Rip sawing Pressure Treated 5/4' flooring.

jerry_njJuly 29, 2011

I needed lumber to trim out a 15 year old ceder deck - it has rotted in spots (only a couple) along the sill against the house. I think was due to trapped water between the sill (on house wall) and the 5/4" decking, which comes in at a 45 degree angle.

I wanted to put a 5/4" by 4" (3.5") strip along the wall on top of the existing decking (again coming in at a 45 degree angle). I would then caulk the trim strip against the house wall to block further water entry - this may have been a better initial design.

My problem came up when going to Lowes and finding they did not have any 5/4" x 4" decking. So, I purchased 5/4" by 6" and need to rip it to narrow it down to the 3.5" range. I would also put a simple trim edge, maybe just a partial 45 degree edge.

My concern is running the pressure treated lumber through my 10" table saw. For one thing the lumber has a "wet" feel to my hand, and another I am concerned about the extensive handling, and saw dust.

I can wear disposable gloves and a simple breathing mask, and eye protection, is that enough?

Will this stuff rip any thing like untreated lumber, or will there be more tendency to bind? I will be ripping one 10' and 2 8' lengths to get the material I need. The trim is just along the house wall. The railing has 4"x4" end posts, so I'd like to cut the trim to match that where the trim buts up against the railing posts at the two wall ends of the deck.

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"I would then caulk the trim strip against the house wall to block further water entry - this may have been a better initial design. "

caulk is a last ditch effort to prevent water intrusion.

Flashing to prevent the water from entering in the first place is preferred.

    Bookmark   July 29, 2011 at 3:20PM
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Pressure treated lumber has gotten better over the last several years as the manufacturers went to less toxic chemicals. But I still would be careful about the sawdust, since a "simple breathing mask" may not quite be good enough. I have a basic respirator with the screw-in can filters that I got at Home Depot. It's not something I would like to wear for hours, but I use it when I am concerned about what I am cutting, and they aren't super expensive. Disposable gloves should be adequate for dermal contact. As for the wetness, that could be either from recent pressure treatment or from getting rained on. I doubt it will present a cutting challenge, but if you let it sit indoors for a week or so, the wetness should disappear.

    Bookmark   July 29, 2011 at 3:26PM
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Using a carbide tipped blade, where the tips are 50% or more greater than the thickness of the blade disc, and using a moderate feed rate, I rarely have any issue with binding.
Having a couple of homemade 'kerf wedges', a little thicker than the kerf is wide, at hand may be useful if the board gets too springy.

    Bookmark   July 29, 2011 at 3:43PM
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Thanks, I think the "wetness" is due to the horizontal stacking at Lowes (maybe everywhere). The boards are lying wide-side against wide-side. That has got to trap any moisture from rain or treatment. I have them raised off the floor at one end to let air circulate around the boards. I don't want to leave them that way very long or they will warp I'm sure.

The warnings on the display at Lowes mentions washing hands after handling (may have suggested gloves), washing cloths separately, and wearing eye protection when sawing, but nothing about respirator.

All my power (round) saw blades are carbide tipped, I still have a few steel only blades but never uses them. I'll have to check to see what clearance the tips provide for the body of the saw.

As for a flashing interface with the house wall, I recall the contractor who built the deck (I finally decided it was too be a job for me to ever get it done, more accurately that's the conclusion my wife reached - correctly) said he wanted to connect the deck to the house differently, but the building inspector would not accept his method. There may be a flashing but if there is it is on the underside of the deck surface and in such a position it could add to the holding of water up against the underside of the decking at the ledger. Just guessing, and I don't recall the design the contractor wanted to use.

    Bookmark   July 29, 2011 at 4:08PM
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Ledgers are flashed from above.

Under the siding, then down and over the ledger.

    Bookmark   July 29, 2011 at 4:59PM
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Install the wood as soon after you cut it, if it lays around for a while it will distort.

    Bookmark   July 29, 2011 at 6:39PM
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Well that could be the "problem"... if it is a problem. That is the deck is about 15 years old and has 5/4" x 6" decking. The flashing lying on the ledger and the decking lying on that would make that a wet area. That is where the only rotting in taking place... and this helps me recall the contractor saying something about the flashing would result in rotting at the ledger.

His design may have been to run the flashing (if it could still be call that, straight down behind the ledger and cutting the clapboard siding to be just above the decking. Not sure how that would work but to my "mind's eye" I see the water going down between the decking boards and some laying on the ledger, which is pressure treated lumber. But as it is wood, the wet would not hold as long as it does on the flashing material, copper, or tin, or whatever it is. I'll take a look through on of the rot holes to see if I can see the flashing material.

In any case my idea is to simply install a pressure treated "trim" strip about 3.5" wide along the wall. The biggest rot hole is about 3" wide. I will use deck screws to attach the trim to the decking and use a good caulk where the trim hits the clapboard. There is at least a couple of inches of clapboard above the planned trim.

This should make rain running down the house wall hit the trim and be deflected away from the house out onto the decking.

Not sure if I'll paint (yes I have my ceder covered with a solid color deck stain - I tried to keep it in semi-transparent for several years and gave up - none of that stuff would keep a water beed finish for more than a few weeks.) the trim to match the deck, or to match the siding. That said, I assume the current pressure treated wood will take a solid latex stain.

