what exactly should construction drawings contain?

MizMix

Is this clean cut with regard to what should be included? We've had numerous builders maintain our architect has not provided adequate detail- two in fact so far have backed out of building our house- one has cited this reason and another had a different reason (but we feel it was just an excuse). We also had a builder decline to price it based on the detail.

Is there specific guidelines as to what should be there to A- price a job sufficiently and B- actually build the price. Is it normal to make numerous additions and changes just before building is due to commence (on a house that was due to start months back, and went through numerous planning appeals- so time was not an issue) ? And give the builder a really hard time for asking for these costs to be covered?

Gumbo

MizMix wrote: »

Is this clean cut with regard to what should be included? We've had numerous builders maintain our architect has not provided adequate detail- two in fact so far have backed out of building our house- one has cited this reason and another had a different reason (but we feel it was just an excuse). We also had a builder decline to price it based on the detail.

Is there specific guidelines as to what should be there to A- price a job sufficiently and B- actually build the price. Is it normal to make numerous additions and changes just before building is due to commence (on a house that was due to start months back, and went through numerous planning appeals- so time was not an issue) ? And give the builder a really hard time for asking for these costs to be covered?

Ground conditions. Depth of foundation. Depth of SR21 compliant fill material and what grades to what depth (T1-T4 etc). Concrete mix, reinforcement in foundation with depths and width.

Thickness of floor slab and what reinforcement.
What air tightness level are you hoping to achieve?
Air tightness membrane, which one and where is it location with regards to wall and insulation. Cavity, internal or mix?


Post up a sample of one of your drawings.

MizMix

I'll probably delete this shortly (possibly paranoid but still)...the spec re the floor slab etc seems fine. Airtightness detailing is pretty much non existent (looked like a copy and paste job)- even though I explained it was important to us to well exceed regs he said he thinks we're crazy and just added in to include an added extra if they can exceed regs....no detail behind it. No mention of detailing around the membrane, location etc. I think being honest we know the answer, we've lost two builders so now it's just where to go from here to make it right. Now we know more I can't see how we're not wide open to being landed with loads of extras mid build as they were not specified.

Thank you

mrsWhippy

MizMix wrote: »

I'll probably delete this shortly (possibly paranoid but still)...the spec re the floor slab etc seems fine. Airtightness detailing is pretty much non existent (looked like a copy and paste job)- even though I explained it was important to us to well exceed regs he said he thinks we're crazy and just added in to include an added extra if they can exceed regs....no detail behind it. No mention of detailing around the membrane, location etc. I think being honest we know the answer, we've lost two builders so now it's just where to go from here to make it right. Now we know more I can't see how we're not wide open to being landed with loads of extras mid build as they were not specified.

Thank you

It's highly unlikely you're going to exceed airtightness regs if the junction details are not included. As far as I know it's one of those things that needs to be explicitly detailed, and managed, in order to get right.

MizMix

That's true but the builder we had appointed was extremely experienced in this area- one of the reasons we appointed him was in hope he would fill in the gaps here. The last straw for him backing out revolved around a dispute over an extra fee to exceed regs

ht9zni1gs28crp

Its a subject that I feel a lot of people who start building aren't paying enough attention to so you are right to raise the question now.

Read Kceire's post above, all those as a standard need to be included in a set of detailed construction drawings. That way both you and the builder are on the same hymn sheet. The more details the better, a lot of people will back out of the detail package to save costs but I guarantee you it will save a lot more than it costs later on down the build, let alone time and decision making. Plus a prelimnary DEAP package would set your 'reg's target a lot clearer...

sydthebeat

Prelim DEAP report is an absolute necessity.
Its actually impossible to say your build complies with B Regs without it.

after that our standard package would include:
*foundation general arrangement and details
*floor general arrangement plans
*elevational drawings showing treatments and finished detail ie downpipes, svps, vents etc
*window schedule
*sections as necessary to describe construction / heights / levels etc
*scaled up structural details as necessary ie rising walls, jams, lintels heads, floor junctions etc inclusive of air tightness detailing
*detailed drawings of individual elements as necessary ie if a bespoke fire place arrangement etc
*fully detailed word document specification describing all construction process and materials, health and safety requirements, standard contract requirement etc

there are other standards out there, not helped by the very vague "building regulation compliant" description of documents required at commencement notice stage.

