Topic: Rotted Joist - HELP!
128 Posts
Fri, 15th June 2012, 7:12pm
I have an old 100 year odd weatherboard house - after doing an excellent paint job in the study!, a couple of months later I noticed a crack appearing in the skirting area - you can see right through to the underhouse area. I got under the house to discover that one of the old joists has rotted through at the mortice joint. In the old days they morticed joists onto bearers it seems. I don't know exactly what has caused this - whether it is age or the amount of rain we had last year (the water flows through our block, under the house, if we get too much rain) or whether the rats that like to winter in that wall have pissed on it so much it has failed. But of course the long and the short is that I have to fix it. It is of course the end joist with only 2 feet or less of space to work in. Is there any correct way of doing this? I figure I have to jack up the house - I have a car trolley jack which should work if I can get it in close enough to jack properly. And then I figure I can bolt another piece of hard wood to the existing joist. That's about as far as I've got with it.
What sort of bolts, wood, should I use? How do you know you've jacked far enough or too far? How long should my piece of wood be? (It's right in the corner of the old house going into the extension.) Should it be level? Do I have to shape a new mortice or can I bodgie it somehow? or pass right through to the extention joists?
Any help would be appreciated!
cheers
Fergy
Illegitimis Non Carborundum
Reply:
491 Posts
Sat, 16th June 2012, 8:08am
Hello, Fergie.
It's a bit difficult to advise you without actually seeing the problem. I'm not exactly sure what you mean about the joist being mortised to the bearer. In good building practice the joist should go over the top, so it is supported by the bearer. I have seen cases where the joist is notched into the bearer, making the top of both at the same level, but I wouldn't have thought a decent builder would use that method back then. Could you give a few more details? or even a few pictures?
Ken
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1 Post
Sun, 17th June 2012, 7:19pm
Hi Fergy
if the joint is rotted as you say, then it must be getting wet from somewhere - If you don't fix up the wetting problem then any repairs will be subject to rotting as well. Wood does not rot or decay when the moisture content is less than 20%. Even in tropical north Queensland, wood kept out of the weather e.g. a floor joist or bearer will not get wetter than about 15% moisture content.
Cheers
Jak
Jack N
Reply:
1 Post
Sun, 17th June 2012, 11:34pm
Hi,
It wasn't unusual for studs to be morticed into the bearers back then, particulary perimeter bearers. My solution would be to fix a 100mm x 50mm piece of dry sawn hardwood on top of the existing bearer after shortening the existing stud by the required amount (same thickness of the new hardwood piece). The reason I recommend dry sawn hardwood is to minimise shrinkage.
Cheers
Stuart
Reply:
491 Posts
Mon, 18th June 2012, 8:28am
Are we talking about joists or studs, here?
Ken
Reply:
1 Post
Mon, 18th June 2012, 9:49am
I came came across this problem in an old farm house I was working on. Here is what I did. If you have access to under the house, support the sub floor with a couple of hydraulic jacks. Fit a new length of joist using hardwood, preferably dry, and bolt this onto the un damaged portions of the existing joist using 2 to 3 gal bolts and nuts each end. Hoping that this helps
Reidie
Reply:
1,479 Posts
Mon, 18th June 2012, 9:21pm
Fergie,
You are certainly on the right track however, in carrying out the repairs, you may only make the problem much worse an less safe.
Is there anyone available near you qualified to look at the problem and advise the correct procedures. Maybe a structural engineer. You would still be able to do the work knowing that the structure will be structurally sound. i.e. you mentioned other rotted members and I mention that the method you plan to use may transfer the risk to another member. Should only take him or her an hour. I have known carpenter tradesmen who would not be sufficiently qualified.
Think about a bot more.
Bob
p.s. how about a couple of pics of the structure
wines65ofMargate(Ex Silentio)
Reply:
128 Posts
Tue, 19th June 2012, 8:39pm
HI Guys,
Thanks for your input. I haven't replied cause I was trying to get me camera working. Here is a couple of photos of the problem. It is the very end of the joist that is rotted. I'm not sure what you mean by studs - I thought they were in the walls not the floor! It's hard to get good photos and I will try again but this is what I got.
