Laying Up Stone Wall. Part 4.

[Greg Mitchell]

Gents,Comparative pics of same section laid up. Undressed and dressed off (scratched out and brushed.)I hope this is good enough to get those of you who are keen started.Take your time, bend your knees and have fun. Good luck with your projects.[]Best regards,Mitch.Image Insert: 46.68 KBImage Insert: 58.33 KBImage Insert: 67.72 KB

[NiqueNaque]

Greg,Thank you for your informative screed, it is nice of you to share it.With the damp course in the photo immediately above are you having a floor line above this?Cheers,Nick.

[Greg Mitchell]

G'Day Nick,That's what it's all about, sharing info and experiences. I've got a question or two for you which you might be able to help with. The foundation walls and slab with mine are at the same finished level. The damp course extends by 1" into interior and floor line is at this level. Suggestions based on possible slate tiles, battened raised floating timber floor or carpet.Nick foundation walls were constructed on footings, then infill panels packed in, plastic laid and meshed up. There were extentions to the footings ( stiffening beams) that got poured in situ with the 100mm slab. Naughty I know but the slab was only bull float finished not coptered like the workshop. Anyway, there are some cracks that I need to fill to keep the weather out. Most of these cracks are in the area of the deeper stiffening beams, though the often transition across slab areas as well. I've been using solution of water and bond crete for the fine cracks and full strength on the wider crack (the one that bothers me)of 1.5mm at it's point of origin, which is directly in a corner over a deep poured stiffening beam. Travels about 1.7 mts toward middle of slab ends in a fine line. The floor slab and stiffening beams are all tied to the original foundations and there is no movement there that I have observed. What you reckon Nick?Any concretors out there can help? Mitch.www.thebutterflyllc.com

[NiqueNaque]

Greg,Photos please... specific cross sectional detail would also help for the area of concern.Bull float is not a problem, helps with adhesion/keying if you are tiling.What slab sizes are we talking about here? Did you cut control joints in a day or so after you poured the slab?Sounds to me like your concrete went off and dried too quickly or you had a cold snap shortly after or when you put the concrete down. We get problems like this in the big freezers that we do a floating slab on, ie, concrete base, styrene slab and then concrete slab on top for insulated construction. When we start up the freezers we have to pull the temp down very gradually or the concrete cracks, much like you are saying. If your temps dropped quickly overnight this probably caused it.Wait for your reply.nick.

[asra]

Howdy MitchMitch,there are a lot of stone masons around here that do very nice work as a trade.The work you do with stone is by far better looking than most I have seen and most of them are clients I work for.Keep up the superb job.CheersSonnyIntelligence is not a privilege,it is a gift and should be used for the good of mankind.

[Brian]

Sonnyi, I dont know anyone who has constructed a house like Greg is building but, I do know this, I havent seen a better looking job done anywhere !!!! What a pity about the concrete slab giving trouble Greg. Sorry I'm unable to help with any constructive comments.BrianYou never know how far you can go, till you get there !

[asra]

Yep me too Brian,just wish I could be there to help digim out.Cheers SonnyIntelligence is not a privilege,it is a gift and should be used for the good of mankind.

[Greg Mitchell]

G'Day Gents,The cracks in slab are not a major problem but annoying and not uncommon. Nick is probably correct, slab may have gone off too quick and followed by a cold snap. Anyway I appreciate your kind words. I'm posting some pics of the main crack which starts in a corner at the base of a wall which sits on foundation wall (internal). Directly beneath this is a stiffening beam about 1200mm deep that was poured in situ with slab. (Shrinkage, possible causative factor). The crack then transitions across the slab thickness of 100mm.I have brushed slurry of water and bond crete into cracks previuosly. The last dressing I injected full strength BC into cracks. Dries to a translucent golden yellow colour, very hard. After rain it returns to its white colour and appears to become flexable in the joint with the moisture added.I need to measure crack at widest point (est 1.5mm) and monitor for movement between this winters wet and next summers dry.Please advise Nick or others as to suggested fixes or repairs if deemed necessary.Also pic of wall after three part days and evenings work. The last pic shows how the current wall will be finished off to take the concrete widow sills and timber sill plates for jamming windows.See ya soon Sonny ole mate. All my papers are in order, everything paid for. Looking forward to the visit.Mitch.Image Insert: 70.47 KBImage Insert: 84.56 KBImage Insert: 64.96 KBImage Insert: 66.68 KBImage Insert: 64.07 KBFly Safe[]www.thebutterflyllc.com

[NiqueNaque]

Greg,With a slab 100 mm thick hanging of a 1200 deep beam you don't have much hope of containing things from moving if they want to, the 100 slab just wont cut it in terms of strength, in such cases I believe cracking is inevitable. My guess is this beam goes around a 90 bend away from the crack and there is a fair distance along to the end of if from the crack. Shrinkage is most likely the main culprit if everything was done in one pour. When raft slabs are done in the circumstance you have they usually float on the beams or are poured later to avoid cracking of this nature, especially when the beams are so deep - do you have boggy ground there? It's the only reason I can think you would need such deep footings, ah, apart that is from earthquake proofing.Was the slab poured on fill?Do the engineers details specify that the beams and the slab had to be poured together?Did the engineer specify that you had to cut control joints into the slab?What control mesh was specified for the slab - say 200 x 200 x 8?I would suggest, seeing as I have no idea of the ground conditions there, that you call on your engineer to give you some guidance on what to do with the crack. What it will amount to is an irritant if you lay tiles over it as it will keep on cracking along that line and any tiles / slate bonded over the joint will crack as well unless you use a rubber based adhesive compound (recommended anyway), then the grout cracks and becomes an issue. If you have a floating timber floor the crack will be a highway for the ants to get into your house (yes, the little black buggers, not termites as you allegedly have none in Tas.) from the sub floor spaces under the slab, obviously a floating timber floor will be a good cover up for the crack and is unlikely to be affected by the crack.Hope this helps..Cheers,Nick.

[NiqueNaque]

I'll add that the masonry is exquisite, well done greg.

[Greg Mitchell]

Thanks Nick,I'll try and dig up some old pics of the foundations laid open prior to the infilling and slab pour. These show the steel reinforcement bars, that had to be left proud (extending out from) the original footing pour. Once the foundation walls were built to slab level to contain the concrete pour the stiffening beams would tie to the footings, (same depth and level, width ect.)I tend to agree 1200mm of conc is going off at a different rate to 100mm and shrinkage becomes a problem. Along with not curing a slab correctly.One of the things most noticeable in grouted stone walls is the fine shrinkage cracks (hairline) that will appear overtime if the joints are very wide and if the mortar was too wet when laid.Engineers didn't want to know about a stone house from day one. Also the site has 72mm of shrinkage and expansion between wet and dry, footings have been taken down to engineers specs.There are no cracks in any of the walls and the crack is not major, so I'll monitor for now. I recollect the mesh was F92, the steel top and bottom in footings was Y 12, 4 bar and starter bars from footing to slab were 12mm deform bar. I dont think it's going anywhere but I dont like seeing cracks of any kind.A mate emailed me and suggested rubber based sealing paint, think I'll throw down a coat try and keep water off it this winter.I like the idea of slate right through, that way you can just hose the joint out, the girl wants carpet in the bedrooms and floating timber in the living areas is high on her list.Thanks for your help Nick.Cheers,Mitch.www.thebutterflyllc.com

[NiqueNaque]

Greg,Most welcome.Nick.