Deck Support Logs Deteriorating

Reply

  #1  
Old 01-15-15, 11:53 AM
Member
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 5
Received 0 Votes on 0 Posts
Deck Support Logs Deteriorating

Hi, I'm a forum noob looking for help regarding a problem with some log deck supports at my dad's house here in Northwest Montana. It looks like there are some nice folks around here who have good knowledge, so thanks in advance to anyone who can offer advice!

The deck extends at the second story level above a concrete patio below. It is approximately 10' by 35' and is constructed of treated and stained wood that receives water-seal every couple of years. The supports are 9" diameter logs spaced about 8' apart. The logs are stained and water-sealed, but I don't know if they were originally treated. Each log sits on a 9" diameter concrete footer that extends about 2" up from the patio level. The deck beam rests on the top of the logs.

The problem: While the footers keep the bottom of the support logs out of standing water, snow piles up around them in winter. The watering of plants up on the deck also provides a moisture source to which the logs are exposed. Long story short, the bottoms of two support logs (about the bottom 4-6") have degraded as evidenced by a waterlogged appearance (swelling and minor splitting) and what I will call "crushing" of the bottom ~2". Obviously, the deck is no longer level but is sagging 1-2" where the affected supports are. None of the other supports are showing signs of rot as yet, but I'm sure it's only a matter of time.

Background information: The house (and deck) is 20 years old. There is a large hot tub on the deck immediately above the two affected posts (I don't think there has been any chemical leakage from the hot tub, though). I estimate the weight of the hot tub to be 2,500-3,000 lbs. I see no evidence of wood-boring insects anywhere around the house.

So, I know this situation isn't good, but I'm not sure how much risk there is in the short term of the deck failing. We can reduce the weight over the two troubled supports by emptying the hot tub if this is an immediate concern. As for repairing the system, is there any option other than replacing the logs? I figure I'll be jacking up the deck to get it level using some temporary steel supports no matter what I do, but I'm curious if I might be able to put some kind of steel collar around the bottoms of the logs and extend their lives. I'm thinking these would be two-piece, bolt-together, 6-8" long collars. Anyone ever heard of such a thing? If that's ridiculous, just say so. The only other solution as far as I can tell is to replace the logs.

Maybe you've seen this problem before and have some ideas, or maybe you got a good laugh out of my crazy idea. Either way, I would surely appreciate any responses.

Thank you kindly, BrianIM (Brian in Montana)
 
Sponsored Links
  #2  
Old 01-15-15, 11:58 AM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 46,158
Received 131 Votes on 117 Posts
Welcome to the forums Brian!

It probably boils down to the fact that the log posts aren't pressure treated. If the posts have deteriorated to the point that the deck above has sunk and inch or two - I doubt the posts can be salvaged, at least not at there current length. If the deck still feels solid there probably isn't any immediate danger .... but I'm just a painter, the carpenters should be along later.

pics could be helpful - http://www.doityourself.com/forum/el...your-post.html
 
  #3  
Old 01-15-15, 12:58 PM
Member
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 5
Received 0 Votes on 0 Posts
Thanks for the quick reply, marksr.

Good idea to post photos. I'll have to do a little snow removal before I can get some!

I figure you're right about these two logs being beyond redemption, but I was just curious if anyone had another solution.

Regards, Brian
 
  #4  
Old 01-15-15, 01:02 PM
Member
Join Date: Apr 2014
Posts: 153
Received 0 Votes on 0 Posts
Run this past a local contractor before doing it since I'm spitballing here, but it might be possible to retain the existing logs if it's possible to build up a taller footer on/into the patio below (some kind of a stone surround filled with rebarred concrete should be able to match the aesthetic of log construction) after jacking the deck back up. Then the bottom portion of the logs could be cut off and re-anchored into the taller footers; if possible it'd probably be a good idea to build the concrete up above the level that the snow would reach in the average winter. Wrapping the bottoms in metal seems risky since if the snow gets above the level of the wrap, then it'll hold the melt-off within the bottom of the log for much longer than it would normally take to dry out.

Since there's something that heavy up there it might even be better to cut out the existing footers from the patio and dig underneath to sink some piers past the frost line (that may already be incorporated into the patio if you can find the original plans) to support the extended footings. I'd also probably drain the tub as long as the deck is sagging just out of caution, wouldn't want to be in or under that thing if something else let go altogether.
 
  #5  
Old 01-15-15, 01:23 PM
Member
Join Date: Sep 2009
Location: Louisville KY
Posts: 578
Received 0 Votes on 0 Posts
Forget about trying to save the logs, it's going to be more work than replacing them and will only be a temporary measure. You're on the right track about jacking up the deck, you can use either steel or wood post for the temporary support. I would replace the logs with pressure-treated 6x6s. Shouldn't really be that bad a job especially if you drain in the hot tub.

I wouldn't worry about any immediate problems but I would monitor the height of the deck to see if the posts collapse anymore. If they do then you should immediately remove the water!
 
  #6  
Old 01-15-15, 01:25 PM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 21,005
Received 226 Votes on 208 Posts
There have been some spectacular and tragic deck failures and far too many have involved serious injuries and deaths so deck issues should be treated very seriously. Your building inspections dept or a professional Engineer may need to be consulted.

