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spacing balusters evenly


On one of the episoids of 'This Old House' Tom Silva explained a mathmatical formula for evenly spacing balusters on a deck railing no matter what the spacing is between posts. Can anyone please tell me this formula or email me this formula, or direct me to an archive on the TOH web site that might address this situation? I really need the help here and would appreciate the info. Thank you for your time and consideration,


Re: spacing balusters evenly

Hi Bob

I am in the same position that you are in. I am trying to build arailing for my covered porch and not having a lot of luck with measurements. Can anyone help us.

Re: spacing balusters evenly

Hi Cissy,

This is what I have come up with so far. It's a rather long file but worth reading; this file contains answers with follow-up question by other users; also I am including the best web site address I have found helpfull so far:


This is a whole lot easier to do than explain, but here goes.
Determine the max clear area allowed by code (4" locally), add the width of balaster. Then divide that number into the length of railing to receive balisters. Round up that number to the next whole number.
Place your tape in lower start corner(back off half the width of a balaster to start. Pull the tape to the end plus half the width of a balaster.
Remember that whole number- move the tape diaganally(holding start point)up until you can get a number that is a multiple of that whole number. Then mark at the multiple number. Use a level to transfer number up. This should divide the balasters so that the space between in slightly less than required by code & be equal.
Place another mark half the width of the balaster to one side of the centerline mark so you can see where to place edge of balaster.
Check that you did it right.
example:So if you have a 4" clear space and 1 1/2" balasters, you can use the 6" mark when the tape is stretched on the diagonal based on a multiple of 6" x rounded up whole number from the length divided by 5 1/2". Start 3/4" before calculated start and 3/4" past end.
Clear as mud? I swear it's easier than it sounds. Maybe someone can explain it better.


This sounds like it might be a lot easier than the math I now go through to figure spacing out, but I want to check my understanding.

If I understand correctly you keep the tape stretched on the diagonal when you get to the multiple of the whole number on the one vertical side. Then you mark the bottom plate at the whole number marks by using a level to get from the diagonal tape to the bottom plate? The marks are the center line of the balusters.

I have a deck railing coming up and wanted to verify my understanding beforehand.


Yes, they will on the centerline. Then mark half the width of baluster over if using an edge line is more convenient than covering centerline.
Don't forget to compensate for half the width of baluster at a support post so all the spaces are equal.



balustrade :bal·us·trade - A rail and the row of balusters or posts that
support it, as along the front of a gallery.

bent nail
Re: spacing balusters evenly

this is what I do to space spindles evenly
find center of rail,mark center and half of spindle width on each side of center mark
when I say center of rail I mean middle of the entire rail run.
from the mark on the side of the center mark use a 2by4(3 1/2)in spacing or cut a piece of lumber to the desired spacing. Attach spindle to rail repeat process.Your last spindle may have a smaller space than the rest but I have never had any complaints.
hold spindle tight to spacer when attaching.

Re: spacing balusters evenly

I made a little wizard on google docs and as a spreadsheet, you can view it here: http://spreadsheets.google.com/ccc?key=plO4hoBWCYYnyzkvoBjwfMw or download it below

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