Wood expansion

[Tricky Dicky]

I have just installed a 1.4m X 150mm X 50mm spruce beam between the garage and house. At present it is a good interference fit but I am a little worri ed when it gets saturated it might expand and put pressure on the brickwork . Is there any place I might find the information?

I also need to attach a 100mm X 100mm gate post to the brickwork, I intend to use some shield fittings with projecting bolts, the drill size being 20m m diam. With the bricks having frogs which in the past I have found not ful ly filled with mortar, I was wondering if I would be better aiming my holes in the mortar lines rather than the centre of the bricks. Any advise welco me.

Richard

[tabbypurr]

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

[The Natural Philosopher]

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.

[The Natural Philosopher]

Wrong, as usual.

[Fredxx]

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).

[The Natural Philosopher]

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

[Fredxx]

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.

[Malcolm Race]

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

Malcolm

[John Rumm]

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.

[Tricky Dicky]

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

[Tricky Dicky]

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

[The Natural Philosopher]

1% is absolute worst case from sopping wet to indoors dry in winter with full CH. In practice I doubt you will see even 5mm in that scenario.

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

[Muddymike]

Can you leave an expansion gap at the ends?

Mike

[Brian Gaff]

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

[Tricky Dicky]

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

[John Rumm]

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.

[Tim Lamb]

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

>

[John Rumm]

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

[tabbypurr]

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

NT

[TimW]

You have got that a bit wrong. TW