LumberJocks

Need advice on bracing for an elevated playhouse

  • Advertise with us

« back to Designing Woodworking Projects forum

Forum topic by doliver posted 05-31-2011 08:12 PM 16148 views 0 times favorited 16 replies Add to Favorites Watch
View doliver's profile

doliver

13 posts in 2017 days


05-31-2011 08:12 PM

Topic tags/keywords: question

Hi all,

I’m new to the forum (and relatively new to woodworking as well)—this looks like the best place to come for advice. I’m building an elevated playhouse for my kids, based on a plan I bought from Rockler. I’m about 75% done with it, and working up there this weekend, there is a noticeable rocking when I walk around on it. It’s not enough movement to be scary, but it’s not rock solid either. And since I’m expecting to have a bunch of kids jumping around on it, I’d feel better about rock solid.

As you can see from the picture & plan, there are plywood gussets on the corners which I assume are intended to minimize racking, but I think I need something more. Can you advise as to what might be the most effective locations to add some 2×4 cross beams (or whatever else makes more sense) to stabilize the structure?

My build is largely based on this plan and the structural detail is as specified. The biggest deviation I did here is that I made it wider, so my deck is 126” wide across the front instead of the 95” called for (but the house on top is the same size as called for in the plan, 8×5’). The only other major change I made was using composite deck boards instead of the PT deck boards called for in the plan.

The height from the base of the post to the top of the deck joists is 60”. In retrospect, it feels too tall and I wish I’d gone with 48” instead, but it’s a bit late for that now.

Thanks for any help you can offer!
-Dylan

-- Dylan, Half Moon Bay, CA


16 replies so far

View sawblade1's profile

sawblade1

754 posts in 2491 days


#1 posted 05-31-2011 08:26 PM

Tighten the lag bolts more first, then notch two 4”x4” post and bolt with carriage bolts in the center then run 2”x8” stretcher joist between them and under the Floor joist ( just look at the center beam in your house for easy reference) Tie all together and you should stabilize :)

-- Proverbs Ch:3 vs 5,6,7 Trust in the lord with all thine heart and lean not unto your own understanding but in all your ways aknowledge him and he shall direct your path elmerthomas81@neo.rr.com

View Gregn's profile

Gregn

1642 posts in 2448 days


#2 posted 05-31-2011 08:32 PM

I noticed that there are no gussets at the bottom. A simple thing to try is to add gussets to the bottom and see if that makes an improvement. Otherwise I would suggest making a X brace that is half lapped in where the X is out of 2×4’s to brace the bottom frame.

-- I don't make mistakes, I have great learning lessons, Greg

View doliver's profile

doliver

13 posts in 2017 days


#3 posted 06-01-2011 01:07 AM

Thanks for the input. Unfortunately I’m having a little trouble picturing these solutions (I’ve never done any deck/house framing like this before). To clarify:

sawblade—so do you mean I should add two new vertical 4×4 posts at the midpoint of the front and back of the structure, and then between those two posts a new 2×8 running beneath and perpendicular to the deck joists? And would I secure it to the joists above it in any way?

Greg—I understand making the half-lap X brace, but not clear on where to place it when you say I should use it to strengthen the bottom frame. Placed vertically along a side wall, or horizontally near the bottom of the structure?

What about adding 2×4 knee braces on the side walls? Or do you expect those gussets already doing as much as can be done on the upper corners?

-- Dylan, Half Moon Bay, CA

View Gregn's profile

Gregn

1642 posts in 2448 days


#4 posted 06-01-2011 02:35 AM

You would place it from corner to corner diagonally for each side of the frame, so that each side looks like a box with an X inside it. Much the same way as you would a gate or wind bracing a building. I think it would give you more strength and support than knee braces. It would also stand up to the kids climbing in and around as opposed to kids possibly tripping over the knee braces. You actually wouldn’t need the gussets with bracing in that manner. Thats what I would do if I had a half dozen little ones running and jumping around up there doing what kids do.

-- I don't make mistakes, I have great learning lessons, Greg

View Grandpa's profile

Grandpa

3256 posts in 2140 days


#5 posted 06-01-2011 04:45 AM

All the ideas above should help. I have a friend that built one of these for his daughter when she was about 5 years old and she is now about 32 I guess. The only difference I see is he has the back 2 corners of the house built to the posts of the platform. By doing this he braced the platform there. Yours appears to have the walk area all around the building. If that is what we are looking at then it will be more difficult to brace. brace 2 of the corners in 2 directions and you have it done. brace all 4 corners below and it will be rigid. We live in SW Oklahoma so the wind load is the greatest force we deal with and there is plenty of that.