Now, I'd say the first step is to drain the hot tub and secure the doors to the deck so people cannot go on it. Wood can go "pop" "crack" without warning and down it comes.

The deck could be jacked and supported on temporary columns. The condition of the existing logs could then be determined. Maybe cutting off the bad section of the posts would leave you with sound, usable wood. If so then the footers might be extended up or some type of structural spacer could be used to make up for the lost post height.

Since you've got several posts that are already failing I would suspect the others might not be far behind. It might be time for a major deck overhaul. It probably would be easier and more "approvable" to replace all the posts with something new either new timber posts, pressure treated ugly lumber or steel columns.
 
  #7  
Old 01-15-15, 02:31 PM
Member
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 5
Received 0 Votes on 0 Posts
bmgreene, Msradell and Pilot Dane,

Excellent, and very sound advice, and pretty much what I figured. You have given me confidence to determine that 1) I will replace the posts (all of them), and 2) I'll be needing help to do it.

I think I'll go ahead and drain the hot tub - it hasn't been getting much use anyway - then wait for spring and do this job. The deck seems solid enough that I'm not too worried about imminent collapse if I drain the tub, but I'm going to have someone come and take a look at it just to be sure.

I really appreciate all the replies. You guys are great.

Regards, Brian
 
  #8  
Old 01-15-15, 02:39 PM
Member
Join Date: Sep 2009
Location: Louisville KY
Posts: 578
Received 0 Votes on 0 Posts
Sounds like a good plan! Let us know how it works out.
 
  #9  
Old 01-15-15, 06:13 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
Received 0 Votes on 0 Posts
I'm not so sure the full hot tub weight is what's causing the 2 columns to compress, without something else going on. Reason being, doing the arithmetic, and presuming a direct load distribution of one half the total tub weight to each column (not very likely, but being very conservative), the resulting applied stress only computes at less than 24 PSI in each column. Most soft woods are good for an allowable compressive strength (parallel to grain) of between 800 and 1000 PSI, meaning the tub weight wouldn't be contributing much more than just 3% of the total strength available. There has to be something else going on, such as the deck's runoff concentrating significant moisture at the column bases, or snow melt being retained inside of them.

Instead of carte blanche column replacement (especially if the majority of what's there is reasonably sound), I'd be inclined to raise all of the concrete footings by casting new concrete on top of what's there, as already suggested, getting the trimmed wooden column bases out of the snow melt zones.
 
  #10  
Old 01-15-15, 10:01 PM
Member
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 5
Received 0 Votes on 0 Posts
Thanks for the input, BridgeMan45. I understand from your comments that it hasn't necessarily been the extra weight of the hot tub that led to the trouble in the two log supports under it, but rather that those two supports are simply in more vulnerable spots. I'm going to approach the situation by first getting things inspected by a professional, and hopefully they will be able to confirm what you're suggesting. Heck, it may turn out that we just had two softer logs to start with. If the inspection deems the rest of the supports to be sound, maybe I won't have to replace all of them after all (and can improve the footers for the two bad logs).

Regards, Brian
 
  #11  
Old 01-16-15, 05:09 AM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 46,158
Received 131 Votes on 117 Posts
PT wood is used for concrete contact for a reason! Anytime non PT wood comes in contact with masonry there is likelihood for rot although some species of wood fare better than others. I do believe moisture is the culprit. Even though the posts were kept well stained, the bottom edge of the post wasn't, maybe never sealed.

Has the deck sunk all the way across or just at these two posts?
 
  #12  
Old 01-16-15, 01:13 PM
Member
Thread Starter
Join Date: Jan 2015
Location: USA
Posts: 5
Received 0 Votes on 0 Posts
Hi marksr,

Well, the only reason I know the deck is lower at the two decaying supports is the observation that the bottom ~2" of them has "crushed" and I can see the sawn edges extending down around the footers. The other log supports have their sawn edges clearly resting on the footer, but I can see signs of water damage in them as well - minor swelling and dark discoloration along small splits. The deck is not noticeably sagging whether looking from on top or below, but it "has to be" given the two shortened supports. It's not a cheaply built deck at all, and everything else about it seems in good shape.

I took a look at the log that seems in the best shape - no real sign of problem at all - and I can see that there is some sort of metal material between the bottom of the log and the footer. It has the appearance of perforated plate, and an edge of it is just visible. It looks like it was placed there as a "barrier" of sorts - or at least some kind of protective insert. I assume it allows water to escape from the log when it gets wet. This function is likely gone in the logs that are damaged since they basically turned to mush at their base. At least it seems the builder made some effort to install something on top of the footers.

This is all good learning for me. I appreciate your patience and contribution.

Regards, Brian
 
  #13  
Old 01-16-15, 03:04 PM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 46,158
Received 131 Votes on 117 Posts
4x4 and 6x6 posts use a bracket that is fastened to the block/concrete which both holds it in place and slightly above the masonry. I don't know what would be used with a log post but there would be something there to hold it in place.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description: