Expert: Bruce E. Johnson - 8/4/2009

Question
QUESTION: We just converted our 10' x 35' patio and want to make a sun room.  It's about 4' feet above the ground and is covered by the original roof. The 10 feet span is supported by four feet tall 4 x 4's, which sit on concrete footing. Seven of which run across the 35 feet front. The house and deck is 3 years old and the patio flooring is constructed of 2 x 6 pressure treated wood. On top of the flooring the seven (plus 1 on the narrow side) 4 x 4's 'continue up' to support the overhang from a truss. The railing and a 'door opening' was in between. No permit is needed where we live.

We planned on adding 8 windows on the long side (360 lbs) and 2 windows on the short side (100 lbs) plus a new door.  We tore out the rails and the new 'pressure treated' framing weighs about 300 lbs (6 lbs per 2x4) and will probably dry out lighter.  The outside and inside OSB which we put up is about 600 lbs. Now, I (the wife) am worried sick about all this weight - worried enough to have my husband concerned.

We also plan to put up tar paper and OSB over the existing flooring for another 600 lbs, plus vinyl sheets or laminate Wood flooring. (max 360 lbs) and outside vinyl siding (maybe 100 lbs) When all would be said and done we might have increased the weight of the structure by 2100 lbs from the previous weight.

Will we need more support (from the ground up) under this 350 sq feet area and if so, suggestions - what and where ?   Any help is greatly appreciated.

ANSWER: Hi Kate, your roof system is already in place and apparently properly supported.  You don't say what kind of floor joists you have or if the joists are supported by beams spanning between the vertical 4x4's.  If anything, I would maybe add a little more support under the walls you are adding the windows and framing to.  But I can't say what kind of support is needed without understanding what kind of beams you have under the perimeter of the deck.  If your perimeter beams are 4x6 and they are supported every five feet then you should be okay.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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QUESTION: HI Bruce, here is how the "previous patio" is still supported:
Single 2 x 8's are running along the 35 foot length (or from left to right). This is repeated every 20 inches across the 10 foot span (width)
Every 8 feet there are TWO  2 x 8s running (next to eachother) from the back (the house) to the front. These are sitting on the 4 x 4's of which we have only 6 and not seven across the 35 feet (the 7th is under the one side of the 36" door opening as kind of an "afterthought" I think. Meanwhile I talked to the builder and he said, well it's o.k the way it is, but if we are worried, we should take some 6 x 6s, put them on concrete footing and space them in between the 4 x 4's around the perimeter where the total of 10 windows are. When my husband called back on how to attach them on top, he said to notch them to accommodate the 2 x 8 which runs the perimeter.

We prefer to hear your answer to make our decision.  Thanks again



ANSWER: Hi again Kate, please look at the attached drawing and let me know if this is the way your deck is built.  I'm sorry but I am not getting the true picture here..sincerely bruce e johnson

---------- FOLLOW-UP ----------

QUESTION: Hi Bruce,
Yes, your drawing is perfect. I am attaching a picture to show the roof  over the patio/future sun room and its weight impact, if any. Also for your info - by mistake I had mailed my original question to another expert. I re-sent it to you and informed the other party of my mistake.

Thank you so much for your time.

Answer
Hi again Kate, If the perimeter (the 35' side) of porch where your new walls and windows are going to sit have a double 2x8 you should be okay.  If not and you can sister another 2x8 under that outside wall it will give you a little more support for the added weight.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com