It is a perrimiter joist, and I'm not sure I will be able to get access to both sides to put a bolt on - I might take off the bottom weatherboard to see if I can get access - will coach screws do the job? Only I find if I use them in hard wood they seem to snap quite easily.
Photo 1 is the exterior position, photo 2 is the section I will have to deal with and photo 3 is the end of the joist. Like I say it is in a bugger of a spot (I can stand easily on the other side of the house!) I will try to get better photos.
I'm not going to rush into this - I will find out as much as I can about the right way to do it. I will look into the moisture issue - this house is a water nightmare - I did have a leak right above this now I come to think of it - fixed. I have a good piece of 4b2 hardwood that I've been saving which should do the job OK - it's old but in good nick - and I've kept it off the ground and dry.
Anyway if these pictures help let me know your thoughts.
Fergy
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Illegitimis Non Carborundum
Reply:
126 Posts
Wed, 20th June 2012, 12:26am
Fergy...the joist joint on the bearer has rotted away...simple fix....find steel "U" channel that fits the wood...drill holes in it to allow fixing to decent wood further along and to fix to the original bearer point....jack either side of the joint...cut away any nails into the bearer....jack up until the flooring is a few MM above true using a decent length level....a metre or more long...fit and fasten the channel....allow to rest and fasten to the bearer....coat with rust-proofing....
Done.
Cheers.
Reply:
491 Posts
Wed, 20th June 2012, 8:33am
Hello, Fergie.
It looks, in picture 2, like part of the flooring has rotted and sagged as well, so you will have to have a wide enough timber to re-support this , too. The 4X2 hardwood will do the job for the joist. Notch it over the bearer, the same as the old one, and fix it alongside the old joist. Ideally it shoild be bolted right through with 12mm bolts, But if you have to use coach screws, use 12mm by100mm. Drill the holes through the new joist large enough for the screw to pass through, drill the other hole smaller than the thread,but about the size of the main shank. Before you start screwing, rub some damp soap over the thread, this will help lubricate the screw as it is biting in.
After this, you may have to fix another piece of timber for extra support under the rotted flooring. This can be just nailed to the side of the new joist.
Hope this helps.
Ken.
Reply:
128 Posts
Wed, 20th June 2012, 10:25pm
Cheers Guys,
Thats some really helpful advice. I feel a bit more confident now!
Illegitimis Non Carborundum
Reply:
126 Posts
Fri, 22nd June 2012, 6:23pm
Fergy writes
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Cheers Guys,
Thats some really helpful advice. I feel a bit more confident now!
Almost forgot...if the join is rotted away completely...cut it away..add a similar piece to fill the gap....and make the channel as long as you like. If the bearer has dropped, now is a good time to add packing to gain true level again.
Have fun...~ I did..the worst part was trenching between the stumps so I could get under the house!~
Reply:
126 Posts
Fri, 22nd June 2012, 6:25pm - updated - Fri, 22nd June 2012, 6:33pm
Fergy writes
--------------------------------------
Cheers Guys,
Thats some really helpful advice. I feel a bit more confident now!
Almost forgot...if the join is rotted away completely...cut it away..add a similar piece to fill the gap....and make the channel as long as you like. If the bearer has dropped, now is a good time to add packing to gain true level again.
Have fun...~ I did..the worst part was trenching between the stumps so I could get under the house!~
P.S...I cheated a bit...welded tags to the underside of the steel channel so I could screw directly into the bearer...at 90% to the direction of the channel..and screwed gal roofing screws x 2 either side...
If you have a tongue and groove floor...with a bit of work..you can punch/ work the nails up a bit before you fasten the joist...makes replacement nailing a lot easier...just so the heads are clear enough to remove...a bit of putty after re-nailing...sand and touch-up the coating.
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