I am looking for help/info concerning a recently constructed patio and outdoor free standing fireplace.
I live in southern Calif in a high desert area. We had a 30 by 20 foot patio poured next to the house. The contractor dug some footings to hold the patio cover (a free standing wood beam structure) and a barbeque and fireplace. He did not disturb the subsoil as near as I can tell, just poured over the ground after some minor digging to achieve grade. He used 3/8 rebar on 2′ center grid and the concrete was pumped in one pour with a 6.5 bag mix. It looked real good to me.
The fireplace is a free standing custom made masonry construction. Again looked good when he built it. The box is lined with fire brick which seems to be holding up well. Cinder block and brick made up the rest of it with appropriate chimney liner. The fireplace burns well and we are very happy with the performance.
The problem: There seem to be a lot of cracks in the patio. Next to the house there are several radiating at a 90 degree angle from the house and a couple of others that are parallel to the house. Additionally, there are cracks forming a circle around two of the peer footings (there are a total of 9 peer footings for the cover). He cut stress releases in the patio basically cutting a large t in the middle. There was no expansion material next to the house. The cracks to not seem to be shifting yet, but the number concern me.
On the fire place, we started with small fires and on the second fire we noticed hair line cracks opening up in the front of the fireplace just above the opening. They closed up when it cooled and then reappeared at the next fire. Last night we had a party at the house and used the fireplace for 4-5 hours (this was the 6th or 7th fire). By the end of the evening, there were cracks showing up in a pattern I would associate with the block pattern of the submaterial. Also there is a large crack at the base of the structure extending down from the right front corner to the ground. The fireplace has a seat like structure that wraps around both sides and the front. This latest crack is through this seat like structure in line with the face and the right side. The crack is also visible in the rear on the same side. The fireplace is covered with stucco. It looks like two things to me. Expansion because of the heat and shifting in the base (not sure why).
I am concerned and have talked with the builder who has mentioned watching the patio cracks to see if they shift and if so, cutting into it to find out why or if they don’t shift, covering the surface with some thin flexible coating. On the fireplace, he mentioned waiting a couple of months, and after 10-20 fires, recoating the stucco.
Should I be worried and are his suggestions a reasonable course of action?
Thanks for any thoughts in advance.
Bob
Replies
Do you know what type of soil you are on? In preparation for my own upcoming building project I've been reading up on expansive soils.
One thought about covering the patio if cracking gets worse: How about a layer of paving brick laid over the patio on a thin layer of sand? Sice you know there is reinforcement in the slab, dry laid pavers should cover nicely and not show seasonal movement.
I believe hasbeen has been there. So has I.
Expansive soils are quite common in California. But more so near the coast. Up there in the high desert I'm not familar with, but would imagine better drainage capacity. That high desert doesn't seem to have the moisture that would be associated with the expansive soil story.
My discussions with the geologist in S. Orange county (when I bought my "project") led me to understand that cracks caused by expansive soils were more spidery in nature - meaning that they went everywhere without much of a pattern. Our poster describes the cracks in a fashion that suggests (at least to me) that these are more of a heaving or sinking effect of the subsoils. Which further suggests to me insufficient removal of topsoil or inadequate footings. I also wonder about these rebars being on a 2' grid.
Bottomline, my take is the guy: 1, did not remove enough topsoil, 2, failed to provide adequate footings under the loads, 3, probably should have used some fiber in the mix. The 6.5 bag mix also seems overkill for the application. Now I don't know (maybe someone else does), but does concrete become more brittle with the higher mix although it does offer higher compression strength?
Furthermore, I would think the mortar he used in the blockwork of the chimney was the wrong type to be used with the heat being generated. Did he put a scratch coat on the block before putting on the stucco layer?
The solutions being offered would not be acceptable to me. But I've been known to be wrong more than once.
I really like hasbeen's suggestion of the pavers.
Me? If it were mine (and I've got more money than sense), both the patio and fireplace would come completely out. A 2' deep reinforced footing would be poured for the fireplace and I would build up with a matching brick or paver to compliment the new paver patio. I really like those tumbled pavers. I don't care for those wood patio covers. My experience has been that they simply become dinner to drywood termites - even if they are redwood. Them suckers don't seem to care when they get hungry.
Edited 2/9/2003 5:06:13 PM ET by stonefever
I live at 6,200 ft in So Colorado / average 14 inches of precip per year (less in recent years)
My understanding is that it can be the seasonal moisture change that causes the problems. When that happens, even for a short period in winter or spring, it can still cause problems - dry climate or not. Like I said, I'm just reading up now on the topic and maybe I've got it wrong.
Hasbeen;
I am told it is an adobe type soil. When it dries, it is like rock, but when wet, it is slick and mucky. One note to add, just before the cracks in the patio started to appear the builder drilled into a water line under the patio. The line was next to the house where the cracks have appeared.
The problem with paving over the patio is the house is on a slab. The patio sits down about 1.5 to 2 inches below the slab. Covering the patio with anything too think would cause problems with water running into the house.
Don't know if there was a scartch coat under the stucco. I was out of town for that part.
Bob