I recently received a specification and plan from an engineer (specification) and architect (plan) for a concrete slab that the company I work for is wanting to tender for.
My initial reaction was that both the plan and specification were of an unacceptable quality.
I told them both this. The architect has since redone the plan and it is now of a much higher quality but here is his initial plan:
The engineer has not redone his specification and says it is fine and not being a civil engineer like him I could not expect to understand it.
Here is the engineer's specification:
i) Slab is to be 30cm thick.
ii) Concrete strength must be a minimum of 30MPa on the 28th day of curing.
iii) Coarse aggregate is 22mm in size and must pass a laboratory test based on ACI codes or other international standards.
iv) Fine aggregates must be washed and conform to ACI codes or other international standards.
v) Mixed design is required.
vi) Soil must be compacted and pass the Field Density Test.
vii) Backfill materials must be subjected to a Dry Density Test.
viii) Rebars must be a commercial standard size.
ix) Tie wire must be #18.
I have grave concerns at the lack of detail contained in the specification. I also have concerns about the design.
The slab is for a workshop where a 200 tonne crane will operate.
What do you think of the specification and plan as something a contractor could work from? Marks out of 10 please.
What do you think of the design?
Please bear in mind that neither the architect nor the engineer have English as their first language so please ignore any typos.
it looks alright to me ted apart from the rebar laying at the bottom of the crete
the deepest i have ever had to lay concrete was 225 and that was in an industrial unit.
i would have thought a 200tonne crane would have 4 pads sunk maybe 3 metres each into the ground?
but i am no engineers
marks out of 10
7
Would sink piles then put in a cage with proper anchors. is it a tower crane or overhead gantry crane Ted? if its for a gantry then a thicker slab a metre thick with a cage with steel top and bottom with links, z bars etc. plenty of cover on the steelwork.
One critical error is that the plan says the crete is to be 25cm thick and the spec says 30cm thick. Whilst I was able to see and understand the error - the covering is part of the slab - a layman might not.
Also, no DPM is included... is this normal.... the engineer says it is unnecessary?
IMO the spec is a sorry bit of paper which says little more than that the materials will be of an acceptable quality.
I would have included a basic Schedule of Works, ensured the plan agreed with the spec (it does not although it is hard to see on the above copy), provided structural calculations as an appendix and padded it out with a bit more spiel!
To me, the spec reads as a direct copy of a generic spec from a textbook and not a specific specification (the words have the same root) for a particular project. In other words, the engineer is covering his/her arse by being as vague as is possible without actually revealing the fact that their knowledge is very limited.
Tony McC wrote:To me, the spec reads as a direct copy of a generic spec from a textbook and not a specific specification (the words have the same root) for a particular project. In other words, the engineer is covering his/her arse by being as vague as is possible without actually revealing the fact that their knowledge is very limited.
I have printed out this response and put it on my noticeboard as a warning to architects and engineers not to give me substandard work!
love it! With the loading I would have insisted on more reinforcement as sean suggests. DPC is always a god idea as it can retain mixture in the crete to stop it drying out too quick. Just as a matter of interest some eejit in nigeria is trying to get me involved in a university build...but all monies are to be directed through some spanish account...must think I'm greener than grass..
general builder, maintenance engineer, gas and plumbing installations, extensions etc
