Builder cut 4.5 off joists due to measurement screw up

LozM · 24 Aug 2021

Having a 2 storey extension done, builders haphazardly measured the floor level and despite saying better to come in under as better to make up height when they knocked through new floor level was good chunk higher - why they didn't knock a pilot hole through despite suggesting it is a mystery. The second storey and roof is now on and last week whilst I was away they laid new floor, didn't realise just how much higher the new joists were. The structural engineer had specified 44x195 C24 ceiling joists @ 400mm c/c. Looks like they have used 8 inch joists a block width apart, to get the floor lower they have cut about 4.5 cm off the joists so the remaining joists are about 17 cm, obviously going to be a nightmare to rectify now, looking at span charts online they are too small. There is an ensuite and main bedroom going in that room. Here are some pictures :

Would have been so easy to have come one small brick lower had they measured correctly, annoyingly didn't look the other way to see if joists are resting directly on steel on the other end, very frustrating, what would people recommend in this situation ?

Many thanks,

Lawrence

tony1851 · 24 Aug 2021

If they take the central blocking pieces out and sister the joist with 6 x 2 that should stiffen the floor. The sister-joists don't have to bear onto the wall or steel, they can stop short a few inches.

JP_ · 24 Aug 2021

I'd call building control and tell them it looks like they've cut the joists in half and can they come to check it's OK.

LozM · 24 Aug 2021

tony1851 said:
If they take the central blocking pieces out and sister the joist with 6 x 2 that should stiffen the floor. The sister-joists don't have to bear onto the wall or steel, they can stop short a few inches.

Uncanny ! - just had a very good chat with structural engineer on phone, all previous meetings had been on site with builder present, he ran the measurements and fails the deflection check, he recommended removing the noggins, then screwing/bolting another 170 joist to existing joist cut tight to wall and then putting back trimmed noggins - seems a good solution as doesn't need any block work just additional timber and labour that I will inevitably pay for somewhere else in the build. Can't picture the other end on the steel as not there at moment and can't remember if joists rest directly on steel, think there is at least one layer of bricks , now have SE on my side can approach builder and see where we go.

Geat forum,

Many thanks,

Lawrence

jeds · 24 Aug 2021

LozM said:
cut tight to wall

Don't do that, leave an 8mm gap. Any expansion would easily displace a block.

catlad · 24 Aug 2021

Lol ! Are you telling me they have cut nearly 2" off that floor in situ because they couldn't be arsed measuring properly?

LozM · 24 Aug 2021

catlad said:
Lol ! Are you telling me they have cut nearly 2" off that floor in situ because they couldn't be arsed measuring properly?

Yep, they never can hold a tape straight, he even said better to come in under as easy to make height up yet due to poor measuring ended up almost 5cm too high, had similar problems elsewhere - incredible thing is they just create extra work for themselves whereas a few mins on measuring could all be avoided, dreading the conversation tomorrow,

Lawrence

catlad · 24 Aug 2021

More worrying is the fact they didn't bother strengthening the floor afterwards.

LozM · 24 Aug 2021

jeds said:
Don't do that, leave an 8mm gap. Any expansion would easily displace a block.

Thats interesting and never occurred to me, the SE said to cut it tight to wall - will double check,

Many thanks,

Lawrence

tony1851 · 24 Aug 2021

LozM said:
Thats interesting and never occurred to me, the SE said to cut it tight to wall - will double check,

Many thanks,

Lawrence

The SE you had a chat with correctly advised that deflection was the issue. However, if you sister the joists, you just don't need to take them right to the end of the span - the only issue at the end of the joist is shear stress, and the remaining cut-down section will be fine for resisting shear.

[A little structures lesson; if you look at old steel railway bridges with built-up girders made from lengths of steel plate, you may see that there are more bottom plates near the middle of the span and fewer towards the ends of the span (in the old days,it was called 'plate curtailment'). It's just a way of showing that you don't usually need as much material at the end as you do in the middle! Here endeth the lesson].

Dereekoo · 24 Aug 2021

So Lawrence which site did you get the best advice from, here or Screwfix

Notch7 · 24 Aug 2021

LozM said:
Yep, they never can hold a tape straight, he even said better to come in under as easy to make height up yet due to poor measuring ended up almost 5cm too high, had similar problems elsewhere - incredible thing is they just create extra work for themselves whereas a few mins on measuring could all be avoided, dreading the conversation tomorrow,

Lawrence

schoolboy error

why didn’t the builders just cut through the joists close to the wall….bolt on a wall plate then fit the joists back with jiffy hangers.

would’ve been less work than cutting them all down.

LozM · 25 Aug 2021

Meeting builder on site this morning- dreading it ! Have quite a few questions to ask and will try and get SE there today as well as seems need to look closely how straight they cut sections off, ask if they used glue on the boards and checking how far sister joists need to go, how they should be joined and how much gap can be left at ends. Personally would prefer them to cut new pockets and use new joists but probably dreaming with this builder.

Lawrence

A Trowel · 26 Aug 2021

Dereekoo said:
So Lawrence which site did you get the best advice from, here or Screwfix

Obviously not Screwfix

Harry Bloomfield · 26 Aug 2021

Notch7 said:
would’ve been less work than cutting them all down.

The cutting down would have been a tremendous amount of work.

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Builder cut 4.5 off joists due to measurement screw up

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