View gfadvm's profile

gfadvm

14940 posts in 2155 days


#6 posted 06-01-2011 05:29 AM

It would appear that your gussets are only adding stability in one direction. I would add gussets going the other direction as well.Adding 2 gussets to each lower corner should improve stability still further.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View David Grimes's profile

David Grimes

2078 posts in 2104 days


#7 posted 06-01-2011 06:59 AM

There are only four gussets (left to right on the pics). There should be front to back gussets as well.

Your drawing is only of the posts and sills. I see the sills are 2×8. Are your joists 2×6 or 2×8 ? Are they 16” or 24” on center ?

You just may be feeling deflection from the 10 1/2 foot “unbroken” span with the joists… compounded by the additional deflection of the Trex (or whatever) versus 5/4” screwed deck boards.

Are you using bond timber to help support your joists ? Are you using joist hangers ?

At this point, I would add two 4×4 posts in the front and back middle of the long span. Add girder lumber on both sides of the 4×4 running front to back. This will break the span in half and greatly reduce deflection. It will stiffen it up nicely. Put the new 4×4’s in the ground and concrete them.

If you are really feeling sway, then keep the kids off it until you do something. I like the project, but that would never be the way I would build that… sitting on the ground, notching 4×4’s and single sill bands, gussets one direction. Hold together ? Yeah, sure. Ridgid ? Nope.

Good luck.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View Craftsman on the lake's profile

Craftsman on the lake

2523 posts in 2902 days


#8 posted 06-01-2011 12:12 PM

Use some of the same 4×4 timber to make braces to replace those small plywood ones.they should be 16-24” away from the corners at a 45 degree angle. Drill and bolt them with carriage bolts. That will brace it up nicely.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View doliver's profile

doliver

13 posts in 2017 days


#9 posted 06-01-2011 08:54 PM

Wow, what an active and awesome community. Thanks to everyone for taking the time to help me out.

David, here’s a little more info on the deck: the joists are 2×6, using joist hangers. The plan calls for them @ 14” on center—that evenly spaces 5 joists across the deck. I used the Trex because I thought it would be better for the kids (no splinters) and maintenance, but didn’t guess that the design would be relying on the stiffness of standard deck boards. Apparently I was wrong on that measure.

Looks like a general consensus that I should add another 4×4 post front & back for support on the centerline.

One more question regarding the cross bracing. Here’s a picture from underneath, looking at the side of the deck. If I were to do the cross brace, can I connect the 2×4 bracing on the inside of the upper and lower sill boards (the red circles below), or do I need to move the gussets out of the way and go post to post where the blue circles are?

-- Dylan, Half Moon Bay, CA

View David Grimes's profile

David Grimes

2078 posts in 2104 days


#10 posted 06-01-2011 09:46 PM

14 on center is great. Very glad to see the joist hangers, too.

2×6 joists on that span IS a problem (deflection). If you do the 4×4 posts in the ground in concrete to support the girder to break the span, then add the gussets the other way I promise you will solve both the deflection and sway problems AND it will still look awesome. Then give it to the kids with no worries.

Regards,

David Grimes

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View David Grimes's profile

David Grimes

2078 posts in 2104 days


#11 posted 06-02-2011 04:16 AM

LOL

or ignore me and follow NotVeryGood’s advice instead.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View Luke's profile

Luke

545 posts in 2758 days


#12 posted 06-02-2011 05:08 AM

ditto david, perfect explanation.

-- LAS, http://www.abettersign.com

View doliver's profile

doliver

13 posts in 2017 days


#13 posted 06-02-2011 06:51 PM

Does the girder need to be connected to the joists above or is it enough just to have it attached with lag screws at the 4×4 and in contact with the joists?

I stopped by the hardware store last night looking for a connector so that I could secure the girder/joist intersection—I was picturing something like the StrongTie BC4 but they didn’t have one for 2x boards.

-- Dylan, Half Moon Bay, CA

View terry603's profile

terry603

319 posts in 2378 days


#14 posted 06-02-2011 07:16 PM

i see you followed the plan,but it is only braced left to right. need to do the same for front to back

-- may not always be right,but,never in doubt.

View David Grimes's profile

David Grimes

2078 posts in 2104 days


#15 posted 06-02-2011 07:50 PM

On the girder, with the ends secured to the 4×4… at the middle just drop a couple of 2×6 blocks down from the joists and attach the blocks with screws to the joist and to the girder. Do both on the inside of the girder and it will look good. Nothing fancy, just secure. Obviously, when you attach the girder to the 4×4 (and the blocking), make sure the girder members are up as tight as possible to the bottom of the floor joists.

Regards,

David Grimes

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

showing 1 through 15 of 16 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com