Wood expansion

e and house. At present it is a good interference fit but I am a little wor ried when it gets saturated it might expand and put pressure on the brickwo rk. Is there any place I might find the information?

what information? It expands sideways but not lengthways.

NT

general wet to dry expansion is around 1% along the grain, 3% tangentially roundn the trunk and 5% radially

But if constrained it should be OK.

Wrong, as usual.

Interesting assertion. I was specifically told to avoid oak as it would shrink lengthways and pull out any plugged screws and to use larch (I think).

All wood moves in all directions, but not the same in every direction

I have no idea. I suspect there is enough pressure from above to stop expansion. Timber generally dries out unless you are exposing the beam to the elements. Which is not a good idea.

How tall is the brickwork? What size is the pier on the end of the wall.

What's wrong in placing the post in concrete as well? I'd be fearful of bolts pulling out the bricks. Placing bolts/screws on the mortar line will just separate the bricks depending on how many courses are above.

Have you considered polyester resin with studs set in it? It may well fill any holes on the frogs.

Malcolm

Expansion is minimal along the grain. However its going to be hard to make any sensible estimate unless you know the water content when it was installed.

Also kiln dried lumber tends to exhibit less seasonal change than air dried wood.

What is currently supporting it?

Even with the frogs you will normally get a better fixing on the brick than the mortar with a sleeve anchor IME.

This is what I am concerned about, at 1.4m 1% means a possible movement of 14 mm with one end pressing against the house wall and the other end press ing against the garage wall. Do I allow for this movement or will the walls constrain it perhaps causing the beam to flex slightly?

Richard

The beam is a section of pressure treated decking joist which along with al l the rest of their timber products was stored in open sheds at the supplie r. It is supported on two gate posts one affixed to the garage the other ab out to be attached to the house wall held in place in rebates by coach bolt s.

Richard

It certainly wont push the house over, just bow the wood slightly.

Can you leave an expansion gap at the ends?

Mike

Yes you don't see many trees getting taller because they are wet, ie when the sap is down and rising do you or the bark would crack. It can twist though as my gate post shows only too well. Bah Humbug.

Brian

Thanks TNP that is reassuring, the timber feels quite moist now mainly due to the way it is stored at the suppliers and despite lying in my garage for a week.

Muddy the answer is yes. That is why I am asking the question now whilst I can still do something about it.

Richard

In the circumstances it seems unlikely it will expand much. Personally I would just trim a couple of mm of the length to create a bit of expansion room, and allow the ends to dry out should they get wet.

My local experience of Builders Merchants storage is that treated timber is stored unprotected from weather/Sun etc:-(

Indeed, so if its staying outside, conditions will likely continue to be similar.

resulting in noticeable sideways seasonal expansion but no noticeable lengthwise expansion, as said a while back.

NT

You have got that a bit wrong. TW