Tree house and Kreg?

[John A]

Hi all -

New to the forum and to the tool, (haven't even used it yet!! Shhh!)

I am planning on building a tree house, 6 feet off the ground, 8x8, with a deck on the outside, ladder, fireman pole, etc.  The plans call for toe nailing some of the rails down for the balcony and some walls, but I wanted to use the Kreg instead...my question is, will the joints be strong enough if someone leans against them?  How strong is the actual joint?

Thanks again for the input!

[James Waller]

I believe the joint is strong for a lot of things, but when someone actually becomes part of the project (like sleeping in bunk beds, playing on a swing or sitting in a chair) then the project becomes a safety issue and you have to take in consideration how to strengthen the joints that will bear the most load and to ensure the safety of the people you are making the project for.

Even if you are using a HD (Heavy Duty) Kreg Jig I would say to still use alternate means of joinery (like nuts and bolts) on load-bearing joints along with the pocket holes.

Six feet is quite a fall for a child (even an adult) to take, but is avoidable if you plan ahead. Always keep safety in your mind for yourself while building the project and for those who will be using the project.

[Jay Boutwell]

Hi John, I have to agree with James on this about safety issue.   The kreg pocket joint is a strong joint for most things however there are occasions when we must exercise a little more caution when it comes to safety.

In building such things as framing for decking and railings you are asking a lot in a joints ability to resist the stresses that are exerted on it.  We have to think about the dead weight that is exerted upon it as well as the live weight that it will be exposed to and the frequency of how often it will be stressed.  The dead weight  means the weight of the structure including anything that does not move.  This would be such things as weight of furniture on a deck , flower pots, and even snow and ice loads.  Live weight would be anything that moves such as people.   It is the live weight that will put the most stress on it.

Adding to this you will be dealing with the stress of the elements such as wind and rain plus the aging of the structure and how good is the material that it is made of. The type of joints that it is made of is also a major factor.

The strength of the structure will be only as strong as the joints and material quality allow it.  There are two factors that are involved in strength.  One is the ability of a joint to resist "sheer forces" and "pull out forces" of the nails and or screws that hold it together.  A common 16 penny nail has a sheer resistance of about 600 lbs and a screw of the same dia will not be as strong due to the material being harder it is more brittle.  The nail being softer has the ability to resist a sheer force in a greater amount and for a longer period of time as it has the ability to bend.  The other force on nails and screws is "the pull out resistance".  A screw driven one inch into a piece of material will resist a pull out force greater than that of a nail driven one inch into the same material.  Therefore  a nail will resist more sheer pressure that a screw but will not be as strong as a screw when it come to pull out pressure.  For example a deck screw has a great pull out resistance however on most occasions with break after a couple bends.  This is the bending that is experienced in the sheer force from movement of live weight or movement from wind.

Another factor is the number of nails or screws driven into a joint.   In some cases too many nails or screws will cause a joint to fail due to cracks and splits in the material joint.

This is why it is best to consider all types of joints and methods of construction in any structure as well as what we use to fasten the joints together. 

In your case where you are talking about ladders, decks and railings.  On these I would consider such things as thru bolts and truss hangers .  It is alright to use the kreg pocket screw as a method of attaching material together but then add  other types of mechanical connections like bolts and hangers.  The are just too many safety risks to consider just using only a pocket screw on any structural element of a project.

 

[John A]

Thanks all for the comments, the plans I have call for lag screws, bolts, etc, which u plan on using, I just wanted to know if the Kreg joints could be used for railings where the plans call for a toe joint, which to me does not seem that strong.
But I will stick with the plans and maybe lower it down from 6 feet to 2 feet, safer and easier to build.

Thanks again all for the great information.

[KregCS]

John,

In this application I would not recommend using the Kreg Jig for safety and building code concerns.  However, the HD jig would be able to be used in this application without any issues.  We have actually tested this to be used with deck railings and it held up to very large forces.  The details of this testing can be found at: http://www.kregtool.com/prodImages/files/KregJigHDForceTestSheet.pdf.  If you have any other questions please let us know. 

[John A]

Thanks for the info on the HD, I didn't even knew one existed!

[Ken Darga]

Thanks for posting the data.

Good info.

KregCS said:

John,

In this application I would not recommend using the Kreg Jig for safety and building code concerns.  However, the HD jig would be able to be used in this application without any issues.  We have actually tested this to be used with deck railings and it held up to very large forces.  The details of this testing can be found at: http://www.kregtool.com/prodImages/files/KregJigHDForceTestSheet.pdf.  If you have any other questions please let us know. 

[John A]

Hey all...

