Putting in new flooring joists

jdpl28

Hi,

i've got a bedroom that has a really squeeky floor, and everytime someone walks on it, the rest of the bedroom flooring shakes like anything. Was thinking of putting in a few new joists to strengthen it up. I'm getting the ceiling downstairs replastered anyway, so i'm thinking now's a good time to do it. The span is about 4 meters, and the joists are 7 * 1.5 inches, and resting on concrete lips sticking out from the side of the walls (its an old council house). Was wondering, what type of wood should i get for the joists. I've heard of these special laminate joists that are supposed to be much stiffer than regular wooden beam joists? Has anybody any experience with them? Are they easy to work with?

thanks,
J

Mellor

The laminates are Glulam, they are stronger for the same size section, but they are much more expensive, they aren't really designed to replace traditional joists, they are better looking and often used exposed. Also properly size joists won't sqeak or move, so that isn't a reason not to use traditional method.

Size the joists from IS444, they might need to be increased in size as the movement may be due to undersizing.

As for what type of wood, its not a case of going to B & Q and buying a few planks, tinber for joists needs to be graded. The grade determines the max span allowable for a paticular section. The timber type could vary depending of whats available. Even though all timber used for joists isn't the same strength, type isn't a concern as timber type is considered when the timber is graded.

Hotwheels

If the joists are in good condition, putting in extra bridging may help reduce movement, and if you can fix the ends using straps. It should help as well.
A new soild timber floor well nailed would help as well..
If you are changing the joists, you could always fit a 7"x3", less likely to flex

ircoha

http://www.jmcmahon.com/SilentFloorSystems.htm is another form of manmade timber:
the gluelaminates http://www.jmcmahon.com/GlulamTimber.htm
are not an runner for your app.

I would screw the new floor down rather than nail unless u are reslabbing u/neath

as noted earlier extra bridging, screwed in, will reduce the springyness.

Before u add in the extra timbers check to see of there is not a sag in floor already, if so u made need to work with 6 by 2 graded timber

I would stitch screw the new timbers to the old timbers at 12" centres along top and bottom edges, the stich pattern will meat each screw is 12" from the next on the same flange but 6" from the one on the other flange
hth

jdpl28

joists aren't great now. There's very little bridging between the joists at the moment, so i'll be putting in some there whatever i do. But i kinda don't think that'll help a huge amount cause theres so much movement when you walk in the room. Also it didn't help with the plumbers just coming along and knocking huge big notches in them either.

Mellor - thanks for the reply. I know obviously this is not bog standard timber. If I went down to Chadwicks, would they be able to recommend a size/type of joist for me? Or how would i be able to find this out?

thanks again,
J

jdpl28

Hey, thanks ircoha. Sorry, not too sure what you mean by stitching the new timbers to old? You bolt the two timbers together at the top and bottom, with a 12'' gap between bolts? but not too sure what your talking about with 6'' on the same flange?

Also, I guess I'll have to leave the timbers in the house with the heating on for a couple of weeks for them to get aclimatized?

thanks,
J

Mellor

jdpl28 wrote: »

Mellor - thanks for the reply. I know obviously this is not bog standard timber. If I went down to Chadwicks, would they be able to recommend a size/type of joist for me? Or how would i be able to find this out?

IS 444 is the relevant irish standard. This contains a span-table for domestic loading. The grade of timber is listed at the top, under this is the centres 300/350/400, and the sectional dims along the side. This will tell you the max span a paticular joist can achieve.

This document is available online, or in homebond if you have a copy. It may or may not be around in a builders providers. I'd check it out first so you know what you need.

The strength classes are C14, C16, C18 etc. They go up to C24 and above and while these timbers are stronger (and will need to be smaller in section) they are also much more expensive.