Concrete joists in 1940s (?) house

[SimonH2]

We've just moved house, we think it was built in the 40s. When I lifted an upstairs floorboard - partly just for a look around, partly looking for the phone line - I found that the joists are concrete with a wooden batten top and bottom (attached with straps presumably cast in). Looking at the ends, they are roughly I section, but the web is distinctly tapered, being thicker towards the bottom.
A search just found lots of information about Bison (T) beams and the like - did the joists we have have any specific name I can look for ? And apart from the practical consideration of not being able to just whizz a hole through with a flat bit like wooden joists, is there anything I need to be aware of - such as any common problems they suffered from ?

 

[Blagard]

I am not familiar with those at all, however I don't see why you should have any concerns different to any other concrete product. So long as whatever reinforcement in them has not started to corrode and blow off bits of concrete they should be fine. Since concrete is poor in tension and excellent in compression the shape compensates accordingly. The neutral axix of such beams would be somewhere near the middle depth wise but without knowing how they were put together I would advise against drilling through them. You may be able to determine what the installers considered safe to do by investigating the installation further for evidence of holes etc.

 

[SimonH2]

Well since these were built long before the days of central heating, the only services through them would have been the old slip conduit wiring. From what little I've seen, I think they just ran that across the tops, notching the wood batten on top as you'd notch a wooden joist (except that the notching won't affect the strength). CH has been added later, and that's just in notches. I shouldn't have any need to drill any of them - just do the same.

 

[Footsoldier888]

Simon I am not really clear about this because if you have concrete joists of a room sized width that would indicate that your house itself is made of concrete, which should have been indicated to you when you bought the house. AFAIK the only houses that have concrete joists are Precast Reinforced Concrete houses.

I am sure you know a lot more than I do about this stuff but if it was a PRC house it would be clearly indicated at the survey stage, if you have bought the house.

Do you mind saying what the house is built out of???

 

[SimonH2]

It's brick built - we think 1940s ish.
It's just that instead of timber, there's a concrete "I" section with wood batten top and bottom. In other respects, these joists are used just the same as normal timber ones would be.

What little I could find online (not having anything particularly useful to search for) suggests that around the time this house was built, timber was in a bit of short supply. Unless they were just the "latest clever idea" at the time.

 

[Nige F]

More than a bit of short supply then. A Sussex mansion was destroyed by fire in 1940 and was rebuilt with concrete floors by it's architect owner. The interesting thing is that quality doors and fireplaces were available as salvage then so they went in. Grade2* listed now.

 

[Footsoldier888]

How many have you got and what is the length??? They will be different in one respect - weight. It is not clear to me how a brick built house of that era could support concrete joists. I am not an expert though!!! It's just I have a few Estate Gazette books on house construction and surveying and the only reference to concrete joists before beam and block was invented is they were used in PRC houses. But the books are not exhaustive.

This sounds like a daft question but you are 100% sure the house is brick and block construction as opposed to an outer brick skin with reinforced concrete on the inner wall??? It's just that in the 1980's there were government grants available to repair these PRC houses and typically the roof was replaced and a brick skin built, so it is not always so obvious, especially if the inner wall is not exposed anywhere.

Do you mind me asking what type of house it is? It will be good to hear what those with better knowledge say.

 

[SimonH2]

OK, had some boards up again the other day (to pull some wires in) and got some photos.

I also double checked, and yes, it's red brick in the walls.

There's going to be a lot of sorting out to do, but that's about what I expected when I bought the house.

 

[Footsoldier888]

I don't understand. You say this is the first floor but it looks like a loft.

Perhaps it is some sort of lightweight support for the pipes?

 

[SimonH2]

No, it's the first floor floor. When I took the photos, there was a board up above the pipes which might be creating a misleading visual effect.

 

[sparkymarka]

Loads of these type houses In sheffield normally with a wood batten on the underside so you can run pipes cables under ( plasterboards fixed to the battern ) all brick internal and external ( some have cast internal walls but not all )

 

[SimonH2]

It was obviously "the way it was done" for a while - a lot less timber when it was in short supply. The main reason for having a batten top and bottom would be to give something to attach the ceiling and floor boards to - you try nailing up the plasterboard if there wasn't a batten on the bottom of a lump of concrete
There are thin straps cast into the concrete, these have been wrapped round the batten and nailed to hold the batten in place.