Another question on the wood being used for the tree house.  This is a little off the subject of Kreg, but I figured, who better to ask then a bunch of experts!

First - I did order a Kreg HD unit...

Second..The plans I have call for pressure treated and cedar....pressure treated for any wood in contact with the ground and tree, the cedar for anything free standing, the problem is, 1...cedar is expensive in my area, and 2..pressure treated is so heavy.

What are your thought on using pressure treated on anything in contact with the ground, and tree, and other areas pine, I plan of staining the outside of the tree house and using shingles on roof area....will pine hold up to the elements?

Thanks!

[Ken Darga]

John,

 

Wood needs to be treated to withstand the elements.

Wood is chemically protected through a process called pressure treating, which wards off insects, microorganisms and fungal decay.

 

The sealer is applied under "PRESSURE"; hence the term "pressure treated".

Pressure treating forces the sealing material, deeper into the wood.

 

''Pressure treated'' lumber is pine, or the like.

 

Newly pressure treated lumber is heavier, because it’s still wet.

When it dries, it’ll lighten-up.

 

I’d use pressure treated lumber for the items that contact the earth and trees.

It's more economical to use pressure treated lumber,  vs adding sealer waterproofing coats.

 

If you plan to use pine, it needs to be sealed---

Use an oil based sealing & stain, for longer lasting effect.

Select a stain that will permit the natural wood to show, for a better visual affect.

[John A]

Thanks Ken, I too, after I posted this decided on pressure treated for any of the wood outside.  I also am looking at cedar, it will add about another $150 to the project, it's already red, so no need for staining.  

The inside of the tree house, calls for fir, but I think I will stick with pine.

Your thoughts on both?

Thanks.

Ken Darga said:

John,

 

Wood needs to be treated to withstand the elements.

Wood is chemically protected through a process called pressure treating, which wards off insects, microorganisms and fungal decay.

 

The sealer is applied under "PRESSURE"; hence the term "pressure treated".

Pressure treating forces the sealing material, deeper into the wood.

 

''Pressure treated'' lumber is pine, or the like.

 

Newly pressure treated lumber is heavier, because it’s still wet.

When it dries, it’ll lighten-up.

 

I’d use pressure treated lumber for the items that contact the earth and trees.

It's more economical to use pressure treated lumber,  vs adding sealer waterproofing coats.

 

If you plan to use pine, it needs to be sealed---

Use an oil based sealing & stain, for longer lasting effect.

Select a stain that will permit the natural wood to show, for a better visual affect.

[Ken Darga]

John,

I've tried taking short cuts---using pine and sealing it myself---

in the long using the PT material is less costly---materials and time.

Alternate(s):

A. Eons ago, some treated post ends using ''old used motor oil''. 

Stand the timbers upright in a barrel of oil---let it soak for several weeks,  before planting the post.

(messy).

B. Boilded Linseed oil is effective---

the first soak treatment, using 2 parts oil to 1 part mineral spirits---

thinned to permit deeper penetration---

followed by  several coats of liinseed oil.

Allow 5-7 days drying, before proceeding to the next coat.

NOTE:  linseed leaves a sticky surface.

C. Liquid roof cement (tar) the post ends.  

The tar gets in the cracks and crevices---seals out moisture.

Cedar

costs over 2X the cost of pine---3.75 - $4 per sq ft.

Cedar can be sealed/stained natural.  

Cedar, when left untreated in the weather, will turn a darked grayish color.

A preferred appearance, for some structures.

Alternate: dog eared cedar fencing material---5/8 x 6" x 6ft---about $3 each.

Option for small tree house walls.

This material is sanded one side---opp side rough saw---makes for an attractive appearance.

Cyprus

Perhaps you can obtain some cyprus, weathered or let nature take its coarse.

I've seen some attractive structures, done in cyprus.

Perhaps you can get your hands on the swamp cyprus logs, that have been cut in boards---the type that has been harvested from the water.

If using pine, it'll need to be sealed/stained.  It will not outlast the cedar.

I'd prefer fir to pine.  Check with your local supplier, what available in your area.

Alternate: redwood (found primarily in the west coast)---the choice for several reasons.

Comparable to cost of cedar.  It some regions, redwood may be a little higher in costs.

Buy larger wide boards, and rip them to size---it could save you up to 20%.

4" wide boards will result in less cupping, vs 6" boards.

10-12" wide boards will develope cupping, over time, and cracking will occur.

John A said:

Thanks Ken, I too, after I posted this decided on pressure treated for any of the wood outside.  I also am looking at cedar, it will add about another $150 to the project, it's already red, so no need for staining.  

The inside of the tree house, calls for fir, but I think I will stick with pine.

Your thoughts on both?

Thanks.