Highly unlikely you'll find it at a big box. You probably need to find a wood specialty or woodworker's store, even then, you might have to look at a number of them as it's not a common wood like say, maple, cherry, birch or oak.

i would doubt it can even be ordered, especially in a small lot like one sheet.

Constantine's sells all sorts of veneer, some designed to be easily applied and in larger pieces.

Here is a link that might be useful: Constantine's

Most mahogany plywoods (except Philippine mahogany) are African mahogany. Honduran mahogany has been priced out. If there is a lumber business in your area that sells lumber and plywood, you can get it there. They may have to order it. Constantine's might have it. You can look on their web site. Be sure you compare prices and the number of plies.

Windsor Plywood - if in Canada you may have a store near you. There are just a few in the US.

Here is a link that might be useful: Windsor Plywood locations

Don't know where your located. In the Chicago area there is OWL LUMBER. Their inventory has KHAYA MAHOGANY.
www is http://www.owlhardwood.com/products/lumber-products/plywood/mahogany

Happy hunting, rredogg

I live in Oklahoma. I don't think we have any wood specialty or woodworker's stores around here. Constantines does have mahogany veneer, but it comes in 36" lengths and I don't think I'm up to the task for my 7' x 21" window seat project. We lowered the height, and unfortunately, the original mahogany veneer plywood couldn't be salvaged. I do have the original mahogany board with routed edge which goes across the front. I wanted to join it with veneer plywood to make a solid seat -- that's how it was originally constructed.

I'll call lumberyards tomorrow to check on mahogany veneer plywood. I didn't realize that plywoods vary in number of plies. What is a good number of plies? Is a higher number better?

I did look at birch plywoods at Lowes. They had tons of it and it was inexpensive. Maybe it would blend with the mahogany board on front after it's stained. That's not my preference, but if I can't find mahogany plywood, it may suffice.

I really appreciate the great advice on this forum. It's so good of all of you to share your expertise. I wish I could contribute, but I'm struggling to muddle through my own projects.

Just as important as the number of plies is their composition.

"Constantines does have mahogany veneer, but it comes in 36" lengths "

They have African Mahogany Veneer in 48 in x 96 in sheets.

Here is a link that might be useful: African Mahogany Veneer

Brickeyee -- thanks for the link -- I hadn't seen that.

An 18"x96" sheet of African mahogany veneer from Constantines would cost about $50, including shipping. I'd also need to add the cost of the plywood.

I did call a local lumberyard and they could order a 4'x8' sheet of 3/4" plywood with African mahogany veneer on both sides for $82. They directed me to Columbia Plywood's website to look at samples.

Cost is reasonable whether I buy veneer from Constantines or buy a sheet of mahogany plywood from the lumberyard, so I won't use that as a determining factor.

I don't have experience applying veneer, so I'm nervous about tackling that. Furthermore, with an 18"x96" sheet of veneer, there's no room for error -- my bench is 21"x83", which includes the 5" wide mahogany board along the front.

If a buy a 4'x8' sheet from the lumberyard, I could actually get 3 pieces big enough to attach to my front board to create the bench top. Because the plywood has veneer on both sides, I could choose the best looking of 6.

The window seat is surrounded on 3 sides, and I want to get a snug fit with no gaps. I guess the routed mahogany board that goes along the front should be glued to the plywood to form a solid piece -- possibly using biscuits.
I'm tempted to try to do this myself. I hired someone to lower the window seat. It is level, so he seemed to do a good job of carpentry work on the inside, but I'm not happy with the top. He used 3 boards (not plywood) and there are gaps between them and at the ends, because he cut them too short. He said that the gaps between the boards are due to warping, and they'll go away. I'm not buying it. Anyway, I'm just rambling here -- I'll probably need to hire someone to do this right.

If I order mahogany plywood from the lumberyard, what questions should I ask about the quality? The supplier would be Columbia Plywood, and I don't understand the quality descriptions they have on the website.

Thanks so much for your help!

Here is a link that might be useful: Columbia Plywood

I just looked at the link and what you want is the face to be A and the back could be B or C, because it will not show. I don't use plywood with a particle board or MDF core if I can help it but sometimes that's all you can get. I might be mistaken, but I think Columbia Plywood makes Apple Ply plywood which is seven plies or more depending on thickness. This is a very good product.
I think your carpenter is trying to s--t you. There should be no gaps. There are several good books out there that explain how to make your own built-ins, and may I suggest you get one before you proceed further. One I have is "BUILT-IN FURNITURE" by Jim Tolpin. You can order this on Amazon or Tauton Press and get it in one or two days. Very good book, lots of widow seats.

