Timbers in ground

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Forum topic by Harryn posted 01-08-2014 04:55 PM 1282 views 0 times favorited 9 replies Add to Favorites Watch
View Harryn's profile


64 posts in 2585 days

01-08-2014 04:55 PM

Planning on building a small shed. Have access to 8X8 timbers from old barn. Want to sink them in ground for the four corners. Thinking of coating the bottom 4 ft. with tar like foundation coating to prevent rot. Any other ideas?

9 replies so far

View Whiskers's profile


389 posts in 2024 days

#1 posted 01-09-2014 01:28 AM

Dig hole for timbers, put a few inches of gravel in bottom and tamp it down hard, for drainage. Put post in hole, and add concrete. Much better than the tar bit. Your shed will rot out in a year or two if you rely on tar.

View HerbC's profile


1756 posts in 2857 days

#2 posted 01-09-2014 01:56 AM

In all likelihood the posts in the ground will rot out in either case.

1. Dig hole (below frost level, 16 – 24 inches diameter.
2. Pour concrete foundation in hole, level with ground).
3. While concrete is wet, set in anchor bold.
4. Mount metal post bracket on foundation.
5. Mount post in post bracket. Bracket isolates post from contact with ground and concrete, minimizes exposure to water, minimizes tendency to rot.
6. Repeat each place you need a post. Depending on size of shed, could must use four short posts, then use timbers to form a sill, build up from there.

Good Luck!

Be Careful!


-- Herb, Florida - Here's why I close most messages with "Be Careful!"

View Bluepine38's profile


3379 posts in 3083 days

#3 posted 01-09-2014 02:23 AM

Before you set the post in the bracket set the end in small plastic bucket with about 2” of chromated
copper arsenate or a similar treatment, let it soak for a few hours then let the extra drip back into the
bucket. Your posts will last a long time.

-- As ever, Gus-the 79 yr young apprentice carpenter

View hydro's profile


208 posts in 1749 days

#4 posted 01-09-2014 01:20 PM

Before you go through all the work and expense of trying to get untreated timbers to survive, just go the store and buy timbers rated for ground contact. That’s the right way to do this and they will last without any special treatment. A lot less expensive than trying to fix this when the untreated timbers rot in place.

-- Minnesota Woodworkers Guild, Past President, Lifetime member.

View mahdee's profile


3883 posts in 1765 days

#5 posted 01-09-2014 02:00 PM

They will rot before you know it and the building will sag in places over time as well. Make your foundations for the posts and use concrete blocks/caps to level them; apply something to create a barrier between the concrete and the bottom of the posts. Better yet, pour you a slab; little section at a time and you will have a nice floor before you know it. Here is some ideas on how to notch large timbers so you have a sound structure.


View bondogaposis's profile


4727 posts in 2349 days

#6 posted 01-09-2014 02:33 PM

Herb C has the right idea. Use Sonna tubes for the pour and you can get them all level and calculate how much concrete you’ll need before you start.

-- Bondo Gaposis

View Kryptic's profile


294 posts in 1658 days

#7 posted 01-09-2014 02:48 PM

if your timbers are from a barn, and old, they will suck up water like a sponge, and in all likelihood rot out very fast regardless of how they are treated, be it tar, on top and surrounded by gravel or encased in concrete ( as concrete loves water and sucks it in )…. the only way I could see this happening is if you lived in a dry climate ?

You could however, dig down below frost level (depth depends on climate zone ) put down concrete footing pads, then put sono tube in and fill with concrete, then place posts on top of that, or take a chance and skip the footing pad and just use sono tube/concrete (without a footing the building will still heave enough, that keeping doors and windows operating smoothly, a perpetual burden of maintenance) .

In my opinion, digging posts into the ground, that are old and as dry as a popcorn fart, will rot out very fast so its almost a complete waste of time. Buy treated treated timbers, they are inexpensive, and use the old posts as an architectural detail, where they can be seen, and utilized : )

View 404 - Not Found's profile

404 - Not Found

2544 posts in 2967 days

#8 posted 01-09-2014 03:04 PM

8×8 Is very heavy for a small shed (what size are you talking here?). I’d pour pads and put 4×4 pressure treated timbers in the corners like you get for decking. The walls and roof will keep it square and rigid.

View AandCstyle's profile


3052 posts in 2255 days

#9 posted 01-10-2014 02:30 AM

If you can get black locust posts you can just put them in a hole in the ground and replace the holes every 40 years. LOL It works for fence posts in the NE.

-- Art

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