Posh loft conversion

[semene]

Hi All,

I am just having a "posh" loft conversion done by a polish builder , he has used 9 x3 to span 4.2m wall to wall then 6 x 2 from the 9x3 on the internal load bearing wall. He has removed the old (I think he said it was binders or blinder) and put it behind the new 9x3 and joined them together with some bolts . The entire new floor is about 1 inch off the old ceiling rafter.

He currently boarding over the top with chipboard

what I want to know is, is this safe as nothing is supporting the 9 x3 wooden beams i.e no wall underneath or steel, if we put too much load on it would it not snap the 9x3's? he says it is safe but if we really want can stick some wood under the new 9x3 beam so that it can touch the old rafters.

 

[JohnD]

Very odd that the 9x3 is not supported, if that's really what you mean. Surely it is fixed to the walls at each end, in some way? Is it in accordance with the plans approved by Building Control?

The BCO is likely to visit during the build, it is useful to discuss with her anything you are concerned about.

 

[freddiemercurystwin]

In addition to Johns comments, what do the structural engineers drawings show? There are structural engineers drawings aren't there?

 

[RonnyRaygun]

I would say the 9x3 would be undersized if spanning 4.2m and carrying floor load, and presumably a dwarf wall at least. What is the span of the 6x2s? But as Freddy says, there should be a set of drawings the builder is working from - you won't get building regs sign off without SE input.

 

[chappers]

I would say the 9x3 would be undersized if spanning 4.2m and carrying floor load, and presumably a dwarf wall at least. What is the span of the 6x2s? But as Freddy says, there should be a set of drawings the builder is working from - you won't get building regs sign off without SE input.

Come on Ronny stop being diplomatic, you know that that 9x3 isn't sufficient, I presume he has backed it out with the old binder as he is going to sit 4x2s on top to form the purlin wall.
Many years ago I did a loft conversion where timber beams were speced, from memory 3 9x2s with flitch plates.
The only other time was a huge plywood sandwich structure, which we had to ditch in favour of steels as the stupid woman hadn't taken account of the escape velux, which was part of the regs at the time

To the OP, it is perfectly normal and advisable for the new floor structure to be independent of the old ceiling ties, for that is what they are, they will never have been designed to take any weight other than the weight of the ceiling, their main purpose is to stop the rafters spreading.

When you say a "posh" loft conversion, do you mean not a loft conversion but a posh boarding out job? I would call a posh loft conversion something with a marble bathroom, gold taps, an oak staircase and a fully leaded roof.
My guess is he has also removed supports that were running from the purlin to the spine wall too, these prevent sag in the purlin and ultimately the roof, if he has and is intending to build a purlin wall off of that 9x3 then that is an extra load imposed upon it too.
We won't even mention the fact that the new purlin wall might not be supporting the roof rafters at the correct point either.
As others have said has there been any input from a structural engineer.

 

[^woody^]

I am just having a "posh" loft conversion done by a polish builder

No you're not.

Two things,
1 What do the approved plans say?
2 What does the building inspector say?

 

[tony1851]

The new 9x3 doesn't physically have to go into the wall, as long as it is securely bolted to the existing beam behind it. There will only be
shear at the end of the existing beam, and with only floor loading, it could well be ok.

The Polish builders often come up with solutions that are not 'by the book', but that doesn't necessarily mean that the structure is inadequate.

 

[semene]

he has just arrived about 20 mins ago and I have just asked him the following question.

Very odd that the 9x3 is not supported, if that's really what you mean. Surely it is fixed to the walls at each end, in some way? Is it in accordance with the plans approved by Building Control?

He has put the 9 x 3 in the wall at both ends i.e into the brickwork , he has then used the old binder behind 9x3 to reinforce it.
He has only removed the blinder , the purlins were not connected to the floor before, the entire purlins are on brick coming out from the wall (Apparently thats how they did it the old days).

I would say the 9x3 would be undersized if spanning 4.2m and carrying floor load, and presumably a dwarf wall at least. What is the span of the 6x2s? But as Freddy says, there should be a set of drawings the builder is working from - you won't get building regs sign off without SE input.