MizMix

Thank you. re air tightness I mentioned sigma and pro clima to him (based on some research but I'm far from an expert). In the spec a radon membrane is mentioned (monarflex or something like that)...is that the same or for something different?

Gumbo

MizMix wrote: »

Thank you. re air tightness I mentioned sigma and pro clima to him (based on some research but I'm far from an expert). In the spec a radon membrane is mentioned (monarflex or something like that)...is that the same or for something different?

Totally different. That goes under the floor,slab to stop any radon gases entering the home.

JonathonS

Did you have a QS? A QS schedule is the only way to ensure that every item required to build is listed and costed.

Fayre

Are you going to have an engineer? I think you will probably need one as well as the architect. After we got planning an engineer took the drawings my arch tech did and added great detail to them to make them into construction drawings before we went to tender. Never had any builder say there wasn't enough detail on them.
Maybe an engineer is the missing link here?

MizMix

I think you're right Fayre. We have another builder pricing the job and he asked for engineering drawings.....mmmm we don't have any. So maybe that's our oversight as we presumed our architects construction drawings would include all the detail. This builder did say some areas were light on detail (we also spotted some 'mistakes' which have been rectified) but he's seen drawings even lighter on detail so he's not overly concerned. Re air tightness I don't think our architect is up to speed with best practice at all.

Fayre

MizMix I've had air tightness done on my house and it's basically air tight tape around teh windows, an airtight membrane over the ceiling of the FF and special white plastic dome things around the spots in the FF ceiling. No expert here but that is the bare bones of it

mrsWhippy

Fayre wrote: »

MizMix I've had air tightness done on my house and it's basically air tight tape around teh windows, an airtight membrane over the ceiling of the FF and special white plastic dome things around the spots in the FF ceiling. No expert here but that is the bare bones of it

To be fair, I think there is a lot more to it than that. Details around junctions, windows, proper plaster coats etc need to be specified. It might be straightforward to an airtightness professional, but perhaps not to a 'regular' builder who hasn't dealt with this stuff before and needs the guidelines. What airtightness value did you get?

MizMix

He hadn't even specified a membrane or brand of tapes etc but we have rectified that in the past few dats. That's my thoughts- we're choosing a builder who has a track record of exceeding regulations regarding air tightness. Based on that we assume they can fill in the gaps and discuss details around junctions etc.

mrsWhippy

MizMix wrote: »

He hadn't even specified a membrane or brand of tapes etc but we have rectified that in the past few dats. That's my thoughts- we're choosing a builder who has a track record of exceeding regulations regarding air tightness. Based on that we assume they can fill in the gaps and discuss details around junctions etc.

Yeah, that's what we're planning to do as well. But we're also going to ensure that these details are all included in the construction drawings so we can be 100% sure what we're paying for. I wonder is it possible to put 'airtightness expectations' in the contract with the builder?

MizMix

Yes Mrs Whippy, we've added a specific target now. When we went to tender early summer our architect put in a general additional cost to 'exceed regs' and it was up to the builder to opt in or not. Our architect as convinced we wouldn't get a builder willing or capable of exceeding regs (which was ridiculous but at the time we accepted his opinion on it)....in the last six months from speaking to builders locally so many have upped their game here, guys that were just meeting regs are now well exceeding them.

Calahonda52

It is truly demoralising to read this thread and see the lack of preparedness for what is, for most people, the most expensive spend in their lives.

