but better safe than sorry and for you it's piece of mind to know that you have a good, strong roof/floor structure.

 

[Nicetoseeyoutoseeyounice]

You seem to know exactly what I mean and thanks for the advice. I will definately be using bigger pieces of timber for the new joists but do I have to attach to old smaller joists all the way along using hangers or are the hangers actually fitted to the walls which will be either end of the new joists. If I dont attached new to old using hangers what is the best method.

Also can anyone help as far as getting my diagram posted on this forum. I have tried Bucketshop but cant seem to upload my pic. Is there any other way, I know I cant copy & paste. Sorry for putting this bit in with 'floor, stairs & lofts' section but this is where I need to post it and would also help if I needed to do it in future. Thanks to all again.

 

[Deluks]

The new higher joists, should be placed at one per existing joist. and the same length as existing joist.

Hangers go at the end of a joist, to hang it at right angles to a wall, steel beam, or another joist. You can fix the new and old joists together, side by side, just with 3" nails, or (better) screws, or drill through and insert bolts. One fixing every 300mm is adequate, 150mm for nails.

However the existing joists are supported at the ends, is also how the new joists should be supported at their ends. Might be metal hangers, might be sitting on and nailed into a timber plate. Might be resting in pocket holes in brickwork, in which case use metal hangers.

For photos, try flickr or Picasa

 

[Nicetoseeyoutoseeyounice]

Thanks for replys re loft floor, it has now been done exactly as you described (by joiner) and thanks for info re uploading of pics and diagrams I will give them a try.