How important is the undercoat

[Alloverthegrapevine]

I'm doing a bit of spur of the moment decorating, using paint I already had. I've got a suitable emulsion and gloss for the woodwork but no undercoat.

It's only the downstairs loo and the woodwork has been well sanded, no bare wood. Do I really need to undercoat or can I go straight in with the gloss?

I was also planning to gloss the radiator which is showing signs of rust. I'm guessing a proper undercoat is more important there? I actually have a tin marked radiator enamel but that's rubbish, it just beads up and wipes off.

I was hoping to do it without spending anything or going out Can I use emulsion instead of undercoat, it seems to have a similar consistency and finish?

[MikeUniformMike]

Is the wood already painted but sanded? If it is you can apply gloss, but if it's sanded to the wood you need undercoat.

You can get interior undercoat in Wilko or B&M for about £5.

[yeOldeTrout]

what happens if no undercoat used?

[MikeUniformMike]

It depends on what paint you apply, but generally it won't adhere properly.

You can use chalk paint or emulsion on bare wood but it will chip off very easily.

[Alloverthegrapevine]

Thank you. I know I could get some without breaking the bank, I just wanted to get on with the job without going out. It was previously painted wood, well sanded, no bare wood, so hopefully OK. The radiator is going to need another coat, so we shall see.

[donkeyoatey]

You need primer on bare wood or metal. The undercoat is less important than primer.

[CottonSock]

Use undercoat. It's cheap. Risk gloss won't stick or be durable. Any bare wood could show through. Learnt from experience here! Also check water based or oil based and choose appropriate product.