Is there a better product to replace existing wood sill?
My screened-in porch has the screened section built on a 3ft high cinder block wall with a rough-sawn cedar wood sill and 4×4 posts to support main roof. The wood sill and base of the 4×4 posts have rotted out from years of weather exposure. I have been in house for 25-years, so original design wasn’t too bad. I noticded the water damage a few years ago but didn’t act then, and now it is beyond repair.
So my question is:
Should I just replace the cedar sills and posts with the same materials (and sealing the end-grain of the posts)? Is there a better weather-proof product (like PVC or composite deck boards I can use for the sill?
There are two sills, each 10ft x12″x2″, and 6 posts. The sills are bolted to cinder block wall (which is where rot is) and the 4×4 posts are attached to the sills with standard decking hardware.
I thought about using the composite decking wood-like product for the sills but I have not seen it available in 1-3/4″ (2″) thick and 12″ wide by 10ft.
See pictures for better understanding of my situation. (sorry that some picturers are rotated incorrectly).
Thanks
Replies
It should be noted that standard wood sills can easily last 50 years if properly installed and painted to start with and if properly maintained. Rough-sawn cedar generally doesn't last as long, as it is rarely very well finished.
I'm not going to comment about structural design issues.
To your point, a 2x wood sill should stand up many years if, as another person has suggested, it is properly treated. I don't necessarily recommend using treated lumber, since it can twist and warp over time. Be sure to seal the gap between the sill and the knee wall on the outside. Do everything you can to prevent the accumulation of water beneath the sill.
The better way: remove the knee wall and bolt your sill to the floor. Use pressure treated lumber and fasten it at multiple points to reduce warpage. Be sure to flash properly beneath the sill. It is not difficult to provide temp. support for the roof structure.
Fasten your support posts to the sill using gal. hardware. Now frame knee wall sections between the posts. Consider making your posts from two pieces of 2 x4 pressure treated lumber, firmly screwed together. This will reduce the likelihood of post warpage. You may want to dress up your posts by wrapping them in 1x composite of true wood boards. Leave a small gap between post and wrap. Seal all ends, edges and all faces of the boards
Cap you knee wall with a composite 5/4 trim board, properly sealed and painted. Remember to cut a drip kerf on the outside underside of this cap board. Be sure to prime/paint this cut. You will have to fit your cap board around the posts. The cap board can be made from wood as well, provided it is properly sealed and painted.
In essence you have transferred roof loads directly to the foundation. The rest is "cosmetic". I hope this helps.
Mel
Thanks for the great suggestions.
However, I want to retain the existing kneewall beacuse if I remove it I would need to modify the existing paver decking and have new screen inserts made.
So to keep the existing openings the same size (to reuse screens), I would need to replace the sill (is "sill" the correct term) with same size replacement material (2"x 12" x 10ft).
With that in mind, is there a better sill-wood material I could use (or is the rough-sawn cedar still the best - with proper sealing/painting and matainenance)?
I replied back earlier - but my post is no where to be found. So here's the short version.
First - Thanks for your great suggestions. However I want to keep the kneewall so I can reuse the screen inserts and don't need to mess with patching in addtional pavers.
The other advice is very good and I will use it.
Since I need/want to use 2x on the sill (is "sill" the correct term?) to allow me to reuse screens, is there any product (or different wood speciies) available in 2"x12"x10ft that would be better than the rough-sawn cedar?
-Mike
CB
You may consider 3/4" Azek or some other PVC or composite. Dummy it up to fit the screen openings necessary.
if there's little or no slope to your sill, you can see the long term result. Trapped water causes big problems with most woods over time.
Yep, any sill should be slanted towards the outside. The standard slope is apparently 14 degrees which I work out to be about 2-3/4 inches difference between front and back, for an 11-1/2 inch board. You may not want to be that extreme, but should do an inch or an inch and a half at least.
another option...
http://www.boralamerica.com/TruExterior/products