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Downstairs Built-ins Extravaganza! #3: I Haz Saw Now. Plz Check Work.

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Blog entry by BethMartin posted 04-03-2009 08:10 PM 1560 reads 0 times favorited 15 comments Add to Favorites Watch
« Part 2: Time to mooch the table saw. Part 3 of Downstairs Built-ins Extravaganza! series Part 4: The saw and I get chummy »

Before I waste a whole bunch of wood. :)

Here is my sketch from before to give you an idea of what it will look like:

Now I’m trying to figure out how to construct the plywood case. I drew out these sketches. This will be in a corner, and I have some play on the wall side so that I can fit it to the wall when I make the face frame. The tricky part of this is that it is 4 feet wide, and will be supporting a big shelving unit on top. So it has to be strong.

I’m thinking that I need to double up the plywood (3/4” doubled) on the big vertical pieces. And maybe part B, too? And add extra supports on the bottom. What do you guys think? What would you do different? Thanks in advance for any advice!

The part of the sketch that got cropped out:

-- Beth



15 comments so far

View BethMartin's profile

BethMartin

111 posts in 2843 days


#1 posted 04-03-2009 08:10 PM

Ack, my sketch is cropped, let me add another…

-- Beth

View PurpLev's profile

PurpLev

8523 posts in 3113 days


#2 posted 04-03-2009 09:06 PM

I think that the 3/4” sides ply should be enough for support and don’t think doubling them up is really necessary. as long as you brace them properly with a square back. also doubling part ‘B’ will do nothing to the ridgidity of the piece to support more weight, as it only acts as a brace to the sides, and does not carry weight itself. make sure you use good quality plywood though.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View lumberknowledgist's profile

lumberknowledgist

30 posts in 2899 days


#3 posted 04-03-2009 09:11 PM

Your design looks good. I agree, I don’t think you would need to reinforce the sides, plywood is very strong and will withstand a great deal of pressure when held vertically.

-- Jason

View oldskoolmodder's profile

oldskoolmodder

799 posts in 3145 days


#4 posted 04-03-2009 10:00 PM

Agree on not needing extra plywood as long as it’s a good quality product. Ply is meant to carry weight, so need to double it up. How will you do the face frame? Brad Nails? Pocket Holes?

I like that you have allowed for the piece to be scribed to the wall. It’s not something DIY’ers always think about.

-- Respect your shop tools and they will respect you - Ric

View BethMartin's profile

BethMartin

111 posts in 2843 days


#5 posted 04-03-2009 10:50 PM

Really? You guys think it will be enough? Even though it’s 4’ wide? (And with a 5’ tall bookcase on top?)Because that seems really wide to me – I’ve been trying to find something to refer to, so I can compare. The widest things in my house are mostly only 3’ wide. And I notice that some of even those are looking really saggy. It’s also going to be 2’ deep, if that makes a difference. Though I can see how the back and face frame will help stabilize it.

How about assembling the case? If I’m using 3/4” plywood, can I use dadoes because the middle vertical will be getting cut into from both sides. Or should I just use biscuits anyway? If the plywood is doubled up then I think the dadoes will not be a problem, right?

I haven’t figured out how to attach the face frame yet. I need something easy but not visible from the front. I need to look that up before I start putting things together.

Thanks for taking the time to help me work out my thoughts. :) It is a big help and reassuring.

-- Beth

View Todd A. Clippinger's profile

Todd A. Clippinger

8901 posts in 3564 days


#6 posted 04-03-2009 10:56 PM

You will not need to double up the carcass sides.

-- Todd A. Clippinger, Montana, http://americancraftsmanworkshop.com

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3141 days


#7 posted 04-03-2009 11:03 PM

You don’t need to doouble up the verticle pieces under compression forces. Spanning 4 feet is where the problem will be with a heavy load.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Pat Cavanaugh's profile

Pat Cavanaugh

158 posts in 2836 days


#8 posted 04-04-2009 12:17 AM

Beth, I agree with everyone, there is no need to double up the plywood. I would cut a dado to let in the horizontal (D) dividers into the sides (3/8”) and center (1/4”). And I would use biscuits to attach the faceframe to the carcass.

