Underfloor access - lintel in load bearing wall

[SproutsDad]

Your help please

I need to allow access to lots of pipe and cable within the 700mm high underfloor void of my suspended wooden ground floor. There are sleeper mid-room floor support walls and a full height solid brick load bearing wall in which I will need to insert lintels to support it. The opening will be approx. 900mm wide and 600 high beneath the floor.

I understand it would be risky to just cut out a course of bricks and put the lintels in unsupported while the mortar hardens, two storeys of the house rest on it. But it is difficult getting acrow props in under the floor.

Q? - How can I support that wall while inserting the lintels? They will be 1200 x 65 x 100mm wide.
Q? - Or do I take floorboards away to allow access through for the Acrow to bear on the ground below?
Q? - Will the acrow go down that low, 600mm off the ground?

Your advice please, thanks.

See sketch photo.

 

[ivixor]

Seems like a lot of faff just for some pipes. Why not just core drill a 110mm hole. Would be more than enough for anything in a house.

 

[SproutsDad]

Seems like a lot of faff just for some pipes. Why not just core drill a 110mm hole. Would be more than enough for anything in a house.

Sorry, maybe it wasn't clear, this isn't a hole to put the pipes/ cables through, this is an access opening to crawl through in the event of repairs, leaks etc.

Following a recent large extension and refurb of a 1930's house, there is now a network of services, soil and waste, heating, H&C water, gas, cables etc beneath a 40m2, 700mm deep void under the suspended wooden floor. All this was done from above, the floor replaced and now a sealed final floor covering, no carpets that could be easily lifted if necessary.

So, for any future access to all this , the only way would be to open up and destroy the expensive top floor. So I want to make the whole underfloor area accessible in case of repairs or disaster, not at all unusual I am told. We have also experienced ingress from flash flood water. A bit of work now but hopefully to make things easier in the future.
So there will be an access lid to get under the floor and from there I will need to crawl through to wherever necessary. But this solid structural wall needs to have an access opening approx. 900w x 600h

And, with a such a lot of services under a permanent floor I wouldn't get any tradesman to work on pipes, wiring etc without some access to it, or they often will only come back after the expensive flooring has been opened up by someone else, understandably.

Q? - How can I support that wall while inserting the lintels? They will be 1200 x 65 x 100mm wide.
Q? - Or do I take floorboards away to allow access through for the Acrow to bear on the ground below?
Q? - Will the acrow go down that low, 600mm off the ground?

Q? - Your help in how I support and get a lintel/s in place on this structural wall would be appreciated.

Your advice please, thanks.

See sketch photo

 

[ivixor]

Ah well. My completely non expert idea would as follows:

Assuming the floor joists are securely embedded into the wall, I would reuse them in situ to act as acro props. So build up some sturdy blocks or timber under the joists on either side of the wall, pushing the floor joists upward.

You can then insert the lintel with the joists transferring the load from the wall down through the temporary props.

 

[SproutsDad]

Thanks, good thinking. From one non-expert as you say to another we seem in agreement.
Do you mean as my sketch shows below?
>> Does anyone else have a view on this?? -
Maybe someone with structural experience or knowledge please? - before I bring the house down!!

Many thanks

 

[Ian H]

900mm seems very wide to me, i’d be thinking more 500mm to crawl through.

 

[SproutsDad]

Ok thanks, yes you're right, no wider than necessary. But a 26" narrow doorway is 760mm wide and it would use the same lintel arrangement as . I'm not that big, but do need space to wriggle and drag things through.
Q? - The main point though is ... do you/ does anyone thing that this use of the floor joists to temporarily hold the house up for a day (!) would work??
Or do I need to speak with a builder structural engineer?
Your thoughts please. Or just get Acrow props, but will they go down that low?

Thanks

 

[Ian H]

Personally, i’d make a 600mm opening with an 800mm lintel and prop 2 joists while I did it.

I made a new opening into my living room without propping at all. I drilled the mortar out below the bricks, removed enough for the lintel, put the lintel in then removed the bricks below it. That had the first floor joists on it.

I put a wider stone lintel into my fireplace and a single brick came loose above it.

 

[Ian H]

You can get short acros.