Reusing old timbers in deck renovation

[Fuzzie]

I'm in the process of renovating an existing deck and need some advice on reusing old timbers. The existing deck was originally finished in synthetic turf over fibre cement sheeting and had various problems as the deck was about 30 years old.

Some of the original structural timber (5"x2" I'm guessing Ironbark) were quite rotten where the cement sheets met over the joists and these have been removed and need to be replaced. Also where the joints were across joists rather than along them, there are some spots of rot that are neither deep nor long as can be seen in the attached photo. The white colouration in the photos is mainly cellulose leached out of the fibre cement, the areas of rot are generally much smaller. The old HW timbers have really held up quite well, even the most badly rotted would probably clean up to a good 100x50 by ripping 20mm off the rotted side. I wish to reuse as many of the old joists as possible, perhaps by simply flipping them over so the old bottom is now the top.

If I do the flip, the light rot area will be well clear of bearers and with new malthoid flashing over the joists before laying new timber decking, it is unlikely they will get wet very often in future. Would it be necessary to treat the rot area in any way before reusing?

Some of the timber however needs to be fully replaced. Since the original deck is old, matching the original joist dimensions and material might be a problem. Currently the joists are on 400mm centres with short spans up to 1800mm. Is there any problem with using treated pine to replace the badly rotted joists (typically every third joist? I'm assuming that ripping the rotted joists to 100x50 and packing them up to 120 over the existing bearers would not be good practise, but would it be worse than mixing new treated pine and old HW?

[Bloss]

That fibre cement would have been asbestos containing , but it's gone now . . . in any case fine to use the joists bottom side up and not a problem to mix the timbers either so long as the tops are even and level. Unless you think it easier why bother ripping them all - just notch them over the bearer. BUT - how high is the deck? A low deck I would be OK re-using, but even so buggering around for the sake of not much saving really still needs thinking about - new HW or TP, but all the same will make things much easier. For a high deck I'd just go new.

[Fuzzie]

Hi Bloss, definitely no asbestos, I spent the $$ for a lab test first. The 80's were the change over period. Seems I was lucky the decking products changed composition early on. Either that or the deck material was replaced sometime since then.

Sounds like it will be OK to go with new TP joists to fill in then. I'll probably be able to recover a decent amount of timber from the other joists for my next project which is a workbench rebuild.

I am however in a bushfire buffer zone. The decking needs to be HW. Will the framing need to fire rated as well or is it just the decking that needs to be fire retardent?

[ringtail]

High set or low set ?

[stevoh741]

Hi Bloss, definitely no asbestos, I spent the $$ for a lab test first. The 80's were the change over period. Seems I was lucky the decking products changed composition early on. Either that or the deck material was replaced sometime since then.

Sounds like it will be OK to go with new TP joists to fill in then. I'll probably be able to recover a decent amount of timber from the other joists for my next project which is a workbench rebuild.

I am however in a bushfire buffer zone. The decking needs to be HW. Will the framing need to fire rated as well or is it just the decking that needs to be fire retardent?

Spotted gum is best bet for fire resiliance

[Bloss]

High set or low set ?

:whs: and as I asked . . .

[Fuzzie]

The deck is U shaped around a pool on a sloping site. Probably average 1.5m above ground.

Are you suggesting rip everything out and start again? That would be a LOT more work.

[ringtail]

The deck is U shaped around a pool on a sloping site. Probably average 1.5m above ground.

Are you suggesting rip everything out and start again? That would be a LOT more work.

Anything over 1 mt changes the game a bit. Your new work will have to comply with AS1684 & the BCA even though you are only renovating a existing structure. Besides, it looks like most of it is sitting on the ground anyway and you dont stuff around with decks over 1 mt. Peoples lifes depend on it.

[Fuzzie]

Hi Ringtail, not all the timber in the stack is from the deck area to be repaired. The original cement sheet decking was pretty heavy. With 5x2 HW joists at 400 centers and spans of between 1 and 1.8 meters I'm pretty sure the framing exceeds as1684 tables. There might be a requirement for diagonal bracing, although its hard to see where a deck between a brick wall and a concrete pool wall is likely to move to. Upgrading pool fencing to current standards is probably more problematic.

Replacing 1 in 3 or 4 old joists is a different issue to rebuilding an entire structure.

[ringtail]

Hi Ringtail, not all the timber in the stack is from the deck area to be repaired. The original cement sheet decking was pretty heavy. With 5x2 HW joists at 400 centers and spans of between 1 and 1.8 meters I'm pretty sure the framing exceeds as1684 tables. There might be a requirement for diagonal bracing, although its hard to see where a deck between a brick wall and a concrete pool wall is likely to move to. Upgrading pool fencing to current standards is probably more problematic.

Replacing 1 in 3 or 4 old joists is a different issue to rebuilding an entire structure.

True, but the entire structure is all old. Depends on how long you intend to stay at the house I guess. Good luck with the pool fencing. Those rules seem to change weekly and retrospective compliance is mandatory

[intertd6]

I'd be saying use that timber in the BBQ for a chook shed or some ground based ornament, recycling structural timber from material thats already been exposed, rotted & degraded in the elements has served its purpose & unless your competent in grading timber more than likely your going to have to let the moths out & buy some structural timber fit for the purpose.
regards inter

[Bloss]

:wts: but if you are prepared to take the punt it's your call of course. Your house, your labour, your money, your responsibility.

[Fuzzie]

So the consensus is to rebuild. That makes an order of magnitude difference to the project in time, cost and council interaction. :smack:

So is it OK to frame in TP and deck in hardwood in a fire zone?

[intertd6]

you can use fire retardant species or coat the timbers in fire retardant coatings. TP is not fire retardant. There are more considerations to restrictions of how & what you can build in bushfire zones which can be found in the code. Step one is the assessment, hopefullysomeone will come along shortly & provide the links to the info sources.
regards inter

[Bedford]

Step one is the assessment, hopefullysomeone will come along shortly & provide the links to the info sources.

Try this, http://www.renovateforum.com/f221/assessing-bushfire-attack-level-bal-93082/#post812134