Patio conversion into home office/living room extension?

[jmcgann333]

Hi all, Jake here. I own a small town home in Davie, Florida and I would like to modify the front patio, but I have questions.

Info: The townhome is on the small side, 900 sq ft living space, 1400 total with both patios. The front patio is approximately 100 sq ft. It is fenced in by a wooden fence typical in association communities.

Goal: My goal is to remove the sliding glass doors, remove the small window in the kitchen that overlooks the small patio and open up the kitchen by doing so ( kitchen is very small with only one entrance) , put up two walls and roofing to enclose it, run electricity to the walls, go over the concrete slab with appropriate flooring preparation and final flooring. ( probably tile to match the house).

I checked with the assocation and they say other tenants in the community have done something similar so permission shouldn't be too much of a problem.

Question: How can I estimate what this will cost me. Online constrution calculators seem to over estimate the project, assuming the concrete slab needs to be laid with excavation performed, etc...

Thanks in advance,
Jake.

[grumpydasmurf]

My first question is will your association allow this? Typically they will not. Let's assume they do though...

How thick is the patio slab? Is it anchored to your foundation? You may need to repour the slab to meet code.

Are you planning on doing this yourself? I can help you bid out the roof and walls and most of the exterior detail but need to know some measurements.

I assume roofing shingles... Basically a square of roofing shingles will cost you about $35 at the low end. Figure another $10 per square for underlayments nails etc... A square is a term meaning 100 sq ft.

I assume vinyl siding for your walls... a square of materials will cost about $45. With trims and tyvek everythign expect to pay $70 for materials.

Don't forget backing board, typically 1/2" CDX plywood. 3 sheets per square. $45 per sheet.

To figure out your use of wood, for the wall studs, first figure how high the addition will be. Let's assume 10'. Next you'll need to know how far apart you will space your studs. Let's assume 16" oc. Take the length of the wall, let's say 12', and convert that to inches by multiplying by 12. We have 144" of wall. Divide that by 16 since we are spacing your studs every 16". Multiply that number by 10'. This is how much woods you will need for framing that wall.

Roof framing is also basically the same, unless you plan to frame a hip roof, which will be different math. Let's assume a gable roof. A gable roof has two sides. Again figure your rafter length as you would your stud height. Figure your spacing, usually 16 oc. and follow the same math as you did with the wall framing.

Note: when joining the new roof to the existing wall, the flashing is critical and this is a COMMON area for additions to leak. Pay special attention to this junction. Also the same goes for where the new walls meet the existing walls. It is common to remove existing material to tie everything together so don't forget too add this material to your estimate. And... And.... And... No matter what numbers you figure always add 10-20% for error and waste. Don't forget permit costs.

[grumpydasmurf]

Oh yeah I forgot to mention I've never built an addition, but have done plenty of dormers and this is the math I use when figuring my dormer prices.

[Rich]

I have a few basic calculators that will figure the SF of your roof, interior and exterior framing, and a few other ones. They don't give you labor costs (except for the concrete ones) but they will give you an idea of quanitity of material. Most of the items that Grumpy talked about can be priced through your LHS. The one mistake I see in Grumpys' math is you need to add one stud to each wall when taking off that way. Not that one stud is that big of a deal...haha. Besides that - Grumpy gave some excellent advice. Let us know if you have more questions.

[grumpydasmurf]

I forgot the bottom plate also, if home construction uses that. I know garages do, and could think of no other way to fasten studs to a concrete floor.

[Rich]

Yep bottom plates are used. Also remember that any wood in contact with concrete should be pressure treated. So you could use a pressure treated bottom plate in place of a typical bottom plate.

[jmcgann333]

A neighbor two houses down from me has done the same thing. I have also contacted the association and was told that I could do it, assuming all permits were obtained. I won't be doing the work myself. My goal is to obtain a realistic estimate from a professional and request a home equity loan for funds.

[TROWLER]

Yep bottom plates are used. Also remember that any wood in contact with concrete should be pressure treated. So you could use a pressure treated bottom plate in place of a typical bottom plate.


if you walls are sitting on a slab, ya have to use pressure treated, otherwise the chemicals in the concrete will slowy errode the wood, and leaks and drafts will be likly