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Clearance between steam line and wood?

Can someone share with me what is the recommended clearance between a steam supply line and a wood surface? I need to run a steam line under a floor in such a way that it will sit about 0.75 inches above some beams it will cross, and about the same distance under the floorboard. Is I put fiberglass pipe insulation on the pipe, is this sufficient? Many thanks! Dan


  • TomM
    TomM Posts: 233
    wood ignition temperature

    i know that wood will ignite at 500F +.  but, charring and structural damage can result at lower temps.  Google 'wood ignition temperature'.  don't forget to convert C to F.  I have zero clearance areas in my house, and some of the wood has discolored but i don't see major damages.  Those joists are 4x10's though.  Not sure what the pros will say in your case.
    beautiful Conshohocken PA
  • jpf321
    jpf321 Member Posts: 1,567
    what is your question?

    are you worried about fire or noise? if you have fiberglass insulation between the pipe and the wood, you need not worry about either.

    you could always put a piece of wood in the oven @ 250dF and watch it carefully with a fire extinguisher in hand to see what happens to your wood at those temps.
    1-pipe Homeowner - Queens, NYC

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  • Dan B_2
    Dan B_2 Member Posts: 6
    Worried about fire

    Thanks - I was worried about fire. I definitely have room to insulate the pipe, but the insulation will be touching the underside of the floorboards.
  • Bill_110
    Bill_110 Member Posts: 52
    Clearance between steam line and wood?

    I think that somewhere in the library resources or in Dan Holohans books this topic is covered. I remember paying special attention when I came accross it because I also have a situation where steam lines in the cellar are right up against the joists, probably because the whole house was moved once and the piping was altered.  The conclusion was that it wasn't possible for wood to be ignited by the temperatures steam is capable of reaching. It concerned me because in my case you could see small blackened areas right above where the steam line was touching the joists. I was in the process of insulating all of the pipes, and I managed to get some insulation on these between the wood and the pipe, though not as much as I would have liked. 

    Thinking about it though, even with an actual fire it's hard to get a big block of wood burning, unless you supply some kindling.
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,552

    Can't possibly be hot enough to ignite the wood. Just think of all the baseboard radiators, and steam radiators, with the pipes coming up through the floor. I've seen plenty with the pipes hitting the wood.

    I imagine that the heat of the pipes will help to dry out the wood and make it easier to burn if another ignition source came into play, but 212° would be too low to ignite the wood, IMO.
  • Auto Ignition

    The subject of long term auto ignition of wood at low temperatures seems to be quite controversial. Here's a pretty good link on the subject.

    On one hand you have a researcher saying that below 200 degrees C. (392 F.) you're okay and another group saying that 70 degrees C. (158 F.) is the threshold. I think I'm more inclined to go with the higher temperature as if the lower temperature was a really viable threshold, we would see a huge number of examples of auto ignition occurring especially when you think of all the steams systems (and hot water systems) that are in existence, past and present.  Perhaps in light of this controversy one should take a cautious position and avoid direct contact between wood and piping especially when passing through enclosed areas where heat could build up. When I first read about this I went around checking my system for possible hazardous conditions and found 7 places where there could possibly be a problem. After worrying about this for several minutes I experienced a flash mental reality check, that if the system hadn't ignited in the hundred + years that it had been installed, it wasn't likely to do so now or in the future.

    - Rod
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