Re
he's seen drawings even lighter on detail so he's not overly concerned

Why would he be concerned: he has free reign here for material specification, detailing, airtightness, insulation requirements, etc as well as
carte blanche to charge what he likes for extras.

Its like an employment contract where all that is signed is a page with the employers name and the employees signature and the employer can do what he likes for working conditions, rates of pay, duties and responsibilities etc.

Good luck.

MizMix

Insulation materials, cavity etc have all been specified to a T. We've reviewed and specified the airtightness system etc...I've specified the air to water system (7kw), MHRV. At times pushing against a wall (e.g. MHRV- why would you bother?) but we've gotten there (or almost). We chose this architect 6 years ago...planning took us that long. If it was now we would identify his lack of knowledge around airtightness right away- 6 years ago, we didn't know any better and the industry has changed too.

I also paid a well known energy consultant for a preliminary PHPP so it's not totally lacking in details...but most have been provided or reviewed by us based on our own research and not the architects.

Since I originally posted- we've added more details we felt we missing. The fact that I'm posting here for advise on what we should get for 'construction drawings' shows we're not taking things lightly and his word on things. I'm doing my homework as best as I can as someone outside the industry.

My feeling is best to close these gaps now before breaking ground but thank you for your constructive feedback. As self builders (not industry experts) there is a reason some of us post here- it's to be educated and get advise.

tradesman

At the end of the day the builder should only build to what is on the drawings supplied to him / her. If they were to deviate from the drawings then they are breaking their contract with the homeowner which could have very serious implications all round. Therefore whoever is supplying the drawings should specify everything required. If they are not up to structural issues then they should employ / subcontract someone to do those details but overall IMO they were contracted to supply the homeowner with drawings so they can build the house they want. Too many builders take this on their shoulders and build to what is required but they should get the homeowner to supply them with full specified drawings.

MizMix

Thanks tradesman- that makes sense. If they don't have those skills in house (which we presumed they did) that they outsource. He is completely defensive of the plans as being detailed enough. Too much ambiguity which no doubt leaves us wide open to extras. I think we've covered a lot off the last two weeks but it shouldn't be such a struggle.

Dardania

MizMix wrote: »

Thanks tradesman- that makes sense.  If they don't have those skills in house (which we presumed they did) that they outsource.  He is completely defensive of the plans as being detailed enough.  Too much ambiguity which no doubt leaves us wide open to extras.  I think we've covered a lot off the last two weeks but it shouldn't be such a struggle.

The architect is a contractor to you, just like the builder will. It is in bother their incentives to do as little as possible, for as much money as possible. Of course they're defending the plans you received

mrsWhippy

When I got the quote from my architect, it was very clear cut.

We paid X euro for Planning drawings, and then another X euro for Construction drawings.

It is these drawings that are going to the QS to create the bill of quantities, and then that and the construction drawings making up the tender pack to go to builders. There should be absolutely no ambiguity anywhere - all details, materials and finishes specified in the drawings and then listed for the builders to cost.

Do you have a quantity surveyor on board? I doubt he could put together a BoQ if the drawings weren't detailed enough .... and if he can't do that, then I don't know how a builder could come up with a reasonable and fair quote either.

JonathonS

mrsWhippy wrote: »

Do you have a quantity surveyor on board? I doubt he could put together a BoQ if the drawings weren't detailed enough .... and if he can't do that, then I don't know how a builder could come up with a reasonable and fair quote either.

Precisely.

MizMix

Our (last) builder used a QS....it was only when they backed out they told us the drawings were basically rubbish. 'Nice design' but so much room for ambiguity.

We met another builder yesterday who had the same concerns...stuff like 'as per manufacturers spec' throughout. We have a type of tile on the chimney- no instructions on how to fix them etc. He is the 3rd builder to say to use the foundations appear over specified (Much wider than normal).

We're getting a 2nd professional opinion on the plans next week before we go further.

Mrswhippy- we did agree this also and he has been paid in full for construction drawings as we believed this is what we got.