The guy at the lumberyard told me that for $82 the 3/4"x8'x4' plywood sheet would have an A face and a 1 back. He said it is not MDF, but rather 7 ply.

This window seat was original to the 1964 house. It was 23" high and I just had it lowered to 16" (chair height with cushion). The guy lowered it, but I'm unhappy with the top. He used three boards for the seat and didn't join them. I want to replace the top with one like the original construction. I kept the mahogany board with a beveled edge along the front (like a window sill) which was seamlessly joined to plywood to form the back of the seat. There were originally no exposed plywood edges. This seems simple enough, but I will look at the book you recommended. I'm also open to hiring someone else. If I find someone who knows what he's doing, I should wind up with a good result at not too much more cost.

It's really discouraging to hire someone who does slipshod work. He told me he would use buscuit joinery, but that's not what I ended up with. I probably have no business thinking of tackling this myself, but I'm a little gun shy.

Unfortunately, the guy was very thorough on nailing in the boards -- he used a nailgun and spaced them 1 1/2" apart, so removing the seat will be a challenge!

Unless someone here talks me out of it, I think I'll order the mahogany plywood tomorrow. That would save me trying to apply the veneer.

Thanks everyone!

someone2010, I ordered the book you recommended. It looks like a good one, and even if I hire someone to cut the top, at least I can make sure they do it right -- probably won't appreciate my micromanagement, but I'm not taking any more chances.

Quandry; if you will email me your address I will send you a book that is more basic and might be better for your purpose. I was looking through the book I recommended and it might be too advanced.

I would still ask hard questions about the plywood quality.

Better stuff is done on Baltic birch.

No voids.

I ordered the mahogany plywood today. I hope it turns out okay.

someone2010, I really appreciate your recommendations. All I need is to get an accurate measurement and cut and attach the front board so that I have a snug fitting top. The seat is already constructed. I really hate to ask you to send me a book.

I noticed when the old plywood was removed that some of the edges were beveled -- probably to allow fitting it between the walls on either end but still getting a snug fit. Maybe this will be addressed in Tolpin's book.

The 4'x8' sheet will allow for 3 pieces of the size I need, so I think I'll attempt one on my own. If I screw it up, I'll still have enough plywood left to hire someone to measure and cut the top -- and he'll have two shots.
I recognize that I'm probably oversimplifying this. I'm not opposed to hiring someone, but I want it done right and within a reasonable period of time.

These forums are such a great resource for information, but maybe sometimes they make me think I can accomplish things which are really over my head. I do like the challenge of trying new things -- and always learn to appreciate just how much skill is involved in seemingly simple jobs.

You will see, in Tolpin's book how to pattern scribe for fit.

Here's some advice you may or may not need. How to make a jig for your cicular saw or jig saw so your cut will be perfectly straight.
Get a piece of plywood or MDF 4ft by about 2ft. Have the home store cut a 4ft by 6in strip off. Place this 6in by 4ft strip on top of the 18in by 4ft strip and line it up with an edge. Glue and screw it down. Now butt the base of the saw against the inside edge of the 4ft by 6in strip and cut through the bottom strip.
Now you have a cutting guide to cut straight lines.

A piece of aluminum strap works even better, and is not going to warp.

I use about a 4 inch wide piece 1/4 inch thick.

Yes -- I'll definitely need to make a jig for my circular saw.

I hope I explained it so you understand. It's simple to make and no measurement when you use it. Just make your cut line on the plywood then line the edge of the jig on the line so you're cutting into the waste portion, clamp it down, and make your cut.

I picked up my mahogany plywood today. It looks like a nice piece. I haven't received Tolpin's book yet -- I should have spent a few more bucks to get quick delivery. I want to read up before I start. I may go out tomorrow and buy the stuff for my jig.

There is another book you can order on Amazon that might be more helpful than the book I first recommended. It is "CABINETS AND BUILT-INS" by Paul Levine. It costs one dollar plus $3.99 shipping for a total of $4.99. I just ordered this book because of the price and got it in about three days. That's the book I was going to have sent to you because I felt bad about recommending another book that may be too advanced. I think this book would be perfect because it shows exactly how to make stuff.

I went to the library this morning in search of information about how to measure and cut a snug-fitting top for my window seat. I was pressed for time but checked out a book which might help. I came home and Tolpin's book had arrived in today's mail.

Leafing through Tolpin's book I found a section on creating cutting patterns. He explains the Joe Frogger method and the jigger stick method. This will be great for getting the perfect size.

Someone2010 -- you needn't feel bad about anything. This forum is such a great resource. I really appreciate being able to post questions here when I need help. I'll study the Tolpin book more closely tonight, and will post here and/or order the other book if I need to.

Thanks for everything!