I would strongly recommend comparing the cost difference between a SRW and a timber wall. You may be very surprised to find out that there are lots of block products that are very cost competitve with timbers. All wood products are expensive right now. Have you priced a sheet of p/t plywood lately

Whenever I have requests for timber walls, I ALWAYS try to steer the customer to SRW.

That said, I've only built them with deadmen going back into the soil, never with vertical supports. Using the same guidelines for a SRW would be beneficial as well. The other factor you should consider is including batter in your construction technique, which means stepping each course back from the one below, about 1" or so.

hth.

 

Thanks, I am aware of the rising cost of lumber...it's costing me a fortune on my new house! Somehow it didn't come to mind during my walk-through with the customer...regarding batter, same principles apply as with stone? A 6"x6", set back 1" every course will have more pitch into the slope than a stone wall based on a higher number of courses, right? Does batter help that much on such a short wall? Could you set back every other course? Also, is a deadman more beneficial the higher it is set on the wall?

 

Thanks, I am aware of the rising cost of lumber...it's costing me a fortune on my new house! Somehow it didn't come to mind during my walk-through with the customer...regarding batter, same principles apply as with stone? A 6"x6", set back 1" every course will have more pitch into the slope than a stone wall based on a higher number of courses, right? Does batter help that much on such a short wall? Could you set back every other course? Also, is a deadman more beneficial the higher it is set on the wall?

Sorry, I didn't pay a lot of attention to the height. But, yes, even with a block wall there can be a fair amount of batter -- all blocks are different. Some faces are near vertical, while others (Allan Block 12 degree for example) set back about 1" each course. 1" may be a little excessive, but remember that timber walls generally have a tendency to lean out. Your batter is not as important on a 2' wall, but you want to keep the look consistent.

I don't know that I would say the deadman are more beneficial towards the top. In SRW's that require geo-grid, the first layer of grid is set on the bottom course, and generally, every second course thereafter. Don't try to compare geo-grid to deadmen though. Grid runs the entire length of the wall, while a deadman only covers a 6" area. Although tempting, I wouldn't skimp on the deadmen. They are needed throughout the wall to do the job. Remember that deadmen on the bottom will do a lot of work too, as they have more soil surrounding them.

I'll find a pic of a 4' block wall with 12 degree (1") batter.

 

here is the 12 degree Allan Block on a wall around 4'.

If you look at the curve on the right hand side of the big stairs, you'll see the batter that equals about 1" per course.

 

Thanks for the help...honestly, I'm not trying to get you to build this thing for me! Are there formulas/ratios for length of deadmen, length of 'T' on deadmen, and deadmen spacing in relation to wall height? Sorry for all the questions, I'm just trying to learn theory for different wall types I can apply to later projects...

 

No problem, I just don't have a lot of experience with timber, because I prefer Block.

I did a search on timber walls. Here's a couple recent threads that might help more.

http://www.lawnsite.com/showthread.php?t=77619&highlight=timber+walls
http://www.lawnsite.com/showthread.php?t=14180&highlight=timber+walls

I didn't visit this site, but sounds like something that might help:
Timber Grid - http://www.timbergrid.com/

Here's a subject appropritate quote from another thread:

Hello,

When building timber walls the one thing I've learned is that you need to almost over-engineer them.....or what I mean is you need a lot of 'dead men' in them to.

What I don't like about this job is that you basically have to build a 'free standing' wall 3 feet tall, and unless you escavate the walk out, you will not be able to have any 'dead men' in the wall because it is being built right along side it.

I have seen way to many timber walls fall over in a matter of 1 or 2 years after construction because they did not have the proper support.

There may be a way to engineer it, but I would suggest going with a concrete block retaining wall in a situation like this. Under 4 feet, you do not need geo-grid (per-say) and I think it would be a much stronger, durable lasting wall.

As for price, I haven't built one for years because I trust the block more than the timbers, so I can't even remember where to start pricing now a days.

steveair

[Edited by steveair on 05-07-2001 at 09:51 PM]

 

Here's another thread that Mark didn't link to:
http://www.lawnsite.com/showthread.php?t=67239&highlight=tiebacks

There's some good info there.

Basically as far as spacing, every third course, every 8 feet is what I've always been told/taught. Obviously, for maximum strength, you should alternate the tieback positions, so you don't have a bunch of them stacked on top of each other.

As for batter, 1/2" per course setback should be adequate.

The only thing I've done differently with timber walls is to rebar the bottom course of timber into the ground. I'm not sure it does anything structurally, but it helps to keep the timbers from moving around on you while you are building the wall.

Oh, and don't use 12" spikes, get 8" timber screws. You'll need a decent sized drill, but you will save a BUNCH of time, plus they are stronger and the timbers don't move around on you while you are driving the screws...

Good luck. I'd still rather have a block wall!

Dan

 

thanks to all...

 

Here is a link to a graphic that shows how we have to build a typical timber wall. As you can see, there is almost as much timber behind the face as in the face. No way is this a cheap way to go anymore. http://www.fairfaxcounty.gov/dpwes/publications/retainingwall/sheet02.pdf

 

Last timber wall I was asked to do a quote on I worked it all up and then also gave them a price using pavestones. Cost with the pavestones was actually cheaper, and looks a ton better.(Not saying that I am a fan of pavestones) These people like the typical timber wanter, thought timbers would be a lot cheaper, that's why they wanted them. My advice would be to calculate costs of both doing everything correctly and not cutting any corners, and if you have access to any type of landscape design software, give them images to compare timber to stone. Timber has places that it looks good, but those places are very few and far between (in my opinion). If you could do that, then between the price comparison, and a computer generated graphical comparison, they'd choose block and you'd probably thank them for it.

 

I would have to agree that if you end up calculating it out the labor involed in a timber retaining wall done will cost more than a an srw wall. he timbers are usually very heavy and you have to consider that a tremendous amount of timber will be used for deadmen. If you do decide to go timber remember to add drainage behind the wall and the deadmen require a timber perpendicular to the timber anchored to the wall. and rebar this piece into the ground. I have taken out walls before that had just timber going straight back with no anchoring. I believe that a timber wall is much more suceptable to hydrostaic pressure than srw's because once they are spiked together there is no way for the water to get through unless the installer has put weep holes. I am working in a development now that the developer put in crappy timber retaining walls and steps and most of the people are hiring me and another lco to remove and replace with srw's and dry laid stone. Last but not least use 13 inch long half inch galvinized spikes to tie the wall together. These spikes will go through two courses and tie into the third.

 

Again, thanks for the info. I guess there's a reason I don't have much experience building timber walls - it's a dying market (and good riddance, too from the sound of it).

 

Worst part is the clay you mentioned will pump into the stone that you use for drainage, unless you provide the proper geo-fabric. The clay/stone mix makes a terrific waterproof barrier and it's nearly impossible to dig it out, short of a backhoe. I see this frequently in MI, blue clay has become part of my daily life.

Best of luck,
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