    Bookmark   July 29, 2011 at 8:04PM
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I've ripped hundreds of PT boards, decking as well as 2by stuff. On contractors saws and jobsite saws. Wet lumber and dry. CCA, ACQ, Wolmonized, and several other kinds of treatment methods. 8 feet long up to 16 feet long.

You never know how each board will react when ripped.

What I learned:

Use a dedicated ripping blade---20 to 24 teeth. Combination or crosscut blades can cause problems and be unsafe. Use a slow feed rate, ripping PT lumber can easily bog a contractor type saw and burn out the motor quickly.

Keep the narrowest cut between the blade and fence. Reason? Less trouble with severely reactive wood. 2" strip warping/waning/curling/etc is not nearly as much a danger as 4" strips are.

Have plenty of infeed/outfeed support. A 10 foot long board can cause a saw to tip if no support is provided. Tipping a saw during a 10 foot rip can be very costly as well as very dangerous.

A splitter is a good idea, but it needs to be matched to the blade kerf. And a splitter can be useless with severely reactive wood.

When ripping for the first time, use two people. One to push the stock through until the trailing end is at the saw top, then the second person pulls the board completely through. Ripping alone can be very unsafe.

Newer treatment compounds, especially ACQ, are very corrosive to aluminum and steel, so cleaning the saw blade and body after the job is very important.

Gloves and a dust mask should be sufficient protection. Just be aware getting a glove near the operating saw blabe is very dangerous(another reason for the two person idea).

    Bookmark   July 30, 2011 at 2:01AM
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Thanks for the great tutorial, I am sure others too will benefit from this effort.

The lumber I have, is limited to 10' and only one of those. I have an older Craftsman 10" table saw with a belt driven motor which will protect against burnout, I think the belt will slip - not sure I haven't had the blade jamb often, but then I am just an concessional DIY'er so the saw has seen only a few uses. That said, I just finished a few days back ripping backing strips for a crown molding job. These I ripped out of construction grade 2x4's The molding was the narrow (only 8' ceiling in the room) 38 degree and the 1.5" side of the 2x4 was just long enough to get the wedge shape strips needed. I mention only to note I have been using the saw to rip 8' boards in a complicated bevel cut, no problem. But, the darn PT lumber does look different, and thus my making this post.

I have only one roller stand, that has been sufficient when used at the output side of the saw for 8' 2x4 rips. Finding a "helper" will be difficult. My wife, also a senior, isn't in any condition to help. She has helped in the past but the years have taken too much of the physical strength to have her help with more than holding the end of a tape measure.

I think I'll give it a try, 8' board first, and follow the careful warnings so generously provided.

    Bookmark   July 30, 2011 at 8:35AM
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Do a search o 'ledger board flashing' and the best method will come up.

It is not that hard, or complicated.

The goal is to prevent any water from entering the structure around the ledger board.

PT wood is not going to rot in your lifetime.

    Bookmark   July 30, 2011 at 12:18PM
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I ripped the PT boards yesterday. Thanks for the help. Here's an outline of what worked and what didn't.

I changed the 10" table saw blade from a 20 point (combination, I think, didn't have a clear label) to a 32 point Rip blade. The 20 point looked more like a rip to me because of the rougher looking cutting edge - fewer teeth. I had used this blade for all none cabinet work, it did a fine job of ripping untreated lumber.

I had only one roller stand and found I didn't need it on the feed side for the 8' boards. I had it set about 4' off the output side so that when the board cleared the blade it didn't "pop up". I used cloths pins (old wooden type with a spring, took apart and used to wedge the cut open, I put one in about every 1' of cut, otherwise the blade did bind and it blew the 15 amp circuit a couple of times.).

I found the 10' board too unwieldy to feed it without help, so I moved the roller to the input side and fed about 3' of the board through the saw then moved the roller stand to the output side. Worked great. Used clothespins again.

Then I set about cutting a 30 degree bevel on the edge that would be the exposed outer top of the board (on deck trim along house). No problem with the 8' boards, in fact the cut was so thin that no wedge was needed. But, on the 10' board I got the feed out of alignment in the early cut and had to back out and start over. This made about 1.5' of the 10' board unusable. I may be all right. I needed just over 24', so 3 8' would be a little short, as would 2 12' boards. I can not carry boards longer than 12' on my small truck. I haven't done a fit yet, but hope the 16' + 8.5' will be long enough.

Some observations I'll add to the good advice I received on this thread.

The saw "dust" on the boards I cut was indeed "dust", very fine. I'm not sure if this was due more to the rather fine tooth blade I used or just a nature of the wood.

What about the interior wood opened to the air by the cut? I assume the PT is only "skin deep"... pressure forces the chemicals in a fraction of an inch. Can I just paint the exposed wood, or should it be chemically treated before painting. The wood will be totally above grade an not in contact with the soil... will be on top of a ceder wood deck.

    Bookmark   August 3, 2011 at 11:46AM
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The whole point of pressure treating is to get total treatment distribution, at least on framing/etc type lumber. 4x4 and bigger is not as deeply penetrated, but 4x4/etc is not usually dimensioned.

    Bookmark   August 3, 2011 at 9:33PM
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"4x4 and bigger is not as deeply penetrated, but 4x4/etc is not usually dimensioned."

4x4 is not penetrated in many cases since it is the core of the tree and contains the pith.

It is often trash wood.

The mill is looking to make money on scrap.

    Bookmark   August 4, 2011 at 7:28PM
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