Is Band Beam usage common for houses

murman

With my limited knowledge of house construction, I always understood that at wallplate level, the wall cavity was closed off by a 4" block on flat (or similar), the wallplate was fixed to this block and secured by galvanised steel straps.

However, my engineer has indicated that a steel reinforced BandBeam should be used to close off the cavity and strenghten the wall. The wallplate is bolted to the BandBeam and then strapped using galvanised steel straps. He has indicated (in his drawings) that this should be used in all areas where there is a wall plate.

My house is a combination of single story and story-and-half. The story-and-half part is L shaped and therefore requires 4 steel RSJs acting as Purlins. 2 purlins in East-West (EW) direction rest on the East and West gable walls and are supported by internal structural walls using padstones. The 2 purlins in NS direction rest on the North Gable and then on the EW purlin where they intersect (congrats if you have followed this!!). I have a raft foundation, will use hollowcore and slates on roof. Admittedly, the wall plate is cut to facilitate dormer windows.

I have spoken to a couple of experienced (I think) roofers who have not seen BandBeams on domestic houses - just commercial buildings. They reckon that the purlins should be able to support the roof and that the bandbeams are over-kill. I even have a single story utility room with floor area of 3mx4m and a bandbeam is recommended for this roof.

My current thinking is that we all could be structural engineers and over spec the amount of reinforcement needed in a house. Our indemnity policy would be safe. I think it is over-kill but if I don't install the bandbeams, then the engineer won't certify. I know its easy to say just install it but I'm looking at time, sourcing/availability of another trade to do the work(I'm doing a self build) and cost (which is minimal enough).

Are there any roofers or structural engineers out there with an opinion.

Thanks

Firewalkwithme

If it's a full reinforced concrete band beam it does sounds like a bit of overkill alright. I would have thought a U-Block band beam would suffice and would be a lot faster and cheaper to construct. If your engineer is concerned about the bearing for your roof beams you could still just use a reinforced conc. bearing pad in those locations.

rooferPete

Hi,

From your description it appears the Engineer is trying to spread the load of the RSJ's over as wide an area as possible and tying the walls together at the same time.

The detail is not as unusual as it first appears, old school maybe but not without merit as you will be interfering with the run of the wallplate at the dormers.

When using a raft foundation it is important to spread the load as evenly as possible around the building to maintain the balance, it also relieves possible stress on sections of the wall being transferred to singular points of the raft.

A perfectly good time proven detail, one I would prefer to any chance of problems later.

.

kadman

You should be greatful that your engineer is in charge of your structural requirements , and not your roofers.

Your band beam detail is an excellent arrangement, and any attempt to change it for penny pinching gains, should be avoided.

Hopefully your engineer won't be reading this and realise you have more confidence in your roofers ,than you have in him. Shame :eek:

Or maybe you want to fork up dough for Rookads detail :rolleyes:

kadman

Victor

Its not uncommon and I suspect its down to you having a slightly more complicated layout than usual.

murman

Thanks for the comments lads. Advise will be taken onboard.