-- Pat - Biloxi, MS

View PurpLev's profile

PurpLev

8523 posts in 3113 days


#9 posted 04-04-2009 12:27 AM

definitely use dadoes, since biscuits will not give you any strength to the structure – only alignment, while dadoes will give you the extra strength to hold the weight. 3/8” dado in the 3/4” material should be fine – no need to double it up – make the dado fit snug + glue, and you’re good to go.

once good tip about dadoes and plywood that I picked up is – don’t try to cut the perfect dado to match the plywood thickness (3/4” undersized) – instead, cut the dado at 5/8” and cut a rabbet at the edge of the horizontal component that will reduce the ~3/4” plywood to perfect 5/8” which will be a perfect fit for the 5/8” dado.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View oldskoolmodder's profile

oldskoolmodder

799 posts in 3145 days


#10 posted 04-04-2009 12:30 AM

Beth, it appears that you have enough support in the middle to do what you want, even with the bookcase on top. If it makes you feel better, you could double up the top thickness. That certainly would help with possible saginess (yes it’s a word I just made up) that is worrying you. You also don’t need to use solid (unless you want to) pieces between what I’m assuming are 3 drawers on the top of this cabinet. You could make frames that would cost a little time, but still be stable enough.

For the face frame, you could go “simple” and just use straight pieces brad nailed onto the front of the plywood, but to make it stronger, I’d suggest looking into a $40 Kreg Pocket Hole Jig (K3) and some fine and coarse threaded screws for your project. That’s just me. No need to use biscuits unless you are set on that way. Brads could easily be used to attach the frame to the cabinet, without worrying about the nails being seen. Especially since as I recall, you want a darker color.

Would a sketch up or more detailed drawing be easier to understand how things could be done?

-- Respect your shop tools and they will respect you - Ric

View BethMartin's profile

BethMartin

111 posts in 2843 days


#11 posted 04-04-2009 01:30 AM

Thanks, guys. You’re right, I’m actually more worried about the span than the vertical supports, now that I think about it. But I’m the worrying type. You’ve all made me feel better. I think having the plywood top + the maple on top of that will be good.

PurpLev, thanks for the dado tips!

I didn’t realize that I could put dadoes into either side of the same piece of wood, leaving 1/4” uncut in the middle. I was worried that it would be too much cutting in, but I guess since it’s all glued that it gets its strength back from the wood going in.

oldskoolmodder, thanks so much for the offer of the drawings, but I think I’ve got it. I’ll have to check out the pocket hole jig (and ask my FIL if he has one!) :)

This weekend the table saw and I will be getting acquainted, and then hopefully I’ll be getting started soon after!

-- Beth

View LesB's profile

LesB

1237 posts in 2908 days


#12 posted 04-04-2009 08:12 AM

The thing you left out is the design of the top “book case” and how it is being structured.
Are you are putting a center divider for support? A 4 foot span of 3/4 wood will sag with heavy books on it. If the shelves are permanently fixed a face frame on them will give some support and fastening the shelves to the back panel will help too. If the shelves are adjustable you definitely need a center divider. In that case you will be transferring part of the load to the center of your bottom unit so make sure your vertical drawer dividers are solid and are supported all the way to the floor (dado them in too). Although your 2” thick top may be enough support it would be a shame if it sagged and the drawers started binding.
I tend to over build at times but I agree the 3/4” sides are strong enough especially when you add the solid verticle dividers between the drawers.
Have fun.

-- Les B, Oregon

View gizmodyne's profile

gizmodyne

1770 posts in 3555 days


#13 posted 04-04-2009 04:40 PM

I drew your drawing up in sketchup. Image A. And made a few changes to it. The only other thought I had was to beef up the middle stile.

The top ones show the comparison with 3” wide middle stile.
the only thing your drawings seem to not show is some type of back for the cases. or nailers.

-- -John "Do I have to keep typing a smiley? Just assume it's a joke." www.flickr.com/photos/gizmodyne

View BethMartin's profile

BethMartin

111 posts in 2843 days


#14 posted 04-04-2009 06:15 PM

Gizmodyne, you are a peach for putting that into sketchup. It’s nice to see all of the options. Now I just have to pick which one I like best. I do like B or maybe F better. I’d like to keep the 3 little drawers on top as I think it adds more visual interest.

There will be a back to the case. I have 3/8” beaded paneling that I was going to use for the bookcases, and I should have a piece left that will fit the back of these drawers. Do you guys think that will be sufficient or do I need to put a thicker nailer part on?

I whipped up a sketch of the whole thing with the shelving on top:

I am going to have some fixed 4’ wide shelves, and I was definitely going to double them up. I was thinking I’d maybe even encase some metal rods between the doubled up shelves and then they’d never sag. That’s probably overdoing it though. :) The top part of the unit will be 18” deep, while the drawer part is 24” deep.

-- Beth

View LesB's profile

LesB

1237 posts in 2908 days


#15 posted 04-04-2009 08:05 PM

The extra sketch helps. I think you will be fine if you are using a 1-1/2” face frame on the book shelf section (use pocket screws or biscuits to attach face frame to shelves) and fastening the shelves to the 3/8” back panel with nails/screws should keep the shelves from sagging. I don’t want to mess with you design but that speaker would probably look better in the top shelf in the center.

-- Les B, Oregon

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