The span of the 6 x2 is 2.3m on one side and 2.4m on the other side

In addition to Johns comments, what do the structural engineers drawings show? There are structural engineers drawings aren't there?

no drawing he just working from this head , he say he has done this many times before and he said it is safe .


He just said if we are worried he can put the wood under the 9x3 so that the old ceiling rafters are touching the 9x3 i.e removing the 1inch or so gap, kind like what was there before with the binder.
he said if the 9x 3 bows , it then would spread the load across the old ceiling rafters in the load bearing walls but he said we don't need to do this.

 

[tony1851]

The BCO is likely to visit during the build, it is useful to discuss with her anything you are concerned about.

Are there no male building inspectors nowadays?

 

[JohnD]

Semene, just to check, am I right in understanding from what you say:

There are no plans
There are no engineering drawings or calculations
There is no Building Regulations approval
There is no BCO inspection
?

 

[tony1851]

If the beams are only supporting a floor, and are clear of the existing ceiling (which appears to be the case), the only issue might be excessive deflection/bounce but that is not a structural matter.
Bear in mind that in lofts, the floor is rarely loaded to the usual 1.5 kN/m² over the whole floor because of the low headroom near the eaves.
What may be more important is that the OP has not mentioned any input from Building Control; no Building Control = no certificate = problems when selling.

 

[semene]

Semene, just to check, am I right in understanding from what you say:

There are no plans
There are no engineering drawings
There is no Building Regulations approval
There is no BCO inspection
?

correct, that loft is just going to be used as office no stairs just pull down ones

 

[semene]

If the beams are only supporting a floor, and are clear of the existing ceiling (which appears to be the case), the only issue might be excessive deflection/bounce but that is not a structural matter.
Bear in mind that in lofts, the floor is rarely loaded to the usual 1.5 kN/m² over the whole floor because of the low headroom near the eaves.
What may be more important is that the OP has not mentioned any input from Building Control; no Building Control = no certificate = problems when selling.

Should we still ask him to put anything under the 9x3?

 

[bernardgreen]

You may have put yourself into a very difficult, and possibly hazardous situation. To resolve it you MUST get a structural engineer involved.

Hangers, in conjunction with a longitudinal binder running at right angles to the joists, are used to help hold the ceiling up. Each hanger is nailed between the every fourth (or so) rafters and the joist below. The larger the joists size, the less likely there will be a need for hangers.

Collars, ridge collars and/or collars further down the rafters, are sometimes used to provide additional binding between the rafters on both sides of the roof. Where used, they are usually fixed to an occasional pair of rafters along the roof.

No part of a timber roof should ever be cut, modified, remove or the covering of the roof changed (i.e. replacing a slate roof covering by a concrete tile covering) without consulting a structural engineer.

Two horror stories following roof work....

The loft of a building near here was converted a couple of years ago by "experienced carpenters" from an Eastern European country. Emergency repairs had to be carried out when cracks began to appear a few months later. It is still being debated by structural engineers if the roof can be saved by adding more braciing or will have to be removed and completely rebuilt. Insurance company say that as the the original work did not have any input from a qualified structural engineer they are not bound to pay any claim for the emergency repairs or the re-build. The carpenters cannot be contacted,

Modifications to the roof of an ancient stone cottage that were completed without any input from a structural engineer resulted in the walls being pushed outwards as the roof tried to flatten out. Steel tie rods had to be installed and slowly ( month by month ) tightened to bring the wall back to a vertical ( and stable ) state.

 

[tony1851]

If the beams are only supporting a floor, and are clear of the existing ceiling (which appears to be the case), the only issue might be excessive deflection/bounce but that is not a structural matter.
Bear in mind that in lofts, the floor is rarely loaded to the usual 1.5 kN/m² over the whole floor because of the low headroom near the eaves.
What may be more important is that the OP has not mentioned any input from Building Control; no Building Control = no certificate = problems when selling.

Should we still ask him to put anything under the 9x3?

No-one can tell without seeing full details of joist sizes and spans etc, and doing some number crunching.

On a more general note - you still haven't mentioned Building Control. Polish builders can be a bit naughty at times and if you have no Certificate, you may have difficulty when you come to sell the property.