Oak beams to support old floor joists

[las1]

Hi. We have just purchased a 150 year old house with bouncy floors due to small floor joists and a large span. We are going to stiffen these up by running an oak beam perpendicular to the joists in the centre of the room. 200 x 200 mm diameter. However, one room we are planning to run an oak beam has an RSJ where a wall has been removed, and one end of the oak beam would run into/rest on this. Is it simply a case of resting the oak beam on the lower flange of the RSJ or would this affect the strength of the RSJ. Are there other methods of tying them together.

Thanks for your help.

Laurie

 

[AronSearle]

You should be able to rest the oak onto the flange of the RSJ in principle but you should speak to an engineer to be certain it is sized to take this point(?) load.


The other thing you need to think about is shrinkage of the new oak beam, even if you get it airdried (good luck), it will still shrink in the cross section by a few %. This means if it is supported underneath a gap will develop between the top of the oak and the bottom of the floor joists, which will then allow that bounce to occur.

To get around this you can just insert packers as the oak dries to fill this gap (which you may have to do in an old building as the bottom of the joists are not likely that level), if you do this be aware that some squeaking could occur until everything has dried and settled and the packers are firmly placed.

Or use glulam to reduce shrinkage.

Be aware kiln dried or air dried structrual timber is still only dried to 20%, which will still result in approx 3% shrinkage (6mm).

 

[tony1851]

Will it be a 'green' oak (ie new) beam, or an old reclaimed beam?

If it is new, be prepared for some twisting occuring and some shakes (splits) developing. Oak is a very sturdy timber, and not for the faint-hearted!